As a person with pro golf management degree and who builds his own engines and father who’s a master mechanic and machinist I will tell you your absolutely correct. Dimples are on a golf ball to make it actually grab air to keep the flight stable and give you the ability to control the ball by spinning it left right etc. if you hit a golf ball without dimples it flys like the craziest knuckleball you’d ever seen. In now way do the dimples causing air friction allow air to travel faster over a surface it’s just the dumbest thing I’ve ever herd.
Exactly, mate. And it's additional flight distance is due to the reduction of the negative area "behind" the ball. The dimples created more boundary interaction (friction), which allows the air to stay connected longer. 👌. Cheers for the comment 👍
It was pretty obvious, but apart from the golf ball I think I know where they got the idea. Back in the dark ages it was actually found that a rough cast or even ported without polish port could flow better than a polished one. The theory IIRC was that "micro-eddies" would occur, acting like little ball-bearings, though laminar flow at surfaces is a pretty esoteric science. Obviously that won't work with dimples, which will actually tend to increase turbulence, hence reduce flow. It is very hard to produce just the right surface, so unless you are keeping the sand cast port it is best just to polish, and that is always the case with exhaust ports.
Yeah, that's it. A lot has changed in our understanding of boundary layers and the type of flow we are dealing with. Many were treating the primary induction length as a laminar condition, not understanding that we are always dealing with an active boundary condition.
My dad said that on old cast heads (60s - 70s sorta thing) polishing the ports often made the cars run worse since the petrol vapour would cling to the walls causing uneven air fuel mixture throughout the rev ranges, and that the rough surfaces would create disturbances that mixed the air and fuel better. Dunno how true it is but does make sense especially the fuel vapor "sticking" and condensating on the smooth walls, if you blast compressed air on a smooth surface it will quickly become wet compared to a rougher surface from the water vapor in the air compressor system. Keep in mind this is when they were teens in the 80s messing around with old holden six's, probably didn't have the most scientific method lol
Yeah all ports need an active boundary layer condition, polished causes fuel to stick to the walls and we don't want that 👌. But the key is about just the right amount of boundary layer thickness, so a sanded or burr or even a light casting finish for older stuff is best 👌
Yeah the main function is to "increase" surface drag, to extend the separation point which makes the negative pressure area behind the ball much smaller. This allows the ball to almost double its distance for the same energy input. As far as flying straight, I think that comes down to more about what spin they put on the ball. But I'm no golf expert. I only really understand how the dimples affect surface drag. Which is our key focus 👌
Yeah, if only a flow bench was the pinnacle for validating primary induction dynamics. If you understand how they work. You will know why they can be deceptive. They don't measure flow. Just depression. A perfect example of this is that our race heads have lost 10-15cfm over a decade and make more everywhere, including HP per PSI, area under the curve, and boost threshold points. Even a dyno can misleading if you dont understand the physics at play. 20 years ago, when testing our custom race intakes. We were adding plenum volume making power only to go slower at the track. Why? Because we didn't understand the secondary harmonic elements of the plenum. Understand the physics at play its key! There's no way we can force energy into the boundary layer and make more hp in a closed system. This is why you're so confused. Understand the conservation of energy. 👌
I have heard that on ports with floors that are too low, dimpling can help to give the effect of a raised floor. Have you seen anything that might support that?
Its not the fact the floors are too low. It's generally on ports that have the wrong CSA so lack air speed and Dimples will "reduce" CSA by increases in thickness at the boundary layer. There are two problems with this though. The first will be the boundary layer thickness, is directly linked to velocity/Ra. Meaning the roughness and the speed at which air is moving will dictate the thickness of the boundary layer. and how much boundary layer energy is removed from the port and added to the boundary layer. So while velocity is low the "effect" of the boundary layer, or the thickness we are trying to achieve. will be quite small. But as we increase RPM, our average velocity increases and can end up hurting top end power. That's because now we have a very dynamic boundary layer which dramatically increases the boundary layers energy, and this robs Horsepower and will "narrow" our power band. The other problem with adding dimples toa floor is, that has only been found on the flow bench in a very small snippet of depression @ 28" in steady state flow. The real world implications would have to be proven and I haven't seen any solid evidence that it works. Also what we need to keep in mind is when testing on a flow bench, what's helping at one point in the depression isn't affecting other rates of depression poorly. Seats and radius valves are a great example of this. they test well on the bench, but the real world results show it fails. Thats because ICE engines are a dynamic environment. In our primary induction length of a ICE engine we have a rapidly accelerating velocity curve., Which accelerates from zero to 690fps and back to zero again, every single valve event. So to conclude that what we find on our flow bench 100% relays real world results has yet to be seen especially in this area. hopefully that helps
Also a major difference between a golf ball and a port is the ball surface is exterior and sees symmetrical flow, the port is the inside of a bend. I was going to go with the floor idea, but just a small patch on the "lee" of the bend.
it hurts CFM in cases when the tunnel is fully dimpled because youre basically making the port larger and losing port energy. In partial dimple or depending on air speed or what wall the air is clung to it absolutely picks up CFM. The reason being is because unless youre starting with a specific sized casting that has the same volume but surface texture changes the size of the dimples ( say an 1/8th inch burr) make the port act larger and lose port energy due to volume. All running engines are turbulent but this helps post fuel injector or in the case of carb runners beneath and keep fuel in suspension. When porting an intake the best surface texture is technically a "dimpled surface" its just on a smaller level than the very obvious deep cuts of what is typically about an 1/8th inch shank size burr. But basically when finishing youre making micro dimples already... but this is mostly for the benefit of atomization. In the case of increasing air speed / CFM in certain areas? yes it can
Other way around mate. Dimples "strink" a port due to the "increases" in boundary layer thickness and no they can't increase CFM as you're reducing port CSA and "increasing" shear stress. Hence why testing shows you lose HP and gain torque. This shows us two things supported by the physics of fluid dynamics. One.. That we have limited peak mass flow and increased velocity earlier as the boundary layer is now thicker. Two... we have "increased" the boundary layers drag coefficient, meaning this finish is more restrictive to flow and we are loosing port energy into the boundary layer. Remember the Ra of a port surface is directly related to its boundary thickness over air speed. Meaning the more course the primary induction surface is. The thicker the boundary layer will be, relative to air speed. And the smaller the available flow path will be. And no it won't help keep fuel in suspension, best it can do its limit wet-down, it's actually optimising velocity in a port that keeps fuel suspended. Fuel can only fall out of suspension in two cases. Lack of velocity, or sudden changes in direction, but again velocity dependent and shape dependent. This is where focus on the shear layer speeds is key and why we must accelerate air speed on the long side of any turn! The the best finish is between 100-200Ra depending on port shape and targeting velocity, not dimples. Dimples create restrictions. Remember, the higher the velocity, the finer the Ra can be which is why you find on much straighter shots like on twin cam heads. And this is why we can finish them much finer like a 60G finish, with radial lines down the port. But doing this, we are reducing how thick the boundary layer is and how much energy we lose into the boundary layer. A 60grit finish has the lowest drag coefficient in the velocity range needed to optimise the inertia mechanism for ICE engines. This is something even Princeton University has shown. So at best "dimples" can be used for is a "bandaid" in limited areas that have very poor velocity profiles. But you would be better off filling those areas and eliminating the dead area in the first place. Which would increase port energy and make more power. Hopefully that helps the confusion.
@@bainracing as I said they make a port act smaller depending on the size of the pock and how few are made. If it's done without crossing a threshold of material removed then yes increase in velocity /CFM. With enough craters relative to each other you're just increasing physical volume . Also in a turn you actually want to increase the apex to slow the air down to better navigate the turn (like a dog leg ) .. calling surface finish technique a "band aid" is confusing . It's a permanent change to the air flow dynamic of the head/intake . And yes micro dimple surface finish are superior as proven in wet flow tests. You're basically letting the burr dance on the surface rather than an 80 grit sand roll .. at least for intake bowls and tunnels. Absolutely help with atomization.. other things that can cause too large of droplets is too much swirl at higher lift value. Go ask David Vizard /Charles servedio about textures and go watch Eric weingartner put a partial dimpled LS head intake on the flow bench and pick up a few CFM . It works . It's like calling a crank scraper/windage a band aid lol . Backwards pistons etc.. what works works . Not saying that your physics are incorrect but as I said initially when you do a complete all over dimple you're actually just increasing volume. They work relative to the right dimensions
@DS-mo6md cheers for the reply mate. Maybe you wrote it wrong mate. But you said "dimples" make it "larger" which they don't. They again as I explained "strink" the ports available volume. They don't "increase" it relative to a running engine of course. Statically yes. But engines run. So we need to look at the dynamic effects. That is key! Same thing can be seen with corner radius. To small a radius will have more port volume, but act smaller when testing dynamically. As the shear stress on two converging walls is much greater. A simple velocity probe shows this. And no it's not increasing cfm, even if the bench tells you it is. You need to remember a flow bench doesn't measure cfm. It measures pressure drop and only at one velocity point, or generally 28"and 300ish fps. Generally this is not even half peak velocity of a running engine. This is why our record heads have actually lost flow "CFM" and not only run faster. But make more peak and average HP. A flow bench lies! So don't confuse flow bench data with realistic real world results. Radius intake seats is another great example, increasing flow bench data. But go backwards in the real world. Even dynos lie mate. Plenum volume is a great example of this. On the dyno you can add Plenum volume more and more and make more and more power on the dyno. Yet the car will run slower as you've dampened the secondary harmonics in the Plenum and the engine's ability to accelerate. And many in the industry call it for what it is mate. Not only I, but Darren morgan calls dimple ports a "bandaid"? ..why? because in true cylinder head development fashion. if you have a dead area. Fix it properly, don't use a poorly thought out "bandaid" to try and fix a poor velocity gradient in that area. And no nothing is permanent. When we were back to back testing dimples on circuit cars in the 90's we would just fill with filler and run again. Or like we do nowadays, we weld up and do a full remodel of the port. And the air speed at the SSR is relative to the long side. That's the key. The speed differential is set by the long side as this is what controls the pressure front and how stable the short side is. And no mirco-dimbles don't work and increase port drag. Again as I explained, the Ra is dependent on the air speed factor. And yes I know Dave. But unfortunately most of what you read has been debunked in motorsport and is outdated. A lot of what he refers to older engines like 23° SBC with very poor port designs where we have to "sacrifice" some port energy into a thicker boundary layer to compensate for a poor old design. See this is where people get confused. We must understand the "whys" or what I call, the what,whys and how. The science at play. As the right Ra finish can't be a blanket set amount acoss all engine designs and many have very different velocity gradients and targets. It's why my calculators on my site have different air speed factors. And yes I know Eric. But again. Flow bench isn't real world! And as I've told him. If you fill the areas behind the guide and fix the dead areas properly, you won't need dimples. And he knows this! And that's exactly what we do and every top race head manufacturer is doing and I know as I've helped develop said heads. And almost all of these heads are now on a fine CNC finish which creates fine radial lines with the least amount of drag coefficient. Which almost all the top race heads I see are finished this way. Especially if you have a stable velocity gradient on a well designed port. Nath from Higgins, Brett from BME, Scott from CHI etc etc has some great examples of this and the surface tension has been Dialed in over many years of testing. Remember what worked in 1970 on poor design heads. Won't always translate to model port design with higher velocity indexes and far more stable velocity gradients. You need to understand what's actually at play here and why different finishes are needed and why. So no, dimples don't work and it's why any serious head development guy will call them a bandaid. Anyway, thx for the comments mate. I'll try to do more videos and break down the science for you to help you understand what's actually happening here. 👌
@bainracing Thanks a lot for your very precise, in depth, explanations. If I understand right, dimples suck energy from the velocity to build the boundary layer. At high velocities the boundary layer gets too thick and chokes the port size.
Thoughts on a 60gr finish with a burr finish on the long side of the bowl ? Possibly even burr finish in vertical lines ? Would you also burr the valve guide ?
Definitely can help if you're having velocity problems in that area and if it's a wet port. Will help to keep fuel off. But it depends on the head shape and especially the short turn shape and local velocity
@bainracing Could it be good to do a rough burr finish where you can see that the injector has sprayed the port clean? I guess you could still choke the port that way at higher air speeds.
That's it! But most importantly, dimples "increase" drag, but extend the separation point, and this reduces the negative pressure behind the ball. This is what allows them to fly greater distances than a smooth ball. 👌
Aerodynamics and common sense don't really go together, that's why we rely on science. Relying on common sense kept us out of the air for decades, until people started applying science to the problems.
The dimples are not to optimize the flow, but rather to atomize the air-fuel mixture and improve burning. Don't try to measure the flow, you will obviously lose some, which can be corrected by increasing the diameter of the duct. Measure engine efficiency.
No, that's not how port science works at all. The right targets on CSA and Velocity is what creates the shear stress for fuel atomisation. Dimples choke ports as our Ra is directly related to our boundary layer thickness. Hence why they don't work 👌
@@bainracing Well, in theory everything is beautiful. As long as there is no performance bench test (and I'm not saying measuring flow, but engine performance) the debate will always be inconclusive.
@@3ldraziel296 Mate we and most top shops have tested this to death. There's a clear cost not only with our peak numbers at around 3-4% while showing a choke limit and rolling off. this is due to the boundary layer swell the dimples cause, and there's a clear lost in area under the curve. And lets face it, even the physics principles show its all wrong for internal pipe flow. So there's not only zero evidence this works by the very physics principles that dictate fluid dynamics. but real world testing showing its a not well thought out. So to be honest mate, I'm confused by your argument. the best Ra finishes have been set in motorsport for near on 20 years. we know this. I've tested this to death. F1 has, NASCAR, Prostock superstock which we build our intake for other race shops. With our custom intake program we cover quite a few series of motorsport. but don't take my word for it. There's Chad Speier, Darin Morgan, Dave from head games. All guys I know, we all found the same thing over the years. And the go to finish for Intakes ports for the best drag coefficient and best 146 rule is between 60grit and cutter finish for all gasoline and Alky fuels.. More course than burr finish and we see choke. And a Golf balls Ra is not percentage points bigger then a course buff finish, its folds greater! So this why dimples in ports choke. The whole principle of the golf ball finish is to create more surface drag, not only for more attachment time to reduce the negative pressure "behind" the ball, but the create lift and spin! So ALL this is creating more restriction throughout ant flow duct. the opposite to what we want, and why you can just make it "bigger" as you only narrow the winder even more.
@@3ldraziel296 Also mate maybe explain what you have been testing to find your results mate, as I would be interested what's led you to your conclusion. as I personally don't know anyone in the game that's made gains with this is ports. if you said piston tops or Plenun floors I would agree, but not in port. But Pease share what you have found mate. I'd love to hear and discuss what you Have found and or why. Thx for the comment.
As far as surface finish goes guys like Larry Meuax found power in very very rough burr finish like a decade ago. Chad Spier has popularized it. And it makes sense watching Kaase's video where he puts his finger and a glove in the port on the dyno to observe pressure waves. Plenum and runner are clear and you see the massive amounts of fuel puddling. Is it a crutch? Yes probably? Does it look pretty - no? But it's shown to make power. Darin Morgan doesn't seem to like golf ball finish but sounds like he's in favor of the very rough burr finish (think the cutter is bent, chipped teeth, held a certain way to create the finish not just normal carbide). And I understand more turbulence in the boundary layer in theory shrinks the port... but if you have rich and lean cycles because fuel falls out of suspension... Also it's (surface finish) pretty small in % terms of power. Definitely not as important as size and shape. So crutch, surely. But it has worked on efficient applications not just a 23° with compromises.
Yeah, I know the boys well and have chatted with Darin a bit. And Joh has helped me a few times in the past. Especially when testing in APSA. Yes, Darin doesn't like the golf ball pattern and physic, along with the data, which makes it pretty clear why it's not an optimal surface finish. The increase in port surface drag coefficient is an obvious one. That and the direct link between surface Ra/boundary thickness and velocity. This is an important reason why the velocity gradient and port shape will indicate what surface Ra is optimal. This is why fewer direct shots need more Ra, more energy in the boundary layer to compensate for the axial force placed on the boundary layer created by the port shape. And this is why most guys like Larry and Chad found burrs to be optimal on a lot of the older stuff like 23 degrees, with poor line of sight. That's because the boundary conditions are directly related to port shape. There's also the argument that their air speeds and targets are built around their burr finish. As if we look at current prostock and even F1, their CSA and velocity and Ra finishes are very different. They are much finer in their surface finish and, in turn, less energy lost on the boundary layer. Generally, the worst the port shape is. The more boundary action a port will need to compensate for the poor port design. So what works in a 23 degree, that needs alot of boundary energy doesn't seem as good in some of the 13, 12 and 11 degree stuff we are involved with and definitely doesn't work in twin cams engines that we have a hell of a lot of testing in and we see this with the some of the record Honda stuff as well coming out of UAE and the US. Even some of the work and testing coming out of Princeton University showing the most efficient boundary conditions are in the range of 100Ra It's a very interesting topic, and I try not to fall into these hard and fast rules that burr is best. Or 60grit is best, as without a deep analysis of what's actually happening and why. It's really more a guess than good science. But I'll finish with one of darins quotes. "Dimple port is a bandaid for a bad port."
@@bainracing probably a good rule to be curious vs simplistic rules. Good feedback. Interesting thought on the maths & CSA. You think it may be in effect shrinking the port and they may've been better off with a smaller port? Do you know of anyone who's tested it on a 11 or 9° modern port? Agree a lot of this is seen in the 23° stuff. Thought Larry did it in a more modern port (for ~ 2010-12) but I may be misremembering. Is is something that you've tried (modern valve angles)?
I always understood that the point of roughening up the port walls and the bowl was to prevent fuel puddling, and lean mixture for high rpm motors while at low rpm, and a little more than a decade ago the reason for dimples on golf balls became mainstream and hotrodders wanted to know if such a modification would help. I never heard that it was a method for increasing air flow.
Yeah, sadly, it actually hinders air flow as the balls ability to fly the future comes down to the reduction in the wake "behind" the ball. Hence, why dimples cost power 👌
@@bainracing you know, I have doubted that the size and depth of the dimples are way out of proportion with the sort of air velocity in an engines intake port anyway, I think it would be more beneficial to use a fine knurling tool after porting, just enough to prevent condensation on the sides of the bowl.
@@werewally3156 Yeah! What you're describing is actually what's left with a porting burr naturally when done right. And when done right it leaves a more course finish than say 60grit, like a very fine dimpling. It does tend to lend itself to old port shapes, that really didn't have a good velocity profile. See what we need to remember is, our boundary layer thickness is directly related to not only air speed, but the Ra of the surface. the Ra is the average distance between the high and low point. So as you can imagine, the golf ball boundary layer thickness will be huge due to the very course Ra. And this is why when we add the golf ball texture to a port, we lose HP and make torque, Proving we are not only seeing a boundary layer swell, but a higher velocity factor sooner, hence the choke we see from a dimple port. The Ra is simply too course for the velocity factors needed in an ICE engine. Also this is and area that has been tested to death by not only people like myself and many others in the racing industry. But by universities like Cambridge. and optimal port finish is in-between a buff finish and 60 grit. The basic rule being, the better the shot and the more stable the velocity gradient. the less boundary energy we need to sacrifice. in short. modern port, 60grit. Old port burr finish. The other problem we haven't covered is that, the more energy we direct into the boundary layer, the more we increase the ports drag coefficient. So as the boundary layer increase, port energy decreases. Hopefully that helps mate
from what ive read its helps atomize the A/F into the combustion chamber. ive recently done dimpling to my intake ports on the top/ roof section and back section leaving the floor polished and exhaust ports high polished. im no expert not do i claim to be. just messing around in the workshop. a friend also told me about guys dimpling the top of their pistons . come across this at all?
Yes, dimple on the piston works well. As the dimple "increases" boundary layer thickness and creates more drag. So, on a piston top, that's what we want. But for the same reason it works on a piston top, it's the same reasons why Dimple Port hinders the port. First as we explain, it creates thicker boundary layers on the piston. But thickening in the port "reduces" CSA. So this will limit the mass potential of the head. For the second reason its not optimal in ports, is the dimples, increase in the drag coefficient. Meaning it tries to slow the air moving acoss the dimples. As remember, the more energy we put into the boundary layer, the more it is removed from the port.
The dimpling is for mixture preparation, you’re only going to see gains on a port injection engine. The gains are the engines ability to make more power from a leaner mixture which in turn means better fuel efficiency, less on board fuel weight and less pit stops.
No, that's not true at all, mate. Air speed controls fuel shear at the right velocity is key. and dimples only choke an optimised port. It's why none of the top heads use them. You need to understand what's happening in the boundary condition. And why dimples only swell the boundary layer while increasing the ports drag coefficient. Too things that kill HP. The more energy we put into the boundary layer, the less HP we make. Again, this has been tested to death, and it's why, from pro stock to supersprint, no one is silly enough to fall for this snake oil. Dimples only help reduce the negative pressure from "behind" the ball. By thickening the boundary layer and creating more drag which mores the attachment point further around and hence reduces the area of the negative pressure pulling baxk on the ball. That's what allows them to fly further. Thx for the comment 👍
@bainracing When he is talking about only efficiency, and not at all about power, could it be true that a very rough wall could help a wet wall to put the fuel back into the airstream in an atomized form, and improve efficiency?
@@bobirving6052 Yes, that is my line of thought. My main point is everyone rights off the dimpling because it doesn’t suit their application. For N/A application the CFM loss associated with dimpling the intake may have a negative effect as the port energy is critical. In forced induction applications the CFM loss is of lesser concern and is outweighed by superior mixture preparation. That said there is also no need to dimple the bowl area or turns, keep it to the straight sections of the runners and port entry and it will have minimal effect on cfm. I should also note and as you mention that finishing with an 80 grit cartridge roll can have the same effect for much less effort.
It's definitely an option if it's a dead area and you want to "thicken" the boundary area up it that localised area. Behind the guide is a common place people use it. It will work if it's flat and not shaped well. But I prefer to fill or weld up and optimise velocity in that area. So yes, it can be used in poorly developed areas. But you're almost always better off fixing dead areas properly by eliminating volume that works against to port.
Yeah, quite a few. Australia's fastest Holden door car. Fastest 1uz, twin turbo, highest NA record, fastest Holden in blown class, NA, records in early head, VN head, 85 and and some in pump fuel the lists go on, then there's all the ones we done over the last 20 years. But records mean nothing if you can't get the physics right first 👌
Yeah, unfortunately, in the racing world, you work out real quickly. A flow bench not only doesn't measure CFM, but in many cases, it doesn't carry over the real world flow in a dynamic variable velocity environment that ICE engines are. It's why all our race heads have lost cfm on the bench yet make more EVERYWHERE! But even if we ignore all that, basic physics shows we are creating more drag! Understand the mechanisms at play, and it will help you see the BS 😉👌
Ada hal yang tidak fair dalam ulasan anda :) Membandingkan permukaan bagian dalam port dengan bola yang sedang terbang bebas di udara dan udara bebas tidak lebih basah dari port kecuali hujan :v. Memiliki blower fan atau vaccum cleaner, karbu, manifold bahkan lebih adil dan cepat untuk mendapatkan jawaban. Jika ide sederhana saya terdengar konyol dan ya setidaknya melangkah satu langkah.
Thx for the comment, mate. But you're not understanding the fluiddynamics of a port properly or a golf ball. We aren't comparing the two. We are explaining why dimples on a ball and in a port create "MORE" restriction more "drag" and more boundary interaction means more energy loss, which means less HP. This is why dimples dont work in ports. The wet flow means very little as if we understand the basics of turbulent shearing and the fact we have an "active boundary" condition, which is controlled by velocity. So, size to port right for the RPM, and your target Ra I very clear. Understand the basics. That way, you won't be confused 👌
What da... hey u guy... can't u all get it.. dimple ports only work on da exaust port... because carbon will fill in the dimple hole so... think of your self.. the benefit of it..
😂😂😂 I wouldn't even be doing on the exhaust. Unfortunately people don't understand the physics or thermal dynamics principles. The trick with all exhaust ports in the "reduce" surface area. Not increase it. This is why mirror finishes work brilliantly
Yeah, exactly! . Here's a better idea. People should learn even the very basics of physics and fluid dynamics principles. Would save them a hell of a lot of time! 😂😂👌
@@bainracingindeed. These ports fundamentaly ain't too different from the ports of speakers. Very simular observations had been made whit those too. Allso seen a nother video where a guy dimpled a port in sections and measured the flow at different valve lifts. Dimpling the whole thing made it worse. As expected. Try to dimple the middle part only vs no dimpling. No more Than 1/5 of total length. An improvment you will find at about half the valve lift vs smooth surface flow figures. Very simular to what hifi stuff has. The same principles apply in Both. Not Just whit ports , but whit exhaust systems , intakes , basicly anything that deals whit pressure waves and gasses.
@@nagyandras8857If only the flow bench was real world mate. But again, a basic understanding of boundary layer thickness and its relationship to surface Ra goes a long way! 😉 Again, the key here is to understand what the bench is telling you and why you got the results. Just because you make more "CFM" doesn't not mean it will translate into more HP and torque. Especially when using a bandaid like dimples. Especially when we know "dimples" increase surface drag. Meaning you're robbing the port of energy. If CFM increases from dimples in a certain area. That means that area is too large and has low velocity. The "increased" drag, thickened the boundary layer, which than increased velocity. Again showing a dead area. Again this is why for 20 years we have ignored cfm and focused on what actually makes power and that's the velocity gradient of the port. The key to making power is energy conservation. You could have just probed that area and seen it was low and filled it, this would "reduce" CSA and feed into both mechanisms that lead to a successful build. And a more balanced velocity gradient means you win in both torque and HP. Unfortunately Again this shows that people don't understand their tools, or the physics at play, and furthermore why they are seeing the results they did. The other huge problem with flow benches is its at 1 pressure differential, usually 28" which isn't even half of the pressure drop and engine creates. And we know boundary conditions are dependent of pressure drop. Also the port and whole primary induction length is bidirectional and goes from zero to 690fps ans back to zero each valve event. And we know that accelerating velocity and greater pressure differential changes the very boundary conditions we are trying to measure on a stationary bench. As ive said for 20 plus years in motorsport, if you're using a flow bench to validate real world hp and torque, you're either new to racing, or don't understand the complexity of what's actually happening or what you're testing. There's a reason our record heads have lost CFM over the decades and continue to make more power everywhere.
@bainracing certainly, specialy the flow test is just part of the tale. Btw, thank you for getting back and providing your input, in legth. thats a very respectible thing. the thing is, i surely never got any cfm values, as i em not an engine builder, or head porter. i design loudspeakers. the thing that is , or should be , quite obvious when it comes to a flow bench is, that engines in real life don't have a constant flow. they take "lumps" of air at the intake stroke. at least pistons engines that is. air is quite springy, changes many of its properities whit pressure and temperature and humidity , and elevation or effective gravity etc.. so not quite a constant material to work whit. You would be surprised how simular is the case when it comes to a ported speaker box. but we don't have the luxury of many horses worth of power moving air.. and in some cases we intentionaly avoid the need of more than a few watts , to pump respectible amount of air, at quite a broad range of freqvencies. port velocity is a thing in both worlds, even if for different reasons, both aim to ensure that the air can move in that port whit the least loss of energy. in our case if air in the port looses energy.. we will loose sound pressure. and that loss will translate into noise we don't want. no mather how big of a speaker we talk about, at the freqvency where the port+box is tuned at, actualy the driver is near stationary and the only source of sound is from the port. engines are different as the primary goal would be to only let air go in, and the preference would be to not let it flow backwards. everytime. whit speaker ports we are selective in freqvency, we out of necessity do choose to restrict flow sometimes in a range of freqvency. now supposedly you got air rushing in like crazy to equalise pressure , that be the intake cycle. but then the valve closes. the air pressure wave hits the closed port and pressure builds up, so the air now wishes to go backwards as pressure is less in that direction. this is where a selectively restrictive port can play a role. just filling in the port where it just has too much cross section area would allow the air to go back just as easy as it got to the valve. to be more precise i owuld need a truckload of data, for a non-direct injection engine even the air fuel ratio would need to be known, to calculate the charge air density, and would need to test the compliance of the mix etc...etc... just to treat everything whit the same precision as a speaker port. however, if you take a .. say, just a random number, 100mm long port, measure both on flow bench and dyno it on an actual engine, than take that head, measure 40mm in, and dimple till 60mm, re-measre it both on the flow bench and on an actual engine, it will show a slight but consistent improvment. that is, unless there is a terrible bottleneck somewhere else. Anyways, thank you for the chat, very refreshing to see that content creators do actually read the comments. and whom may know, you may even give it a go if you got the free time to experiment. makes for an acceptible video material on the subject.
@nagyandras8857 This is exactly what we do for racers all over the world. We run extensive analysis of the primary induction length and analyse the frequency to tune the 3rd harmonic. And everything is calculated from density, temperature, peak velocity, average etc. All top race engines target the 3rd harmonic. And yes the valve closing is what creates the shock wave. Tho if your inertia supercharged mechanisms in dialed in properly, the air has slowed to a stall, this is when we close the valve. So because of this mechanism, we don't want to create any more drag either way. Also you need to understand the relationship between the surface Ra and boundary layer height. This is another reason why dimples cost power and "narrow" the power range. That's because at low velocity, the CSA is too big, but as the velocity accelerates, it "swells" the boundary conditions and now "chokes" the engine. But we and many others have tested this to death. It doesn't work in the real world, nor do the principles of fluid dynamics support this in our primary induction length. Especially at the air speed targets needed for optimum performance 👌 The key here is what the dimples do to the boundary conditions. The more interaction the air has in both directions with the dimples. The more drag we create. So the more power we lose. Hopefully that helps you understand why no one in the race seen runs this snake oil. 😉.
@@invent-cf1yo Maybe learn even the basics of boundary layer conditions, fuel shear lengths and and the mechanisms that control fuel atomisation before commenting in the future. But you're clearly an expert. best of luck👍
No, they don't work. If they give you a "smaller" port. Then you never sized if right in the first place. Also, we know the boundary layer thickness is directly related to the air speed. This means dimples will make the port too big at first, and as velocity increases, the port will "shrink" that's the opposite of what we need. Then there's the drag coefficient factor. Any basic understanding of fluid dynamics we tell you that the more energy we put into the boundary layer, the more energy we put into the boundary layer. The less energy the port has. So no, if you understand the mechanisms at play. You will understand why they are detrimental to any well designed port.
@@bainracing Air has less resistance than metal. You don't really know too much but like to argue like you do. How well is a cast iron or cast aluminum port tuned to the razors edge to begin with? It's not, most of the crap most people deal with isn't pro-stock level. Just because dimples don't work universally doesn't mean they don't work in any application. That's reductionist logic and stupid.
@rolandotillit2867 I noticed, after a video or two, that bainracing is an absolute top of the line company. I also only work on mass produced “junk” but I still very much appreciate what bainracing is sharing here! Much of this information still applies, and maybe someday I will work on something awesome!
@rolandotillit2867 You have to understand the “dynamic” environment. The airspeed must go from 0 - 600 - 0 mph. The thicker boundary layer may fix a bad port design at 200mph but totally choke the port at 600 mph. Now you have lost your inertial charge and your higher rpms. I think Darin Morgan calls it High Speed buffeting, or something. Power Plateau.
As a person with pro golf management degree and who builds his own engines and father who’s a master mechanic and machinist I will tell you your absolutely correct. Dimples are on a golf ball to make it actually grab air to keep the flight stable and give you the ability to control the ball by spinning it left right etc. if you hit a golf ball without dimples it flys like the craziest knuckleball you’d ever seen. In now way do the dimples causing air friction allow air to travel faster over a surface it’s just the dumbest thing I’ve ever herd.
Exactly, mate. And it's additional flight distance is due to the reduction of the negative area "behind" the ball. The dimples created more boundary interaction (friction), which allows the air to stay connected longer. 👌.
Cheers for the comment 👍
YES!!!! Great vid! We tested throwing a head with the dimple port and without off our dock and the dimple port did fly farther though!
🤣🤣👌 I did see that. I thought that was a hilarious video. Keep up the good work, mate.
Finally someone brave enough to say it.
😉👌
It was pretty obvious, but apart from the golf ball I think I know where they got the idea. Back in the dark ages it was actually found that a rough cast or even ported without polish port could flow better than a polished one. The theory IIRC was that "micro-eddies" would occur, acting like little ball-bearings, though laminar flow at surfaces is a pretty esoteric science. Obviously that won't work with dimples, which will actually tend to increase turbulence, hence reduce flow. It is very hard to produce just the right surface, so unless you are keeping the sand cast port it is best just to polish, and that is always the case with exhaust ports.
Yeah, that's it. A lot has changed in our understanding of boundary layers and the type of flow we are dealing with. Many were treating the primary induction length as a laminar condition, not understanding that we are always dealing with an active boundary condition.
My dad said that on old cast heads (60s - 70s sorta thing) polishing the ports often made the cars run worse since the petrol vapour would cling to the walls causing uneven air fuel mixture throughout the rev ranges, and that the rough surfaces would create disturbances that mixed the air and fuel better.
Dunno how true it is but does make sense especially the fuel vapor "sticking" and condensating on the smooth walls, if you blast compressed air on a smooth surface it will quickly become wet compared to a rougher surface from the water vapor in the air compressor system.
Keep in mind this is when they were teens in the 80s messing around with old holden six's, probably didn't have the most scientific method lol
Yeah all ports need an active boundary layer condition, polished causes fuel to stick to the walls and we don't want that 👌.
But the key is about just the right amount of boundary layer thickness, so a sanded or burr or even a light casting finish for older stuff is best 👌
I'm no scientist but I always thought the dimples on a golf ball were to help the ball stay traveling in a straighter path.
Yeah the main function is to "increase" surface drag, to extend the separation point which makes the negative pressure area behind the ball much smaller. This allows the ball to almost double its distance for the same energy input. As far as flying straight, I think that comes down to more about what spin they put on the ball. But I'm no golf expert. I only really understand how the dimples affect surface drag. Which is our key focus 👌
Talk talk talk. Flow Bench test it. Another has !. I'm with them.
Yeah, if only a flow bench was the pinnacle for validating primary induction dynamics. If you understand how they work. You will know why they can be deceptive. They don't measure flow. Just depression.
A perfect example of this is that our race heads have lost 10-15cfm over a decade and make more everywhere, including HP per PSI, area under the curve, and boost threshold points.
Even a dyno can misleading if you dont understand the physics at play. 20 years ago, when testing our custom race intakes. We were adding plenum volume making power only to go slower at the track. Why? Because we didn't understand the secondary harmonic elements of the plenum.
Understand the physics at play its key! There's no way we can force energy into the boundary layer and make more hp in a closed system. This is why you're so confused. Understand the conservation of energy. 👌
I have heard that on ports with floors that are too low, dimpling can help to give the effect of a raised floor. Have you seen anything that might support that?
Its not the fact the floors are too low. It's generally on ports that have the wrong CSA so lack air speed and Dimples will "reduce" CSA by increases in thickness at the boundary layer. There are two problems with this though. The first will be the boundary layer thickness, is directly linked to velocity/Ra. Meaning the roughness and the speed at which air is moving will dictate the thickness of the boundary layer. and how much boundary layer energy is removed from the port and added to the boundary layer.
So while velocity is low the "effect" of the boundary layer, or the thickness we are trying to achieve. will be quite small. But as we increase RPM, our average velocity increases and can end up hurting top end power. That's because now we have a very dynamic boundary layer which dramatically increases the boundary layers energy, and this robs Horsepower and will "narrow" our power band.
The other problem with adding dimples toa floor is, that has only been found on the flow bench in a very small snippet of depression @ 28" in steady state flow. The real world implications would have to be proven and I haven't seen any solid evidence that it works.
Also what we need to keep in mind is when testing on a flow bench, what's helping at one point in the depression isn't affecting other rates of depression poorly. Seats and radius valves are a great example of this. they test well on the bench, but the real world results show it fails.
Thats because ICE engines are a dynamic environment. In our primary induction length of a ICE engine we have a rapidly accelerating velocity curve., Which accelerates from zero to 690fps and back to zero again, every single valve event.
So to conclude that what we find on our flow bench 100% relays real world results has yet to be seen especially in this area. hopefully that helps
@BainRacing
Does his mean that a radius on an exhaust valve margin and exhaust valve seat does nothing for flow in the running engine?
Also a major difference between a golf ball and a port is the ball surface is exterior and sees symmetrical flow, the port is the inside of a bend. I was going to go with the floor idea, but just a small patch on the "lee" of the bend.
it hurts CFM in cases when the tunnel is fully dimpled because youre basically making the port larger and losing port energy. In partial dimple or depending on air speed or what wall the air is clung to it absolutely picks up CFM. The reason being is because unless youre starting with a specific sized casting that has the same volume but surface texture changes the size of the dimples ( say an 1/8th inch burr) make the port act larger and lose port energy due to volume. All running engines are turbulent but this helps post fuel injector or in the case of carb runners beneath and keep fuel in suspension. When porting an intake the best surface texture is technically a "dimpled surface" its just on a smaller level than the very obvious deep cuts of what is typically about an 1/8th inch shank size burr. But basically when finishing youre making micro dimples already... but this is mostly for the benefit of atomization. In the case of increasing air speed / CFM in certain areas? yes it can
Other way around mate. Dimples "strink" a port due to the "increases" in boundary layer thickness and no they can't increase CFM as you're reducing port CSA and "increasing" shear stress.
Hence why testing shows you lose HP and gain torque. This shows us two things supported by the physics of fluid dynamics.
One.. That we have limited peak mass flow and increased velocity earlier as the boundary layer is now thicker.
Two... we have "increased" the boundary layers drag coefficient, meaning this finish is more restrictive to flow and we are loosing port energy into the boundary layer.
Remember the Ra of a port surface is directly related to its boundary thickness over air speed.
Meaning the more course the primary induction surface is. The thicker the boundary layer will be, relative to air speed. And the smaller the available flow path will be.
And no it won't help keep fuel in suspension, best it can do its limit wet-down, it's actually optimising velocity in a port that keeps fuel suspended.
Fuel can only fall out of suspension in two cases. Lack of velocity, or sudden changes in direction, but again velocity dependent and shape dependent. This is where focus on the shear layer speeds is key and why we must accelerate air speed on the long side of any turn!
The the best finish is between 100-200Ra depending on port shape and targeting velocity, not dimples. Dimples create restrictions.
Remember, the higher the velocity, the finer the Ra can be which is why you find on much straighter shots like on twin cam heads. And this is why we can finish them much finer like a 60G finish, with radial lines down the port.
But doing this, we are reducing how thick the boundary layer is and how much energy we lose into the boundary layer. A 60grit finish has the lowest drag coefficient in the velocity range needed to optimise the inertia mechanism for ICE engines. This is something even Princeton University has shown.
So at best "dimples" can be used for is a "bandaid" in limited areas that have very poor velocity profiles. But you would be better off filling those areas and eliminating the dead area in the first place. Which would increase port energy and make more power.
Hopefully that helps the confusion.
@@bainracing as I said they make a port act smaller depending on the size of the pock and how few are made. If it's done without crossing a threshold of material removed then yes increase in velocity /CFM. With enough craters relative to each other you're just increasing physical volume . Also in a turn you actually want to increase the apex to slow the air down to better navigate the turn (like a dog leg ) .. calling surface finish technique a "band aid" is confusing . It's a permanent change to the air flow dynamic of the head/intake . And yes micro dimple surface finish are superior as proven in wet flow tests. You're basically letting the burr dance on the surface rather than an 80 grit sand roll .. at least for intake bowls and tunnels. Absolutely help with atomization.. other things that can cause too large of droplets is too much swirl at higher lift value. Go ask David Vizard /Charles servedio about textures and go watch Eric weingartner put a partial dimpled LS head intake on the flow bench and pick up a few CFM . It works . It's like calling a crank scraper/windage a band aid lol . Backwards pistons etc.. what works works . Not saying that your physics are incorrect but as I said initially when you do a complete all over dimple you're actually just increasing volume. They work relative to the right dimensions
@DS-mo6md cheers for the reply mate.
Maybe you wrote it wrong mate. But you said "dimples" make it "larger" which they don't. They again as I explained "strink" the ports available volume. They don't "increase" it relative to a running engine of course. Statically yes. But engines run. So we need to look at the dynamic effects. That is key!
Same thing can be seen with corner radius. To small a radius will have more port volume, but act smaller when testing dynamically. As the shear stress on two converging walls is much greater. A simple velocity probe shows this.
And no it's not increasing cfm, even if the bench tells you it is. You need to remember a flow bench doesn't measure cfm. It measures pressure drop and only at one velocity point, or generally 28"and 300ish fps. Generally this is not even half peak velocity of a running engine.
This is why our record heads have actually lost flow "CFM" and not only run faster. But make more peak and average HP.
A flow bench lies! So don't confuse flow bench data with realistic real world results. Radius intake seats is another great example, increasing flow bench data. But go backwards in the real world.
Even dynos lie mate. Plenum volume is a great example of this. On the dyno you can add Plenum volume more and more and make more and more power on the dyno. Yet the car will run slower as you've dampened the secondary harmonics in the Plenum and the engine's ability to accelerate.
And many in the industry call it for what it is mate. Not only I, but Darren morgan calls dimple ports a "bandaid"? ..why? because in true cylinder head development fashion. if you have a dead area. Fix it properly, don't use a poorly thought out "bandaid" to try and fix a poor velocity gradient in that area.
And no nothing is permanent. When we were back to back testing dimples on circuit cars in the 90's we would just fill with filler and run again. Or like we do nowadays, we weld up and do a full remodel of the port.
And the air speed at the SSR is relative to the long side. That's the key. The speed differential is set by the long side as this is what controls the pressure front and how stable the short side is.
And no mirco-dimbles don't work and increase port drag. Again as I explained, the Ra is dependent on the air speed factor.
And yes I know Dave. But unfortunately most of what you read has been debunked in motorsport and is outdated.
A lot of what he refers to older engines like 23° SBC with very poor port designs where we have to "sacrifice" some port energy into a thicker boundary layer to compensate for a poor old design.
See this is where people get confused. We must understand the "whys" or what I call, the what,whys and how. The science at play. As the right Ra finish can't be a blanket set amount acoss all engine designs and many have very different velocity gradients and targets. It's why my calculators on my site have different air speed factors.
And yes I know Eric. But again. Flow bench isn't real world! And as I've told him. If you fill the areas behind the guide and fix the dead areas properly, you won't need dimples. And he knows this!
And that's exactly what we do and every top race head manufacturer is doing and I know as I've helped develop said heads.
And almost all of these heads are now on a fine CNC finish which creates fine radial lines with the least amount of drag coefficient. Which almost all the top race heads I see are finished this way.
Especially if you have a stable velocity gradient on a well designed port. Nath from Higgins, Brett from BME, Scott from CHI etc etc has some great examples of this and the surface tension has been Dialed in over many years of testing.
Remember what worked in 1970 on poor design heads. Won't always translate to model port design with higher velocity indexes and far more stable velocity gradients.
You need to understand what's actually at play here and why different finishes are needed and why.
So no, dimples don't work and it's why any serious head development guy will call them a bandaid.
Anyway, thx for the comments mate. I'll try to do more videos and break down the science for you to help you understand what's actually happening here. 👌
@bainracing
Thanks a lot for your very precise, in depth, explanations.
If I understand right, dimples suck energy from the velocity to build the boundary layer. At high velocities the boundary layer gets too thick and chokes the port size.
@bainracing
Three angle valves and seats for intakes?
Radius ok for exhaust?
Thoughts on a 60gr finish with a burr finish on the long side of the bowl ? Possibly even burr finish in vertical lines ? Would you also burr the valve guide ?
Definitely can help if you're having velocity problems in that area and if it's a wet port. Will help to keep fuel off. But it depends on the head shape and especially the short turn shape and local velocity
@bainracing
Could it be good to do a rough burr finish where you can see that the injector has sprayed the port clean?
I guess you could still choke the port that way at higher air speeds.
A golf ball soars through endless atmosphere, a cylinder head port is limited by length and cross sections.
That's it! But most importantly, dimples "increase" drag, but extend the separation point, and this reduces the negative pressure behind the ball. This is what allows them to fly greater distances than a smooth ball. 👌
It's common sense but common sense isn't very common. Thickening the boundary layer thins the flow path.
Bingo!!!👏👏👏
Aerodynamics and common sense don't really go together, that's why we rely on science. Relying on common sense kept us out of the air for decades, until people started applying science to the problems.
The dimples are not to optimize the flow, but rather to atomize the air-fuel mixture and improve burning. Don't try to measure the flow, you will obviously lose some, which can be corrected by increasing the diameter of the duct. Measure engine efficiency.
No, that's not how port science works at all.
The right targets on CSA and Velocity is what creates the shear stress for fuel atomisation. Dimples choke ports as our Ra is directly related to our boundary layer thickness. Hence why they don't work 👌
@@bainracing Well, in theory everything is beautiful. As long as there is no performance bench test (and I'm not saying measuring flow, but engine performance) the debate will always be inconclusive.
@@3ldraziel296 Mate we and most top shops have tested this to death.
There's a clear cost not only with our peak numbers at around 3-4% while showing a choke limit and rolling off. this is due to the boundary layer swell the dimples cause, and there's a clear lost in area under the curve. And lets face it, even the physics principles show its all wrong for internal pipe flow. So there's not only zero evidence this works by the very physics principles that dictate fluid dynamics. but real world testing showing its a not well thought out.
So to be honest mate, I'm confused by your argument. the best Ra finishes have been set in motorsport for near on 20 years. we know this. I've tested this to death. F1 has, NASCAR, Prostock superstock which we build our intake for other race shops. With our custom intake program we cover quite a few series of motorsport. but don't take my word for it. There's Chad Speier, Darin Morgan, Dave from head games. All guys I know, we all found the same thing over the years. And the go to finish for Intakes ports for the best drag coefficient and best 146 rule is between 60grit and cutter finish for all gasoline and Alky fuels.. More course than burr finish and we see choke.
And a Golf balls Ra is not percentage points bigger then a course buff finish, its folds greater! So this why dimples in ports choke. The whole principle of the golf ball finish is to create more surface drag, not only for more attachment time to reduce the negative pressure "behind" the ball, but the create lift and spin! So ALL this is creating more restriction throughout ant flow duct. the opposite to what we want, and why you can just make it "bigger" as you only narrow the winder even more.
@@3ldraziel296 Also mate maybe explain what you have been testing to find your results mate, as I would be interested what's led you to your conclusion. as I personally don't know anyone in the game that's made gains with this is ports. if you said piston tops or Plenun floors I would agree, but not in port.
But Pease share what you have found mate. I'd love to hear and discuss what you Have found and or why.
Thx for the comment.
As far as surface finish goes guys like Larry Meuax found power in very very rough burr finish like a decade ago. Chad Spier has popularized it.
And it makes sense watching Kaase's video where he puts his finger and a glove in the port on the dyno to observe pressure waves. Plenum and runner are clear and you see the massive amounts of fuel puddling.
Is it a crutch? Yes probably? Does it look pretty - no? But it's shown to make power.
Darin Morgan doesn't seem to like golf ball finish but sounds like he's in favor of the very rough burr finish (think the cutter is bent, chipped teeth, held a certain way to create the finish not just normal carbide).
And I understand more turbulence in the boundary layer in theory shrinks the port... but if you have rich and lean cycles because fuel falls out of suspension...
Also it's (surface finish) pretty small in % terms of power. Definitely not as important as size and shape.
So crutch, surely. But it has worked on efficient applications not just a 23° with compromises.
Yeah, I know the boys well and have chatted with Darin a bit. And Joh has helped me a few times in the past. Especially when testing in APSA.
Yes, Darin doesn't like the golf ball pattern and physic, along with the data, which makes it pretty clear why it's not an optimal surface finish.
The increase in port surface drag coefficient is an obvious one. That and the direct link between surface Ra/boundary thickness and velocity. This is an important reason why the velocity gradient and port shape will indicate what surface Ra is optimal.
This is why fewer direct shots need more Ra, more energy in the boundary layer to compensate for the axial force placed on the boundary layer created by the port shape.
And this is why most guys like Larry and Chad found burrs to be optimal on a lot of the older stuff like 23 degrees, with poor line of sight. That's because the boundary conditions are directly related to port shape.
There's also the argument that their air speeds and targets are built around their burr finish. As if we look at current prostock and even F1, their CSA and velocity and Ra finishes are very different.
They are much finer in their surface finish and, in turn, less energy lost on the boundary layer. Generally, the worst the port shape is. The more boundary action a port will need to compensate for the poor port design.
So what works in a 23 degree, that needs alot of boundary energy doesn't seem as good in some of the 13, 12 and 11 degree stuff we are involved with and definitely doesn't work in twin cams engines that we have a hell of a lot of testing in and we see this with the some of the record Honda stuff as well coming out of UAE and the US.
Even some of the work and testing coming out of Princeton University showing the most efficient boundary conditions are in the range of 100Ra
It's a very interesting topic, and I try not to fall into these hard and fast rules that burr is best. Or 60grit is best, as without a deep analysis of what's actually happening and why. It's really more a guess than good science.
But I'll finish with one of darins quotes. "Dimple port is a bandaid for a bad port."
@@bainracing probably a good rule to be curious vs simplistic rules. Good feedback.
Interesting thought on the maths & CSA. You think it may be in effect shrinking the port and they may've been better off with a smaller port?
Do you know of anyone who's tested it on a 11 or 9° modern port? Agree a lot of this is seen in the 23° stuff. Thought Larry did it in a more modern port (for ~ 2010-12) but I may be misremembering.
Is is something that you've tried (modern valve angles)?
I always understood that the point of roughening up the port walls and the bowl was to prevent fuel puddling, and lean mixture for high rpm motors while at low rpm, and a little more than a decade ago the reason for dimples on golf balls became mainstream and hotrodders wanted to know if such a modification would help. I never heard that it was a method for increasing air flow.
Yeah, sadly, it actually hinders air flow as the balls ability to fly the future comes down to the reduction in the wake "behind" the ball. Hence, why dimples cost power 👌
@@bainracing you know, I have doubted that the size and depth of the dimples are way out of proportion with the sort of air velocity in an engines intake port anyway, I think it would be more beneficial to use a fine knurling tool after porting, just enough to prevent condensation on the sides of the bowl.
@@werewally3156 Yeah! What you're describing is actually what's left with a porting burr naturally when done right.
And when done right it leaves a more course finish than say 60grit, like a very fine dimpling. It does tend to lend itself to old port shapes, that really didn't have a good velocity profile.
See what we need to remember is, our boundary layer thickness is directly related to not only air speed, but the Ra of the
surface. the Ra is the average distance between the high and low point.
So as you can imagine, the golf ball boundary layer thickness will be huge due to the very course Ra. And this is why when we add the golf ball texture to a port, we lose HP and make torque, Proving we are not only seeing a boundary layer swell, but a higher velocity factor sooner, hence the choke we see from a dimple port.
The Ra is simply too course for the velocity factors needed in an ICE engine.
Also this is and area that has been tested to death by not only people like myself and many others in the racing industry. But by universities like Cambridge. and optimal port finish is in-between a buff finish and 60 grit.
The basic rule being, the better the shot and the more stable the velocity gradient. the less boundary energy we need to sacrifice. in short. modern port, 60grit. Old port burr finish.
The other problem we haven't covered is that, the more energy we direct into the boundary layer, the more we increase the ports drag coefficient. So as the boundary layer increase, port energy decreases.
Hopefully that helps mate
Yeah because we all know puddles tend to happen on very smooth surfaces not in groves or lower spots…😂
Rough spots are like radiators to hold, heat, and re-atomize the fuel that hits them.
Yeaaaas. Thank you 🙏 it's never made any sense to me.
Yep! It's not a well thought out idea at all 🤣👌
from what ive read its helps atomize the A/F into the combustion chamber. ive recently done dimpling to my intake ports on the top/ roof section and back section leaving the floor polished and exhaust ports high polished. im no expert not do i claim to be. just messing around in the workshop. a friend also told me about guys dimpling the top of their pistons . come across this at all?
Yes, dimple on the piston works well. As the dimple "increases" boundary layer thickness and creates more drag. So, on a piston top, that's what we want. But for the same reason it works on a piston top, it's the same reasons why Dimple Port hinders the port.
First as we explain, it creates thicker boundary layers on the piston. But thickening in the port "reduces" CSA. So this will limit the mass potential of the head.
For the second reason its not optimal in ports, is the dimples, increase in the drag coefficient. Meaning it tries to slow the air moving acoss the dimples.
As remember, the more energy we put into the boundary layer, the more it is removed from the port.
Even if it helped atomize the fuel, that's something you can improve without sacrificing your flow.
@@DrewLSsix 👏👏
The dimpling is for mixture preparation, you’re only going to see gains on a port injection engine. The gains are the engines ability to make more power from a leaner mixture which in turn means better fuel efficiency, less on board fuel weight and less pit stops.
No, that's not true at all, mate. Air speed controls fuel shear at the right velocity is key. and dimples only choke an optimised port. It's why none of the top heads use them.
You need to understand what's happening in the boundary condition. And why dimples only swell the boundary layer while increasing the ports drag coefficient. Too things that kill HP.
The more energy we put into the boundary layer, the less HP we make. Again, this has been tested to death, and it's why, from pro stock to supersprint, no one is silly enough to fall for this snake oil.
Dimples only help reduce the negative pressure from "behind" the ball. By thickening the boundary layer and creating more drag which mores the attachment point further around and hence reduces the area of the negative pressure pulling baxk on the ball. That's what allows them to fly further.
Thx for the comment 👍
@bainracing
When he is talking about only efficiency, and not at all about power, could it be true that a very rough wall could help a wet wall to put the fuel back into the airstream in an atomized form, and improve efficiency?
@@bobirving6052 Yes, that is my line of thought. My main point is everyone rights off the dimpling because it doesn’t suit their application. For N/A application the CFM loss associated with dimpling the intake may have a negative effect as the port energy is critical. In forced induction applications the CFM loss is of lesser concern and is outweighed by superior mixture preparation. That said there is also no need to dimple the bowl area or turns, keep it to the straight sections of the runners and port entry and it will have minimal effect on cfm. I should also note and as you mention that finishing with an 80 grit cartridge roll can have the same effect for much less effort.
What about just dumpling the valve guide or injector bunghole
It's definitely an option if it's a dead area and you want to "thicken" the boundary area up it that localised area.
Behind the guide is a common place people use it. It will work if it's flat and not shaped well.
But I prefer to fill or weld up and optimise velocity in that area. So yes, it can be used in poorly developed areas. But you're almost always better off fixing dead areas properly by eliminating volume that works against to port.
Curious, do you have any championship holding engines or record setting engines currently using your product ?
Yeah, quite a few. Australia's fastest Holden door car. Fastest 1uz, twin turbo, highest NA record, fastest Holden in blown class, NA, records in early head, VN head, 85 and and some in pump fuel the lists go on, then there's all the ones we done over the last 20 years.
But records mean nothing if you can't get the physics right first 👌
Flow bench doesnt agree. A correct partial dimple port showed more cfm
Yeah, unfortunately, in the racing world, you work out real quickly. A flow bench not only doesn't measure CFM, but in many cases, it doesn't carry over the real world flow in a dynamic variable velocity environment that ICE engines are. It's why all our race heads have lost cfm on the bench yet make more EVERYWHERE!
But even if we ignore all that, basic physics shows we are creating more drag!
Understand the mechanisms at play, and it will help you see the BS 😉👌
it only work at very high speed, even a golf ball don't fly at high speed long enough to be really effective.
It doesn't work at all. As it "chokes" a port. The more energy we add to a boundary layer. The less the port has.
But dimple ports must at least be worth 100 placebo credibility points yeah.
Definitely! 🤣🤣👌
Ada hal yang tidak fair dalam ulasan anda :)
Membandingkan permukaan bagian dalam port dengan bola yang sedang terbang bebas di udara dan udara bebas tidak lebih basah dari port kecuali hujan :v.
Memiliki blower fan atau vaccum cleaner, karbu, manifold bahkan lebih adil dan cepat untuk mendapatkan jawaban.
Jika ide sederhana saya terdengar konyol dan ya setidaknya melangkah satu langkah.
Thx for the comment, mate. But you're not understanding the fluiddynamics of a port properly or a golf ball.
We aren't comparing the two. We are explaining why dimples on a ball and in a port create "MORE" restriction more "drag" and more boundary interaction means more energy loss, which means less HP. This is why dimples dont work in ports.
The wet flow means very little as if we understand the basics of turbulent shearing and the fact we have an "active boundary" condition, which is controlled by velocity. So, size to port right for the RPM, and your target Ra I very clear.
Understand the basics. That way, you won't be confused 👌
What da... hey u guy... can't u all get it.. dimple ports only work on da exaust port... because carbon will fill in the dimple hole so... think of your self.. the benefit of it..
😂😂😂 I wouldn't even be doing on the exhaust. Unfortunately people don't understand the physics or thermal dynamics principles. The trick with all exhaust ports in the "reduce" surface area. Not increase it. This is why mirror finishes work brilliantly
well if you must.. here is an challange. don't dimple the whole thing. then you can see improvement.
Yeah, exactly! . Here's a better idea. People should learn even the very basics of physics and fluid dynamics principles. Would save them a hell of a lot of time! 😂😂👌
@@bainracingindeed. These ports fundamentaly ain't too different from the ports of speakers.
Very simular observations had been made whit those too.
Allso seen a nother video where a guy dimpled a port in sections and measured the flow at different valve lifts.
Dimpling the whole thing made it worse. As expected.
Try to dimple the middle part only vs no dimpling. No more Than 1/5 of total length.
An improvment you will find at about half the valve lift vs smooth surface flow figures.
Very simular to what hifi stuff has. The same principles apply in Both. Not Just whit ports , but whit exhaust systems , intakes , basicly anything that deals whit pressure waves and gasses.
@@nagyandras8857If only the flow bench was real world mate. But again, a basic understanding of boundary layer thickness and its relationship to surface Ra goes a long way! 😉
Again, the key here is to understand what the bench is telling you and why you got the results. Just because you make more "CFM" doesn't not mean it will translate into more HP and torque. Especially when using a bandaid like dimples. Especially when we know "dimples" increase surface drag. Meaning you're robbing the port of energy.
If CFM increases from dimples in a certain area. That means that area is too large and has low velocity. The "increased" drag, thickened the boundary layer, which than increased velocity. Again showing a dead area.
Again this is why for 20 years we have ignored cfm and focused on what actually makes power and that's the velocity gradient of the port. The key to making power is energy conservation.
You could have just probed that area and seen it was low and filled it, this would "reduce" CSA and feed into both mechanisms that lead to a successful build. And a more balanced velocity gradient means you win in both torque and HP.
Unfortunately Again this shows that people don't understand their tools, or the physics at play, and furthermore why they are seeing the results they did.
The other huge problem with flow benches is its at 1 pressure differential, usually 28" which isn't even half of the pressure drop and engine creates. And we know boundary conditions are dependent of pressure drop.
Also the port and whole primary induction length is bidirectional and goes from zero to 690fps ans back to zero each valve event.
And we know that accelerating velocity and greater pressure differential changes the very boundary conditions we are trying to measure on a stationary bench.
As ive said for 20 plus years in motorsport, if you're using a flow bench to validate real world hp and torque, you're either new to racing, or don't understand the complexity of what's actually happening or what you're testing.
There's a reason our record heads have lost CFM over the decades and continue to make more power everywhere.
@bainracing certainly, specialy the flow test is just part of the tale. Btw, thank you for getting back and providing your input, in legth. thats a very respectible thing.
the thing is, i surely never got any cfm values, as i em not an engine builder, or head porter. i design loudspeakers.
the thing that is , or should be , quite obvious when it comes to a flow bench is, that engines in real life don't have a constant flow. they take "lumps" of air at the intake stroke. at least pistons engines that is. air is quite springy, changes many of its properities whit pressure and temperature and humidity , and elevation or effective gravity etc.. so not quite a constant material to work whit.
You would be surprised how simular is the case when it comes to a ported speaker box. but we don't have the luxury of many horses worth of power moving air.. and in some cases we intentionaly avoid the need of more than a few watts , to pump respectible amount of air, at quite a broad range of freqvencies.
port velocity is a thing in both worlds, even if for different reasons, both aim to ensure that the air can move in that port whit the least loss of energy. in our case if air in the port looses energy.. we will loose sound pressure. and that loss will translate into noise we don't want. no mather how big of a speaker we talk about, at the freqvency where the port+box is tuned at, actualy the driver is near stationary and the only source of sound is from the port.
engines are different as the primary goal would be to only let air go in, and the preference would be to not let it flow backwards. everytime. whit speaker ports we are selective in freqvency, we out of necessity do choose to restrict flow sometimes in a range of freqvency.
now supposedly you got air rushing in like crazy to equalise pressure , that be the intake cycle. but then the valve closes. the air pressure wave hits the closed port and pressure builds up, so the air now wishes to go backwards as pressure is less in that direction. this is where a selectively restrictive port can play a role. just filling in the port where it just has too much cross section area would allow the air to go back just as easy as it got to the valve.
to be more precise i owuld need a truckload of data, for a non-direct injection engine even the air fuel ratio would need to be known, to calculate the charge air density, and would need to test the compliance of the mix etc...etc... just to treat everything whit the same precision as a speaker port. however, if you take a .. say, just a random number, 100mm long port, measure both on flow bench and dyno it on an actual engine, than take that head, measure 40mm in, and dimple till 60mm, re-measre it both on the flow bench and on an actual engine, it will show a slight but consistent improvment. that is, unless there is a terrible bottleneck somewhere else.
Anyways, thank you for the chat, very refreshing to see that content creators do actually read the comments. and whom may know, you may even give it a go if you got the free time to experiment. makes for an acceptible video material on the subject.
@nagyandras8857 This is exactly what we do for racers all over the world. We run extensive analysis of the primary induction length and analyse the frequency to tune the 3rd harmonic. And everything is calculated from density, temperature, peak velocity, average etc.
All top race engines target the 3rd harmonic.
And yes the valve closing is what creates the shock wave. Tho if your inertia supercharged mechanisms in dialed in properly, the air has slowed to a stall, this is when we close the valve.
So because of this mechanism, we don't want to create any more drag either way.
Also you need to understand the relationship between the surface Ra and boundary layer height. This is another reason why dimples cost power and "narrow" the power range.
That's because at low velocity, the CSA is too big, but as the velocity accelerates, it "swells" the boundary conditions and now "chokes" the engine.
But we and many others have tested this to death. It doesn't work in the real world, nor do the principles of fluid dynamics support this in our primary induction length. Especially at the air speed targets needed for optimum performance 👌
The key here is what the dimples do to the boundary conditions. The more interaction the air has in both directions with the dimples. The more drag we create. So the more power we lose.
Hopefully that helps you understand why no one in the race seen runs this snake oil. 😉.
its to "mix" fuel not to get more in 😂
Boundary layers don't "mix" fuel 😉
@@bainracing nope the carburetor does, thats why people be talking absolute 💩about a wet and dry intake
@@invent-cf1yo Maybe learn even the basics of boundary layer conditions, fuel shear lengths and and the mechanisms that control fuel atomisation before commenting in the future. But you're clearly an expert. best of luck👍
@bainracing
I’m pretty sure invent-cf1yo was just being sarcastic at other bad ideas but not insulting your information.
@@bobirving6052Ah! 🤣🤣👌
Dimples work, they give you an effectively smaller port, which increases flow velocity.
No, they don't work. If they give you a "smaller" port. Then you never sized if right in the first place.
Also, we know the boundary layer thickness is directly related to the air speed.
This means dimples will make the port too big at first, and as velocity increases, the port will "shrink" that's the opposite of what we need.
Then there's the drag coefficient factor. Any basic understanding of fluid dynamics we tell you that the more energy we put into the boundary layer, the more energy we put into the boundary layer. The less energy the port has.
So no, if you understand the mechanisms at play. You will understand why they are detrimental to any well designed port.
@@bainracing Air has less resistance than metal. You don't really know too much but like to argue like you do. How well is a cast iron or cast aluminum port tuned to the razors edge to begin with? It's not, most of the crap most people deal with isn't pro-stock level. Just because dimples don't work universally doesn't mean they don't work in any application. That's reductionist logic and stupid.
@@bainracing If the dimples cause the port to neck down, guess what, that increases velocity, we are dealing with subsonic flow in the port.
@rolandotillit2867
I noticed, after a video or two, that bainracing is an absolute top of the line company. I also only work on mass produced “junk” but I still very much appreciate what bainracing is sharing here! Much of this information still applies, and maybe someday I will work on something awesome!
@rolandotillit2867
You have to understand the “dynamic” environment. The airspeed must go from 0 - 600 - 0 mph. The thicker boundary layer may fix a bad port design at 200mph but totally choke the port at 600 mph. Now you have lost your inertial charge and your higher rpms.
I think Darin Morgan calls it High Speed buffeting, or something. Power Plateau.
So its 100% increase Hp?like 300% 😉
Like. No HP! Gone backwards. But it likes cool! 🤣🤣👌