Nice demo Eric! I've always thought that once the choke point was reached, the air became unstable within the port, SLIGHTLY reducing the flow. Your test demonstrated that that's not the case, the flow actually drops off DRAMATICALLY! Interesting video subject well outside the more common knowledge, well known stuff!
Seems like the bottom line is application. If you need a torque curve from 2500 on, you want different head characteristics than if you’re drag racing with a 5000 or 6000 stall converter. Great video, keep ‘‘em coming!
One of your best videos. Hopefully a bunch of the guys who are always touting CFM and cc's will watch it. Good demonstration of choke. Looked like some serious turbulence
I had this first hand... I willingly put a stock crossfire injection intake on top of a typical 350 short block... roller cam, profiler 195s etc. It made excellent power from about idle to 4000rpms and then made absolutely no more power or torque to about 6000. Felt great until 4k and then it was just like running it for the sake of running it. Swapped on a renegade intake which has a roughly 1204 port size... it matched power from 1500 up and just freight trained beyond 4k. It made almost 80 more horsepower at the peak at the tires than the stock intake on a day with a 3000' DA vs a negative 200' when the stock was tested. I do feel there is something to optimizing the port for its given size... but physics is physics. You can polish a straw and have it be the smoothest best flowing straw there is... are you still going to breathe through it when you run a marathon? That's what I think when I see people talk about small high flow ports...
😂😂 your set up kinda reminds me of the 79 El camino I had in school. It had a 350 with a comp 280h and stock 882 smogger heads when I bought it. It would leave two 40ft black marks at 45mph when you kicked the 4 barrel (about 2500rpm in 2nd gear) and was completely done by 4,200rpm. Was a turtle race to 5,500😂😂 it was so painful I usually shifted at 5000.
Very informative video. Basically we need to develop the head to suit the intended purpose. Thanks for showing the choke, that couple of minutes was worth more than reading 10k words.
Hey Eric, Tim here......one of the BEST vids of tech stuff, busting myths, so younger folk can begin to understand our beloved ICE!!.....I got Kauffman heads on my 462 Poncho.....(d-ports), yes they make good power (flow 310)......but i wanted a flow sheet when i bought them........wish they wudda done so, cuz where is that 310 at?? .800 lift??....i'm at around .575 or so (flat tappet).....i wanted the flow sheet, so i cud see where i mite spec my cam a bit difrent.....also, is it flowin enuf to feed it, as i cant turn it past 6300 or so.......(dont wanna see internal parts) haha.....my point......YOU including a flow sheet wud be a GREAT idea, so one cud see whats goin on.......i've wondered for a while now, if i send 'em back to KRE to open them up to their 340cfm program, if it wud do better, as i dont know WHERE the max flow is, or if i wudnt have (bigger port) enuf velocity, and the motor will choke......GIMME A FLOW SHEET!!!.....great idea sir!!....PEACE to you!!.....(I'm gonna have to re-fresh my Weingartner Racing t-shirt soon, as i've wore mine almost out).....will get one soon!!!....TY SIR!!
Thanks for the great video.hunderds of people need to watch this. Not kidding. I always wondered why GM put such big ports and intake valves in a LS engine. They usually go the opposite.
Straight talk Eric. I can't tell you how many times I've had to try to explain to people wanting to build a motor by installing a huge cam and a set of old double humps with 2.02 and 1.60 valves. That's just a noisy slug. It takes critical thinking, planning, and as much data as possible to build an engine that is optimized. That's why many professional race engine builders get PAID for their engines, it isn't just the hardware, it's the software between the engine builder's ears that makes the difference.
Rad video interesting demonstration. Man my machinist had a hard time talking me out of my afr rac cnc port 195. Motor was 427 sbc and he was telling me I needed to replace afr with brodix dragonslayer 225. Motor does like larger head in all honesty at 440c.i. now and I prolly need bigger but these will do.
Good stuff. Depression is also quite different bench vs engine at rpm. Would be interesting to see what you could learn from a bench that could do a better job representing an engine. Guess CFD would be nice for this kind of thing if you had a good setup and knew what you're doing. Never had that luxury though.
Sometimes the education we receive from these efforts is priceless. I hope to one day be able to articulate these circumstances in a more simplified fashion that works and doesn’t step on too many toes. The fact remains that when you’re conducting business with anyone you’re agreeing to play by their rules. Which are often dictated by extraneous circumstances.
Thanks for this explanation! A friend and I have had many conversations over about 25 years to which is the right head for an engine. We both have 400 cid but he's using afr 195's and I'm using 210's. Makes me think that both of us need bigger heads. Both engines are also procharged and vastly different cams and compression.
John Kaase talked about filling ports in a bbf head and saw an increase in cfm on the bench. But the same head compared to unfilled made less horsepower on the dyno.
What is the range of max velocity before airflow falls off? Isn’t it a certain percentage of the speed of sound? I’m sure it varies some depending of other factors/properties....
Eric , great video . I was wondering if you would do a video on port size , cross section and running airspeed . Port volume and cross section and cubic inch , rpm to get a speed that’s 550 ft per second to say 600 ft per second So on a drag application that’s 6000 to 7500 550 fps at 6000 and 600 fps at 7500 . Combination specific
So this is why my old corvette L98 113 heads 165cc just died at 5500 rpm? Still saving them for a budget truck motor tho. The Afr 195 cnc ported really woke up my gm original zzz motor even with giving up .5 compression. Thanks for all the info Eric!
Great video. Maybe i missed it but do you have a formula to figure out a optimum head size for a given application? I have head a podcast that Darrin Morgan mentioned one butci do not remember what it was.
Frankly, the second the intake manifold is installed, the total runner length changes also. I find this similar to picking a turbocharger, a smaller, but more restrictive turbo comes up on boost quicker, lower in the rpm range, and will feel more responsive, but loses efficiency on the top end, where a larger turbo will ne less responsive, and spool later, but pull hard through the middle, and make more power on top, but gives it away on the bottom.
I had Tony Mamo work up some heads for a 408 LS that’s in my single cab Silverado. It’s my daily driver so it lives on the street. I was shocked when he said we were using 205 cc heads. Now they flow 300 plus cfm. This engine is wild on the street but I’ve wondered what the downside is of such a small head. It will be interesting to get on a dyno and see where they choke out. It seems strong all the way up to 6k though. Good info here.
Geeezzz this is why i love bracket racing are my heads right wrong flowing or not?? I run old steel merlins on methanol .do they flow like afr or brodix?probly not .goes down the track doesnt break much never had heads flowed or engine dynoed dont know the hp just know its consistant 560s at 120.. i still like watching tech stuff even if i never will worry bout how im flowing or how much power im making ..just kerp building biger engines goin fasyer every time but care less about any number but the dial in !!
Great video Eric! Yes multiple items contribute to engine performance. I use CC like I use duration @.050" to get in the general area for the cubic inch & desired RPM range. I always say; "out of two identical heads that flow the same, the smaller port will generally make more power & be most responsive." There is nothing you can say always works or always does this or that as there are too many variables. Speaking about one size & brand engine for one specific purpose & RPM helps narrow the conversation.
. . To include and agree with Eric's explanation. The thing with cylinder heads is what you got you want to make efficient at every point. The port should have a target of 300 fps at peak lift of the cam you are going to use.
Has anybody run intake port flows in a CFD program with the intake valve opening and closing. Looking at the ram air in the intake port build up in the bowl and stall at the back of the closed valve. Verses a significantly reduced bowl area to create a tapered area so the ram air is focused into a smaller area by the closed valve. My thinking is how much air volume is stalled and needs to be restarted as the valve opens. What. The intake valve is only open during the intake stroke. The other 3 strokes the intake valve is closed.
Seems to me the smaller head moving more cfm will require more velocity which will be harder to control around short turn and cause turbulence and fuel separation
I purposely chose a very small port for thr sbc in my old pickup. Port velocity is fantastic. 245cfm@175cc. Trick flow super 23 175cc heads. What velocity does the airspeed need to actually reach before choking? I was under the impression that the heads flow enough to support 490hp. How quickly does power drop off after the port chokes? The demonstration made it look immediate. I ask this because I also have a centrifugal supercharger further increasing port velocity in the upper rpm range. I have not noticed any strange issues like boost pressure spiking at a certain point.. such as that critical port speed that causes a choked intake port. Another note: the exhaust ports are considerably smaller than intakes. Do they choke as well? Do heat and air density affect the choke point? I'm genuinely curious about this as I've never heard it before. I thought higher flow numbers were better when selecting a head, regardless of port size.
@@WeingartnerRacing I'm interested whenever you've got time. No rush. I've been a subscriber for years and don't plan to go anywhere. Lol. Thanks for all of the knowledge.
@@WeingartnerRacing I think it's a great idea for another video. I'm assuming you have enough experience to estimate what size pushrod pinch size is needed for the cubic inch/ RPM that is application specific, but is there a formula that can estimate it?
I always go with a bigger head than the math says to use because the loss of torque at lower rpms is less noticeable than losing the higher rpms, end of the track unless it's a truck for towing applications. Even streetrodders agree with me after feeling the difference. No one likes coming out of the hole fast just to get passed just before the finish line.
I think this highlights that the flow bench is showing a dynamic event “statically”. It does not take into account many other variables. If it was that easy you wouldn’t have all these port variations from various manufacturers and porters.
Great video, I'm just wondering if there's a formula to tell you how much cross-sectional area you need for your power goals or maybe a ratio for area to CFM? It doesn't have to be perfect or official, even just a rough estimate that you would use to know where that choke point will be.
so when comparing Edelbrock Performer RPM 290cc bbc heads with 110cc chambers vs 100cc chambers (that flow a little less), which would be better for power?
Combustion chambers are different than intake ports.. that being said, everything else being equal, the smaller chambers would increase compression and provide more power. That is assuming that the valves aren't shrouded by the smaller chamber. As long as the airflow and port size is equal and there is no detonation, higher compression will make more power.
I would love the forced induction perspective to this. That 400 with the TorqStorm for example. How does all this (like the choke point) get affected by forced air.
Because the boost increases the pressure drop across the valve the airspeed goes up this causes the rpm that peak power occurs at to drop but you are also increasing the density of the air and so it's mass and this helps carry the power past peak better so what you see on a Dyno is a little lower rpm for peak but a flatter curve that goes past peak better
@@scotthatch4548 centrifugal superchargers have a rising boost curve. More boost as you rev them higher. This will effectively push peak hp rpm higher in the rev range.
@@EricErnst correct which also changes the pressure drop across the valve .... I was commenting on the effect of a steady boost on the cylinder head flow .... With something like a turbo where you can control the boost you can move the power around by changing the boost but that is not really the discussion in this video
@@WeingartnerRacing Okay, that makes sense, but on velocity, does a bigger port allow an increase in the maximum useful velocity compared to smaller ports, or does it just achieve more flow at a similar velocity due to its area?
@@brianbrigg57 if you look at average velocity, if a small port flows the same cfm as a larger port, the average velocity will always be higher on the smaller port. Sure, there will be particular areas of the ports that have low velocity, and others with higher velocity. But if a predetermined amount of air flows through 2 ports, the smaller will always have more velocity.
Ok .... But that's looking at the port as just itself ... Larger cross section so lower airspeed at the major turn (short side) can help the air make the turn and get around the valve at the peak rpm this is only detrimental if the intake manifold airspeed is to low a balanced induction is key to making work
You do have to slow air down as it goes over the shortside. However you can have a scenario where you slowed it down and it looks good on the bench but on the dyno it is a turd because you slowed it down too much.
I’ve heard if an engine has heads and an intake manifold that is capable of flowing more air than the engine needs, the fuel will drop out and it won’t run well. Is that correct?
Flow demand is CID x RPM.. big head on little engine is just an engine tuned to a very high rpm and yes at low rpm it will have trouble but at it's tuned rpm it will work fine ... Because of rpm all engines are basically variable displacement so you choose a head based on the cid and rpm you are planning on running at like he said in the video
I dont think the smallest head that flows the most air will make the most power but it will probably make the most torque. A bigger minimum csa will probably make more torque after peak with the trade off being less torque before peak. This is only within reason. You end up with sonic choke coming into play with the smaller port sooner and once that happens it doesnt matter what you do, nothing will get more air through the minimum csa.
Pressure differential created by the piston moving down the bore v what the port can flow determines the airspeed within the port (average airspeeds) The peak piston speed at around 73 degrees creates the highest pressure differential so you have to have a port that is sized correctly to avoid the average airspeed going above 0.6mach This is the science of engines and a hell of a lot more complex than most realise.
It is all about the operating rev range and engine size, as you said. Tighter CSA flattens out the torque curve, and larger gives more peak torque. But, there's another number that stirrs the pot even further; runner length. To make the most out of your engine, you need to have your runner length to match your CSA and your cylinder volume. Usually the runners are way too short and this kills low end torque too.
And to add on top of that, camshaft valve overlap (both duration and lift) will change the amount of draw on the intake port of the head at specific RPMs. It's amazing many little factors play into how an engine performs over the RPM range, and how they compound on each other.
@@wyattwunderlin4445 Indeed. Valve overlap especially needs to be tuned with both runners, in and exhaust, in mind. To make the camshaft work there has to be incoming charge @ intake and draft @ the header. And then there's valve profile to tune the valve pulse which also is partially created by lobe profile and these all change if the fuel itself is changed to bring us to spark energy, not yet timing, but the amount of joules in each spark.. Tricky business.
8:58 the second head will make more power BUT that wasn’t your target of 6000rpm then was it? All you have done is move the window further up the rpm range with area. If the first head had the same area but maintained it’s better efficiency then it would make even more power than the second head at the higher rpm points. The better the efficiency of the head which is the flow number v min cross sectional area the wider the window will be. So the statement should be, the higher the flow number from the correct min cross area that suits the cubes and rpm target, the better the head is.
I have heard Warren Johnson say that very same thing....."the smallest port that flows the most air will make the most power". Of course that's just a generalization, and thanks to Eric for explaining in further detail why it's both true AND false at the same time. And even at that, it's not that it's really a case of true/false -- good/bad -- right/wrong. It's just the facts of the dynamics of airflow through a passage, and the effects that it shows when it speeds up and slows down.
Given ports that are equal in flow at a given pressure, the port with the highest velocity (within logical reason) will generate the fastest acceleration. Of course, everything else must be correct.
Isn't it the "intake port volume" not the "intake port area"? Your explanation at the front made it sound like the given number (270cc vs 230cc) was only for the frontal 2d area of the port and did not take length into account...but volume has to take length into account or it wouldn't be volume.
I mentioned length. That’s why volume is almost useless as it can’t be used to compare heads that have different lengths. Also it doesn’t tell you where in the port you are big or small.
@@WeingartnerRacing but bigger volume is still bigger and smaller is still smaller? That doesn't make sense unless the area is more important than the volume
The air fills a total volume each type the valve is open right? What about this...mock up and LS3 with ITBs. Run it on the dyno. Add a 1" spacer to each port to lengthen it, but fill the floor to make the overall volume the same. Say 270cc in both examples. Run it again. Would there actually be a difference?
@@chipcurrey653 Area is more important than volume. You can have a port go big to really small or a port that is really small that goes to really big. They can have the same volume and make very different amounts of power.
Just watch top 1000cc motorcycles heads They have gone bigger and bigger and straighter for every generation. For learning head watch motorcycle 1000cc
Nice demo Eric!
I've always thought that once the choke point was reached, the air became unstable within the port, SLIGHTLY reducing the flow. Your test demonstrated that that's not the case, the flow actually drops off DRAMATICALLY!
Interesting video subject well outside the more common knowledge, well known stuff!
Seems like the bottom line is application. If you need a torque curve from 2500 on, you want different head characteristics than if you’re drag racing with a 5000 or 6000 stall converter. Great video, keep ‘‘em coming!
Thanks
Explained pretty well. Didn’t really think about choke but it makes sense. Enjoy the videos, especially this one, thanks.
One of your best videos. Hopefully a bunch of the guys who are always touting CFM and cc's will watch it. Good demonstration of choke. Looked like some serious turbulence
Great demonstration of the intake port Mach index!
Thank you!! You just answered a lot of questions.
Eric I watched it all. Good explanation. And good test demonstration.
Thanks for sharing again, all the best to you and your loved ones
Makes perfect sense, never thought about it that way before!
I had this first hand... I willingly put a stock crossfire injection intake on top of a typical 350 short block... roller cam, profiler 195s etc. It made excellent power from about idle to 4000rpms and then made absolutely no more power or torque to about 6000. Felt great until 4k and then it was just like running it for the sake of running it. Swapped on a renegade intake which has a roughly 1204 port size... it matched power from 1500 up and just freight trained beyond 4k. It made almost 80 more horsepower at the peak at the tires than the stock intake on a day with a 3000' DA vs a negative 200' when the stock was tested. I do feel there is something to optimizing the port for its given size... but physics is physics.
You can polish a straw and have it be the smoothest best flowing straw there is... are you still going to breathe through it when you run a marathon? That's what I think when I see people talk about small high flow ports...
😂😂 your set up kinda reminds me of the 79 El camino I had in school. It had a 350 with a comp 280h and stock 882 smogger heads when I bought it. It would leave two 40ft black marks at 45mph when you kicked the 4 barrel (about 2500rpm in 2nd gear) and was completely done by 4,200rpm. Was a turtle race to 5,500😂😂 it was so painful I usually shifted at 5000.
Really good demonstration. When the flow hit the wall it fell off dramatically. The 2inch restriction high lighted the effect, very nice
Very informative video. Basically we need to develop the head to suit the intended purpose. Thanks for showing the choke, that couple of minutes was worth more than reading 10k words.
Hey Eric,
Tim here......one of the BEST vids of tech stuff, busting myths, so younger folk can begin to understand our beloved ICE!!.....I got Kauffman heads on my 462 Poncho.....(d-ports), yes they make good power (flow 310)......but i wanted a flow sheet when i bought them........wish they wudda done so, cuz where is that 310 at?? .800 lift??....i'm at around .575 or so (flat tappet).....i wanted the flow sheet, so i cud see where i mite spec my cam a bit difrent.....also, is it flowin enuf to feed it, as i cant turn it past 6300 or so.......(dont wanna see internal parts) haha.....my point......YOU including a flow sheet wud be a GREAT idea, so one cud see whats goin on.......i've wondered for a while now, if i send 'em back to KRE to open them up to their 340cfm program, if it wud do better, as i dont know WHERE the max flow is, or if i wudnt have (bigger port) enuf velocity, and the motor will choke......GIMME A FLOW SHEET!!!.....great idea sir!!....PEACE to you!!.....(I'm gonna have to re-fresh my Weingartner Racing t-shirt soon, as i've wore mine almost out).....will get one soon!!!....TY SIR!!
Thanks for the great video.hunderds of people need to watch this. Not kidding. I always wondered why GM put such big ports and intake valves in a LS engine. They usually go the opposite.
Straight talk Eric. I can't tell you how many times I've had to try to explain to people wanting to build a motor by installing a huge cam and a set of old double humps with 2.02 and 1.60 valves. That's just a noisy slug. It takes critical thinking, planning, and as much data as possible to build an engine that is optimized. That's why many professional race engine builders get PAID for their engines, it isn't just the hardware, it's the software between the engine builder's ears that makes the difference.
Rad video interesting demonstration. Man my machinist had a hard time talking me out of my afr rac cnc port 195. Motor was 427 sbc and he was telling me I needed to replace afr with brodix dragonslayer 225. Motor does like larger head in all honesty at 440c.i. now and I prolly need bigger but these will do.
That was a great video Eric.
Good explanation Eric.
Good stuff.
Depression is also quite different bench vs engine at rpm. Would be interesting to see what you could learn from a bench that could do a better job representing an engine.
Guess CFD would be nice for this kind of thing if you had a good setup and knew what you're doing. Never had that luxury though.
Note to self wait till video is over to leave a comment 😅
Still would like to see what you can learn from realistic depressions.
Sometimes the education we receive from these efforts is priceless.
I hope to one day be able to articulate these circumstances in a more simplified fashion that works and doesn’t step on too many toes.
The fact remains that when you’re conducting business with anyone you’re agreeing to play by their rules. Which are often dictated by extraneous circumstances.
Ty ! Super educational!
Thanks for this explanation! A friend and I have had many conversations over about 25 years to which is the right head for an engine. We both have 400 cid but he's using afr 195's and I'm using 210's. Makes me think that both of us need bigger heads. Both engines are also procharged and vastly different cams and compression.
cheap gm rec ports are 260cc. a fully forted 5.3 cathedral is pushing 230.
Well done Eric. Good stuff.
Thanks
John Kaase talked about filling ports in a bbf head and saw an increase in cfm on the bench. But the same head compared to unfilled made less horsepower on the dyno.
What is the range of max velocity before airflow falls off? Isn’t it a certain percentage of the speed of sound? I’m sure it varies some depending of other factors/properties....
Thank you for your knowledge.. USA 🇺🇸
Eric , great video . I was wondering if you would do a video on port size , cross section and running airspeed . Port volume and cross section and cubic inch , rpm to get a speed that’s 550 ft per second to say 600 ft per second
So on a drag application that’s 6000 to 7500
550 fps at 6000 and 600 fps at 7500 . Combination specific
Eric can you please touch on boosted applications. I love the lifters you sold me by the way. Thank you.
So this is why my old corvette L98 113 heads 165cc just died at 5500 rpm? Still saving them for a budget truck motor tho. The Afr 195 cnc ported really woke up my gm original zzz motor even with giving up .5 compression. Thanks for all the info Eric!
Good video wet flow also comes into the picture with excessive velocity causes fuel drop out
Super cool video. Thanks
Thanks for watching.
That is really cool information you shared
Thanks
Great video. Maybe i missed it but do you have a formula to figure out a optimum head size for a given application? I have head a podcast that Darrin Morgan mentioned one butci do not remember what it was.
Great Content
Great info
Frankly, the second the intake manifold is installed, the total runner length changes also. I find this similar to picking a turbocharger, a smaller, but more restrictive turbo comes up on boost quicker, lower in the rpm range, and will feel more responsive, but loses efficiency on the top end, where a larger turbo will ne less responsive, and spool later, but pull hard through the middle, and make more power on top, but gives it away on the bottom.
I had Tony Mamo work up some heads for a 408 LS that’s in my single cab Silverado. It’s my daily driver so it lives on the street. I was shocked when he said we were using 205 cc heads. Now they flow 300 plus cfm. This engine is wild on the street but I’ve wondered what the downside is of such a small head. It will be interesting to get on a dyno and see where they choke out. It seems strong all the way up to 6k though. Good info here.
Geeezzz this is why i love bracket racing are my heads right wrong flowing or not?? I run old steel merlins on methanol .do they flow like afr or brodix?probly not .goes down the track doesnt break much never had heads flowed or engine dynoed dont know the hp just know its consistant 560s at 120.. i still like watching tech stuff even if i never will worry bout how im flowing or how much power im making ..just kerp building biger engines goin fasyer every time but care less about any number but the dial in !!
Great video Eric! Yes multiple items contribute to engine performance. I use CC like I use duration @.050" to get in the general area for the cubic inch & desired RPM range. I always say; "out of two identical heads that flow the same, the smaller port will generally make more power & be most responsive." There is nothing you can say always works or always does this or that as there are too many variables. Speaking about one size & brand engine for one specific purpose & RPM helps narrow the conversation.
cant find any info online.....i made my exhaust header port 1mm bigger ? will this make me lose power ? this is for a Subaru EJ20
. . To include and agree with Eric's explanation. The thing with cylinder heads is what you got you want to make efficient at every point. The port should have a target of 300 fps at peak lift of the cam you are going to use.
Can't you use the the intake runner as a runner combination ?
Has anybody run intake port flows in a CFD program with the intake valve opening and closing. Looking at the ram air in the intake port build up in the bowl and stall at the back of the closed valve.
Verses a significantly reduced bowl area to create a tapered area so the ram air is focused into a smaller area by the closed valve.
My thinking is how much air volume is stalled and needs to be restarted as the valve opens.
What. The intake valve is only open during the intake stroke. The other 3 strokes the intake valve is closed.
can only imagine the choke on when a manifold is on too
Depends... If you're desired rpm is within the port limiting velocity then the small efficient port will make the most torque .
Seems to me the smaller head moving more cfm will require more velocity which will be harder to control around short turn and cause turbulence and fuel separation
I purposely chose a very small port for thr sbc in my old pickup. Port velocity is fantastic. 245cfm@175cc. Trick flow super 23 175cc heads. What velocity does the airspeed need to actually reach before choking? I was under the impression that the heads flow enough to support 490hp.
How quickly does power drop off after the port chokes? The demonstration made it look immediate. I ask this because I also have a centrifugal supercharger further increasing port velocity in the upper rpm range.
I have not noticed any strange issues like boost pressure spiking at a certain point.. such as that critical port speed that causes a choked intake port.
Another note: the exhaust ports are considerably smaller than intakes. Do they choke as well? Do heat and air density affect the choke point?
I'm genuinely curious about this as I've never heard it before. I thought higher flow numbers were better when selecting a head, regardless of port size.
This takes an additional video to answer.
@@WeingartnerRacing I'm interested whenever you've got time. No rush. I've been a subscriber for years and don't plan to go anywhere. Lol. Thanks for all of the knowledge.
@@WeingartnerRacing I think it's a great idea for another video. I'm assuming you have enough experience to estimate what size pushrod pinch size is needed for the cubic inch/ RPM that is application specific, but is there a formula that can estimate it?
I always go with a bigger head than the math says to use because the loss of torque at lower rpms is less noticeable than losing the higher rpms, end of the track unless it's a truck for towing applications. Even streetrodders agree with me after feeling the difference. No one likes coming out of the hole fast just to get passed just before the finish line.
I think this highlights that the flow bench is showing a dynamic event “statically”. It does not take into account many other variables. If it was that easy you wouldn’t have all these port variations from various manufacturers and porters.
The flowbench is just a tool, not a bible. Thanks for watching and the comment.
Great video, I'm just wondering if there's a formula to tell you how much cross-sectional area you need for your power goals or maybe a ratio for area to CFM? It doesn't have to be perfect or official, even just a rough estimate that you would use to know where that choke point will be.
Follow up question: How much air speed is too much? I've heard someone else say the speed of sound. Is that true?
Mach .55 is the limit realistically
There is a formula for calculating min csa. Stain Weiss website has one.
@@WeingartnerRacing Thank you so much, I could not find the info anywhere without you.
Very interesting
so when comparing Edelbrock Performer RPM 290cc bbc heads with 110cc chambers vs 100cc chambers (that flow a little less), which would be better for power?
Combustion chambers are different than intake ports.. that being said, everything else being equal, the smaller chambers would increase compression and provide more power. That is assuming that the valves aren't shrouded by the smaller chamber. As long as the airflow and port size is equal and there is no detonation, higher compression will make more power.
iv hear this to the choke or the port backing up and and the air becomes turbulent and makes a different port noise on the bench
It does
I would love the forced induction perspective to this. That 400 with the TorqStorm for example. How does all this (like the choke point) get affected by forced air.
Because the boost increases the pressure drop across the valve the airspeed goes up this causes the rpm that peak power occurs at to drop but you are also increasing the density of the air and so it's mass and this helps carry the power past peak better so what you see on a Dyno is a little lower rpm for peak but a flatter curve that goes past peak better
@@scotthatch4548 centrifugal superchargers have a rising boost curve. More boost as you rev them higher. This will effectively push peak hp rpm higher in the rev range.
@@EricErnst correct which also changes the pressure drop across the valve .... I was commenting on the effect of a steady boost on the cylinder head flow .... With something like a turbo where you can control the boost you can move the power around by changing the boost but that is not really the discussion in this video
@@scotthatch4548 ok. You specifically mentioned torqstorm so I thought you meant centrifugal superchargers.
@@EricErnst I did not but the original post did
You should see how close pipemax is on needed csa and choke
Great infor
Thanks
Good vid. Now there needs to be a way to figure out choke point
There are math formulas for the area.
Is there an "ideal" port velocity for a particular port size/length and valve lift or is it all about wide open valves?
There is an ideal min cross sectional area for a given rpm and size of engine.
@@WeingartnerRacing Okay, that makes sense, but on velocity, does a bigger port allow an increase in the maximum useful velocity compared to smaller ports, or does it just achieve more flow at a similar velocity due to its area?
@@brianbrigg57 if you look at average velocity, if a small port flows the same cfm as a larger port, the average velocity will always be higher on the smaller port. Sure, there will be particular areas of the ports that have low velocity, and others with higher velocity. But if a predetermined amount of air flows through 2 ports, the smaller will always have more velocity.
Ok .... But that's looking at the port as just itself ... Larger cross section so lower airspeed at the major turn (short side) can help the air make the turn and get around the valve at the peak rpm this is only detrimental if the intake manifold airspeed is to low a balanced induction is key to making work
You do have to slow air down as it goes over the shortside. However you can have a scenario where you slowed it down and it looks good on the bench but on the dyno it is a turd because you slowed it down too much.
I’ve heard if an engine has heads and an intake manifold that is capable of flowing more air than the engine needs, the fuel will drop out and it won’t run well. Is that correct?
Flow demand is CID x RPM.. big head on little engine is just an engine tuned to a very high rpm and yes at low rpm it will have trouble but at it's tuned rpm it will work fine ... Because of rpm all engines are basically variable displacement so you choose a head based on the cid and rpm you are planning on running at like he said in the video
I can understand that. You made it easy.
Thanks
Nice 👍
I dont think the smallest head that flows the most air will make the most power but it will probably make the most torque. A bigger minimum csa will probably make more torque after peak with the trade off being less torque before peak. This is only within reason. You end up with sonic choke coming into play with the smaller port sooner and once that happens it doesnt matter what you do, nothing will get more air through the minimum csa.
Lots of boost?
makes sense to me.
That's crazy
Doesn't swept volume of the cylinder x rpm create the port velocity??
Pressure differential created by the piston moving down the bore v what the port can flow determines the airspeed within the port (average airspeeds)
The peak piston speed at around 73 degrees creates the highest pressure differential so you have to have a port that is sized correctly to avoid the average airspeed going above 0.6mach
This is the science of engines and a hell of a lot more complex than most realise.
Bigger=Better got it. Lol
It is all about the operating rev range and engine size, as you said. Tighter CSA flattens out the torque curve, and larger gives more peak torque. But, there's another number that stirrs the pot even further; runner length. To make the most out of your engine, you need to have your runner length to match your CSA and your cylinder volume. Usually the runners are way too short and this kills low end torque too.
And to add on top of that, camshaft valve overlap (both duration and lift) will change the amount of draw on the intake port of the head at specific RPMs. It's amazing many little factors play into how an engine performs over the RPM range, and how they compound on each other.
@@wyattwunderlin4445 Indeed. Valve overlap especially needs to be tuned with both runners, in and exhaust, in mind. To make the camshaft work there has to be incoming charge @ intake and draft @ the header. And then there's valve profile to tune the valve pulse which also is partially created by lobe profile and these all change if the fuel itself is changed to bring us to spark energy, not yet timing, but the amount of joules in each spark.. Tricky business.
For the street towing a heavy load of rather have smaller port heads.
8:58 the second head will make more power BUT that wasn’t your target of 6000rpm then was it? All you have done is move the window further up the rpm range with area.
If the first head had the same area but maintained it’s better efficiency then it would make even more power than the second head at the higher rpm points.
The better the efficiency of the head which is the flow number v min cross sectional area the wider the window will be.
So the statement should be, the higher the flow number from the correct min cross area that suits the cubes and rpm target, the better the head is.
Terminal velocity
What FPS do you tune to on bottom rpm and top rpm.
That depends on the head. Raised runner vs standard port is much different. Ideally that would be close to the same.
makes sense
Makes sense
Better change that 5500rpm converter to the one that is right for that engine.
I have heard Warren Johnson say that very same thing....."the smallest port that flows the most air will make the most power". Of course that's just a generalization, and thanks to Eric for explaining in further detail why it's both true AND false at the same time.
And even at that, it's not that it's really a case of true/false -- good/bad -- right/wrong. It's just the facts of the dynamics of airflow through a passage, and the effects that it shows when it speeds up and slows down.
like it hit a brick wall
Given ports that are equal in flow at a given pressure, the port with the highest velocity (within logical reason) will generate the fastest acceleration.
Of course, everything else must be correct.
Interesting.
This is why making a street/strip engine really stirs the pot.
Cool…
Isn't it the "intake port volume" not the "intake port area"? Your explanation at the front made it sound like the given number (270cc vs 230cc) was only for the frontal 2d area of the port and did not take length into account...but volume has to take length into account or it wouldn't be volume.
I mentioned length. That’s why volume is almost useless as it can’t be used to compare heads that have different lengths. Also it doesn’t tell you where in the port you are big or small.
@@WeingartnerRacing but bigger volume is still bigger and smaller is still smaller? That doesn't make sense unless the area is more important than the volume
The air fills a total volume each type the valve is open right?
What about this...mock up and LS3 with ITBs. Run it on the dyno. Add a 1" spacer to each port to lengthen it, but fill the floor to make the overall volume the same. Say 270cc in both examples. Run it again. Would there actually be a difference?
@@chipcurrey653 Area is more important than volume. You can have a port go big to really small or a port that is really small that goes to really big. They can have the same volume and make very different amounts of power.
@@chipcurrey653 The air doesn't fill the entire volume. There are almost dead zones.
CAN WE CALL IT PORT ENERGY ?
no
Just watch top 1000cc motorcycles heads
They have gone bigger and bigger and straighter for every generation.
For learning head watch motorcycle 1000cc
Biggest head possible and add port energy with biggest turbo possible
Doesn’t work that way unfortunately, the sizing should be the same as a N/A engine 👍
@@seanb250 mach # changes w/ density
@@HerrPoopschitz and as the density increases the airspeed does what? considering the pressure differential will be the same.
@@seanb250 Bernoulli dictates sizing will be the same. Helmholtz says it changes the resonant freq of the port.
@@HerrPoopschitz so the sizing stays the same like I said 👍
Dude you’re all over the place
That’s me.
David Frieberger disagrees... lol jk jk