MIND BOGGLING ENGINE GEOMETRY - Rod Ratio Explained
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- čas přidán 1. 05. 2024
- Here we have two engines. Both have the same bore and the same stroke. As you can see the only difference is the length of their connecting rods. At the same engine speed so at the same speed of rotation, the same rpm. Which engine has a faster accelerating piston?
As you can see the question I asked you was a trick question because the piston in the short rod engine accelerates faster from top dead center going down while the long rod piston accelerates faster from bottom dead center going up. So why does this happen if both engines have the same bore, same stroke and are obviously spinning at the same rpm. Well the culprit behind is obvious. It's the connecting rods, as they're the only thing different between the two engines. And this video I promise to strain your mind to the redline by explaining how something as simple as different connecting rod lengths create different piston acceleration and then using real life engine examples we will see how this impacts everything from power and torque to engine longevity, responsiveness, vibrations and even things like coolant temperatures.
So these two engines have different rod lengths, this means that they have different rod ratios. The full name is actually rod to stroke ratio. And it's the ratio of the center to center length of your connecting rod to the length of your engine's stroke which is determined by your crankshaft.
A connecting rod is essentially a fixed length line. It's absolute length obviously never changes. But the relative length of the connecting rod is constantly changing when the engine is running. In other words the connect rod length changes in relation to the piston and the crankshaft as the engine is running.
At top dead center and as you can see the connecting rod is fully upright. In this state it's at its maximum length in relation to the piston and crankshaft. Now as the engine rotates towards 90 degrees the connecting rod assumes it's fully angled position. In this position it is obviously at it's shortest in relation to the piston and the crankshaft. As we said an angled line has a shorter relative length than that same line when fully vertical.
So as the engine rotates from 0 to 90 degrees the connecting rod is becoming shorter in relation to the piston and the crankshaft. As it does so it pulls down the piston an additional distance. The piston is already traveling downward so adding distance in the same direction forces the piston to accelerate more to cover that added distance.
In fact we can observe this con-rod added distance in practice on every single piston engine ever made. Simply take any engine and rotate it to 90 degrees, or to half the stroke. Obviously at half the stroke the piston should also cover half the stroke distance? But it never does, at 90 degrees of rotation the piston of every engine will have traveled beyond half the stroke. This additional distance is the distance added by the connecting rod as it's relative length shortens.
So why does the piston in the short rod engine accelerate more? The reason is simple and it's that a shorter rod length in relation to the same stroke results in the connecting rod assuming a steeper angle against the piston and crankshaft centerline. The steeper the angle the shorter the rod becomes in relation to the piston and crankshaft.
So now we understand why the short rod piston accelerates faster away from TDC and we can use the same principles of relative rod length to understand what happens throughout the entire engine revolution.
Now let's look at the rod ratios of some real life engine examples to see how these differences in acceleration actually impact the engine.
Our first engine is the 1.6 liter Hyundai Gamma engine as found in numerous different Hyundai and Kia vehicles. As you can see this your typical daily driver engine with a modest redline, decent power and a pretty low rod ratio.
Next up we have the 2 liter Honda K20 engine. We're looking at the performance version of this engine and as you can see it makes quite a bit more power than the Hyundai engine and it also has a noticeably higher redline and also a higher rod ratio.
Our final engine is the one from the 2013 to 2018 Kawasaki ZX6R. As you can see it makes impressive power for it's very small displacement and has a redline that's almost twice that of the Honda K20. It also has by far the highest rod ratio. Somewhere around 2.2 or 2.3 is the highest realistic rod ratio for mass produced engines. Some of the highest rod ratios were found in Formula 1 cars at about 2.8
Awesome video proving rod ratio effects on a dyno by Garage 4age: • Rod Ratio - Dyno tested
A special thank you to my patrons:
Daniel
Daniel Morgan
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Zwoa Meda Beda
00:00 Piston acceleration in detail
09:40 Rod ratios of real engines
#d4a #rodratio - Auta a dopravní prostředky
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Fun fact, if the conn. rod is 2x the stroke, the acceleration of the piston is the same on both piston directions
The science is interesting but if any young person asked me about going into internal combustion engineering I would dissuade them and steer them into electronics. Combustion engines have done their time. Their life evolvement has come to its end and will bow out over the next 10 years to electric motors
@@horsebee1 The modern Nostradamus has spoken 😂
@@horsebee1 yeah...... Sure....... 0-100 in 2 second and 0-200 in 2 minutes and empty batteries...............
I think there is a lot more stuff on this channel that I am curious about. I subbed!
4 years of automotive engineering and never seen someone explain this subject so well
Same!
No years of automotive education, but a great HS physics teacher 47 years ago, had me seeing all of this intuitively before he even started to speak. And if he wanted to simplify he does not need to review all 4 quadrants of the revolution, any one suffices to explain the others.
Same ❣️👍🏼😁
Same here
If you studied automotive engineering and didn't pick this up, your school sucked or you sucked.
I have been an engineer all my life, (I'm now 57) I have to say that you explanation of what is essentially dynamic geometry, is the most straightforward and understandable that I have seen. Great video, thanks for helping others understand this fascinating field of engineering.
Absolutely Right.
How the rod to stoke ratio geometry affects efficiency was explained to us in high school physics class. It's also why the 340 Mopar engines would terrorize (and mop the floor with) the small block Ford's and Chevy's back in the day. Because of that geometry - only the 302 Ford's and 302/327 Chevy's had a slight chance. The weakness of the stock SB Mopar was in the hydraulic lifters (neg lash preload+ pump up) and non adjustable rockers, creating valve float and power loss above 6000 rpm. Solve the valve float issue with solid lifters and the 340 became a nightmare for the big block boys and girls. Efficiency = free power.
I don’t have a degree for anything and I’ve built a lot of engines over the last 30 years and always take into consideration rod and crank lengths for the proper rod ratio for its intended use.
😊😊😊
@@jackandblaze5956 Spitting straight facts.
been a racing mechanic for 5 years (im 26) and I’ve never had anyone have such a good explanation I loved this
If you don’t mind me asking, how’d you get into that? That’s gotta be my dream career
Same
As someone who grew up working on cars and even went on to being an engine builder in two countries before changing careers, you taught me something today. Thank you for this 🙏🏽
I'm not exactly an ignorant on IC engine internals, but every time I watch one of your excellent videos, I learn a lot of new stuff. What a PLEASURE !
I second that
I knew that rotatary to oscillating movement is unbalanced, that’s why the cv joint was invented, but I never gave what happens in one rev of an ic engine any thought. Till now. Brilliant video.
Oh man, I got to hand it to him for the quality of his videos for teaching engineology!
100% agree with you.
An ignorant, what?
17 minutes and I now understand something I had no idea understanding of before, even having an above-average knowledge of how ICE's work (not saying much). This was so great. Nice job!
I coursed engineering, mec tec, and multiple multiple courses in my county. I've also learned more and faster here tho!
Suck, squeeze, bang, blow. Simple to remember
Been a motorcycle mechanic and amateur motocross racer for 30 years.
I absolutely love your content. Fabulous explanations and animations. I use your content to help other techs all the time! Thank you for all the hard work you put in!
Almost 50 years as a mechanic and this is the best presentation I have seen - going back to my college days I remember the instructor telling us the wild angle of the short connecting rod created greater side thrust on the piston/cylinder wall; so far so obvious, but surprisingly he told us that was a good thing and set about constructing a triangle of forces to prove how the equivalent of that side thrust adds to the force of combustion and causes the engine to produce more torque. It was a long time ago and I don't remember the finer details, in fact I think I did well remembering that much, considering I have never needed to use that calculation in my entire career...
After 40 years of tuning Ford engines for club racing in the UK I can say that increasing the rod ratio gave race winning improvements to the engines power, to maximise this effect I also shortened the stroke and increased the bore diameter to restore the capacity allowed in the race class and had some great results. "Sausage" HT Racing Ltd
What kind of cam changes did you do to go along with this? Increasing rod ratio makes cams naturally better for lower rpms (its a relatively small change) while a stroker will naturally move the cams Powerband higher.
This is because of the change of piston position at valve opening times
David Vizard said in his Tuning A Series engines that long rods gave better rev performance. His race engines used a 1275 block with short stroke crank and longer rods to restore the piston deck height. Longer stroke engines (eg the 1100) also have longer rods as the cylinder bore can’t accommodate a wide rod angle.
Far more performance was gained by the larger bore and shorter stroke. In the simplest terms, the combustion pressure pushes down on the piston, larger pistons gain more PSI directly for the same exact displacement.
@@Justin-bd2dg yes in theory, but remember that the flame front from the spark plug moves nearly the same speed at all times. So your spark advance has to be earlier creating more pumping losses. Larger bores tend to work better at lower speeds because of this. Typically larger bores are less efficient but make more power with quantity. Another advantage of larger bores is more space for larger valves.
There are countless tradeoffs in designing an engine. I wrote an excel spreadsheet once just to help me understand the interactions better
@@BrokeWrench I didn't change the cam, everything was working so well there seemed little point
Using a longer rod length not only helps to reduce secondary vibrations, but also helps to reduce higher-order oscillations that can be difficult to suppress.
Most people know that, in any piston engine, the piston's secondary motion can be broken down into a primary component (one that varies at the same speed as the crankshaft) and secondary component (varying at twice the engine speed). However, what most people don't realise is that the secondary vibration itself is not perfectly sinusoidal and will have _harmonics_ (whole number multiples of the fundamental frequency).
The secondary motion becomes more "pointed" at mid-stroke (less sinusoidal) with lower rod ratios, and as the secondary motion gets more and more "pointed" both the secondary oscillation itself and its harmonics (4th order, 6th order, _et cetera_ oscillations) increase in amplitude.
The peak-to-peak amplitudes of the secondary oscillation's fundamental and harmonics can be calculated by:
A = 2 / π * ∫(cos(nθ) * √(L^2 - (S sin(θ) / 2)^2) dθ, -π to π)
Where _n_ is a non-zero even number, L is the rod's centre-to-centre distance, and S is the stroke length.
This effect is most prevalent on large two-stroke low-speed marine Diesel engines, where the rod ratio is often around 1 or less than 1. -(to the point where they need crossheads to take up the lateral thrust).- The reason is that these engines have extremely long strokes, so by using crossheads and short rods they can make the engine shorter in height.
Most of these engines also lack balance shafts, so they transmit almost all of their external forces and external rocking moments to the ship (for a marine application) or foundation (for stationary land-based power generation). This problem is aggravated by the fact that the components are all very heavy, which makes the forces even greater.
Take a look at MAN Diesel's project guides for their two-stroke engines (K-model, L-model, S-model, and G-model engine families, though as of 2022 they don't make K or L engines anymore), and on the section where they list the firing orders of each of the variants they will also list not only the first- and second-order vibrations, but also the second- and third-order harmonics of the secondary vibrations (fourth- and sixth-order vibrations). For example, although the 12G90ME has perfect primary balance, they do _not_ have perfect secondary balance. Although there is no second-order rocking moment, the second harmonic of the secondary vibration is still significant and produces a _fourth-order_ rocking moment of 724 kN•m (534000 lb-ft) at 84 RPM (which is conveniently twice that of the 6G90ME's fourth-order rocking moment of 362 kN•m).
The greatest offenders are the secondary rocking moments on five- and six-cylinder engines, which is why they sometimes _are_ fitted with balance shafts.
Large six-cylinder engines also have a sixth-order vertical shake. The heavy components and short rods already make fourth- and sixth-order oscillations a problem, and the 60° spacing between crank throws doesn't help either, as the sixth-order forces (the secondary vibration's third harmonic) for each cylinder all point in the same direction. The sixth-order vertical shake on the 6G90ME has a magnitude of about 32 kN (7200 lbf) at 84 RPM. The same is true for four-cylinder engines, as regardless of the firing order the secondary vibrations' second harmonics all point in the same direction, resulting in a fourth-order vertical shake.
You'll also notice that the 10- and 11-cylinder engines have non-zero net external forces. This makes me suspect that the 10- and 11-cylinder engines are odd-firing, because if they were even-firing the net forces should all be zero.
The reason you only have to deal with primary and secondary vibrations on most engines you'll come across is because their rod ratios are relatively high and their components are relatively light. So not only are the secondary vibrations smaller, they are also much closer to being sinusoidal, which means the higher-order harmonics of the secondary vibrations are negligible.
I'd like to know what the results would be if it was run with a vibration damper. Very likely make a world of difference.
@@elgoog7830 wouldn't a damper also absorb some energy that you want to go to the load. it's all about reaching that balance between what you need and what you want. those 2 stroke diesels are not running at hi RPM, although the counter weights on the crankshaft actually act as dampers. here's one to thank about... a scotch yoke crank the rod stays inline with the piston???
You've also got to take extreme piston side loading into consideration the shorter the rod. Higher speed engines of larger displacement like the Big Block Chevy always tend to favor a slightly shorter stroke with the longest connecting rod you can get - Now of course there are all sorts of caveats & considerations to that, but for the majority of street & race applications you're more often than not to want the longer rod every time.
@@elgoog7830 in larger marine engines their are vibration dampers, which dampens excessive lateral vibrations.
And what happen if you displace the crankshaft from the piston???
Brilliant explanation,although simple in principle, the comparative dynamics become complicated and this guy takes us through the whole process so coherently, we’ll done,thank you man.
You literally make things easy to understand, you’ve got a gift, thank you for sharing it with us
Absolutely brilliant. There's no other channels so dedicated to explaining the science behind combustion engines than D4A.
This was awesome dude! I really liked your animations. I don't think people gave high school geometry class enough respect - little changes in engine geometry seem to be what make the difference between average engines and great engines. Before your channel i hadn't really learned much about engines (even with a mech. Engineering degree lol), but you have some really great info
50 years ago my father gave me the knowledge to build race engines, and the patients to help me turn that into wisdom.... now think of that piston going up & down. F=MA now calulate the G (small g) load on the piston and the connecting rod. heres where the engineering comes in, but its more like material sciences when lightning up the pistons (roods & pins too) almost to the point of failure. street engines are designed to last >10years maybe and a performance engine not so much,,, BTW i said the same thing it my comment about math in school LOL
Think you mean trig classes. The use of geometry here is just an expression for shape. Sounds cooler, though.
wasn't that bad but one diagram was dyslexia as after the power stroke the piston is speeding up to max after on the exhaust stroke it slows down and in the compression stroke is being stopped but the mass of the hole engine keeps it going cycling wise
@@dksaevs still rather have a long rod BBM/hemi than a short one same point apply's for the 454 chevy's that side ware out. did you see a 2 pieces pistons? as some geometry's put the pin into the top ring/crown area's and or tricky looking parts
@@richardprice5978 actually the ones i've used are a three piece piston with a bridge on each side for the oil rings... LOL
I learned more from the 20 minutes of this video that 4 years plus of study! Not only a very professional graphic presentation that displayed it all so accurately but you were able to explain it all and speak in a manner that us lowly wannabes could easily understand. Thank you!
Huge respect for the time and effort you put into your content! Keep up the great work!
I used to put a lot of effort into building performance Ford 300-6 engines. My pinnacle build was going to be a twin turbo with decently high compression, and one of the things I played around with was rod ratio. Luckily, I could mix and match off the shelf parts to get a decent boost here. Rods from the 240-6 were more than 1/2" longer, 6.2 vs 6.8". Combined with pistons intended for a stroker 347 V8, they fit and gave a compression ratio of about 9.2:1, with the head I was planning on using. Unfortunately, I got married, moved a bunch of times, and the project never got beyond the parts collection stage. I did later build a high compression torque monster 300 for my van, but that's a whole other story.
you seen those rail dragsters with 300 fords? oh my god. they sound like f1 engines.
@@frigglebiscuit7484 There are some pretty wild power potentials with these things. I pretty much stuck with mixing and matching stock block and heads, porting and polishing, various intakes, and custom ground cams usually from Delta.
I owned an F150 with the inline 300-6,what a workhorse I wish I still had it.
Sounds like a neat van. Man
I just found this channel, and I absolutely love this guy. While I'm not an engineer, listening to your videos is awesome and the explanations are extremely well made!
L
Learned more from this absolutely top of the deck explanation/lecture than what I learned from many in the past. It’s really esoteric knowledge as rod lengths as you rightly said could be so easily overlooked. Keep it up!!
I don't care about how engines work really, yet I find his explanation so clear and compelling that I not only watched the whole thing, I was actually interested.
I have an above average understanding of engine dynamics, but every time I watch one of your videos, I learn some nuance that I didn't understand before. Congratulations on the very good videos you produce. Keep up the good work! I hope others appreciate your expertise.
I read about these things ages ago (wrt to motorcycle engines) but for someone new to the subject, this discussion is brilliant and I'm sure you've helped many people understand the concept.
That was incredibly articulate. You nailed the detail without making it overcomplex. Well played sir
I’ve been trying to comprehend piston speed since your first video on it, but never could figure it out (not for lack of good description from you). However this video made it all just click. Thank you so much. Just shows sometimes it take many different ways of explaining something for different people to understand
Angular velocity needs to be converted into linear velocity. You have to omit the angular velocity of X axis and use just the Y axis.
Piston acceleration is higest at TDC and BDC, this also happens where the relative piston speed is zero. It also goes the other way around, piston acceleration is zero where the speed is the greatest. Holton is also correct, plotting the acceleration and speed in a graph where the x-axis is crank degrees helps visualizing the princip.
@@bigcheese781 It has always amazed me that what most people dint think about is, that piston has to come to a complete stop twice per revolution! That's an amazing thing to do at even 6,000 rpm!
Was aware about the affect of rod length on piston acceleration after studying Kliens construction in my engineering course and playing with high performance 2 stroke engines all my life but the way this guy explains it with the graphics etc is fantastic...great work mate.
What degree? Never touched on engine geometry in my mech eng degree
Q
This dude explains everything in the best possible way in order to understand even the most complicated things
I'm not even a car person but I put this in my liked videos because you explained everything so clearly and I feel like it could teach somebody a thing or two about it
Wow, the amount of information you passed on in this video is astounding. I seriously can appreciate the engineering behind even just these components so much more now. It's crazy because this is just *one* aspect of these mechanical marvels, and the complexity is still so insane. Huge props to your explanation, excited to learn more from your other things!
This is why you see many builders move to the 6 inch rod in the 383 /400 small block Chevy engines.
One thing that amazes me here is how did they determine the size,location and diameter of oil passages and oil pressure to make it all work!
@@stanleyhornbeck1625 Yea, like how the clearances between components is so, so tiny, just enough for the oil molecules to fit through and lubricate every piece. Especially with so many pieces too!
I don't find it to be insane. Once you start learning how to disassemble and reassemble engines and transmissions it becomes simpler to understand how they fit together and understanding each part's purpose makes it easy to see why they are there.
@@stanleyhornbeck1625 Science and engineering is how. Thankfully it has since advanced enough you don't need oil tasters to tell the weight.
Rod ratio is an engine spec that is almost never published in the basic specs that you might see on the manufacturer website. Before this video I had never even considered rod ratio, but I can see that it can tell you quite a lot about an engine's characteristics.
Great content. Thorough, honest and correct nomenclature. I learned this years ago but I love a refresher course.
I do research on combustion engines and even after working indepth with them for a time, I still find myself coming back to your videos for summary
I saw this tested on Engine Masters. They did a great test. Where the conventional wisdom is that longer is better in theory, the short rod was more powerful at every point in the rpm curve. The theory is that the shorter dwell time at TDC for the short rod, was the reason. The theory also suspects that there would be a crossover point at rpm higher then 7000, but below 7000 is doesn’t really matter. So for practical application anything running lower than 7000 rpm, rod ratio doesn’t matter. We don’t know the crossover point, but I suspect it’s somewhere over 8000. ‘High reving’ is somewhat nebulous in street car applications. Anything running to 7500 rpm or less rod ratio shouldn’t affect you life. 8000 and up is when you need to consider it. That’s my take. Great video!
Did they test for wear and fuel efficiency?
@@Ijusthopeitsquick no. Just power.
Check the link to the vid in description, another test, but different results. It's likely highly engine dependent I think.
I also saw the Engine Masters episode, the differences between the two engines were very small. It is a shame engine masters is so focussed on V8 engines and power at wide open throttle. I think it would be more educational if they look at other engines and other parameters too (i.e. European/Japanese engines, durability, part-throttle, driveability, emissions, etc.).
@@d4a I should have added that the changes were minimal. No more than 12 hp at any point, less than 10 ft lbs. Many places it was the same or 2 or 3 numbers at any point. The rod length difference was .58 in, I believe. I love your channel! I have learned so much.
The technical term for the changing angle of the connecting rod, depending on whether it is a short or long Rod engine, is angular displacement. I started playing around with this stuff when I was 15 years old.
You made a excellent explanation of all this.
🤔🤔🤔, k
Ws
@@davidsanders6957 Its a physics term...more specifically, Engineering Dynamics.
Awesome video!! I definitely learned something
Thanks for watching ☺️
I must say, a very thorough and well-explained video concerning this very subtle, overlooked, yet consequential geometric condition. Most people, and vids, are all about bore v. stroke, etc.; which are really functions of different factors. I did know about this, but the quality of the OP's concise and accurate explanations, as well as illustrative quality, compels me to subscribe to this channel. Well done!
Fascinating! Bravo! I always learn a little something from every D4A video. This time I learned A LOT about something I had never considered before! Thank you!!!
you can observe what short rods can do to a cylinderwalls in peugeot 2.0 xu10 family of engines.
Early ones had a rods that were 152mm in lenght and it is very unlikely to find early block with cylinder bores in spec, but when they introduced revised version with 158mm rods cylinder bore wear wasn't as big of an issue anymore
That's definitely not rod ratio problem, with 86 mm stroke, rod ratio is 1,76 which is considered as Ideal, sr20 from nissan has rod ratio 1,58 and don't suffer on cylinder wall demage.
I can go and observe what a rod can do to a cylinder wall just by going and looking at my 1.4 HDi . Cos the French pile of crap put it straight through the bloody sidewall..
That's enough said about Peugeot's...
1.76 is ideal if everything else is ideal. But in the real world an injected engine that is also boosted will run cooler last way longer with a higher rod ratio engine. Sr20s are not all known for high mileage capability. The old volvo 4 bangers from the 80s-mid 90s will go 300,000 and then when they throw a rod the cylinder walls still have cross hatch marks in them and are good for just a re ring....if the rod didnt go thru the block. Some of the turbos would get a loose number one hole around 250,000 but thats partly because volvo thought that because that was the cold cylinder it needed more clearance but a lot of the turbos that were not run hard when cold will last up to 300,000 and still not burn any oil. The 85-87 were the only ones with the goofy number one clearance. Anyhow, 61-84 volvo 4cylinders and B30 straight six from 78-75 have a rod ration of 1.8125:1. 85-95 red block 4s have rod ratio of 1.92:1. By far the longest lasting 4 bangers ever. Chevy guys and even Toyota guys will not dispute that.
Insanely awesome information man! Thanks so much for all the research that has gone into it and presenting it for the ICE heads like me in the world! Keep doing it mate, you’ve got a lifelong subscriber!
This guy explains his subject superbly well. I have wondered about rod ratio for a long time. I didn’t even know what this design parameter was called.
The late Professor Antoni Oppenheim did a lot of work with our small group regarding this issue. From the mid-1990s to his death he helped our team of engineers to develop a more ideal piston dynamic that could be carved into the profile of a cam. CNCs can make any cam profile now to a tolerance of 0.02 mm. The result was the building of now 6 prototypes with such cams driving the pistons. The pistons of these engines are accelerated and decelerated at a constant rate, which more closely matched the dynamic of the flame front. We got complete combustion inside the engine. We reached almost 50% efficiency. Exhaust temperatures were only 450 C, so low we used aluminum exhaust headers. In his last book, he gave us another goal. So in our current design, we incorporated higher temperature, more insulating materials inside the combustion chamber. This permitted us not to have to concern ourselves with the 2300 C fast-moving flame fronts that produce NOX. HCCI (Homogeneous Charge Compression Ignition) ignites the charge at much lower temperatures, around 850C. This further increased the efficiency and eliminated NOX. Sadly in 2013 political pressure forced us to move to Asia where doubling the efficiency of the IC engine was not considered by the "Deep State" to be "too disruptive" to the tax structure and the employment of society. We are working to bring this technology to be used in REEV vehicles, which will have less than half the carbon footprint than battery-powered EVs that use Utility generated grid power. REEV technology is now are facing strong lobbying efforts by the so-called "Zero Emission Transportation Association". Whose foremost players are the utilities that generate most of their power with high carbon footprint, massive heat engines. see www.kamtech-sa.com/t-vi
When politicians empowered by their ignorance in engineering start to mandate things, engineering and science became just another slang in their speeches.
Why is it that these forces arrayed against you have not blocked you from CZcams comments? And why would any company not want a 25% improvement in fuel efficiency over all through fairly minor modifications of the con rod length and cam shaft design?
@@EdDale44135 clearly you are not understanding the fundamentals of
what Is being explained here buddy, give the comment a read again carefully and make note of who, he says, is doing the lobbying in relation to whom he represents. Specifically the very last bit. It's USA politics at its finest 👌
[02/06/22] Has anyone documented this "political pressure" that shutdown your group's innovative advances, and caused them to leave North America? Surely, some major articles and documentary exposure could expose these so-called "Deep State" energy actors and bring their nefarious machinations to light. It's difficult to believe that if tomorrow Honda, or Toyota could improve their fuel economy instantly across the board by ≥25%, some government or "Deep State" entity could swoop in and say "there is no way that you will be permitted to do this, it would be far too destabilizing" and thus cause these innovations to be suppressed and snuffed out. People that like to "upset" the status quo like documentary filmmaker Michael Moore would be more than delighted to kick the "Deep State" in the nuts and expose this nonsense. At the very least your group could start its own CZcams channel.
Improving combustion energy engines is NOT the direction the elite-deep state people are directing the planned economy infrastructure to go. They want those IC engines GONE from the market. I hope the elite-deep state, WEF, central government controllers all fail. Otherwise do you like being their pawns? And the entire electric car concept is flawed as the reason behind global warming being caused by CO2. The young are heavily swayed in schools and the media to believe the world is going to end in a few more years due to burning gasoline and diesel. The entire population can become hypnotized, under the spell, and controlled, that is shown true throughout human history of government control over the people. We have seen numerous attacks against energy infrastructure by them, and in the past, they were shut down, but unless you devastate the opponents to the point of death, they just keep coming back, like in the moves. So the entire ideology of the 'greens' has to be utterly killed, or it will keep coming at you, to wear you down bit by bit. What the end will be is energy poverty for many people, high costs to enjoy the little your allowed to do.
THANK YOU FOR TAKING THE TIME TO EXPLAIN THE DIFFERENCE IN ROD RATIO IN A MANNER THAT WAS VERY HELPFUL AND UNDERSTANDABLE
You sir, are a MASTER of finding facts that, on the surface, SEEM unimportant, and then showing people why they ARE important.
I often know some (or most) of what you say already, but I never dare to skip through a video. BRAVO!
I enjoyed watching all of us. We worked on this extensively in the 1970s, using longer connecting rods (custom) with custom-made pistons with the wrist-pin in Oil ring Grove, we could get rod ratios around 1.9. This was the secret to winning many races in s/stock eliminator. Having the piston reside at top dead center a little longer seem to be a little more compatible with the camshafts we were stuck with. Intake Plenum and runner volume played an important part to make the perfect combination with ratios this high. Great content.
I'm in a mechanical engineering technology program right now. It specializes in automotive. Currently taking geometry class, and hadn't even considered this. Cool video, definitely gonna keep it in mind.
Very interesting. Makes me want to look up all the rod ratios of engines I'm currently driving just for fun!
Congratulations on 400k subs👍 Amazing effort!
Thanks for this video. I never thought about this before, only piston speed relative to bore/stroke and the desire for over square engines to keep piston speed low for a given displacement. Rod ratio adds another factor in there, not only on piston speed, but also on cylinder wall side loading. Very cool.
Well done! Thank you for taking the time to put this together.
Mind blown! I love that you explain that so clearly and simply! Again thank you so much for your work in explaining engines to us! It is very greatly appreciated! This was truly a wonderful video!
This is indubitably one of the most interesting and well documented motor channel of the entire CZcams. Very, very, very well done!!!!!!
Google Jon Kaase
He is the GOAT.
Wow! Great information and exceptionally well presented! Over 60 years of turning wrenches and I had no idea about this! Thank you, thank you!
Ive been building race engines for approximately 20 years and i learned from this video. I understood this concept but havent seen such a great explanation or its repercussions.
Back in the 1980s I built up some high performance 2 litre engines based on the Ford Pinto engine. Wiseco produced a forged piston for this engine which had the gudeon pin much higher so that you could fit a longer con rod and hence increase the rod ratio
Great video. I have never actually thought about additional acceleration/deceleration due to the rod being at an angle, but now it seems so obvious.
One of the best explanations to the issue of oversquare engines I have ever seen.
Thank you.
Yay, I finally understood the secondary imbalance! Great informative video overall.
This was an excellent video explaining the main functions of varying rod ratios... I have read about rod ratios in David Visard's and Smokey Yunick's various books, and they explained it very well too.. But this video actually showed the viewer the change of acceleration rates between TDC and BDC... And then this video explained that these changes in acceleration can set-up linear vibration... This is the first time that I heard this explained in this way...👍
I geek out a lot on engineering... how have I only just cone across this channel?!
Absolutely brilliant stuff, many thanks and new sub👌🏽
That was the clearest and best explained engine design video I've ever seen. I don't even tinker around with the internals of my engine, just simply repairs, but it was fascinating to learn from you.
Such an excellent presentation man! Absolutely covering everything. The part about the force with rod angle is also critical regarding maximum engine speed. Primarily speed limits are at 25 meters per second based on stroke and exacerbated by low rod angle. It's the G-Force at TDC that rips the bolts out of the rod and slams the piston into the cylinder head. Running a low rod ratio decreases max safe RPM due to exceedingly high inertial forces as the piston reverses direction at TDC. The long rod slows deceleration and acceleration. The dwell is time for the inertia to dissipate as well. Significant in the exhaust stroke.
The best explaination of secondary imbalance till date....!!keep the good work going mate....:)
This is one of the best engineering videos i have seen in a long time. Big cheers!
I’ve been taking in a lot of info about connecting rod length, piston speed, and side loading of the piston and how they affect engine efficiency and longevity. This video was very helpful for me to visualize what I’ve been learning.
Nice job explaining this. An extreme case of a short rod situation is the small block Chevy 400ci.
Dad explained this to me some years back when I asked why F1 engines are so stubby and it was enough back then. This is now the explanation I needed to answers all the technical questions that arose from back then. Thank you for this video
I think this shows the exact opposite, having F1 engines with higher rod to stroke ratios, allowing them to hit high RPM where their HP is maximized.
@@joshualong7517 exactly what I was talking about but sure go off king! ❤️
I am glad you have put this video out. I have known the importance of rod/stroke ratio for a long time. However I could not have explained as well as you have. Well done
Fascinating! There is just so much more to building an engine than I ever knew. Great video!👌
Learned more again sir- thank you!
This is really an awesome explanation and a fantastic engineering channel. Very well explained and graphics are wonderful.
im planning on going to uti after high-school and i feel like your channel is genuinely giving me a free leg up.
Brilliant! I love your videos, recently subscribed and been through 4 videos already. Great explanations!
So now I understand why my engine builder wanted to go to a longer rod when building my stroker. Thank you
A good engine builder there. Better keep him.
Another great, informative video, clearly explained. The use of the same bore and stroke showed the effects of different rod ratios with no other changes. Are you going to do another video explain the trade-offs of over-square and under-square engines as well as stroker cranks including their effects on rod ratio?
Best automotive engineering youtuber there is, I've never come across a youtuber where I am left with 0 questions at the end of their videos.
I about to embark on a project of stoking a couple of 5.7 litre V8 boat engines to 6.2 litre for a friend. Your videos are giving me great insight into areas I hadn't thought of checking. Thank you for making these videos, excellent work.
The rod is most efficient at turning rod motion into crankshaft rotation when the angle between the rod axis and crank throw is 90 degrees. With longer rods, this condition also makes a smaller angle between the rod axis and bore axis, so more of the combustion energy is used to move the rod instead of shoving the piston sideways. So for a given crankshaft rotation a longer rod is more efficient at doing work on the crankshaft, and thus greater torque. Longer rods are heavier, though, so have lower RPM limits, so shorter rods can make more power by allowing the engine to rev higher for the same piston/rod acceleration limits.
But horsepower is torque x rpm and longer rods make more torque
It's not that easy - with a shorter connecting rod the angle is better for applying the force from the piston to the crankshaft during the period where the cylinder pressures are highest.
Then there are concerns with the valve operating periods - the dwell periods at TDC and BDC are going to be different - port velocities, secondary vibrations, etc.
There's a difference between the length of the rod and the length of bore stroke. A longer bore stroke means the crankshaft has more rotational circumference and therefore more torque. Which is why diesel engines have huge torque and less HP because of the stroke length not rod length
@@landenevans4938
That is not the reason. It's much more involved than that and, with diesels, the most critical reason is being able to minimise the volume of the combustion chamber to achieve the very high compressions required to initiate combustion.
These are simplified generalisations, but should give you something for you to ponder on -
An engine's capacity is the area of the piston x the stroke x the number of cyinders.
So for the same engine capacity and cylinder number, there is a direct relationship between the piston area and the stroke - double the stroke, half the area.
Now, for the same cylinder pressure, the force acting on the piston is going to be proportional to the area of the piston - double the piston area, double the force, half the area half the force.
The engine's torque is (simplified, remember) force on piston x the throw of the crankshaft - this is half the stroke.
From those basics, one can see that the engine's torque is pressure x area x 1/2 stroke.
Now if we simplify by dividing the torque equation by the capacity equation be get -
torque = (is proportional to) pressure/2 and as the 1/2 is a fixed value, torque : pressure for the same capacity, regarless of configuration.
Again, that's a simplification purely to illustrate why the "long stroke = torque" mantra is simply BS repeated by the ignorant. There are many other important factors, even with diesels, such as the discussed "'rod to stroke ratio, and valve area which is where 'large bore-short stoke' engines have a big advantage, and why high rpm engines almost exclusively are designed that way.
@@landenevans4938 doesn't rod length and stroke length work with each other? you can fit a longer rod that goes about TDC. of you can put a short rod in that same stroke length but you better make sure its boosted.
Fantastic video. Time to go look up the rod ratios of all my favorite cars! 😁
Fantastically understandable explanations of complex concepts! Loving your channel
Well explained. I didn't learn anything new, but it did put things in perspective more clearly in my head.
Thank you for this video.
Very well explained. Thank you. I have a much better understanding of the advantages and disadvantages of both Long Stroke, Short Stroke and Over-square engines now and their various stress involved.
You may not be confusing stroke and rod ratio, but in case you are: if you can keep rod ratio the same you can stroke an engine and still keep powerband up where it is and not have cylinder walls go out of round or have the thing run really hot but most guys who stroke ( thats on the crank, not the rod) their street rod engine will do it on the cheap end up with a shorter rod yet so a terrible rod to stroke ratio but the thing will start up run great and make torque so most dont care. I dont build lawn mower engines though. I like engines that last and that are daily drivers. But thats just me.
As a complimentary topic to this, can you please do a video on the different bore/stroke ratios, and their effect on power/torque/vibration? Love your videos!
I am subscribing in faith that you will do this video!
I suggest the same, to see how over squared or undersquared engine combined with different rod ratios affect the engines. And comparing sports bike engine / cruiser bike engine..
Good discussion, we've been increasing Rod Ratio's in North American performance/musclecar/drag Engines used for racing since the 60's.... and for exactly the reasons you discussed.
So simple, yet so complex. Very good explanation.
Fun fact, that was NOT mentioned...: Max piston speed occurs when rod and crank are 90° of each other, AND usually occurs within 1-2° of 74° ATDC. This will cause you to consider Camshaft, Rocker ratio, and cyl head configurations in a different light. (seasoned racer, self taught)
Awesome video! I am following the channel for a long time and you never stop impressing me with the things you cover. Just one question if you are comfortable answering, did you learn all those things at a university or a professional school, or did you learn them by yourself?
Absolutely brilliant, Your incredibly detailed and descriptive videos are genius. Thank you.
Clear and precise explanations at just the right pace 🙂
AWESOME job! Clear and concise.... made the "fuzzy" science of rod length very understandable! Thank you!
In my experience, there is very little in science and engineering that is properly fuzzy. Some of it just has so many layers of knowledge to be able to understand it...
The short connecting rod, in the intake phase, makes the piston spend more time in near bdc. It allows to improve the filling. This is fundamental in the 2-stroke, Ducati also kept short connecting rods in the twin-cylinders.
Claudio. You are backward.
Actually, the piston moves out of the head faster causing a greater pressure differential which acts to fill the cylinder quicker. But at some point the volume that the piston is creating overcomes the ability of the port to fill it resulting in a lower torque peak speed, the engine falls off. Traditional solution is to increase the size of the valve and port to allow more filling at higher engine speeds, but the torque falls off at lower rpm's due to reducing charge velocity. Longer rod will give better results as piston dwells longer at tdc while camshaft continues to open valves so that when the piston begins to move downward in long rod engine, it is drawing from a larger port area. I am glad he mentioned the effect of rod angularity on friction as it was one of the main reasons why the 2-strokes gained more power due to less frictional losses.
@@postulator890 yep
That was fascinating. I'd never considered that so much (math, both pure and applied) could be attributed to the rod length. Very well explained. I'll certainly be watching the episode again! So much to learn.....
You brilliantly explained the rod ratio. You have such a gift at breaking down the seemingly complex. Thank you, again.
Love it. Gonna start my automotive engineering classes next year. Hoping to be the best student in the class since I already know such stuff thanks to D4A. Really a great channel for enginehads and car nerds.
The electric revolution is already here so ICE knowledge is starting to become irrelevant
@@siggelindell1931 never buying an electric car unless the s16 is actually a silvia
Automotive engineering is a broad topic, not necessarily covers only ICE.
Would it make sense to aspire becoming the best student YOU can be??
I had always wondered at the source of second level vibrations other than the blanket terms of reciprocating mass and acceleration. Thank you for the enlightening video.
As always, excellent video. You really do an awesome job.
Engine builders making an existing engine higher performing often includes moving the pin up in the piston to get as long a rod as possible in the block. I've seen a few where they dished the head some to allow some piston mass above the top of the block to make the piston strong enough to deal better with the higher pin ... of course tumble and optimizing the flame front are factors too. Everything you change changes everything else :)
Back to add that I should learn not to comment before I get to the end of the video :)
Great video! I’d love to see a discussion about the effects of offsetting the bore centerline from the crank centerline.
Or tilting the bore away from the cranck.
@@metrikmechanik Talk to Volkswagen about their V5 and VR5 engines
@@dennisloobman8013 What do you think they'd tell us?
@@podulox They’d probably tell you something like “we’ve been there, done that and got the t-shirt”.
Thank you for putting this in a fairly concise package. The main reason to use longer rods is to stay farther under the fatigue limit of the rods in my opinion. Sure, the piston motion is more ideal, but that doesn't really matter all that much.
Your explanation are always explicit love this sir
It’s interesting seeing what happens when you turn vertical movement into rotational movement
Thank you so much for this video! I tried learning about this years ago in my efforts to think about the longest lasting engine possible and barely succeeded, this would have helped so much back then! (A strange idea I had then was to have the connecting rod, wrist pin, & crank rod bearings all angled in the other axis to achieve zero piston slap and smoothness) Boy that would be hard to machine.
big ship engines has upper connecting rod that moves just up/down, and lower rod moves as in car engine
In automotive engines the wrist pin is typically offset 1 to 1.5 mm with the offset trailing the crankshaft direction of rotation. As I understand it this is done to 1) help the piston to begin the downward stroke. And 2) to reduce piston slap. Piston slap can also be reduced with tighter clearances between the piston and cylinder walls.
@@makantahi3731 The Doble E-20 is the only car I know that does the exact same thing, but it's powered by steam. I wonder how well it would work with an ICE
@@mpetersen6 Indeed! I have not been able to figure out if all, or not most engines do this? This being said, the load and wear is still there even with both these measures. I shouldn't have used the term piston slap, maybe sideload wear would have been better?
@@carllinden533 Side load wear and piston slap are two different things. Piston slap is the piston rocking side to side as it goes up and down. The amount of rocking is directly related to the side clearance between the piston skirt and the cylinder walls. Piston skirts actually are not round. they are slightly elliptical with the major axis of the ellipse at 90 degrees to the wrist pin. Also since the advent of modern cnc controled turning equipment the skirt may also be barrel shaped top to bottom. The turning machines i was familiar with used an amplifier to control the tool when cutting the skirt. The service engineer when in house during install had a special tool that he could load in. After machining the skirt would have G & L on one side and Giddings and Lewis on the other.