Exactly, and whenever you don’t understand you can watch his videos over and over again until you understand it and it’s free, but with the teacher in class if you don’t understand then the teacher gets mad and don’t wanna re teach you. Also sessions are expensive in classroom
@@academiaengineering5136 A bit more complex than that Fabian. I was the math teacher out the front for apprenticeships for motor mechanics. We have a syllabus that has to be covered in a set time. We have students that have poor maths and numbers skills and that can be due to a lack of application by students before they reach trade school, or a lack of support by the community for education funding. And of course there are terrible teachers. In Australia we offered after class support and a significant number of students wanted the 20 minute fix. Came once and found they had to work. That was me when younger and ended up expelled. I video all my classes and make them available. We could track student access and we found a small group accesses the online videos. Strangely those that did access the videos were also the students that came to the support classes.
Bravo! I worked hands on a NHRA ProStock engine, on and off the track and you got it. There’s also more positive snowball effects of large bore performance engine such as raised camshaft and shorter pushrods to name just a few that all stack up to max hp & efficiency at a targeted rpm range. Great video.
My step father worked at SWRI in the engine department. He tried explaining this to me when I was a kid when he ran the engines for this series of tests. RiP C. Wilke. 2019
Long stroke is very common with large ship engines. I've regularly worked with 600mm bore but a 2400mm stroke, though the max rpm is only about 100rpm.
Exactly, this is engineering explained and not the mathematical calculation tutorials. He has given you the formula and the value, plug them in and analyse the result freely as per your requirements.
a note on increased piston speed mentioned at the end of the video--increased piston speed "pulls" on the intake charge harder. this puts a little more fuel charge in the cylinder and boosts power.
.. When engine rotates, with an itty bitty stroke, and huge bore in your face, you get sprung... Wanna pull up tuff, cause you noticed that slug was stuffed, deep in the hole I'm swearin', I'm hooked and I can't stop starin'. Oh, baby, I wanna get wit'cha, and take your picture.. My homies tried to warn me, but that bore you got, makes (m-m-m-m-me so horny!) Oh, bore-o-smooth steel, so you say you wanna get installed in my Benz?,... Ha ha, only if it's 5 point oh.... ..Baby got bore...
For a given displacement, a bigger bore will exert a stronger force on the crank throw, which compensates for a shorter stroke. The reason is because as the bore gets bigger, the piston top has a larger area for combustion pressure to work on. So from a torque perspective (F x L), bore increases F, but stroke increases L. The bigger bore allows for higher revving though.
I would figure stroke allows higher revving. Bore allows for higher torque at lower RPM? I would’ve figured that at least In my mind I had thought focusing more on strengthening those parts and making them light plus less stress would mean high rev. I guess chodes are good for something after all Very interesting!
In a pure moment, yes. But remembering flame propagation of most fuel types is about the same speed no matter the rpm or bore size, peak pressures will differ on oversquare vs undersquare designs. So two things happen. Timing will be diferent between the two to get best hp output, and rod vs crank angle will be different at time of peak pressure - torque output necessarily is different. The F1 guys get deep into fuel choice factors which... I'm no chemist, so just tip my hat to the unreal time investment of development and testing optimizing milliseconds of every cycle..
@@HardlyaDavidsonhigher stroke means higher piston speeds, because the piston travels a longer path every stroke. If you rev up a higher stroke motor the piston can basically outrun the flame which kills performance.
And that's why I like them. I got my 81mm bore here with 95.5mm stroke, which isn't exactly an extreme case but is much punchier at low rpm. The only times on the street when power is actual useful rather than just fun, is when taking off from idle, or overtaking on the highway. And if you can just lurch forward without having to drop 3 gears it's much nicer. My partner didn't believe me so I had him test drive a 110kw 4cyl turbo diesel vs a 150kw petrol V6 but I didn't mention the performance differences. He genuinely thought the diesel was more powerful and after a year of ownership still loves it. Additional benefit is it's 30% cheaper to register and uses half as much fuel for the same distance.
Exactly. If you bore and stroke a given engine, all you are doing is increasing displacement. You do not receive the individual benefits of either boring or stroking. Each change has its specific uses on an engine High HP at peak or high HP at lower RPM.
Great video indeed. Impressive to fit such amount of details in just 15 minutes. I used to work as an engineer on a container vessel / car carrier (MS Tampa) equipped with a MAN B&W 8 L90GB Main engine, utilizing a 900/2180 mm bore/stroke. That would be just above 7 feet stroke, providing 36 000hp @ 94 rpm. Quite the opposite of an F1-engines bore/stroke ratio.
I feel really good when someone walks in while I'm watching one if EE's videos. Don't get me wrong, I've learned a lot, but this is like getting caught reading about quantum mechanics, or reading the dictionary.
Great video! In going with a longer stroke, I wish you mentioned stroke to rod ratio. This is the relationship between the stroke length and piston rods. The lower the rod ratio, the greater the side forces exerted by the pistons against the cylinder walls. At some point, some of your energy is extremes against cylinder walls instead of up and down motion which increases wear against the cylinder wall. With a short rod and long stroke when the crank is halfway between the bottom and top (9 o’clock or 3 o’clock positions) the angle of the rod will be pushing the piston up against the cylinder wall resulting in some efficiency lost compared to a longer rod with the same stroke.
Thats true. I recommend You "The Workshop" YT channel. Host name is Matt and He talks about mechanics. He knows all about engines. He loves motorcycles, not cars, but dont worry, its worth watching. Excuse my English.
A short rod to stoke ratio moves the point of peak piston speed to a higher point - closer to TDC. Having the point of peak piston speed closer to TDC means that the piston moves further during the combustion period and this reduces the thermal efficiency of the engine. In building high performance engines i have used longer than standard rods and used pistons that feature a higher gudeon pin. I have seen pistons that have the gudeon pin so high that it is no longer located below the oil scraper ring.
This is the explanation I've always wanted on creating power based on cylinder geometry. Seriously! Thanks so much for filling in all the gaps in what I put together on my own.
I would have really appreciated being taught some of my engineering classes in this style of teaching. It seems so much easier and I am not even a native speaker in english, yet I still think I am understanding everything 😀
Unfortunately there is a large part of false logic to his theories. He is taking practical results and attributing them to assumptions. In a practical sense he is right, but his overall theory is largely speculation. And that is why internal-combustion piston engines rarely exceed 40% efficiency.
Thank you , that is an awesome explanation of the relationship of bore and stroke ratios, something I pondered for many years , keep up the great work, I enjoy your channel.
My 1986 Corvette uses a 1973 400 SBC block, its bored .030 to 4.155 and the engine is stroked to 3.875... 420 cubic inches. 6" Rods and a very short skirt forged piston from JE. 11.28:1 compression
@@hojnikb no, the block has been decked and the head gasket is .039... it's the optimum squish area for a clean burn without detonation. No pinging with 93 octane.
Lets go a little further. The longer connecting rods mean the angles at which they connect to the crankshaft are greater which gives it more leverage making it take less energy to move the crankshaft on a longer stroke. This is why longer strokes generate more low end torque. I would love to see more detailed videos like these. I ran the car club at my technical college where I got my automotive degree. I share your videos with students all the time. Keep up the amazingly detailed videos.
Something to remember about this is that a longer stroke means the throws on the crankshaft of a longer stroke motor results in both a higher piston speed as well as more torque, which is why longer stroke motors tend to produce more torque but can't be revved as high rpm.
everyone sees that . but a bigger bore means more piston area for the charge to push on resulting in torque also . probably the reason why he dont mention it
I studied mechanical engineering years ago. I remember watching your lesson on strut and other suspension stuffs. They helped me a lot in my course works. Still following you until today. Terima Kasih, Tuan 👍
The original Camaro Z28 was, as I recall, a 327 Block using a 283 crankshaft, giving a high reving 302 cid engine. 6000 rpm was quite impressive in the late sixties.
Similarly, the Ford Hi-Po 289, with a 4” bore, 2.87” stroke made excellent power and could rev to 7,000 rpm. Sorry about the inch dimensions, metric is a foreign language to me.
Similar chevy displacement engine, 305, with similar heads, intake, and breathing characteristics was nowhere near as good. Major difference was the inverse more to stroke ratio.
I love the older V10 F1 engines, 3 litre capacity with a 10mm piston stroke and could hit 20,000rpm. Those cars were around 1000bhp and made a noise like the angels singing😊😊
I was watching some vintage car exhibition on TV a long time ago and the had an old F1 car out there and they were talking to the head mechanic. He said you couldn't floor it until halfway through fourth gear or you'd lose control. They asked him how much horsepower it had: "I don't know. Our dyno only goes up to 1200."
Bro you got me dying right now because that's how I felt 😭 I swear God he should be advanced math college teacher I wish I could be as fast as him doing this math haha .
Nice comprehensive explanation which covers the variables and tradeoffs in an understandable way. Grandma was right, even when it comes to engine design. The answer for most situations is not found in the extremes, it is found in moderation (something tweaked plus or minus from a "square" bore/stroke ratio depending on the goals sought for the engine.
I've always wondered why long stroked engines (used in old cars in ~ 1930's ) gave way to short stroked engines. Just seems to me short strokes waste away some energy left in the cylinders thru exhaust. I've heard longer stroke engines wear out faster? A topic he seemed to overlook was longer stroke crankshafts produce more torque. He did nicely but was brief on fuel combustion burn rate - important consideration in that it is same value for all designs he discusses. This is an extremely complicated subject! 🤯
Ray Bin; Complicated, yes. I would like to suggest that other important things about the development that make it possible but not mentioned are the development of better material and alloys, the development of better bearings and the better machines and machining to much better tolerances that make them possible, and the development on the petroleum side, of lubricants refined and fortified to take the tremendous loads put on the bearings when developing these extreme power outputs and advancements in petroleum engineering that produce incredible amounts of clean consistently high quality fuels at reasonable cost. (+ taxes that give us roads to burn it at 75mph hour after hour) I am very pleased to see you younger people interested in these things that were a great part of my life as I grew up when Model Ts and Model As were daily use cars. I'm sure that if you look around you may find an older person chock full of information an all these things and he'd love to share it!
A larger stroke requirea a larger diameter crankshaft That means the crank shaft will be pulling the rod further sideways Increasing wear on the cylinder walls This be mitigated by going with much longer rods to reduce the angle of the rods But since long bores already tall, thats hard to do.
I’ve had a bunch of different BMW’s over the years but my favorite was the E28 520i with 2.0 liter inline 6. It was a smooth as butter and sounded awesome. 80mm bore x 66mm stroke
The smoothness of BMW's inline 6 has nothing to with bore or stroke. An inline 6 has no primary nor secondary imbalances. The engine itself runs smooth naturally. When all internal parts are perfectly balanced in a straight six they can be one of the worlds best engines, look at Toyota's JZ and Nissan's RB engines for example. What BMW did in the 80s and 90s was using heavy flywheels on the 6 cylinder engines as well. This adds another type of smoothness because a heavy flywheel increases smoothness in drivability (not the engine).
Yes like the k20 compared with the k24 big difference in torque for just stroking the engine, but peak hp is similar cause you lose about 1000 rpm, not gonna notice that unless going above 7,000 rpm though
I gotta just take a moment to praise you for this unbelievably excellent presentation! You've clearly and thoroughly explained one of the most basic variables of ICE designs and made it completely understandable. Nearly all your videos simply mathematically complex auto engineering, but this video is the top of the list for (1) taking such a _universal_ ICE design principle and (2) so thoroughly described it for anyone with a basic understanding of math and a minimal understanding of physics, with no hand-waving needed. Simply brilliant! (However, I was expecting you to define "over-square" and "under-square" because I can _never_ remember which is which... though, if you had defined them, I probably would still not have remembered which was which after the video was over).
LD9user yes sir that’s what we do in my camp. Although I have a sbc 400 and I kinda want to destroke it using a 350 crank and running domed pistons to up my compression and that’s a 377cid and they are a high revving bad to the bone race motor. I’ve done a couple 383 strokers but it would be a first to go the other direction. Can smaller be better? You bet it can, my 383 is a torque monster that eats big blocks for breakfast everyone always wants to argue that and well the performance of my C10 pickup speaks for itself.
@@larryheard3462 That's awesome. We were doing that back in the 70's before the 400 cranks were considered "strong enough" for performance use. One things for sure, the sky's the limit on rpms with the shorter 350 crank (as long as everything else up to the task). It's easy to keep piston speed under control and you can use a nice long connecting rod as well. :)
Yes I did, but what I found was like every internet research, full of people telling the truth and full of people telling the opposite. Moreover I didn't have the time to go and read research papers to have the true reason. In fact I knew why large bore could give more power but didn't know the details about valves sizes and stuff... Anyway I could have done more internet research but I would still not be able to understand all of this in 15minutes so please don't devaluate populazer's job here on YT.
As a former instructor (of Electrical Engineering) this guy is great. "Pull back the curtain" was a catch phrase in my classroom. Too often the instructor winds up down in some esoteric corner and students can't see the whole picture. Obviously there's a lot going on here....highly simplified...but after this presentation the typical (young) engineering student is ready for deeper concepts. Excellent! Now we're ready for "volumetric efficiency".....
Ah yes, my favorite class in ME school. Good job and thanks for rekindling my roots, I'm stuck in software land (Silicon Valley) and gotta get out! Very good presentation.
EE very interesting! I’d love to see a comparison like this on Diesel engines like say 6.7 Cummins vs 6.7 Power stroke efficiency and like 8 slightly smaller pistons vs 6 slightly larger and such
Engines are generally more efficient with fewer cylinders for a given displacement because there is less total friction. Only past a certain cylinder bore can it become an issue due to excessively long distances for the flame to travel. Diesels are less affected by this than gasoline engines because of the different combustion (the flame doesn't need to travel the whole volume of the cylinder, as long as an adequate amount of oxygen is still present near the injector).
The thing is, this is much better learning/teaching than it will ever be at my university. Why can't lecturers be this clear about the stuff instead of talking a lot while transmitting minimum amount of information.
I love the way you break down the concepts and always give multiple explanations on the given scenario!!! Do you offer a complete course? I would definitely be interested!!
Thanks for putting this on, I actually think about bore and stroke all the time. Wouldn't it be fun to have a machine shop where you could build any kind of engine you'd like just to see it run? Also, there are so many more things that could be included in this video it would put us all to sleep, now where's my calculator?
What was not talked about is rod length and how it affects the overall performance and combustion effeciency. Generally speaking a long rod length promotes a better combustion because the leverage of the rod keeps the piston at TDC longer as it sweeps over allowing to burn more fuel and air. And, some builders will claim a shorter rod creates more wear and tear because of the angularity of the rod and more scraping of the piston skirt on the walls of the cylinder. But, some also claim that initially, a shorter rod gives more leverage off the line.
I seen info that the ideal stroke to rod length ratio is 1.75. How true that actually is I'm not sure. Stan Wiess has a web site with data on rod ratios, bore and stroke etc. A Chevy 327 is 1.7538. A Buick V-6 or 300 SB is 1.7529. A lot of Hondas are around 1.5. The only engine I can find data on that is right at 1.75 is an AMC 232. There's another factor that enters into this. And that's deck height. Plus with a really small bore and long stroke you start running into clearance issues unless the bore is noted or the deck height gets really tall. Big bores raise another issue. Unless you siamese the cylinders the crank gets really long. A good example of the effect on deck height is the Boss 302 vs the 302 in the Z-28. Both 4" bore with a 3.0 stroke. But the Chevy rod 5.700 while the Ford is 5.150. The rod to stoke ratios are 1.8968 vs 1.7166 respectively. The Ford could actually accommodate a longer rod by the use of a piston with the wrist pin higher in the piston. There are a large number of factors involved in the design of any engine. Longer rods, more reciprocating mass. Short deck height, smaller packaging. Plus on a OHV engine lower deck height, shorter pushrods*. Yes I know OHV is practically prehistoric technology. But ask yourself. Just how many drivers really make use of all the engine power they have any way *Another way to shorten push rods is to make the rocker arms so the pushrod seat is below the pivot point of the rocker. Another way is to place the camshaft much higher in the block so that the lifters are pretty much even with the deck face. Renault actually built a 1.6 liter with this set-up. Very short pushrods, cross flow head and a hemispherical combustion chamber. I've often wondered just how a V-8 with 2 camshafts mounted high in the block would be like. I don't know if it's ever been done.
In fact, I don't speak much English and I don't have a vocabulary, but your way of explaining is wonderful, it made me understand honestly.. Esther brother ❤
Finally, i got an answer to my doubt which kept bugging me for years about the parameter which is actually held responsible for the Power of a vehicle. Thanks much for the clear explanation as usual...
This is the best explaination I have ever heard and it makes perfect sense the way you described it. I was told for years the best combination was a stroke that was 75% of the bore. Fully understand the need for a square motor. Thank you so much👍👍👍👍👍😁
The professor, a little better than my first teacher in automotive tech. My first year was all book, if all the machinery was available and you paid attention you could have built your own engine after that class from casting the block to machining the cam and carb of mechanical fuel injection. Unfortunately I've lost a good part of that class over the decades and it's coming back thru these videos, Thank You.
Very interesting and very well explained!! Unfortunately I can't do much more than liking, subscribing and commenting your video to support it! Continue this quality content!! 🙏🙏🙏
When I first started my Mechanical Engineering studies to improve my Race Engine Building, my professor told the class it's physically IMPOSSIBLE for a car to accelerate from a standing start, and go 300 m.p.h. in 1320 feet. I left the class and began my Engine Building career without my degree. Thank GOD.
Most of the old farm tractors, IH-Farmall, Case, John Deere 270 "Johnny Pop" etc. all had long stroke and narrow bores; 2 to 1 or greater. Better for torque and lugging, pulling plows and slow driving. Very good presentation.
I'm a motorcycle mechanic so not trainedin engineering or engine design but I've done a lot of reading over the years. Doesn't connecting rod length have an effect on piston acceleration, side loading and when maximum torque is developed?( rpm) Burn time is relatively fixed which is why ignition has an advance curve to start burn BTDC with maximum pressure somewhere around 14 degrees ATDC. Unless a manufacturer is designing a totally new engine, 'ordinary people' are looking for ways to maximise what they already have , bigger bore generally being the cheapest and easiest but with limitations on maximum bore size due to cylinder spacing. The largest overbore I've ever done was 14mm which actually utilised the oversize ports way better than the manufacturer (1970's designs, big ports, high cfm, low gas speed)
I've always heard that small bore, long stroke engines are more efficient because they have more "time" (remember crank angle = time in an engine 😉) for the fuel to burn, giving more time to extract that useful energy
@@mikerammelt2420 Yes, I seem to recall that historically, British manufacturers like Jaguar and Aston Martin utilised "long" engines (long stroke / smaller bore) and this proved successful at endurance racing like Le Mans 24 because the greater torque available and, consequently, fewer gear changes. Most continental European manufacturers focused on "square" engines.
One of the interesting things I did many years ago, which more applies to steam engines at low RPM than internal combustion engines is calculate the difference stroke and bore make on torque output. The answer is none at all. But that does assume that your valve gear can get as much steam or combustion mixture in as needed which is easy to do on a steam engine but harder on a IC engine. It also ignores the effect of drag of the piston in the bore which will have an odd relationship.
You could say that (for a piston engine) power depends on a combination of Brake mean effective pressure (BMEP) and revolutions per minute (RPM). You could also say that power is proportional to the amount of air that the engine consumes.
The arithmetic here is actually very simple, not much beyond about 8th grade or so. The tougher part is understanding how its application determines hp, torque, etc. That's where the Engineering part comes in.
The main problem is that their cylinders vary... Not to mention how lightweight(usually brittle material, even if they are selflubricated, if somewhat used, not hundred thousand miles used old ones, can tear and the walls can start to leak) their cyl.are.. so the piston can be too big too
Thanks for your explanation, very nice. I have been a mechanic for years and years and the 'best' engines I have come across all seem to be 'square' they seem to have the best combination of power, torque, smooth running and reliability. Look at BMW, 2 litre 4 cyl, 3l 6 cyl, 4 litre 8 cyl, all square engines with the advantage they only need to make one size piston for all of them.
for coming up short, it's more correct than you realise, because diesel is more prevalent than petrol in the construction industry (source: I'm a crane operator and I've yet to see a petrol-powered crane, they're all diesels, and the 'capacty vs recharge' issue around electric is why I don't think they'll ever catch on for construction.) Diesel, tends for a higher-compression, so it'll have a longer stroke to bore. And since everything in construction is diesel, it means everything is a longstroke. and so being called a shortstroker, is basically saying you're stalling on the job. Also doubles for applications where the torque is really needed rather than horse power but you bring a 'petrol' to do the job. It aint gonna cut it mate.
Why 25 m/s? Is it to do with mechanical stresses due to the acceleration and deceleration of the piston and con rod or is it to do with flame front combustion limitations?
Here's why according to Wiki: "Piston velocity is a test of the strength of the piston and connecting rod subassembly. The alloy used to make the piston itself is what determines the maximum velocity that the piston can reach before friction coefficients, heat levels and reciprocating stress overcome the maximum levels that the piston can sustain before it begins to fail structurally. As the alloy tends to be fairly consistent across most manufacturers, the maximum velocity of the piston at a given rpm is determined by the length of the stroke, that is, the radius of the journal of the crankshaft." en.wikipedia.org/wiki/Mean_piston_speed
Holding focus and track to your explainations are so much less of a drag than any of my dried out teachers. I wish I rather had you in front of my class room :D
Hey! Love your videos. In regards to small bore, long stroke engines, do you think it would be possible/beneficial to have a single VERY large valve in the combustion chamber to allow for more airflow (or have multiple valves that all open at the same time), and have separate valves in the intake/exhaust manifolds (or somewhere close to the combustion chamber) to determine air flow direction?
I've learned so much from you over the years! I would love to see a video on what the perfect engine size for a caterham kit car to use on the road and track without having to change your underwear every time it goes on the road - especially in the wet. The variables would be traction in dry and wet, hp, weight, acceleration. Cheers Jason!
I remember when I was a teen and begin to interest about engines, my older brother (RIP) told me the simple formula: "If You want torque, get stroke. If You want Horsepower, go for bore. If You want both, You need displacement. Displacement is only to replace by more displacement." That was in the early 80's. Then came the turbos - and displacement was no longer irreplaceable. The magic word is called "boost". ;)
But now you have another decision, large single turbos give more horsepower up top, but large positive displacement superchargers give more down low. From idle, a turbo does stuff all, but as you rev it up you get increasingly more and more of power boost. Where as positive displacement superchargers take the existing dyno graph, don't change the shape at all, but just shift it up higher. For example +20% over the entire rpm range, or +30% only in the top quarter. Modern factory turbo engines though are often balanced to favour mid-range, with smaller turbos that spool faster or sometimes multiple turbos to balance out the whole rev range.
And if u ask Koenigsegg,: it's all about advanced engineering: displacement, light weight, electric power, highly specified timing, ethanol, boost (why only have one turbo when u can have many even on a 3 cylinder I3, u could complicate even more with 6 turbos)...
This guy just makes everyone enjoy listening and easy to understand all the complicated stuff. Really enjoy this guy explain things. Just a quick question: I have not come across any information, video or anything that explains as to why a piston has to be round and if it was ever tried to be in a square or other shape.
Technically yes but there a many other variables. Your engines max rev is based on obviously what's been highlighted in this video but also takes into consideration internal balance, rod/rod bolt material, and valve spring strength.
@@jc0326 accurate but that's more advanced stuff like rod size width spring stiffness lifters rockers and stuff like that but in a nutshell you will get more torque out of a bigger stroke that's why diesels usually have a bigger stroke and are usually high capacity engines
Yes and no. Yes if all you change is the stroke your engine will roll over sooner. You will reach the flow limits sooner, lower rpm. No in that material red line is typically not the red line in most engines use today. The typical red line used is just after the peak power roll over. In most application you wont hit the physical limitations of piston speed. You will almost certainly be limited ultimately by flow and where the engine rolls over on the power curve. Even with a 4.5" (114mm) stroke you could build an engine to hold at 6700, for drag racing or street type stuff you could build it to safely handle well past that for brief stints. That 25m/s or about 4900f/s is for holding revs that high for a fair amount of time. That is why you see long stroke dyno queens blowing way past limit, they don't hold it long for heat to weaken the parts to point of failure.
c- man Not necessarily; longer stroke can have more pressure on the side walls of the cylinder, and also much more stress on internals. Piston speed increases as well.
I just wanna say. That even though I'm not math whiz(i leave all that stuff to you..lol), I find your analytical explanations FASCINATING!!! Idk how many "nerdy" motor heads there are out there watching this stuff, but you explain it in a way the more advanced thinker can still comprehend. Now, knowing this stuff is not for the faint of mental comprehension, I'm sure it's much to chew on for many.. Lol but I LOVE IT. and I've learned quite a bit from the science of it all you explain so well. And I want to thank you for doing all the hard work of breaking it down. This is what I love about your channel and thank you for being a top "educator of the masses", in my book. 😀
I set out to optimize a small motorcycle engine. I stroked it to a 13-1 compression ratio and used a cam modeled after an RV motorhome. It left the intake valve open just long enough to lower the ratio to about 10-1, giving me the advantage of the longer stroke, being able to run on pump gas and being easier to start with a nice idle thrown in, to boot.
Unless you're racing, having max power at the expense of torque will have you shifting more frequently instead of being able to cruise up & down hills!
Paid 30k for school on cars and this guy explains it better than almost any teacher
thank you for the heads up 😂
30k for a piece of paper 😂 I know the feeling 🤦🏼♂️
UTI? Been there, done that, got the tee shirts still
Exactly, and whenever you don’t understand you can watch his videos over and over again until you understand it and it’s free, but with the teacher in class if you don’t understand then the teacher gets mad and don’t wanna re teach you. Also sessions are expensive in classroom
@@academiaengineering5136 A bit more complex than that Fabian. I was the math teacher out the front for apprenticeships for motor mechanics. We have a syllabus that has to be covered in a set time. We have students that have poor maths and numbers skills and that can be due to a lack of application by students before they reach trade school, or a lack of support by the community for education funding. And of course there are terrible teachers. In Australia we offered after class support and a significant number of students wanted the 20 minute fix. Came once and found they had to work. That was me when younger and ended up expelled. I video all my classes and make them available. We could track student access and we found a small group accesses the online videos. Strangely those that did access the videos were also the students that came to the support classes.
Extremely complicated concept meets extremely simplified answer...this is why I love this EE!
i wait several years for this video and is come to me in the rite moment (i wanna star to bild own 2 cyl flat ednige)
Complicated to some...
Hal 1000, Thanks for existing, bro!
complicated concept? I think the words you used are more complicated.
What a great teacher he is
One thing for sure. There was nothing boring about this video. I was so mesmerized, I nearly had a stroke.
Wonderful
Excellent pun, well done
Lol don’t BORE me with your rant
Very good...
you should not have applied the theory to masturbation
Bravo! I worked hands on a NHRA ProStock engine, on and off the track and you got it. There’s also more positive snowball effects of large bore performance engine such as raised camshaft and shorter pushrods to name just a few that all stack up to max hp & efficiency at a targeted rpm range. Great video.
My step father worked at SWRI in the engine department. He tried explaining this to me when I was a kid when he ran the engines for this series of tests. RiP C. Wilke. 2019
If I knew what SWRI meant, I might agree with you.
Southwest Researchinstitute
I love these videos with a host who is actually educates on the subject and can illustrate the information. Thank you Engineering Explained
Long stroke is very common with large ship engines. I've regularly worked with 600mm bore but a 2400mm stroke, though the max rpm is only about 100rpm.
That might help explain the 1000 miles per gallon per ton of fright.
I love those engines
Torque 🔥
Are you referring to the MAN B&W S60 engines?
@@electric7487 yes indeedy, worked both 5 and 7 cylinder versions of the s60mcc
"If you do some math..."
This is Engineering Explained. There's no "if" about it; it's going to happen.
He says You so it’s still my choice if i do the math or he does lol
Just let it happen, bro!
Exactly, this is engineering explained and not the mathematical calculation tutorials. He has given you the formula and the value, plug them in and analyse the result freely as per your requirements.
Read your very first word..
I read this as "if you do some meth..."
Liked it better tbh
a note on increased piston speed mentioned at the end of the video--increased piston speed "pulls" on the intake charge harder. this puts a little more fuel charge in the cylinder and boosts power.
So...volumetric efficiency. Yep
That explains a lot. When I got married, my wife was very efficient. However, her horsepower has been increasing every year we’ve been married.
Is this a you shrink as you age joke?
honestly engines with high stroke just bore me at this point
This comment will get over 1k likes very fast
I c wut u did thar
Unless you're high while you have a stroke. Nothing boring about that.
Thanks, dad.
i wait several years for this video and is come to me in the rite moment (i wanna star to bild own 2 cyl flat ednige)
i like big bores and i cannot lie, you other brothas cant deny
I can already see Rachel slapping Ross' butt XD.
My daily has a 137mm bore and I love it!
.. When engine rotates, with an itty bitty stroke, and huge bore in your face, you get sprung...
Wanna pull up tuff, cause you noticed that slug was stuffed, deep in the hole I'm swearin', I'm hooked and I can't stop starin'.
Oh, baby, I wanna get wit'cha, and take your picture..
My homies tried to warn me, but that bore you got, makes (m-m-m-m-me so horny!)
Oh, bore-o-smooth steel, so you say you wanna get installed in my Benz?,... Ha ha, only if it's 5 point oh....
..Baby got bore...
Stroke stroke, stroke stoke, stroke stroke,
Everybody, everybody
The lady’s love us
When we pour...
@Southern Fun maybe he's working with a bulldozer who knows ^^
Holy crap I’ve always wondered about this thank you
i wait several years for this video and is come to me in the rite moment (i wanna star to bild own 2 cyl flat ednige)
Thanks man.
@@valentinuiliqnow6198 me too.
Strokes make cars faster. Bore makes more torque.
no way we have the same pfp
For a given displacement, a bigger bore will exert a stronger force on the crank throw, which compensates for a shorter stroke. The reason is because as the bore gets bigger, the piston top has a larger area for combustion pressure to work on. So from a torque perspective (F x L), bore increases F, but stroke increases L. The bigger bore allows for higher revving though.
I would figure stroke allows higher revving.
Bore allows for higher torque at lower RPM?
I would’ve figured that at least
In my mind I had thought focusing more on strengthening those parts and making them light plus less stress would mean high rev. I guess chodes are good for something after all
Very interesting!
In a pure moment, yes. But remembering flame propagation of most fuel types is about the same speed no matter the rpm or bore size, peak pressures will differ on oversquare vs undersquare designs. So two things happen. Timing will be diferent between the two to get best hp output, and rod vs crank angle will be different at time of peak pressure - torque output necessarily is different. The F1 guys get deep into fuel choice factors which... I'm no chemist, so just tip my hat to the unreal time investment of development and testing optimizing milliseconds of every cycle..
Will a bored engine weigh less or more?
@@HardlyaDavidsonhigher stroke means higher piston speeds, because the piston travels a longer path every stroke.
If you rev up a higher stroke motor the piston can basically outrun the flame which kills performance.
In the very simplest of terms, longer stroke, more low end torque, shorter stroke, more high end HP.
Simply put: Short stroke creates power at high RPM. Long stroke creates more power at low RPM.
And that's why I like them. I got my 81mm bore here with 95.5mm stroke, which isn't exactly an extreme case but is much punchier at low rpm.
The only times on the street when power is actual useful rather than just fun, is when taking off from idle, or overtaking on the highway. And if you can just lurch forward without having to drop 3 gears it's much nicer.
My partner didn't believe me so I had him test drive a 110kw 4cyl turbo diesel vs a 150kw petrol V6 but I didn't mention the performance differences. He genuinely thought the diesel was more powerful and after a year of ownership still loves it. Additional benefit is it's 30% cheaper to register and uses half as much fuel for the same distance.
Exactly. If you bore and stroke a given engine, all you are doing is increasing displacement. You do not receive the individual benefits of either boring or stroking. Each change has its specific uses on an engine High HP at peak or high HP at lower RPM.
@@jmaclaren4147
1. Bore=Stroke. Square Engine. Therefore, HP=Torque.
2. Bore>Stroke. Over square Engine. Therefore, HP>Torque
3. Bore
That is an oversimplification as rod length is just as important.
Which is why it's common for diesel engines to be 4cyl with long strokes
Great video indeed. Impressive to fit such amount of details in just 15 minutes.
I used to work as an engineer on a container vessel / car carrier (MS Tampa) equipped with a MAN B&W 8 L90GB Main engine, utilizing a 900/2180 mm bore/stroke. That would be just above 7 feet stroke, providing 36 000hp @ 94 rpm. Quite the opposite of an F1-engines bore/stroke ratio.
These long stroke ship engines must be a big factor in the 1000 miles per gallon per ton of fright.
I mean, you just described a torque monster... Ofc speed is irrelevant here.
I feel really good when someone walks in while I'm watching one if EE's videos. Don't get me wrong, I've learned a lot, but this is like getting caught reading about quantum mechanics, or reading the dictionary.
Someone walks in on you in the bathroom... while you are brushing your teeth.
Hilarious. You are right.
I have a problem, I enjoy reading the unabridged Oxford English Dictionary. All 25 volumes.
or like looking up the word dictionary in the dictionary
True, better than being observed watching some of the useless crap I end up staring up sometimes.
Great video!
In going with a longer stroke, I wish you mentioned stroke to rod ratio. This is the relationship between the stroke length and piston rods. The lower the rod ratio, the greater the side forces exerted by the pistons against the cylinder walls. At some point, some of your energy is extremes against cylinder walls instead of up and down motion which increases wear against the cylinder wall. With a short rod and long stroke when the crank is halfway between the bottom and top (9 o’clock or 3 o’clock positions) the angle of the rod will be pushing the piston up against the cylinder wall resulting in some efficiency lost compared to a longer rod with the same stroke.
Thats true.
I recommend You "The Workshop" YT channel.
Host name is Matt and He talks about mechanics. He knows all about engines.
He loves motorcycles, not cars, but dont worry, its worth watching.
Excuse my English.
This is why engines have different deck heights and also why some stroker kits recommend deck spacers.
boostedmaniac this is why offset rods are becoming more popular
@@h22bomb offset rods aren't new. Ford flatheads were designed with them along with many other engines.
A short rod to stoke ratio moves the point of peak piston speed to a higher point - closer to TDC. Having the point of peak piston speed closer to TDC means that the piston moves further during the combustion period and this reduces the thermal efficiency of the engine.
In building high performance engines i have used longer than standard rods and used pistons that feature a higher gudeon pin.
I have seen pistons that have the gudeon pin so high that it is no longer located below the oil scraper ring.
This is the explanation I've always wanted on creating power based on cylinder geometry. Seriously!
Thanks so much for filling in all the gaps in what I put together on my own.
I would have really appreciated being taught some of my engineering classes in this style of teaching. It seems so much easier and I am not even a native speaker in english, yet I still think I am understanding everything 😀
Der rappelt ohne pause, ungeschnitten
@@Beinhartwie1chopper And you think I understand German ? (I understand it better than I'd like to admit.. 8-)
Be proud knowing Trump Supporters understand this too.
@@benjurqunov
Your name says it all.
Unfortunately there is a large part of false logic to his theories. He is taking practical results and attributing them to assumptions. In a practical sense he is right, but his overall theory is largely speculation. And that is why internal-combustion piston engines rarely exceed 40% efficiency.
Thank you , that is an awesome explanation of the relationship of bore and stroke ratios, something I pondered for many years , keep up the great work, I enjoy your channel.
My 1986 Corvette uses a 1973 400 SBC block, its bored .030 to 4.155 and the engine is stroked to 3.875... 420 cubic inches. 6" Rods and a very short skirt forged piston from JE. 11.28:1 compression
are you running e85 ? 11.2 compressions seems pretty high for such an old design.
@@hojnikb no, the block has been decked and the head gasket is .039... it's the optimum squish area for a clean burn without detonation. No pinging with 93 octane.
Lets go a little further. The longer connecting rods mean the angles at which they connect to the crankshaft are greater which gives it more leverage making it take less energy to move the crankshaft on a longer stroke. This is why longer strokes generate more low end torque. I would love to see more detailed videos like these. I ran the car club at my technical college where I got my automotive degree. I share your videos with students all the time. Keep up the amazingly detailed videos.
Something to remember about this is that a longer stroke means the throws on the crankshaft of a longer stroke motor results in both a higher piston speed as well as more torque, which is why longer stroke motors tend to produce more torque but can't be revved as high rpm.
everyone sees that . but a bigger bore means more piston area for the charge to push on resulting in torque also . probably the reason why he dont mention it
What about the intake, compression and exhaust strokes? The long lever benefit is reversed.
@@MrRasZee that sounds like bs
I studied mechanical engineering years ago. I remember watching your lesson on strut and other suspension stuffs. They helped me a lot in my course works. Still following you until today. Terima Kasih, Tuan 👍
The original Camaro Z28 was, as I recall, a 327 Block using a 283 crankshaft, giving a high reving 302 cid engine. 6000 rpm was quite impressive in the late sixties.
Similarly, the Ford Hi-Po 289, with a 4” bore, 2.87” stroke made excellent power and could rev to 7,000 rpm. Sorry about the inch dimensions, metric is a foreign language to me.
In nascar the big blocks were holding near 8000 rpm. Remember that
@@codyparker679 True, but nowhere near being production engines. Big difference.
Similar chevy displacement engine, 305, with similar heads, intake, and breathing characteristics was nowhere near as good. Major difference was the inverse more to stroke ratio.
@@andystreets4660
The 302 had a huge bore suze advantage 4.0 inch vs. 3.74, and thus could breath far better.
I love the older V10 F1 engines, 3 litre capacity with a 10mm piston stroke and could hit 20,000rpm.
Those cars were around 1000bhp and made a noise like the angels singing😊😊
The flow and combustion thermodynamics of those engine were more similar to a turbine engine than a reciprocating engine. They did sound cool, though.
I was watching some vintage car exhibition on TV a long time ago and the had an old F1 car out there and they were talking to the head mechanic. He said you couldn't floor it until halfway through fourth gear or you'd lose control. They asked him how much horsepower it had: "I don't know. Our dyno only goes up to 1200."
More like deranged banshees to me
@@elroyfudbucker6806 I miss deranged babshees.
@@Bob5mith You mean the old V6 Turbo F1s of the 1980's? From the looks of it being driven, the drivers don't want to floor that thing at lower gears.
Jason:...so this design if more efficient right?
Me: right
Jason: WRONG
Me: oh ☹
Lol, I hate it when that happens.
Bro you got me dying right now because that's how I felt 😭 I swear God he should be advanced math college teacher I wish I could be as fast as him doing this math haha .
me be like aaaaaaaaa riiight
8:10
I know, I felt that too. :(
Nice comprehensive explanation which covers the variables and tradeoffs in an understandable way.
Grandma was right, even when it comes to engine design. The answer for most situations is not found in the extremes, it is found in moderation (something tweaked plus or minus from a "square" bore/stroke ratio depending on the goals sought for the engine.
I've always wondered why long stroked engines (used in old cars in ~ 1930's ) gave way to short stroked engines. Just seems to me short strokes waste away some energy left in the cylinders thru exhaust. I've heard longer stroke engines wear out faster?
A topic he seemed to overlook was longer stroke crankshafts produce more torque.
He did nicely but was brief on fuel combustion burn rate - important consideration in that it is same value for all designs he discusses. This is an extremely complicated subject! 🤯
Ray Bin; Complicated, yes. I would like to suggest that other important things about the development that make it possible but not mentioned are the development of better material and alloys, the development of better bearings and the better machines and machining to much better tolerances that make them possible, and the development on the petroleum side, of lubricants refined and fortified to take the tremendous loads put on the bearings when developing these extreme power outputs and advancements in petroleum engineering that produce incredible amounts of clean consistently high quality fuels at reasonable cost. (+ taxes that give us roads to burn it at 75mph hour after hour)
I am very pleased to see you younger people interested in these things that were a great part of my life as I grew up when Model Ts and Model As were daily use cars. I'm sure that if you look around you may find an older person chock full of information an all these things and he'd love to share it!
@Russell Gerdes r/woosh
@@slimsqde7397 So much r/whoosh. I'm honestly baffled.
When blueprinting you should have a goal in mind. That way you can build for the job that shes going to be doing.
A larger stroke requirea a larger diameter crankshaft
That means the crank shaft will be pulling the rod further sideways
Increasing wear on the cylinder walls
This be mitigated by going with much longer rods to reduce the angle of the rods
But since long bores already tall, thats hard to do.
I’ve had a bunch of different BMW’s over the years but my favorite was the E28 520i with 2.0 liter inline 6. It was a smooth as butter and sounded awesome. 80mm bore x 66mm stroke
The smoothness of BMW's inline 6 has nothing to with bore or stroke. An inline 6 has no primary nor secondary imbalances. The engine itself runs smooth naturally. When all internal parts are perfectly balanced in a straight six they can be one of the worlds best engines, look at Toyota's JZ and Nissan's RB engines for example.
What BMW did in the 80s and 90s was using heavy flywheels on the 6 cylinder engines as well. This adds another type of smoothness because a heavy flywheel increases smoothness in drivability (not the engine).
The 2.0 liter engine runs way smoother than its 2.5 liter brother.
I own both engines.
So your theories may overlook some facts.
I have learned more in this 15 minute video than my 2 years of college. :P
I hear you. College nowadays really seems to be a waste of money. Although it's still a necessary evil to get a good paying job.
@@jeff40 not at all. Trades don't require college, and pay more reliably and a lot of times more than traditional random college jobs.
Longer stroke also tends to lead to greater torque too. Love your videos!
Yes like the k20 compared with the k24 big difference in torque for just stroking the engine, but peak hp is similar cause you lose about 1000 rpm, not gonna notice that unless going above 7,000 rpm though
I gotta just take a moment to praise you for this unbelievably excellent presentation! You've clearly and thoroughly explained one of the most basic variables of ICE designs and made it completely understandable. Nearly all your videos simply mathematically complex auto engineering, but this video is the top of the list for (1) taking such a _universal_ ICE design principle and (2) so thoroughly described it for anyone with a basic understanding of math and a minimal understanding of physics, with no hand-waving needed. Simply brilliant!
(However, I was expecting you to define "over-square" and "under-square" because I can _never_ remember which is which... though, if you had defined them, I probably would still not have remembered which was which after the video was over).
this video is equivalent to 3 years of engineering classes .. so useful, very didactic , the best video about engines i have ever seen !
Problem: Big bore or big stroke?
Solution: Bore it...and stroke it.
you mean 1:1 , bore: stroke, it is the same as small bore: small stroke
LD9user yes sir that’s what we do in my camp. Although I have a sbc 400 and I kinda want to destroke it using a 350 crank and running domed pistons to up my compression and that’s a 377cid and they are a high revving bad to the bone race motor. I’ve done a couple 383 strokers but it would be a first to go the other direction. Can smaller be better? You bet it can, my 383 is a torque monster that eats big blocks for breakfast everyone always wants to argue that and well the performance of my C10 pickup speaks for itself.
@@larryheard3462 That's awesome. We were doing that back in the 70's before the 400 cranks were considered "strong enough" for performance use. One things for sure, the sky's the limit on rpms with the shorter 350 crank (as long as everything else up to the task). It's easy to keep piston speed under control and you can use a nice long connecting rod as well. :)
I don't want my stroking to be boring.
Find stock engine with longer stroke and then bore it up.
YES, HELL YES that's the kind of video I like to see, you answered a ton of questions I had. Thank you.
i wait several years for this video and is come to me in the rite moment (i wanna star to bild own 2 cyl flat ednige)
Yes I did, but what I found was like every internet research, full of people telling the truth and full of people telling the opposite. Moreover I didn't have the time to go and read research papers to have the true reason. In fact I knew why large bore could give more power but didn't know the details about valves sizes and stuff... Anyway I could have done more internet research but I would still not be able to understand all of this in 15minutes so please don't devaluate populazer's job here on YT.
I love this page, incredible wisdom, common sense and reasoned delivery. KUDOS Jason! TYTY!!!
As a former instructor (of Electrical Engineering) this guy is great. "Pull back the curtain" was a catch phrase in my classroom. Too often the instructor winds up down in some esoteric corner and students can't see the whole picture. Obviously there's a lot going on here....highly simplified...but after this presentation the typical (young) engineering student is ready for deeper concepts. Excellent! Now we're ready for "volumetric efficiency".....
Huh? Hard to believe you squeezed that into 15 min and I do appreciate the technical "no free lunch" break down.
And all the data on the white board just appeared magically. There was at least an hour of work to get that on the board and correct.
Really enjoyed this, I definitely appreciate the time it takes to make these kinds of videos
Ah yes, my favorite class in ME school. Good job and thanks for rekindling my roots, I'm stuck in software land (Silicon Valley) and gotta get out! Very good presentation.
EE very interesting! I’d love to see a comparison like this on Diesel engines like say 6.7 Cummins vs 6.7 Power stroke efficiency and like 8 slightly smaller pistons vs 6 slightly larger and such
Engines are generally more efficient with fewer cylinders for a given displacement because there is less total friction. Only past a certain cylinder bore can it become an issue due to excessively long distances for the flame to travel. Diesels are less affected by this than gasoline engines because of the different combustion (the flame doesn't need to travel the whole volume of the cylinder, as long as an adequate amount of oxygen is still present near the injector).
I played this video back at 1.25 times normal speed and smoke started coming out of my ears! Seriously though, great video, thank you.
The thing is, this is much better learning/teaching than it will ever be at my university. Why can't lecturers be this clear about the stuff instead of talking a lot while transmitting minimum amount of information.
I love the way you break down the concepts and always give multiple explanations on the given scenario!!! Do you offer a complete course? I would definitely be interested!!
Thanks for putting this on, I actually think about bore and stroke all the time. Wouldn't it be fun to have a machine shop where you could build any kind of engine you'd like just to see it run? Also, there are so many more things that could be included in this video it would put us all to sleep, now where's my calculator?
What was not talked about is rod length and how it affects the overall performance and combustion effeciency. Generally speaking a long rod length promotes a better combustion because the leverage of the rod keeps the piston at TDC longer as it sweeps over allowing to burn more fuel and air. And, some builders will claim a shorter rod creates more wear and tear because of the angularity of the rod and more scraping of the piston skirt on the walls of the cylinder. But, some also claim that initially, a shorter rod gives more leverage off the line.
I seen info that the ideal stroke to rod length ratio is 1.75. How true that actually is I'm not sure. Stan Wiess has a web site with data on rod ratios, bore and stroke etc. A Chevy 327 is 1.7538. A Buick V-6 or 300 SB is 1.7529. A lot of Hondas are around 1.5. The only engine I can find data on that is right at 1.75 is an AMC 232. There's another factor that enters into this. And that's deck height. Plus with a really small bore and long stroke you start running into clearance issues unless the bore is noted or the deck height gets really tall. Big bores raise another issue. Unless you siamese the cylinders the crank gets really long. A good example of the effect on deck height is the Boss 302 vs the 302 in the Z-28. Both 4" bore with a 3.0 stroke.
But the Chevy rod 5.700 while the Ford is 5.150. The rod to stoke ratios are 1.8968 vs 1.7166 respectively. The Ford could actually accommodate a longer rod by the use of a piston with the wrist pin higher in the piston. There are a large number of factors involved in the design of any engine. Longer rods, more reciprocating mass. Short deck height, smaller packaging. Plus on a OHV engine lower deck height, shorter pushrods*. Yes I know OHV is practically prehistoric technology. But ask yourself. Just how many drivers really make use of all the engine power they have any way
*Another way to shorten push rods is to make the rocker arms so the pushrod seat is below the pivot point of the rocker. Another way is to place the camshaft much higher in the block so that the lifters are pretty much even with the deck face. Renault actually built a 1.6 liter with this set-up. Very short pushrods, cross flow head and a hemispherical combustion chamber. I've often wondered just how a V-8 with 2 camshafts mounted high in the block would be like. I don't know if it's ever been done.
In fact, I don't speak much English and I don't have a vocabulary, but your way of explaining is wonderful, it made me understand honestly.. Esther brother ❤
Finally, i got an answer to my doubt which kept bugging me for years about the parameter which is actually held responsible for the Power of a vehicle. Thanks much for the clear explanation as usual...
I learned about this playing a computer game called Automation
Same here ✋
And now it's on my Steam wishlist
Cool, I'm gonna look that up
yep and not without BeamNG drive to test out your models
Phill Gizmo oh yeah I still need BeamNG but haven’t found the time to😢
0:59 Love that elaborate 💥
I was waiting years for this explanation!!! THANK YOU
This is the best explaination I have ever heard and it makes perfect sense the way you described it. I was told for years the best combination was a stroke that was 75% of the bore. Fully understand the need for a square motor. Thank you so much👍👍👍👍👍😁
The professor, a little better than my first teacher in automotive tech. My first year was all book, if all the machinery was available and you paid attention you could have built your own engine after that class from casting the block to machining the cam and carb of mechanical fuel injection. Unfortunately I've lost a good part of that class over the decades and it's coming back thru these videos, Thank You.
I would love to see a follow up video on the ideal conditions for power vs fuel efficiency.
Thank you.
Very interesting and very well explained!!
Unfortunately I can't do much more than liking, subscribing and commenting your video to support it!
Continue this quality content!! 🙏🙏🙏
When I first started my Mechanical Engineering studies to improve my Race Engine Building, my professor told the class it's physically IMPOSSIBLE for a car to accelerate from a standing start, and go 300 m.p.h. in 1320 feet.
I left the class and began my Engine Building career without my degree. Thank GOD.
If a professor actually said that, then you made the right choice man. 👍🏿
Most of the old farm tractors, IH-Farmall, Case, John Deere 270 "Johnny Pop" etc. all had long stroke and narrow bores; 2 to 1 or greater. Better for torque and lugging, pulling plows and slow driving. Very good presentation.
I'm a motorcycle mechanic so not trainedin engineering or engine design but I've done a lot of reading over the years. Doesn't connecting rod length have an effect on piston acceleration, side loading and when maximum torque is developed?( rpm)
Burn time is relatively fixed which is why ignition has an advance curve to start burn BTDC with maximum pressure somewhere around 14 degrees ATDC. Unless a manufacturer is designing a totally new engine, 'ordinary people' are looking for ways to maximise what they already have , bigger bore generally being the cheapest and easiest but with limitations on maximum bore size due to cylinder spacing. The largest overbore I've ever done was 14mm which actually utilised the oversize ports way better than the manufacturer (1970's designs, big ports, high cfm, low gas speed)
EE: A bunch of math
Me, an Automation intellectual: Yes.
Thank you for your efforts and your way to make complicated things sounding easier! :-D
I've always heard that small bore, long stroke engines are more efficient because they have more "time" (remember crank angle = time in an engine 😉) for the fuel to burn, giving more time to extract that useful energy
And the rod to crank angle makes better torque.
@@mikerammelt2420 Yes, I seem to recall that historically, British manufacturers like Jaguar and Aston Martin utilised "long" engines (long stroke / smaller bore) and this proved successful at endurance racing like Le Mans 24 because the greater torque available and, consequently, fewer gear changes. Most continental European manufacturers focused on "square" engines.
And rod length, it puts more dwell and has a better rod angle
One of the interesting things I did many years ago, which more applies to steam engines at low RPM than internal combustion engines is calculate the difference stroke and bore make on torque output. The answer is none at all. But that does assume that your valve gear can get as much steam or combustion mixture in as needed which is easy to do on a steam engine but harder on a IC engine. It also ignores the effect of drag of the piston in the bore which will have an odd relationship.
You could say that (for a piston engine) power depends on a combination of Brake mean effective pressure (BMEP) and revolutions per minute (RPM). You could also say that power is proportional to the amount of air that the engine consumes.
EE: "Well, the math on this is simple enough".
ME: laughs nervously "Ah, yes, yes, of course, very simple".
💀💀😂🤣
The arithmetic here is actually very simple, not much beyond about 8th grade or so. The tougher part is understanding how its application determines hp, torque, etc. That's where the Engineering part comes in.
@@cactuscanuck6802ME: keeps on laughing nervously "yes, I was only joking"
So you're asking the question every guy wants to know. What's better, length or width? LMAO😂
Both, bore and stroke. That's what the girl's tell me. No replacement for displacement. Lol
Length. Because you can easily change width. Oot but I hope this will help.
The main problem is that their cylinders vary... Not to mention how lightweight(usually brittle material, even if they are selflubricated, if somewhat used, not hundred thousand miles used old ones, can tear and the walls can start to leak) their cyl.are.. so the piston can be too big too
@@marcalampi5036 😅🤣🤣😂
circumcised men loose compression
A wide bore will also cause a greater leakage between piston and cylinder.
Which will be offset by the hp gains.
Thanks!
Thanks for your explanation, very nice. I have been a mechanic for years and years and the 'best' engines I have come across all seem to be 'square' they seem to have the best combination of power, torque, smooth running and reliability. Look at BMW, 2 litre 4 cyl, 3l 6 cyl, 4 litre 8 cyl, all square engines with the advantage they only need to make one size piston for all of them.
When i worked construction the guys always called me a shortstroker
🤣
Don't get it........
@@incognitohuman1959 derogatory, for somebody coming up short ( in more than one way). Construction workers crude talk...
@@Beinhartwie1chopper aah bully. That sucks. I feel you sir
for coming up short, it's more correct than you realise, because diesel is more prevalent than petrol in the construction industry (source: I'm a crane operator and I've yet to see a petrol-powered crane, they're all diesels, and the 'capacty vs recharge' issue around electric is why I don't think they'll ever catch on for construction.) Diesel, tends for a higher-compression, so it'll have a longer stroke to bore. And since everything in construction is diesel, it means everything is a longstroke. and so being called a shortstroker, is basically saying you're stalling on the job.
Also doubles for applications where the torque is really needed rather than horse power but you bring a 'petrol' to do the job. It aint gonna cut it mate.
Why 25 m/s? Is it to do with mechanical stresses due to the acceleration and deceleration of the piston and con rod or is it to do with flame front combustion limitations?
Here's why according to Wiki: "Piston velocity is a test of the strength of the piston and connecting rod subassembly. The alloy used to make the piston itself is what determines the maximum velocity that the piston can reach before friction coefficients, heat levels and reciprocating stress overcome the maximum levels that the piston can sustain before it begins to fail structurally. As the alloy tends to be fairly consistent across most manufacturers, the maximum velocity of the piston at a given rpm is determined by the length of the stroke, that is, the radius of the journal of the crankshaft." en.wikipedia.org/wiki/Mean_piston_speed
Engineering Explained awesome! Thanks!
Ah! Girth or Length??? The age old question.... How fast you can bang the hammer also has an affect! 🤣
Less stroke makes banging that hammer reach new limits! So long as the displacement is adequate tho the job should get done with perseverance
As Jason said, if you want a high frequency, you gotta decrease the stroke.
25m/s max you say, I like the challenge
What’s going on here 😂
Short and fat is where it's at? Or was it long and thin will always win? 🤔
Professor! Your lessons are top notch! Frankly, I don't know how you do it, without taking a breath!
Holding focus and track to your explainations are so much less of a drag than any of my dried out teachers. I wish I rather had you in front of my class room :D
Hey! Love your videos. In regards to small bore, long stroke engines, do you think it would be possible/beneficial to have a single VERY large valve in the combustion chamber to allow for more airflow (or have multiple valves that all open at the same time), and have separate valves in the intake/exhaust manifolds (or somewhere close to the combustion chamber) to determine air flow direction?
"So this is the most efficient, right? WRONG."
You almost had me there!
Its so good to see Metric being used!
And then he translates it to imperial/american... 8-(
8-)
Stuff I had a general idea of all my life and now you quenched my thirst on this topic with a fire hydrant. Fascinating!
As someone who wants to build a two-stroke opposed piston diesel enginge, I find this really helpful. Thanks a lot
This was very insightful on various fronts.
But what if you had a wide bore and two or more spark plugs?
An xD meme *4 SPARK PLUGS*
I've learned so much from you over the years! I would love to see a video on what the perfect engine size for a caterham kit car to use on the road and track without having to change your underwear every time it goes on the road - especially in the wet. The variables would be traction in dry and wet, hp, weight, acceleration. Cheers Jason!
That's easy: As much power as possible and a contract with a diaper company!
A 4 cylinder with about 200-250 hp would probably be just right. That way it’d have enough power to be fun, but still be easy to manage in the wet.
@@NBSV1 A 260hp R500 Superlight is ridiculously fast already though
I remember when I was a teen and begin to interest about engines, my older brother (RIP) told me the simple formula:
"If You want torque, get stroke. If You want Horsepower, go for bore. If You want both, You need displacement. Displacement is only to replace by more displacement." That was in the early 80's.
Then came the turbos - and displacement was no longer irreplaceable.
The magic word is called "boost". ;)
But now you have another decision, large single turbos give more horsepower up top, but large positive displacement superchargers give more down low.
From idle, a turbo does stuff all, but as you rev it up you get increasingly more and more of power boost.
Where as positive displacement superchargers take the existing dyno graph, don't change the shape at all, but just shift it up higher. For example +20% over the entire rpm range, or +30% only in the top quarter.
Modern factory turbo engines though are often balanced to favour mid-range, with smaller turbos that spool faster or sometimes multiple turbos to balance out the whole rev range.
wow im a studend in a medical high school and you are inspiring me to pursue car education in the future, your videos are great
07:14 "Okay, so now that we understand power, let's talk efficiency"
Me: "More power!"
MO POWAH BABEH
Nissan/Infiniti: hold my variable compression ratio engine a sec...
James Haulenbeek apparently it’s pretty good in the new altima SR
Saurabh Kulkarni I wonder how long it will last.
You know that variable compression ratio has nothing to do with stroke right?
@@BigUriel uhhhh... you do know how internal combustion engines work, right? That's how they change the compression ratio.
@@BigUriel there is a video about variable compression engines. It is all about the stroke.
So what you're saying is, there's no replacement for displacement.
Sure there is. It's called BOOST!
@@lenpolidori3568thesis: displacement
Antithesis: boost
Synthesis: turbo big blocks
@@lenpolidori3568 yeah until you boost something with a larger displacement.
And if u ask Koenigsegg,: it's all about advanced engineering: displacement, light weight, electric power, highly specified timing, ethanol, boost (why only have one turbo when u can have many even on a 3 cylinder I3, u could complicate even more with 6 turbos)...
Went to UTI in 2009, just got this eye-opening mesning today as well as compression ratio, this is 2021!
This guy just makes everyone enjoy listening and easy to understand all the complicated stuff. Really enjoy this guy explain things.
Just a quick question: I have not come across any information, video or anything that explains as to why a piston has to be round and if it was ever tried to be in a square or other shape.
So if I increase my stroke my max rpm lowers?
Pretty much
Technically yes but there a many other variables. Your engines max rev is based on obviously what's been highlighted in this video but also takes into consideration internal balance, rod/rod bolt material, and valve spring strength.
@@jc0326 accurate but that's more advanced stuff like rod size width spring stiffness lifters rockers and stuff like that but in a nutshell you will get more torque out of a bigger stroke that's why diesels usually have a bigger stroke and are usually high capacity engines
Yes and no.
Yes if all you change is the stroke your engine will roll over sooner. You will reach the flow limits sooner, lower rpm.
No in that material red line is typically not the red line in most engines use today. The typical red line used is just after the peak power roll over.
In most application you wont hit the physical limitations of piston speed. You will almost certainly be limited ultimately by flow and where the engine rolls over on the power curve. Even with a 4.5" (114mm) stroke you could build an engine to hold at 6700, for drag racing or street type stuff you could build it to safely handle well past that for brief stints. That 25m/s or about 4900f/s is for holding revs that high for a fair amount of time. That is why you see long stroke dyno queens blowing way past limit, they don't hold it long for heat to weaken the parts to point of failure.
getting weird looks from my girlfriend like 20 seconds in
It's weird till her car won't start.
This guy teaches a lot more useful information than the school system, so it’s not weird imo.
She may wish to try out the stroking and boring...
I watch these things in the privacy of my man cave.
The talk of boring and stroking is soaking her panties and she wants you to bore and stroke her guts! Go get her homie! 😁
Wider bore = more power
Longer stroke = more torque
Lower RPM means the motor you spent the last year building will last years longer.
c- man Not necessarily; longer stroke can have more pressure on the side walls of the cylinder, and also much more stress on internals. Piston speed increases as well.
@@dr.lyleevans6915 low rpm long stroke engine are reliable or not?
... with longer rod, put rod ratio back, same side force.
Two lines, and you've explained this whole vid. 👍🏻
I just wanna say. That even though I'm not math whiz(i leave all that stuff to you..lol), I find your analytical explanations FASCINATING!!! Idk how many "nerdy" motor heads there are out there watching this stuff, but you explain it in a way the more advanced thinker can still comprehend. Now, knowing this stuff is not for the faint of mental comprehension, I'm sure it's much to chew on for many.. Lol but I LOVE IT. and I've learned quite a bit from the science of it all you explain so well. And I want to thank you for doing all the hard work of breaking it down. This is what I love about your channel and thank you for being a top "educator of the masses", in my book. 😀
I set out to optimize a small motorcycle engine. I stroked it to a 13-1 compression ratio and used a cam modeled after an RV motorhome. It left the intake valve open just long enough to lower the ratio to about 10-1, giving me the advantage of the longer stroke, being able to run on pump gas and being easier to start with a nice idle thrown in, to boot.
Awesome video I've often wondered this exact thing!
I learned a lot! Thank you. Now if you could only find a way to make me remember it.
Become an engineer like him then... 😀
@Charl Jacobs This comment brought me back here and as predicted I cant remember a thing he said. Oh well.
Unless you're racing, having max power at the expense of torque will have you shifting more frequently instead of being able to cruise up & down hills!
Truly one of the greatest videos of all time ... Excellent work.
A man who truly understands what he says can explain it simply so everyone understands it