Bore vs Stroke - What Makes More Power?
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- Опубликовано: 20 май 2024
- What Makes An Engine Better? Big Bore vs Long Stroke
Bore and stroke cause differences in both power and efficiency.
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All piston-cylinder internal combustion engines have a choice to make with regards to bore and stroke. Should an engine have a large bore (the width of the cylinder)? Or would it be beneficial to instead have a small bore and a long stroke? Or should the bore and stroke dimensions of the engine be identical? We'll discuss how bore & stroke affect engine RPM, engine airflow, heat losses with regards to surface area, and flame duration. What makes the most power may not always be the most efficient.
With regards to bore and stroke, an engine is called "oversquare" if the bore is longer than the stroke, "square" if the bore and stroke are identical, and "undersquare" if the stroke is longer than the bore.
SAE - A Study Isolating the Effect of Bore-to-Stroke Ratio on Gasoline Engine Combustion Chamber Development
www.sae.org/publications/tech...
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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
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.
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
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
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
"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
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
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
I love these videos with a host who is actually educates on the subject and can illustrate the information. Thank you Engineering Explained
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.
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.
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)
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?
@@blakemcdowell4146higher 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.
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 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 ^^
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. :(
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.
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.
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.
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.
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 👍
I love this page, incredible wisdom, common sense and reasoned delivery. KUDOS Jason! TYTY!!!
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.
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.
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 was waiting years for this explanation!!! THANK YOU
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.
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.
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.
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.
Really enjoyed this, I definitely appreciate the time it takes to make these kinds of videos
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 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).
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.
0:59 Love that elaborate 💥
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!! 🙏🙏🙏
Thank you for your efforts and your way to make complicated things sounding easier! :-D
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!!
I would love to see a follow up video on the ideal conditions for power vs fuel efficiency.
Thank you.
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.
Stuff I had a general idea of all my life and now you quenched my thirst on this topic with a fire hydrant. Fascinating!
this video is equivalent to 3 years of engineering classes .. so useful, very didactic , the best video about engines i have ever seen !
I love your chanel, but as an european engineer the imperial units always give me a headache when I want to follow the calculations. So I appreciate the videos with only metric. Thank you.
he actually used metric units in this video, execpt for horespower
@@96tankist In fact, he said he appreciates these videos. And Horsepower is commonly used in Europe except for schools and legal documents, but don't ask me why.
Because it's not an SI unit, we use kilowatts for everything official.
@@User-th6yy I meant I don't know why we use horsepower, not why we use kilowatts...
This was very insightful on various fronts.
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".....
You are absolutely incredible in the clarity of your explanations. I'm not a science student but I'm definitely in love with science stuff. You make it so easy for me to understand all this cool stuff. I want you to be my teacher forever (I wanna be your student forever). Keep up the great work 👍🏾
Awesome video I've often wondered this exact thing!
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
First video I've had an issue with. Valve area covered but not Duration. Keep the awesome videos coming.
Was actually looking for the difference between 2 engines and you answered all of my questions and even more cheers for that!
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 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😢
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👍👍👍👍👍😁
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.
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?
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.
Professor! Your lessons are top notch! Frankly, I don't know how you do it, without taking a breath!
Truly one of the greatest videos of all time ... Excellent work.
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).
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.
Really appreciate the data and details!! ...good job! 😊
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...
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?
A wide bore will also cause a greater leakage between piston and cylinder.
Which will be offset by the hp gains.
Extremely well explained and illustrated.
Went to UTI in 2009, just got this eye-opening mesning today as well as compression ratio, this is 2021!
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
Thanks for another great vid ! You have a great way of explaining things.
That was a hell of an explanation bud. Thank you!
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
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.
Excellent vid. All understandable engineering presented with no BS drama. Thanks
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.
Its so good to see Metric being used!
And then he translates it to imperial/american... 8-(
8-)
Metric all over the board, so satisfying!
Indeed !
I'll second that comment.
Fernando Sousa Communist units...
Well, he did actually use imperial measurements for power and torque, but still, I agree with the general sentiment!
Hurrdurrrrrr muh metric durr
Man it's wild how smart you are. Awesome explanation man I learned a lot.
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.
EE: A bunch of math
Me, an Automation intellectual: Yes.
I'm literally never going to loose an engine argument watching your channel!! Glued from start to finish
Thanks for watching! :)
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 ❤
Very informative, more than I could take in on “one” watching. Thanks for the lesson.
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. 👍🏿
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!
Literally engineering! Keep these awesome contents coming. More power!
great explanation .. Thank You for sharing
6:30 @Engineering Explained: First off, I really enjoyed this video! I have one question: Since the area for airflow is increasing by around 35% from one example to the next (moving up to the larger bore sizes), whereas moving in the opposite direction (toward the longer stroke lengths) increases the potential duration of the intake and exhaust strokes by around 83% (assuming a constant piston speed as shown in your example), does the fact that the piston has a longer time available for each stroke compensate for the reduced area for airflow? Thanks so much, and keep up the great work!
Very instructive and understandable ! Your a good teacher !
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.
Thank you for explaining all these things
I already know this one's gonna be good!
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
It was an excellent explanation based on simple (pure and accurate) comparison between 3 possible bore/stroke states. wow!!! To keep this video and share as much as I can.
Your tutorial are brilliant thankyou
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)...
Great stuff, Jason. Maybe soon you'll do a vid on a question I asked long ago: How do engine designers tweak the torque curve of their designs?
Is this not done with software, the shape of the pistons, cylinders, camshaft, ignition timing and maybe even the timing when they inject fuel?
I'm not an expert tho so maybe i'm totally wrong :P
- cam timing and lift
- intake lenght/volume
- ignition timing + afr
I had been of the short stroke wide bore theory was the best choice in a competition engine. I look at pro/stock and formula 1 engines as a benchmark of sorts with I am a huge fan, and how you explain the physics. Keep the videos coming and I'll be watching. Cheers!
Thank you for educating on Bore and stroke of Engine. I am owner of Royal Enfield 650 Interceptor as well as Honda fuel efficient bike. Now i understand why there is difference in performance technically.