Bore vs Stroke: Which One is Better?
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- เผยแพร่เมื่อ 13 มิ.ย. 2024
- Article: dustrunnersauto.com/bore-vs-s...
If you were for example engineering an engine designed for race use, it would more sense to use a large bore and short stroke so you could more easily increase the RPM limit to increase power.
If you were engineering an engine designed for a truck, it might make more sense to use a large stroke to increase power while having a low RPM limit, since you wouldn't want a truck to be revving to the moon while towing.
If you were engineering an engine for simple commuter, somewhere inbetween would make the most sense, since you would have acceptable power at low and high RPM.
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As a retired Dodge dealer mechanic w all 8 ASE tests (master technician) advanced level engine diadnostics and a machinest test for engine assembly I found this video very interesting and informative. And it explains things in laymen's terms so everyone can understand. Around 2006 I bought an 88 turbo LeBaron conv with an auto trans and 2.2 L turbo 1 engine. It ran good but my goal was to make it a mid 14 sec car. I don't remember the bore which was the same in the 2.2 and 2.5 engine. It was approx 3.5. the 2.2 had a 3.6 inch stroke and the 2.5 had a 4.09 inch stroke. I met my goal with a 14.1 ET at 97.3 MPH. I embaressed a lot of V8 cars. After watching the video I can't believe the engine shifted at 6000 RPM. With a 4.09 in stroke. And nothing broke. The 80s Mopar 4 cylinders were bulletproof. Also the 2.2 and 2.5 was designed by the same person who made the famous slant 6. From 1984 to 2013 I only saw only one 2.5 come apart and was due to driving it with NO OIL (had a hole in the oil pan). I still have a hard time believing an over 4 inch stroke could hit 6000R PM!! The only weak spot was the head gaskets on the turbo engines. And those motors were so easy to work on, a head gasket could be replaced in 3 hours or less. These motors are in my opinion were the best domestic 4 cyls, just like a small block Chevy was the best. And don't forget the origional Ford 302.
1:43 this is in US measurements. In metric system, is different.
●INTERNATIONAL:
▪P=Power in Kilowatt (kW)
▪M=Torque in Newton-metre (Nm)
▪N=Crankshaft speed per Minute (rpm)
■Definition: P=(M×N)/9550
●TECHNICAL METRIC:
▪P=Power in Horsepower (HP)
▪M=Torque in Kilogram-metre (kgm)
▪N=Crankshaft speed per Minute (rpm)
■Definition: P=(M×N)/716
Thanks for explaining Bore vs Stroke, as I never understood HP vs Torque till now lol.
Ya ya sis masi ya wan aku I have to be ready for the trat ttcareful to try done with ready stok so you guys are going out ready careful to the other side done with this ready stok tiada ready stok so you guys are
Big hp n torque = fast
@@falahsamisyahdan7962 More like.
HP (or other measurements like bhp, kw) = speed
Torque= strength/pulling power.
@@madcat4563hp= maximum work that can be done
Torque= how fast that work can be done or the ability to get work done
I don't want to bore anyone but the gearbox also plays a relevant role. AUTO, MANUAL or CVT in the stroke/bore ratio. Sheers from Sydney, Australia ( Planet Earth )
Damn, great video. Simple and straight forward explaination.
My wife of 25 years now has a large bore... 😟 in BOTH cylinders. 😢
Compression is WAY down today also... The number one hole is shot, there's nothing left. The number 2 hole still has some PSI, but that one doesn't fire very often. It's a shame... 😦
Hi DRA, recently subscribed to your channel cause I love how you do your videos! I was wondering if you would consider doing videos going over various transmissions and transaxles? I would love to see you go over them in as much detail as you do with the engines.
Thanks , good content
Very nice video
There must be more to the explanation behind more stroke-> more torque, because if displacement remains constant, the longer stroke engine also has a smaller bore, with a proportionally smaller piston surface area, which means less force. If the pressure inside the cyilinder is the same, you would end with the same torque either with a big bore-short stroke engine and a small bore-long stroke engine. It is true that big bore-short stroke engines can rev up much higher, which make them suitable for sports cars, and small bore-long stroke engines are more efficient, so there's that.
Great info.
Well done
That was informative. I like you included so much engineering aspects that influence engine design.
Will u talk about the Mercedes F1 engine and the honda v6 f1 engine i think there both 1.6L v6
Do a video on the Toyota u engines, preferably the 4u gse
Steve from Annapolis that is explaining bore and stroke speak text sometimes gets it wrong keep up the good work
Here's a Q - what is done differently for two engines with identical bore and stroke, where one has more torque, and other has more hp? Example: the 1970 Ford 429cu.in. The Thunderjet had 360hp and 480 ft/lb of torque. But the Super Cobra Jet had 375 hp but 450 ft/lb of torque (and at a higher rpm). It seems like the things you do to increase hp would also increase torque, or at least not decrease it. Maybe we chalk it up to Ford lying about the output of the SCJ. Pretty sure they underrated the hp of the SCJ, but manufacturers in those days didn't seem to also underrate torque.
What if u use custom pistons where the pin sits higher and pistons are shorter. U can use longer rods with the same stroke and bore and reduce angel of the conrod.
I'm wondering whether or not to de-stroke a Subaru ej257 from 79mm to 75mm it's turbocharged and I'm thinking it will be much more dependable... Decisions..🙄
what if i converted an 848cc Reliant motors I4 into a short stroke from a long stroke. These engine don't like high rpms but are very light and low on capacity.
And even though it has a long stroke it still handles high rpms well which makes me wonder if a Reliant engine could rev up to 10k rpm after the conversion.
You forgot to mention one thing,
Piston dell time after Sparks Ignition to and overlap Camshaft degree..
About poor or not when combustion occur in long stroke or big bor, it's depen on how you set up the Camshaft duration, lsa, overlap, when to open and when to close, it's affect how your combustion do, even long stroke can be not properly combust if cam is to big or overlap is to big, or can be Camshaft lift is to high that can cause so many air and gasoline flow to the engine and cause not all the gasoline was but properly.
One question about oversquare engine . How about large stroke but we used a short connecting rod . Like example
motorcyle A
Stroke 56mm
Bore 53mm
Then we up stroke 2mm up
Then stroke must be 4mm because TDC 2mm ( up ) and BDC 2mm (down) and total motorcyle A is 60mm stroke . Distance BDC to TDC is long right ? But if we used a short rod like standrt motorcyle A is 96 large and we change use 94 large rod . How about distance from BDC to TDC or TDC to BDC its still large and take a time to full compress engine ?? Can u explain ? Tq sir
For economy stroke is usually more important. For performance bore us usually more important
Insightful video, "alright boys" intro nearly made me skip it though.
If an engine have long stroke it will have a small piston. A small piston will create a smaller force on the crank so it loose the same amount of torque ending up equal.
Fooking brilliant! Thank you for this simple enough but thorough preso ;)
This was excellent. You only missed the definitions of oversquare and undersquare. You only talked about square (without defining it either I think).
The correct ratio is a Stroke of genius.
You can increase fuel efficiency with a big bore cylinder by adding compression say like a domed piston but it will also affect the fuel intake a little
Do you also need to change your cylinder head if you put in a domed/hemi piston? Also is hemi and dome piston the same?
@@DeezyNut changing the cylinder head is not necessary but be sure to test the gap to prevent the piston and the valvels from knocking on each other
ok listen up
with flat piston, actualy it's also the same as piston like domed piston, just play in intake valve in and close, just set valve close around 45 to 40 degree after bottom dead center to close the valve, and walla get that dynamic compression more higher without changging to domed piston
You are amazing
How you calculate displacement blew my mind.
I always wondered how they calculated the sizes.
This video was very insightsful and helped me understand bore and stroke better.
So for a (NA) Diesel 4wd it would be better to have a longer stroke to get better pulling power.
Diesel engines also rev a lot lower than petrol so you sidestep a lot of the pitfalls a petrol experiences with a longer stroke. (at least that is my understanding of it)
Great video! Thanks for the info. Question, I’m getting a 2022 Suzuki GSX-S750, ships any day 😁. Anyways is the engine a big bore short stroke? I had a 2016 Suzuki GSX-S1000 and it definitely had a big bore long stroke engine. These are naked street bikes, the power ban is lower than a conventional crotch rocket super sport bike which has its power at the top. the crossplane engine, was on my last bike 2021 R1, it was to dam fast around here for me power everywhere. I’m near the 🐉Tail of the Dragon 🐉 318 turns in 11.6 miles no side roads
I was a car bro until I turn 28 years old and finally bought a motorcycle the best decision I ever made, recently I went back to try cars and got a 2018 Ford focus ST, traded it for a 2019 Ford fiesta ST and then realized bikes are so much more fun and sold that fiesta
what if you where to bore AND stroke
You left out the constant .7854 when calculating displacement. Example 4x4x3x.7842=37.7x(#cylinders).
My 302 has a pretty wide bore compared to its stroke, does that give it high rpm potential?
yes..
Tractor engine. Limited rpm to 2500 up draft carb, big bore or big stoke I like idea of 4.5 stroke and 4.60 bore.
Is there a ratio of bore vrs. stroke which yields a most efficient combustion process - gas or diesel - regardless of total displacement?
it's typically near 1:1, because that shape has the minimum surface area/volume ratio. The smaller the surface area the less heat is lost.
Thanks James, the reason I ask was that I'm old and remember and used to read the Nebraska Tractor Test results, seems that the John Deere 2 cylinder diesels had the highest rating in the Horse power-hours-per gallon of fuel. I guess this was a measurement these guys made to determine efficient conversion of fuel to power. This engine JD used had a relative long stroke. I would like to see current automobile engines connected to a dyno and rated in a similar fashion.
@@jeffsnider3588 OEM advertised power ratings are done with a standard test so results will be directly comparable. Often long stroke engines have good fuel economy figures for lower power ratings because the smaller combustion chamber has smaller ports which increases port flow speed, creating better tumble of swirl, better mixing, better flame propagation and lastly better in cylinder pressure. The problem is they begin to run out of power around 30 - 40 bhp/litre. Whereas a square bore stroke will make 40-70bhp/litre.
How come the S54 is undersquared and rev, but the S62 is actually oversquared and torquey?
1:33 that was redundant redundant, as RPM stands for revolutions per minute.
Which engine has more life span ?
undersquare or long stroke can be cooled faster and have low rpm its more reliable and longer life span
Can you stroke a motor that’s been bored?
Yes
What is beter? Both at the same time of course! ;)
@ 9:56 Harlry Davidson did change , They have come out with an E-bike , It's really quite Funny .
Unfortunately it’s terrible compared to other e-bikes and more expensive.
@@Dustrunnersauto Hi there
I have a question lets say my car has a 1.6 L engine and a 81mm bore
If I just make the bore bigger to roughly 86mm will I gain power?
E-cars and E-bikes are for bitches!
Stroke
Steve from Annapolis excellent for being a young man explaining about engines or in stroke and I can understand you you speak English
Bigger the bore = higher potential rev limit and can mean more power.
Longer the stroke = more TQ due to the engine being able to use more of the combustion energy. Tq in a engine is how efficient it is. Power is just tq over time.
I thought I would write in a bit of information that you are probably uninformed about. Harley Davidson, during the '30s and '40s made a water cooled 101 cubic inch Knucklehead engine for the makers of a 3 wheeled racing car. I cannot, for the life of me remember which manufacturer it was, though. Morgan and Hispano Suiza come to mind, but there were others as well. I was always hoping to run across one of them, even as a fused hunk of mangled remains, to somehow, some day... Well, you know the rest. In trying to explain these principles to those eager boys who hung around the shop, I sometimes spent more time drawings diagrams and the like until the boss made them leave. Thanks for helping with the explanations.
Also to be considered is fuel mileage. A long stroke engine will deliver better fuel mileage.
Then there is the connecting rod to stroke ratio.
I rather choose long stroke for my family. Short stroke is for a man without family waiting to go home.lol
I'll take bore ANY day over stroke... those small bore, long stroke engines just have too hard of a time breathing to make big power
9:56 Harley-Davidson have the new Pan America which shows that they're finally taking new tech seriously and trying to sell modern bikes instead of being stuck on trying to cater to a generation that is literally dying off.
Electric bikes and cars are for bitches!!! The only thing dying off is a mans soul
HD came out with the water-cooled engine with the Vrod back in 1999. I think they made them for about 20 years. Not all Harleys are air-cooled torque monsters. LOL
What about the girls that watch this? ;)
Gasoline does not explode, it burns.
not when it is compressed
@@jackhanson1065 interesting. What is the speed at which it changes from a burn to an explosion
@@davidreed6070 speed? Do you mean pressure?
Gasoline burns, the more you compress it the faster it burns, but it doesn't explode. If you put dynamite in your engine and lite it off, that would be an explosion. But you would not have an engine anymore. When you build a higher compression engine you slow down the timing because the burn rate is faster.
@@davidreed6070 interesting. Can you please define an explosion vs a fire then? how do you know at what point a "fast burn" becomes an explosion?
Can you please talk a little faster, I found this to be boring (NOT)!