Bore, Stroke?
- Thread starter TsLeng
- 16 comments
- 787 views
- 1,695
Ok, do you know what bore and stroke are?
Here is my quick run down:
Bore is the width or diameter of the cylinder chamber which the piston moves up and down in.
Stroke is the distance the piston moves up and down, from the top of the highest position in the chamber to the lowest.
Large bore draws in more air as the piston moves down and Bore is generally no bigger than 4.00 inches, any more and the engine cant bring in enough air to fill up that fast.
Small bore takes in less air and doesn't require high breathing heads to feed the engine and iis used on fuel economic engines usually because when the cylinder fires, everything is closer together and burns more efficiently.
A long stroke gives more torque in low and mid range because the whole piston counter weight dips lower and has more leverage or twist. however, it cannot rev as high because there is more weight being swung around on each revolution per minute or RPM.
A short stroke can rev higher but doesn't have as much torque for the opposite reasons that a long stroke engine HAS torque.
A long stroke engine also doesnt react as fast or gain and drop revs as fast as a short stroker engine when for instance the throttle is blipped.
Examples: A Honda S2000 has a short stroke and wide bore, so it can rev high but it doesnt have much torque and it has high breathing heads.
My Jaguar has a long stroke and a very large bore as well. It has enormous low end torque, but can only rev to 5,500rpm. It also has a big bore as well because every dimension has to be big on a 4.0L Inline 6. it also has Double Over Head Cams so it can bring in alot of air easily.
I can go into alot more detail, but just ask if you want to know more.
Here is my quick run down:
Bore is the width or diameter of the cylinder chamber which the piston moves up and down in.
Stroke is the distance the piston moves up and down, from the top of the highest position in the chamber to the lowest.
Large bore draws in more air as the piston moves down and Bore is generally no bigger than 4.00 inches, any more and the engine cant bring in enough air to fill up that fast.
Small bore takes in less air and doesn't require high breathing heads to feed the engine and iis used on fuel economic engines usually because when the cylinder fires, everything is closer together and burns more efficiently.
A long stroke gives more torque in low and mid range because the whole piston counter weight dips lower and has more leverage or twist. however, it cannot rev as high because there is more weight being swung around on each revolution per minute or RPM.
A short stroke can rev higher but doesn't have as much torque for the opposite reasons that a long stroke engine HAS torque.
A long stroke engine also doesnt react as fast or gain and drop revs as fast as a short stroker engine when for instance the throttle is blipped.
Examples: A Honda S2000 has a short stroke and wide bore, so it can rev high but it doesnt have much torque and it has high breathing heads.
My Jaguar has a long stroke and a very large bore as well. It has enormous low end torque, but can only rev to 5,500rpm. It also has a big bore as well because every dimension has to be big on a 4.0L Inline 6. it also has Double Over Head Cams so it can bring in alot of air easily.
I can go into alot more detail, but just ask if you want to know more.
GilesGuthrie
Staff Emeritus
- 11,038
- Edinburgh, UK
- CMDRTheDarkLord
12 Sec, that's a good explanation. How about a fuller one, posted in the Car Physics thread?
- 1,695
What specific info are you interested in GG? There isn't much more to say really.
- 1,695
Hey, just for ****s and giggles my brother took his 1988 Mustang LX 5.0 (302ci) and got it stroked out to 5.7 (347ci). Thus he has more torque throughout the RPM band and more hp on top of the torque. Basically he justed kept his power band in the same spots but just increased all of them. I am not sure if his engine is not able to rev as high now?
GilesGuthrie
Staff Emeritus
- 11,038
- Edinburgh, UK
- CMDRTheDarkLord
Well it was just the way you said you could go into more detail. I already had a reasonable idea of the issues involved, and thought it was a good article, ripe for inclusion into the Car Physics compendium.
- 1,695
Are you taunting me?
Deisels do have a long stroke; my uncles Dodge Ram with the cummins deisel I6 has 465lb-ft and 245hp due to its 3,300rpm redline!
- 1,695
Hey read some of my other articles. I have about 5 or 6 on here.
- 1,695
Deisels may be reliable, but they aren't any fun to drive. My ex-girlfriend drove a VW Golf TDI with a 1.9L Turbo deisel with 90hp. It was VERY uneventful.
