Bore/stroke ratio & volume efficiency & torque curve shape
Bore/stroke ratio & volume efficiency & torque curve shape
(OP)
Hello,
If we keep the same valve diagrams, does the bore/stroke ratio have any influence on the torque curve shape or the volume efficiency especially at low revs ?
Regards
If we keep the same valve diagrams, does the bore/stroke ratio have any influence on the torque curve shape or the volume efficiency especially at low revs ?
Regards





RE: Bore/stroke ratio & volume efficiency & torque curve shape
Regards
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RE: Bore/stroke ratio & volume efficiency & torque curve shape
The VE is affected by the bore as Pat stated above
RE: Bore/stroke ratio & volume efficiency & torque curve shape
Please explain why longer stroke/smaller bore produces more low speed torque.
I think this is a myth. Within reasonable limits the torque output of an engine should be related to many factors other than bore/stroke ratio.
RE: Bore/stroke ratio & volume efficiency & torque curve shape
If this is a myth, all the manufactures of vehicles, tractors, lawn mowers, aircraft etc have been terribly wrong all these years.
Now if by low speed you mean a drag engine, where low end is 6000 rpm plus then that is another story.
RE: Bore/stroke ratio & volume efficiency & torque curve shape
However, when it comes to torque curve shape, I dont think that stroke to bore ratio will have significant effect to the overall torque curve. It will slightly increase the achievable volumetric efficiency at low rpm but it's not enough to create extra bump or anything.
To change the torque curve significantly, you need to vary the intake and exhaust configurations or to change the cam timing or lift.
RE: Bore/stroke ratio & volume efficiency & torque curve shape
Engines designed to spin fast tend to have high bore to stroke ratios so that they can breathe well and to keep piston speed under its limit and keep friction low.
Example: The Ferrari Enzo has a bore/stroke ratio of 1.23 (big bore, short stroke). It's a naturally aspirated V-12 with the red line at 8,000 RPM.
Engines that spin slow (like very large diesel engines) have low bore to stroke ratios. Why? Engine speeds are low, so air velocities are low, so pressure drops are low.
RE: Bore/stroke ratio & volume efficiency & torque curve shape
With bigger B/S ratio, it is also possible to keep the mean piston speed below the limit at say 19,300 rpm.
High performance bike engine that I know have 1.5 b/s ratio
High performance car engine that I know have 2 b/s ratio
RE: Bore/stroke ratio & volume efficiency & torque curve shape
al1
RE: Bore/stroke ratio & volume efficiency & torque curve shape