BHP / Torque

[speedy_thrills]

Pigeon said:

But in order to maintain the same capacity, the bore must be reduced as the stroke is lengthened. This results in a smaller piston area and therefore a smaller force on the piston, which exactly cancels out the extra leverage of the longer crank throw. The torque therefore remains the same.

This is completely true…except that the combustion gasses are compressible. Actually the force ends up being almost equal (except for minor dynamic losses and the force used to make the piston travel further).

A longer stroke does actually mean more torque. Incidentally as in interesting side not Torque in lb/ft is always = Horse Power at 5252RPM.

[NST]

really interesting thread!!

what is significance of the 5252 value?

also having a rising torque curve above 5252rpm would result in some serious power (S2000 springs to mind)

[steve_D]

NST said:

really interesting thread!! what is significance of the 5252 value? also having a rising torque curve above 5252rpm would result in some serious power (S2000 springs to mind)

5252 comes from the torque formula

HP = rpm x T(torque)
---------------
5252(constant)

A horsepower is a unit of power equal to 746 watts or 33,0000 lb-ft per minute

33,000 divided by 3.14 x 2 = 5252

When you see a torque/HP graph the torque will be a gentle curve over or (if your lucky) a straight line and the HP will rise from below crossing at 5252 and continuing on upwards (again if your lucky).

Steve


>> Edited by steve_D on Wednesday 27th July 18:04

[NST]

cheers !