rod stroke theory?
pitbullgst
11-27-2004, 11:47 AM
i read a theory earlier and just wanted to run it by you guys. o.k here is a example of what i was wondering. if you take for example a 350 chevy engine if you lose the longer 6.0 rod you will end up with more torque but if you use the shorter 5.7 rod you can end up with higher horsepower and be able to rev higher.would this be true? can you guys give me a few of the rules when choosing rod length? i believe i will be going with a ford 302 stroked to 347 but was just wondering about this theory. is it BS or truth?
Evil Result
11-27-2004, 01:27 PM
Basicly between the distance a piston travels the stroke of the crank and the length of the con rod will effect many factors like piston velocities through the stroke such as dwell time at TDC and BDC also along mid stroke.
During a pistons stroke it travels 60% of its total stroke at 90 deg of crank rotation. This is where the force from the piston would be most effective...
The shorter rod usually decrease mid stroke piston velocities which means more force can be applied over a certain period of time which means more torque in the range. although the decresed rod length increases cylinder wall loading which increases wear and increasesmax piston velocities during TDC and BDC.
A longer rod increases mid stroke velocities which means you loose torque but you also gain it back during the power stroke at TDC where max pistion velocities or lower but since we are not at a good angle to applie force this effect is reduced. but this means your cylinder wall loading is lower which means decreased wear also the piston is spending more time at TDC and BDC so your engine can spend more time breathing.
Formula F1, and NASCAR use larger rod ratios on there engines, up and over 2.0.
uhhh, if feel confusion :)
During a pistons stroke it travels 60% of its total stroke at 90 deg of crank rotation. This is where the force from the piston would be most effective...
The shorter rod usually decrease mid stroke piston velocities which means more force can be applied over a certain period of time which means more torque in the range. although the decresed rod length increases cylinder wall loading which increases wear and increasesmax piston velocities during TDC and BDC.
A longer rod increases mid stroke velocities which means you loose torque but you also gain it back during the power stroke at TDC where max pistion velocities or lower but since we are not at a good angle to applie force this effect is reduced. but this means your cylinder wall loading is lower which means decreased wear also the piston is spending more time at TDC and BDC so your engine can spend more time breathing.
Formula F1, and NASCAR use larger rod ratios on there engines, up and over 2.0.
uhhh, if feel confusion :)
public
11-27-2004, 06:00 PM
A longer rod simply will put TDC higher in the cylinder, yielding higher compression. This gives more torque because the expansion of the combustion gasses act upon the piston with more force.
If you want a longer or shorter stroke you MUST change the crank. Changine connecting rods moves the inertial mass and position of TDC but does not change stroke length. The stroke is the same as the diameter of the crank rotation. Good Luck.
If you want a longer or shorter stroke you MUST change the crank. Changine connecting rods moves the inertial mass and position of TDC but does not change stroke length. The stroke is the same as the diameter of the crank rotation. Good Luck.
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