Engine Tech Guys - Have Question

[tjm73]

Long rods and cylinder filling in a naturally aspirated setup.....

My understanding of the benfit of a long rod is the increased, effective piston dwell time at TDC and BDC (the benfit being had at TDC). With the piston staying at or near TDC longer combustion pressure builds higher and results in more force being exerted on the power stroke.

But my question deals with the filling of the cylinder with the air/fuel charge. Does the long rod cause an increase in piston velocity (vs a standard rod configuration) as the piston pulls the a/f charge into the cylinder which would result in the cylinder filling more completely?

Or more simply does the long rod increase the cylinder filling efficency?

 

[tjm73]

Just found some good long rod theory. It's from a Mopar site, but the theory is still the same. Just in case anyone else is curious.

http://victorylibrary.com/mopar/rod-tech-c.htm

 

[crunchie12268]

Longer rod = less cam lift... right? Which would take away from the benefits of having a longer rod. Sorry, just like to feel smart

 

[tjm73]

Longer rod = less cam lift... right? Which would take away from the benefits of having a longer rod. Sorry, just like to feel smart

I don't think I understand your question.

A longer rod has nothing to do with cam lift.

 

[crunchie12268]

longer rod means you would have to run less lift cam, or notch the pistons. That would take away from compression and air delivery, which would take away from what you gained.

or do you mean offsetting the wrist pin so the rod is closer to the head. Maybe I don't understand your question. Ohh well, I am sure somebody can give you better help then me.