Engine load vs RPM and torque

[Tom Sharpe]

Matt Beaubien wrote:

> Greg,
>
> > >I'd like to be able to input the weights of the piston and rod, and the
> > >torque value to obtain their loadings. Most people will tell you the largest
> > >loads are seen on the exhuast stroke at TDC,
> >
> > This is in tension---
> >
> >  but that doesn't explain why
> > >those turbo Honda's start bending rods at 10 psi...
> >
> > This is instability under compressive loading (column failure.
>
> I realize the difference, even though my first year statics course was 5
> years ago ;-). What I'm getting at is most references say that the tension
> loads are so much greater that you don't have to worry about the compressive
> loads. Not so when artificial aspiration or severe knock is encountered.
>
> > Aluminium is not good for SUSTAINED high revs because of no fixed endurance
> > limit in tension.
>
> Drag racers sure can get away with a lot that OEM's or even oval/road racers
> can't. Are you uncomfortable driving cars with Al suspension pieces due to
> no endurance limit...?

I had a 440 Dodge that ate rod bearings over 7500 rpm. One rod came out bent in a
half moon shape, so short that the piston skirt was banging on the crank throws,
with 55 psi at idle. I also took many pieces of piston skirt out of a running turbo
motor after detonating. One set of full grove main bearings looked like they were
heated until putty like, then squeezed out by the crank.

My point is that rod failure can be caused by overloading the bearings... maybe the
Honda just doesn't have enough bearing surface area or crank diameter to handle the
power.

Sharpe