U.R. pulley vendor??

Jon Davis turboser@comcast.net
Thu, 24 Jul 2003 22:38:56 -0500

I4 engines are not balanced. The acceleration of the pistons at the top of
the stroke is not the same as the ones at the bottom, so an I4 always shakes
even if the parts are perfectly matched. Balance shafts help. The harmonic
balancer has nothing to do with engine balance or mismatched part weights.
The harmonic balancer is there to damp torsional harmonics which become
damaging when the pistons twist the crank at its resonant frequency. A
better name for it would be "harmonic damper", probably cause less confusion
that way. I have had a UR pulley on my car for 50k and the crank hasn't
broken yet, so it seems reasonably safe but I'm 100% certain Nissan had a
good reason for putting it there.

Jon Davis

> Mike Kojima's talked about this several times, and it pretty much boils
> down to the simple statement that there is no harm running an undamped
> pulley on an SR20DE[T].  I4s are *balanced* by nature (6-cyl engines are
> largely not), and the *harmonics* are not dangerous enough to hurt
> anything without *damping*, including bearings and whatnot.