Browar

Hi,
I would like to ask for input of those who knife-edged crankshaft in 8V or S2. Is there special procedure? I am asking because I have custom lightweight Pauter rods and counter weights were knife edged. Workshop that did work balanced crankshaft and all stuff (pulleys, flywheel, pressure plate) individualy and then as a one unit. Now I have doubts regarding balance shafts and possibility of vibrations... For e.g. Lindsey offers lightweight crankshaft and says nothing about additional work..
TIA.

V2Rocket

because the 944 is an inline-4 the crank weight has nothing to do with the piston/rod weight.
the lightened crank is balanced against itself - it is only so massive to keep its own vibrations/whipping down.

the balance shaft weight is matched against the piston/rod combination weight. most people don't bother to mess with the Bshaft weight even with those parts changed out for lighter pieces.
but some have experimented by lightening the Bshafts weights a proportional % relative to the % of weight removed with the lighter piston/rod.

odonnell

The big ends of the rods are balanced by the crank, no?

V2Rocket

Not on a straight 4.

The pistons and rods balance eachother out because the pairs are always opposed in motion.

mikey_audiogeek

I think both you and V2Rocket are correct. A few more words might help?

The secondary out-of-balance forces which cycle at twice crank speed, are a function of the reciprocating mass and the rod-to-stroke ratio.
The rotating mass is not a factor.

http://www.eng-tips.com/viewthread.cfm?qid=376751

Cheers,
Mike