Danno

"I'm kind of suprised with them as heavy as they are that they needed to add the balance shafts, but I guess there's only so much that can be done with the crank alone to elimanate the inherent vibration in a 4-cyl."

Actually, the bigger and heavier parts are why we need balance shafts. Small displacement 4-bangers don't use them at all, it's just when you cross over the 2.0L mark that balance-shafts start appearing. Honda and Toyotas have them too.

Robby

Thanks for the post- I love info like this- even if it IS basically worthless to me- I've been trying to decide on whether or not to delete my balance shafts- supposed to save ~16lbs & it definately cleans up the engine- JM says they remove them from 2.5's but NOT 3.0's- Gomes removes them from ALL of his- other people say to NEVER remove them, etc... just like everything else w/this car- NO ONE can agree on ANYTHING....

The complete engine is supposed to weigh:
968: ~385lbs
S2: ~380lbs
951: ~404
944NA: ~355lbs

VW W8: 419lbs
Carrera GT (10 or 12?): ~479lbs

I'm trying to fine others to compare to...

Porsche-O-Phile

Hmmm. . . I would've figured bigger crank = bigger counterweights and less vibration, but I guess not. . .

Robby

it would be a good guess, but, evidently, not the case- even JM says he leaves the shafts ON when doing the longer stroke (88mm) engines... I've also heard many people who have driven BOTH 951 & 968's, etc, who have said the 968's were not as smooth- evidently, there's something to all that...

Voith

crankshaft does not vibrate, you can spin it by itself to crazy speeds and if its properly balanced will not vibrate.

Reciprocating mass vibrates because 4 bangers do not self cancel (no opposing cylinders) vibrations that are consequence of piston moving faster around TDC because of rod / crank relation.

HICKS

No idea how to delete post on new app, disregard this please.