PorscheDude1

Mine was out of balance by something like 27 grams out of the box. I got my DMF directly from Porsche.

LTCMontana

I beleive the DMF would cause vibrations at all revs.

RajDatta

All DMF's and clutch kits come balanced from the factory. You can see counter weights on them.
If you reused your DMF after your rebuild and did not have the vibrations before, it would mean that something else is causing your vibrations.
As stated, DMF would cause problems at all revs. Even if use the example of a DMF being out by 27grams, the imbalance is miniscule.
Grams to Pounds Conversion :
27 g = 0.059524 lb
Raj

PorscheDude1

Thats fine and dandy if it were a static object.
I am surprised you just threw that number out, I thought you may know better.

Look up Centripetal force's and see if that number holds up.
27 grams is huge for something that is "balanced"..
BTW it may have been far less than 27 grams.

You may find this of interest:
http://www.babcox.com/editorial/ar/eb10330.htm
http://en.wikipedia.org/wiki/Centripetal_force

PorscheDude1

Also most of the imbalance may have come from the pressure plate.

RajDatta

Could you please share with us exactly how you did your rebuild? What was changed, what was kept the same?
Its hard to come up with potential causes without understanding what was done. Also, be specific on any parts that were interchanged.
Thanks.
Raj

Damian in NJ

Centripetal force

Huh?

Centipedal? The force of many legs?

FRporscheman

That doesn't sound right to me. With cyl 1 at TDC, the BS sprockets should be aligned using a little notch on the back lip of the sprocket. For the upper shaft, that notch is aligned with a notch in the rear plastic cover directly behind it (towards the 12 o'clock position). For the lower shaft, the notch is aligned with a plastic tab on the rear plastic cover, towards the 8 o'clock position.

PorscheDude1

Go back to physics class....


Yea, centripetal force is the external force required to make a body follow a curved path.

Excerpt from one of the links I posted for someone who thinks it has to do with many legs. Thats almost as funny as the popsicle analogy.

"The centripetal force created by a crankshaft imbalance will depend upon the amount of imbalance and distance from the axis of rotation (which is expressed in units of grams, ounces or ounce-inches). A crankshaft with only two ounce-inches of imbalance at 2,000 rpm will be subjected to a force of 14.2 lbs. At 4,000 rpm, the force grows to 56.8 lbs.! Double the speed again to 8,000 rpm and the force becomes 227.2 lbs."

sergiomartins

Heres some pics of the Balance shafts

Also the odd bit is that under the car with the engine idling i can feel the vibration on the body and on the engine but not on the crossmember or the suspension?!!

RajDatta

Could you please tell us in detail what was done to rebuild the engine? Were all parts marked and used in their same locations?
Raj

LTCMontana

I still say motor mount.

Your comment about where the vibration is pushes more for a mototr mount. I think it is coincidental that it was only noticed after the recent work.

FRporscheman

Those balance shaft sprockets are pointing the right way, but they go on the shaft 2 possible ways (two keyways in the sprocket). Are you sure the sprockets went on the correct way? I don't know which keyway is used with the key, I always just keep the front sprocket plate with the sprocket, and that plate plugs the unused keyway, so I always know which way to put it back on. Sorry I can't be more informative than that.

Check that the motor mount bolts are tight, and the bolts for the motor mount brackets into the engine block are tight.

It could be a misbalanced PP, it does happen.

austex

there is a few pages in the manual on which is right keyway to use, I dont have my manuals any more as they went with the car, I really think that this is what is wrong with this car sound like and idenical problem to a friends old 944 S2 when he still had it and it was put back together wrong,

RajDatta

+1 on the bs.
Raj