Do lightened crankshaft may cause engine vibrations?
06-16-2010, 01:55 PM
#1
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Do lightened crankshaft may cause engine vibrations?
Does anybody knows if a lightened and balanced crankshaft may cause engine vibrations over 3800-4000 rpm?
Tx.
c.
Tx.
c.
06-16-2010, 02:20 PM
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Not if it is done correctly. Guess it depends to what level/speed they balanced it to, which I would think was above 3800RPM, at least for a our engines anyway.
06-16-2010, 03:09 PM
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Well, I think it was done properly.
Do the fact that the balance shaft are designed for a standard crank may change anything?
The engine does not vibrates at all before 3800-4000 rpm and then starts to vibrate like crazy...
Balance shafts are ok.
Strange
c.
Do the fact that the balance shaft are designed for a standard crank may change anything?
The engine does not vibrates at all before 3800-4000 rpm and then starts to vibrate like crazy...
Balance shafts are ok.
Strange
c.
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06-16-2010, 07:17 PM
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Lightening a crank will not result in out of balance vibrations (as long as it is done right). Reducing the counter weight on a crank can increase the internal torsional stresses but nothing that you would feel. The balance shafts are weight matched to the reciprocating mass and not the rotating mass. – so lightening a crank will not have any effect on the balance shafts.
If the vibrations are really noticeable you have a different problem.
If the vibrations are really noticeable you have a different problem.
06-16-2010, 07:34 PM
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to follow up with chris' statement... NO (fishy) it won't cause what u are describing. I'm guessing one of 2 things.. 1. balance shafts were out of alignment when belt was replaced, or 2. Your engine mounts are blown.
lightened flywheel also changes harmonics, but once again, not like anything you described
lightened flywheel also changes harmonics, but once again, not like anything you described
06-16-2010, 07:52 PM
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Motor mounts are solid (Lindsey).
Balance shafts are aligned.
The engine is very smooth until 3800-4000rpm. Then the vibration becomes unpleasant. I have run with no balance shafts on an atmo 944 and it's not the same vibration.
The engine pulls strong, temps are fine, AFR too, oil pressure too.
There also a new clutch and flywheel (Fidanza).
I don't know where to look for...
c.
Balance shafts are aligned.
The engine is very smooth until 3800-4000rpm. Then the vibration becomes unpleasant. I have run with no balance shafts on an atmo 944 and it's not the same vibration.
The engine pulls strong, temps are fine, AFR too, oil pressure too.
There also a new clutch and flywheel (Fidanza).
I don't know where to look for...
c.
06-17-2010, 02:33 AM
#14
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Yes exactly my thoughts.
You never ever ever ever.... install an aftermarket flywheel without having the balance checked.
Furthermore, the Fidenza flywheels are known to almost always be way off.
TonyG