Please Help!!! I recently got a lightweight alum flywheel...

[JazzC]

I recently got a light weight alum flywheel installed, after the installation I lost my mid range acceleration... (from 1800RPM - 3400RPM it feels like the engine is choking, once it gets pass it it runs fine). I can't seem to find anyone to help me with this problem, had anyone experienced the same before? what was the problem?

[Danglerb]

Details on the car please, model, AT/5 spd, stock, modified etc.

[Mrmerlin]

Put the old flywheel back on, the car should run fine, inspect the crank position sensor

1985 928S.. my guess is a 5 speed

[Barbapapa]

The flywheel does have teeth for the sensor to pick up and if there's something out of whack it's possible to get weird behaviour such as you describe. The material and relation to the sensor affect the signal the sensor puts out. Where did this flywheel come from?

[rhjames]

the flywheel stores energy. the mass/weight of the steel flywheel allows you to have off idle acceleration more than an aluminum flywheel would. in other words, a heavy flywheel will launch a heavy car better than a light flywheel. (a 928 is a relatively heavy car---3500+ lbs). However, with a lighter flywheel, the engine should be able to rev quicker while in neutral, as opposed to a heavy flywheel.

if-- because we have no other info--if the aluminum flywheel does not have the necessary crank trigger teeth, and your year model car requires this, you would not be able to run the engine at all due to the teeth being missing (for the crank sensor to "read"). if the flywheel does have the necessary teeth, it is possible that the sensor is not preforming properly. it is possible that the teeth "ring" is not installed properly on the flywheel as well, but unlikely. You would have a timing or misfire issue, not just a low rpm performance issue, unless the timing became severely retarded.

sometimes when we change things, the perception we have as to performance lost or gained is not really what has happened....think about it.

so, you have other questions to answer:

does this car require a crank trigger flywheel?
did you change anything else during the flywheel exchange?

--R

[Mrmerlin]

Carl had a similar problem on his race car the flywheel timing ring slipped and the engine wouldnt run, the fix remove the flywheel and pin it in the correct position with about 4 pins

Edit Carl, 928 Pikes Peak contestant

[JazzC]

Thank you all for the responses... very helpful information =>

I originally needed some clutch work and found the site 928mortorsports.com. I ordered the clutch and figures it'll be a good time to swap out the flywheel (didn't do my homework prior to the swap, stupid). Everything is stock on the car and will probably stay that way for a few months... maybe it's best to swap the flywheel back?

And yes, it's a 1985 928S, 5 spd.

[Mrmerlin]

Are you racing this car?? If its a street car , I would put the stock flywheel back on.