Author Topic: is it possible to lighten a stock flywheel? (Read 7435 times)

Wise Old Dog · « **Reply #15 on:** September 26, 2007, 01:06:37 PM »

Both. The viscous coupling between the two flywheel halves makes the flywheel unstable when the surface is machined. This leads to in imperfect machining process. That's why they don't mess with it. If the surface is not tore up to bad, just break out the ole trusty belt sander or equivalent and go to it. The results are good enough to throw the new disc on without any problems.

kramerica5000 · « **Reply #16 on:** September 26, 2007, 01:37:21 PM »

The m20 flywheel is more like 18 lbs, and the pressure plate and clutch are heavier too, so figure about 19-20 lbs by the time its all installed. That's still a significant savings over the 28lb stock flywheel.

I had m20 FW's lip machined off and lightened a bit more. It ended up around 15 lbs which was what I wanted.

I think 9lbs is excessive for the m20 FW and I'd imagine you'd have a hard time finding a shop that could get it that light. I think around 12lbs is more typical.

IMHO 12-15lbs is about ideal. I noticed a huge difference, not just in acceleration, but shifting is improved all around. Get much lighter and you can get chatter, and your passengers will complain about the jerky ride.

Quote from: gearheadE30;33713

The clutch and flywheel out of a 6-cyl m20, the m20 starter gear, and a trowout bearing from the e21 323i euro car are all needed. iirc our flywheels weigh close to 30 lbs. The m20 is 12-14.

DZick · « **Reply #17 on:** September 26, 2007, 10:12:17 PM »

well i know what i am doing this winter after the season!!111

johna · « **Reply #18 on:** September 27, 2007, 01:34:47 AM »

Quote from: D. Clay;33858

If not all US M42's come with dual mass flywheels the overwhelming majority seem to. Have never seen or heard of OEM US model w/o dual mass. Australian models seem to be single mass also.

Actually, in Australia we only got dual mass flywheels. Perhaps because we got air conditioning standard.

But Australia also received the E30 318i with M40 engine so we have a ready supply of conventional flywheels that bolt straight in (+M40 clutch kit and shorter bolts).

bmwman91 · « **Reply #19 on:** September 27, 2007, 10:05:03 AM »

M20 complete setup.

M42 complete setup.

Swap details here. This was a stock M20 flywheel, no lightening. The car still felt more revv-happy. The M20's has a lot less mass at the outside compared to the M42's, which makes a big difference regardless of total mass.
http://bmw.e30tuner.com/my318is_pic_rebuild6.php