M42 Lightened Flighwheel?

[fitz318is]

is the m40 clutch a sprung hub like the m20?

[johna]

is the m40 clutch a sprung hub like the m20?

It sure is.

M42:


M40:

[M42boy]

Okay, so I ordered the 323i T/O bearing and flywheel bolts from the dealer.  The throw-out bearing was about $100 alone, and it's about $25 for the bolts.  I didn't order the bolts from the dealer as I figure they can be reused off the flywheel I'm pulling from the yard.  Gotta save somewhere.  

PN's are listed below:

21-51-1-204-525     323i Clutch Release Bearing        $106.48
11-22-1-717-840     Flywheel Hex Bolt    Qty 8             $3.26 (ea)

Hope this helps.  My dealer, fortunately gave me a discount for BMWCCA membership.  But, cost is something to think about when considering the M20 flywheel conversion.  I figure about $150-200 in parts, not including the clutch.  I guess this narrows the gap on the aluminum flywheel though.  

I just think the aluminum flywheel is going to be TOO light for me.  I think a 16 lb flywheel vs. 27 lbs, and I'll probably shave a few off.  Should maintain drivabilty and give faster accelleration from a dead stop, yet not be too tricky for shifting.

[fitz318is]

How does the m40 flywheel drive?  If you could post details on how it idles, accelerates and if there is any noise with it.

It sure is.

M42:


M40:

[johna]

How does the m40 flywheel drive? If you could post details on how it idles, accelerates and if there is any noise with it.

Keep in mind my flywheel is a stock M40 flywheel, nearly 10kg. It is possible to take off around another 2kg.

I haven't noticed any difference at all with the idle or any change in noise. Under certain circumstances there is noticably more vibration - mainly at very low revs in too high a gear.

Acceleration is little changed, not really noticable. I used a Gtech to measure 0-60mph before and after and did 9.51 before and a best of 9.38 after. I also changed from 14" to 15" wheels between so that may also have some effect.

It is slightly faster to gain and lose revs so upchanges can be a little quicker.

If I could do it again I would certainly remove the extra weight.

The other advantage is that it is not possible to machine the dual mass flywheel and after changing the standard clutch you can be left with some clutch shudder. Also the M40 clutch kits are cheaper than the M42.

[Gunni]

I vote for a machined M20 flywheel any day, I have a 5,5gk one, and I think it makes a huge diffrence

[fitz318is]

John418isau thanks for the desc.  

im considering both the m20/40, but I like the simplicity of the m40 setup.

Can the clutch handle the power (relative) of the m42, wernt m40's about 105hp?

[Gunni]

115hp,
I only have a 228mm 320i (129hp ) clutch and pressure plate and it never slips
a 325i set would NEVER slip

[johna]

Can the clutch handle the power (relative) of the m42, wernt m40's about 105hp?

The M40 and M42 clutches are the same diameter. I haven't experienced any clutch slip.

[M42boy]

115hp,
I only have a 228mm 320i (129hp ) clutch and pressure plate and it never slips
a 325i set would NEVER slip

Do you have an M20 or other lightweight flywheel in your car?  

Can you tell us, if any, effect on drivability?  How fast do the revs drop.  Someone scared me away from this the other day stating that driving in traffic is a real PITA with a light flywheel.  But, he started with a single mass and shaved it down.

I speculate that the 318is flywheel could shed some significant weight and still be very easy driver.  Just would like to here some impressions from those that actually HAVE done the M20 flywheel conversion, or are running a similar weight drop on the flywheel.  So, what's it like living with on a daily basis?  Do the revs fall off real quick or is it still pretty easy to drive.  

I learned to double-clutch all the time on downshifts with an old Jeep with no synchros left, so it's force of habit now, but I guess I'm not exactly "track master" fast with the operation either.  Heel-and-toe is a skill I have yet to master.  Still very much a beginer when it comes to performance driving.  :rolleyes: