M40 vs M42 clutch torque capicity

[Leo_328i]

Hey guys,

I'm trying to find out some information regarding the difference between the M40 and M42 clutches in terms of their power/torque capicity.

I've done some research and found that the M42 clutches used in conjunction with the Downing Atlanta Supercharger kit have stood up really well with over 200ft/pd of torque which is great information.

My question is then related to using the M40 clutch and flywheel with a setup that has this sort of power - is the M40 clutch much worse in terms of power handling?

I cannot seem to find any information regarding this.

Cheers.

[ose30]

Euro spec M40/M42 clutch is the same. Only M42's with AC uses dual mass "thing"

[MikeDE]

This^

The Single mass non-AC FW is also about 5lbs lighter, and naturally uses a sprung-hub cliutch disc.

[robrez]

Hey guys,

I'm trying to find out some information regarding the difference between the M40 and M42 clutches in terms of their power/torque capicity.

I've done some research and found that the M42 clutches used in conjunction with the Downing Atlanta Supercharger kit have stood up really well with over 200ft/pd of torque which is great information.

My question is then related to using the M40 clutch and flywheel with a setup that has this sort of power - is the M40 clutch much worse in terms of power handling?

I cannot seem to find any information regarding this.

Cheers.

Bumping this thread up. I have an M40 single-mass, non-AC flywheel (ironically, I bought it from MikeDE) to replace my dual mass 91' 318i m42 flywheel. However, I've since installed a DASC, which I'm running basically as intended by Downing Atlanta. Is the M40 single-mass flywheel with oem clutch going to be stout enough? If not, is there a beefier clutch I can use with the M40 flywheel?   

[johna]

Bumping this thread up. I have an M40 single-mass, non-AC flywheel (ironically, I bought it from MikeDE) to replace my dual mass 91' 318i m42 flywheel. However, I've since installed a DASC, which I'm running basically as intended by Downing Atlanta. Is the M40 single-mass flywheel with oem clutch going to be stout enough? If not, is there a beefier clutch I can use with the M40 flywheel?

I bought my 318is already with a DASC (M44 but same dual mass flywheel/clutch as M42). Not sure how old the clutch was when I bought it, but it didn't like some acceleration "testing" I did and started slipping after that.

I found that M50/M52 flywheel/clutches (dual mass) were a similar weight (some are a little lighter) and are a bit larger in diameter so should stand up to the extra power/torque from the DASC.

I found a used M50 flywheel and good clutch and fitted them. Although a touch heavier I don't notice any difference.

Years ago I had a M40 flywheel fitted to my E30 318is (M42, no DASC) and didn't notice any difference due to the lightweight except a bit more vibration at lower engine speeds under load. It didn't seem any faster to me and I did some acceleration testing and it was at best 1/10s better to 100km/h.

If you really want some significant improvement I would look at much lighter flywheels with bigger clutches like the RHD Engineering flywheels (http://racehead.com.au/products-page/engine-components/bmw-light-flywheel-m50-m52-m42-m44/).

But you can also get a heavy duty clutch and pressure plate for the M40 flywheel (or get the pressure plate modified to be stronger).

[Jay-Vee]

Hi John / All


I'm considering the M40 flywheel option as well and am thinking of getting it lightened to make it worthwhile, but I'm concerned about the vibration talked about.

Would lightening the flywheel increase these vibrations? My project is leaning more toward restoration than for track purposes, but I did want to change the flywheel as one of the few modification to make it a bit zingier.

If it makes the engine feel particularly harsh then I think i might stick with the stock Dual-Mass flywheel and retain the smoothness this gives.


Appreciate your / anyone's input.

[robrez]

Thanks for the detailed responses Johna. My stock clutch is holding up fine so far so I have time to consider other options. But having a non-A/C M40 flywheel in my parts bin is making me want to just go with it. Hopefully, I can find a beefier clutch.