M20 flywheel on S50 / M50 / M52 swap.

[ste]

Update - the M20 flywheel DOESN'T fit straight on an M52. I thought it did when I had it all together finger tight, after torquing it up the back face of the flywheel touches some of the block's webs and the 'tunnel' for the flywheel inspection/locking cover. It's a 2 minute job to grind the webs back the fraction enough to clear though.

What diameter id the M20 clutch? I have an S50B32 engine and the M3 3.0 (5spd) gearbox and would like to loose the heavy flywheel too..

Will the clutch be up to the job?

The M50/M52/S50 flywheels are 240mm diameter, the M20 is 228mm. I worried that the clutch wouldn't be up to the job so did some investigating. A 4wd Sierra Cosworth and a Subaru Imprezza both use flywheels the same size as the M20 one. They make 300 lb/ft easily with bolt ons and are harder on clutches due to the 4wd. Neither seem to have excessive clutch problems. I reckon it'll be fine, especially with an uprated plate and cover.

The M52 might have more than 200 bhp but it won't have anything like the torque of a blown 300 bhp M10

Won't it...?

[m-dtech]

im led to believe that the m20 clutch and flywheel will work with the m40 box.

[m-dtech]

i will tell you soon.

[jaistanley]

I'm sure you're right, especially using the uprated parts. The 4wd'd are evil on clutches. A friends pulsar used to chew them!

In solid mechanics, the power of a clutch is a function of area so bear in mind the inner diameter of the pad also has a baring on its capacity..(smaller inner and larger outer 'better' for the same pressure).

Jai

[DanThe]

I finally got round to measuring the standard clutch setup on my M50, from the back of the block to the back of the clutch it is 100mm. Anyone got any measurements with an M20 clutch setup to compare?

[Andyboy]

Not as yet. The gearbox to use with the M50/52 is definitely the M40 box. The 320i/325i one will sit at an odd angle. A mate of mine is going to see if a 325i flywheel and clutch will fit within an M40 bellhousing. He recently had a 200+ bhp 2.8 M52 in a Compact running the standard 1600 'box with no problems.
If it all bolts together, the M40 'box will make the M50 conversion a whole lot easier. Sod paying £300 for an M3 diff!

[Jimbob]

Couldn't you get away with using the M20 prop if using the M20 gearbox? Granted you have the extra issue of mounting the M20 'box though.

[DanThe]

Yes, of course you can. Im using an M20 prop with my E36 gearbox

[Jimbob]

Just making sure, mentioning the M3 prop got me thinking!

[DanThe]

The M3 prop is used to get around the larger size of output flanges. But for less money you can have your prop modded with the front end of a prop the right size.

[Jimbob]

I'm led to believe the M40 'box does fit Andy

[m-dtech]

i will tell ya in a few days once i get the gearbox from Neils IS.

Im hoping that the m50 clutch and flywheel will fit too.

[320Touring]

i will tell ya in a few days once i get the gearbox from Neils IS.

Im hoping that the m50 clutch and flywheel will fit too.

we'll find out dude, once we get the gearbox out.....

[m-dtech]

Here is a pic of the flywheel on my m50 lump.
This is single mass as i cant see any springs on it ??

Can anyone clarify ?

[ian332isport]

That's dual mass. If it was single mass, you would have springs on the friction plate.

Ian.

[Brianmoooore]

There's also an obvious gap between the ring gear and the part with the driving face.
There should be rotary movement between these two.

[jaistanley]

Whats the best option to reduce the rotating mass on an M50/S50 engine? I've seen these Fidenza ally flywheels but obviously they are quite expensive. Will using the M20 flywheel/clutch combo reduce the mass as much as a Lightweight flywheel and the std clutch?

My friends M3 (S50B30) is a nice smoothe revvy engine but it's obvious the rotating mass is very high, especially after my 318iS and previous tuned MK2 Golf 16v (2.0). Gearchanges can become a little ponderous, I like to heel and toe whilst downshifting and find it a bit harder in his car due to the mass.. I suppose it's something you get used to.

Jai

[DanThe]

What would the effects be of using a solid clutch plate like the one pictured with a single mass flywheel, would it be more likely to fail? I ask because those are the only type of friction plates I can use with my E46 box. I expect it to be not too much different to using a racing type clutch as I have seen lots without springs.

[m-dtech]

will the dual mass fit in the m40/m42 gearbox ?

[m-dtech]

i have been thinking about this and reading on E36coupe forum,

the m42 318IS uses a dual mass flywheel, a common mod is to use either an m40 flywheel and clutch or mod an M20 one.

so.................

the lightest flywheel to use is an m40 flywheel. (9.7 kgs)
the m20 flywheel fits the m50, so the m40 will fit.

so all thats needed is a good performance clutch and we are making progress.

[Gunni]

A M20 flyhweel machined down to 5.XX kg´s (I´m using one on my M42)
+ 228mm stock E30 325i clutch + Sacsh 618 sport pressure plate.

This combo will hold any form of NA Tuning on any of the M20/M40/M42/M50/M52/S50 engines

And will hold I belive about 600nm torque.
What might need to be done to work on M50/S50 engine is the flywheel spacer or space the starter back with 1.5mm shims, And change the starter gear to the M20 teeth setup(extending length and number of teeth on the gear)
Wich is really easy to be honest.

[DanThe]

What might need to be done to work on M50/S50 engine is the flywheel spacer or space the starter back with 1.5mm shims, And change the starter gear to the M20 teeth setup(extending length and number of teeth on the gear)
Wich is really easy to be honest.

Or use an M20 starter motor

[m-dtech]

Apprx Clutch Sizes,

M10 - 220mm
M40 - 220mm
M20 - 230mm
M50 - 230mm - dual mass

[ste]

M20 - 228mm
M50 - 240mm

I've no idea if your M10 and M40 figures are wrong too.

[Gunni]

Apprx Clutch Sizes,

M10 - 220mm
M40 - 220mm
M20 - 230mm
M50 - 230mm - dual mass

Thats not right

M10 / M40 / M42 - 215mm
M20 / M50 / M52 - 228mm
S50 / S38 / M30 / M60 / M70 -240mm

[jaistanley]

Looks like we've got ourselves a clutch geek-off!!!

PARTY!!!

Out of interest, what flywheel and clutch do the E46 M3 S54B32 engines use? A friend (with the M3GT and previously a tuned E36 325i) fitted the gearbox from an E46 M3 to his car (with 3.2 M3 Evo Schnitzer running gear and prop). The clutch plate had to be retained from the E46 as the splines were very thick and strong looking. To get it to fit the M50 flywheel he had it machined and re-balanced (which was cheap and worked well).

Jai

[m-dtech]

Apprx Clutch Sizes,

M10 - 220mm
M40 - 220mm
M20 - 230mm
M50 - 230mm - dual mass

Thats not right

M10 / M40 / M42 - 215mm
M20 / M50 / M52 - 228mm
S50 / S38 / M30 / M60 / M70 -240mm

i took my sizes from LUK website

[DanThe]

What would the effects be of using a solid clutch plate like the one pictured with a single mass flywheel, would it be more likely to fail? I ask because those are the only type of friction plates I can use with my E46 box. I expect it to be not too much different to using a racing type clutch as I have seen lots without springs.

Any ideas on how this type of clutch would hold up?

[ian332isport]

What would the effects be of using a solid clutch plate like the one pictured with a single mass flywheel, would it be more likely to fail? I ask because those are the only type of friction plates I can use with my E46 box. I expect it to be not too much different to using a racing type clutch as I have seen lots without springs.

Any ideas on how this type of clutch would hold up?

The springs in a sprung clutch disc, and the movement in a dual mass flywheel are both there to absorb shock loads in the transmission. If you removed this, you will probably start breaking other parts of the transmission system. You may be okay if you just go shopping in it, but if used in anger, then something will probably break.

Ian.

[DanThe]

Yes, it could put stresses on the gearbox, should have thought a bit more really
I was thinking more about the clutch itself slipping etc.

Going to have to find a sprung clutch disc that will fit it then as my light singlemass flywheel is already in production

[jaistanley]

The springs are a take-up safety measure yes but they are equally there as a measure against NVH. The spring/mass/damping of the system of the crank/grearbox/prop/dougnuts/bushes/wheels has a specific frequency or three where it oscillates at different conditions. The springs are there to counteract this and allow a smoother idle and pull away without judder or strange noises etc.

Without them the system can be excited at it's resonant frequency and it's these uncontrolled oscillations that break stuff (and make customers return cars with complaints). I personally wouldn't remove the springs from my road car but I wouldn't sweat it too much if you use it track wise or can put up with it; make sure all moving parts and bushes are new or perfect. We've all fitted parts to our cars that ruin the NVH in the past (such as poly bushes etc).

Jai

[DanThe]

Custom made clutch disk for me then

Jai, your wanted parts link isnt working

[jaistanley]

I know man.. No-one had any parts for me for ages (other than some cosmetic stuff which I passed on till I have the mechanicals sorted).. I shall write another presently. Nothing better to do at work!

You can tell the boss is out of the office today. I'm lame!

Jai

[jmc330i]

i have been thinking about this and reading on E36coupe forum,

the m42 318IS uses a dual mass flywheel, a common mod is to use either an m40 flywheel and clutch or mod an M20 one.

so.................

the lightest flywheel to use is an m40 flywheel. (9.7 kgs)
the m20 flywheel fits the m50, so the m40 will fit.

so all thats needed is a good performance clutch and we are making progress.

Unless Im confused (quite likely), this could be getting better and better

Are people saying that this could be the way to go - M50/M52 engine, M40 flywheel, clutch (uprated) and gearbox?? If so, does the M40 flywheel need modding to fit the M50?

[DanThe]

Theres nothing good about an M40 flywheel, its just a big unnecessary lump with a smaller diameter clutch