E30 Zone

I know that my IS has a duel mass flywheel and this slows the low down acceleration due to weight.
What do I need to convert to solid? Can I use a m40 1.8 flywheel?

Thanks!

What are you trying to gain from doing this?

For increased acceleration off the line starts you can possibly try the m20 flywheel after getting it lightened and balanced. you will also need a m20 clutch and starter as far as i am aware. This will improve acceleration and overall drive quality.

Let those who have done this Mod on the zone explain to you further as i have not personally done this and was in the thoughts to do so.

Check the zone wiki it has loads of information on there and await for further responses from the real e30 gods.

Sound man!

Are you absolutely sure yours has a DMF? I remember someone on here saying that its quite unlikely a UK iS will have a DMF.

If it does however, yes you can use an M40 flywheel and clutch (Possibly you'd need the M40 starter) - I will be using an M40 setup on mine.
An M20 setup also works, but there's not a massive difference in weight over the M40/M42 setup, unless you start getting things lightened and balanced.

Ahh that's good news. I'll have to have a proper look next time it's own the ramp to double check. M40 route it is, if needs be

i've never seen/had a dual mass flywheel on any of the 15 or so 4-pots i've owned .

this is an m40 solid flywheel ....



a dual mass one has parts inside the raised lip of the pic above ^^^^

iirc an m40 one like the one above weighs 12-13kg and a standard m20 one weighs 7kg but you can get the m20 one lightened to 5.5kg if you wanted to.

i had an m20 one fitted to my 318is m42 and it beat another 318is with a standard flywheel down the strip @ santa pod in 2010 by 1.7 secs, so it's well worth doing .

Ok so regardless off duel mass flywheel or not, you would recomend a lightened m20 flywheel?
What's starter motor and clutch can I run with it?

aaronsmart wrote:Ok so regardless off duel mass flywheel or not, you would recomend a lightened m20 flywheel?
What's starter motor and clutch can I run with it?

run m20 clutch and starter with m20 flywheel.

I concur with the post above mine does NOT have a dmf

Brilliant! Thanks for all the good advice guys

magpie wrote:i've never seen/had a dual mass flywheel on any of the 15 or so 4-pots i've owned .

this is an m40 solid flywheel ....



a dual mass one has parts inside the raised lip of the pic above ^^^^

iirc an m40 one like the one above weighs 12-13kg and a standard m20 one weighs 7kg but you can get the m20 one lightened to 5.5kg if you wanted to.

i had an m20 one fitted to my 318is m42 and it beat another 318is with a standard flywheel down the strip @ santa pod in 2010 by 1.7 secs, so it's well worth doing .

I'll get a pic of my DMF (M44) tomorrow for comparison.

I've just posted the below in another thread re the weights....

As standard, the complete setup (flywheel, clutch and release bearing) weigh almost the same, M42 - 15.5kg, M20 - 15.48kg (info from M42club)

Looking at the posts above, I think we can say an M42 flywheel can be taken down to roughly 7kg.
I seem to remember people on here saying 5.6kg is the lightest for an M20 flywheel, but reckon on 6kg for safety.

So all in, about a 1kg-1.5kg difference once lightened.


If 5.5kg is safely possible from an M20 flywheel, then its definitely worth it over a lightened M42 in terms of acceleration.

Another question is when it's being lightened I assume it will be take from the side that the clutch connects to?

aaronsmart wrote:Another question is when it's being lightened I assume it will be take from the side that the clutch connects to?

no it comes off the engine side .



you need to leave 10mm of metal at the ring gear or it will be f00ked .the pic above is one i had done a while ago .

jmc330i wrote:

magpie wrote:
this is an m40 solid flywheel ....

As standard, the complete setup (flywheel, clutch and release bearing) weigh almost the same, M42 - 15.5kg, M20 - 15.48kg (info from M42club)

Very much an over simplification! You can see from the pic. that the M40/42 flywheel has a massive, deep band of iron around it's outside - where it has the most effect. You can't remove a great deal from this area, because it's where the cover plate bolts on to. In comparison, the M20 flwheel is almost a flat disc, with a much deeper cover plate than the M40/42 one.
This makes the M20 plate much heavier than a M40/42 one, but the pressed steel is much lighter than that thick band of iron it replaces.

So the m20 can be milled down for the engine side aswell i assume?

Brianmoooore wrote:

jmc330i wrote:

magpie wrote:
this is an m40 solid flywheel ....

As standard, the complete setup (flywheel, clutch and release bearing) weigh almost the same, M42 - 15.5kg, M20 - 15.48kg (info from M42club)

Very much an over simplification! You can see from the pic. that the M40/42 flywheel has a massive, deep band of iron around it's outside - where it has the most effect. You can't remove a great deal from this area, because it's where the cover plate bolts on to. In comparison, the M20 flwheel is almost a flat disc, with a much deeper cover plate than the M40/42 one.
This makes the M20 plate much heavier than a M40/42 one, but the pressed steel is much lighter than that thick band of iron it replaces.

Yup, but someone asked for the complete weights (not this thread, but same subject).
The standard M40/42 flywheel is 9.9kg, the M20 (late IIRC) is 8.5kg, although I've seen reference to the ring gear not being included in that weight, so the total could be around 9.2kg.
I think it was you (Brian) that also made mention of where the weight is on the flywheel - I would think a lightened M20 flywheel would be beneficial over a lightened M40/42 flywheel of the same weight due to the large band of mass around the outside of the M40/42 flywheel??

jmc330i wrote: I would think a lightened M20 flywheel would be beneficial over a lightened M40/42 flywheel of the same weight due to the large band of mass around the outside of the M40/42 flywheel??

Exactly. Much less rotational inertia with the M20 compared to the M42 than the simple difference in weights would suggest.

This seems an interesting Mod to gain a little better driving experience for the little baby m42.

how many people have actually done this and what have you experienced ?

After much conversation on the zone I am seriously considering this Mod for sometime in the near future.

I need to consider the cost for parts and labor. How much would it cost for the following:

M20 Lightened Flywheel
M20 Starter
M20 Clutch

Considering the above parts are all that's needed, how much would it cost in Labor or is this something to do on the drive on one weekend with a few friends.

where would i go to hunt these parts ?

jon-m42 wrote: how many people have actually done this and what have you experienced ?

magpie wrote: i had an m20 one fitted to my 318is m42 and it beat another 318is with a standard flywheel down the strip @ santa pod in 2010 by 1.7 secs, so it's well worth doing .

jon-m42 wrote: how much would it cost in Labor or is this something to do on the drive on one weekend with a few friends.

i took my engine out to fit the flywheel .

It really depends what else you want to do at the same time, and what sort of tools and equipment you have.

The gearbox can come out on its own, which will give enough space to get the flywheel off, however its not much fun trying to get it lined up and back in whilst laying on your back.

Taking the whole engine out might seem pretty drastic, but in some ways it's easier.

you could get a quote from a clutch only supplier/fitter to do the work ,it's only 8 more bolts to change a flywheel ?

I am spanner friendly and would enjoy a weekend working on the motor however i must admit i have never worked with or around gearboxes before, so i will most likely get a quote.

Guys where would I get all the parts from? any companies/auto shops that sell the parts i will be after ?

Or is it just put a post in the wanted section?

most importantly when I eventually have the parts to which engineering shop would i go to?

can anybody recommend one in and around east london and or south/east london?

to what weight would i ask them to take it down to ?

thanks again

Just a quick question with regards to the flywheel "upgrade"?

When swapping out flywheels, is there no need to be concerned with the flywheel weight in relation to the engine's harmonic balancer or overall engine balance?

(m42club)The reason I ask is this - when wanting to install a lighter flywheel on a Mustang, you also have to change and match the harmonic balancer to the flywheel's weight in order to retain overall engine balance and to avoid premature wear (or destruction) on the internal bearings. For example, a stock 5.0 flywheel is 50oz, so is the harmonic balancer. If wanting to swap out to a 28oz flywheel, the 50oz harmonic balancer would need to be removed and a 28oz balancer installed so that the total rotational mass was still balanced. You can't install a lighter flywheel and not change out the balancer or visa versa.(m42club)

When installing an M20 flywheel on an M42, there is no need to change the harmonic balancer out as well? Going with a lighter flywheel over the heavier dual mass flywheel has no impact on overall engine balance if leaving the factory M42 balancer in place?

Does the M42 balancer weigh the same as the M20 or visa versa?

Please enlighten me a little more... I understand swapping out the flywheel in order to increase the spin up wanted for spining the rotational mass faster and the fact of "losing weight" (as this is a common upgrade or mod for MANY vehicles), however, I'm not seeing any mention of the impact to overall engine balance or any mention of the need for also upgrading the harmonic balancer. I'm only assuming that the M20 harmonic balancer and the M42 balancer weigh the same, therefore there would not be a need for swapping out this part...

e30 engines dont have a harmonic balancer as such, just the front pulley with a rubber suspended outer section, which weights a heck of a lot less than the flywheel. The masses of the rotating parts, and the natural balance of a small capacity inline 4 are completely different to a 5 litre crossplane v8!

In an ideal world you'd get the whole bottom end balanced, but factory tolerances for the rest of the moving parts are pretty tight anyway, so as long as the flywheel has been machined properly it's unlikely to cause issues unless.

BMW call it a twin mass flywheel but that's because it weighs so much. Definitely worth binning it for an M20. I haven't tried it for myself but I'm told it makes a huge difference to throttle response. I have one waiting to go in my 318ti.

Whilst were on the subject of the drivetrain. What ratio diff can I expect mine to be running?

So am I right in thinking that to do this conversion accruately i will need to following:

- M20 flywheel lightened and balaned.... to whah weight would i have to take it down to (kg)?

- M20 starter

- M20 Clutch

& Finally a mechanic who can insall all parts prviding quality worksmaenship

I would not need to wory about getting the bottom end ballanced with the crankshaft?

would this all work and function in harmoney ?

Jon

It would be fine. Use a standard unlightened 320i flywheel and clutch.

an m20 flywheel is 8.5 kg's and not 7kg's that i said earlier ...just weighed two of them this morning and there now off for a slimming sesh at the Lathe shop

Sorry for may being a tad repetitive in my atempt to understand exactly what it is that is required.

Is it safe to say o take the weight down to around (5kg)?

5.5kg's is all i go to .

As I've already said earlier in this thread, it's the rotational mass that matters, not the static mass, and although there's not a great deal of difference between the latter for M20 and M40/42 flywheels plus clutch, there's a considerable difference between the former.
Forty years ago I cold have written out all the maths to back this up, but now you'll have to take my word for it, or look it up for yourself.
As with most things, a little is good, but more is not necessarily better. Rotational inertia is essential on a four cylinder engine for it to run, and a standard M20 flywheel is as light as I would go.

i can see someone's 4-pot not ticking over any more .

Brian so you are saying a straight swap between the m42 clutch/starter and flywheel to he m20 parts would be more then sufficent ?

Are they parts easily transfurable ? Would the flywheel not catch on the back of the sump while intalling the m20 flywheel ?

The standard weight of the m20 flywheel and clutch atached is 12kg+, dont quoe me on his im just assuming if thats the case then would it not be better to just keep the m42 set up at 10.0kg?

jon-m42 wrote:
The standard weight of the m20 flywheel and clutch atached is 12kg+, dont quoe me on his im just assuming if thats the case then would it not be better to just keep the m42 set up at 10.0kg?

Static mass isn't relevant! It's where the mass is positioned on the wheel that matters.
AFAIK, the M20 stuff fits in a M42 bell housing with no problems, but as with all engineering work, fitting is what's important, often many times, before fixing.