318is duel mass flywheel

[Demlotcrew]

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.

Im running a very light and low inertia ali flywheel (3.6kg mass) no issues, in fact because it was zero balanced, my engine (with cams and no AFM) actually idles much better than with the stock BMW one.

And thats from cold!



Andrew

[jmc330i]

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?

9.9kg is the weight of the M42 flywheel, no clutch attached.
Both the M42 and M20 setups (flywheel, clutch and bearing) weigh almost the same at around 15.5kg.

The question would be which is better - having more mass around the outer edge of the wheel (M42) or not (M20) when the rotating mass is pretty much the same. I guess it will depend what you want from the car.

[jmc330i]

Im running a very light and low inertia ali flywheel (3.6kg mass)

Nice. I'm guessing it doesn't get used for commuting/popping to the shops much, but how is it driving under normal conditions?

[Demlotcrew]

Honestly, once you get over the instant throttle its like driving any other car. No issues at all, having experienced a light setup first hand and how well it behaves makes me question why everyone else seems to have such a negative outlook on light flywheels for 4 cylinders.

Are they speaking from experience? Or are they just regurgitating what they read or are told?

[Kedge]

I had an M50 alloy JBR flywheel and M50 clutch kit on my iS and it idled and drove fine (yes even town driving) as my daily. I fitted it in 2007, i think, and the setup is still going strong a couple of owners later in Ireland.

Same old Zone scaremongering in my opinion.

[jmc330i]

That's interesting. The only car I've driven with a lightweight flywheel has been an S50 converted E30. IMO, it wasn't nice for town/traffic driving - I don't know how light the wheel was, it was some ally thing from the US.
It was enough to put me off a lightweight flywheel for mine, which is 90% everyday transport.

[aaronsmart]

i can imagine an S50 E30 drive slightly diffrent to an M42, so it would be wrong to judge IMO, we need some opnion from people who have actually done the mod and driven the car in all driving conditions

[Kedge]

Well you've had one from Magpie and one from me, and my flywheel was considerably lighter than any lightened M20 flywheel and it was still easy to drive.

[jon-m42]

All the read up on the actual converison seems a simple yet quiet effective modification to do which allows for that tad bit more of a better driving experience.

I suppose if one would like to go to santa pod have a bit of fun in a safe enviroment and or enjoy the beaut of pulling away quicker then you modern contempory sports cars of today excluding M3's, R32's, Skyline and yes the list goes on.

But it seems as if so much had been documented however only 2 people no the zoone have done this which with whom hav provided no negative feedback for it. I will be strongly looking into getting this upgrade done on my vehicle at some point this year and for me so far it sounds a reasonable enhancment for the lil bab 4 pot m42.

I would not like to lighten it too much where by it makes driving a headache.

5kg seems as if its the safe ball part figure it should show after its been lightened.

[ross_jsy]

How many times have you been told 5kg is below the safe amount to lighten it?

Do you really want that tiny gain in performance opposed to losing your legs if the flywheel lets go?

[jon-m42]

how low would you go ?

7kg?

[ross_jsy]

5.5kg's. Its what on my m50 and the throttle response is pretty nuts.

[aaronsmart]

So it sounds like we have decided it is a worth while upgrade. I plan on doing it in the coming months...
My next question is, when I take it to the engineering shop what shall I ask them to do? As in, where's the best place to remove the weight? And is there any complications that need to be noted?

[jon-m42]

Ask them to lighten and balance the flywheel to 5.5kg.

Any good engineering shop should know exactly how to do it.

[aaronsmart]

But like people said you need to take it off of the correct side etc

[jon-m42]

Have a look through here prity much same conversation over here:

http://www.e30zone.net/modules.php?name ... c&t=239437

[Brianmoooore]

Have a look through here prity much same conversation over here:

http://www.e30zone.net/modules.php?name ... c&t=239437

There's one very significant difference with that conversation - in the first post, after "Hello all".

[jon-m42]

Brain apologies kid, just thought conversation was on same matter of m42 flywheel's