Aluminium flywheel, safety concern.

[yamoda]

I'm putting a ally flywheel from Ireland Engineering on my M30 before I stick it into the E30. I have always been a bit weary of flywheels letting go at high revs (Old mate of mine is still on crutches 15 years after a flywheel let go in his car) Any thoughts on the strength of the bellhousing on the manual 535 box? Or should I stick a safety blanket over the bellhousing?

[jkarran]

It's logitudinal instalation isn't it? At least the bits go out the sides if it does blow!

I missed a shift in my old MR2 on the track and buzzed it off the tacho scale 9000+rpm ... scary indeed when you realise the flywheel is right behind your ass

jk

[Ziggy]

It's logitudinal instalation isn't it? At least the bits go out the sides if it does blow!

... through your legs...

[sam325is]

if its been known to go throught a bell housing and floorpan on any car its never worth the risk imo, i dont even think its worth the cost of doing it before thats take into consideration

[jkarran]

It's logitudinal instalation isn't it? At least the bits go out the sides if it does blow!

... through your legs...

Better than your ass Seriously, does it sit that far back, I thought my M20 one was in front of the firewall but then again, I've never really looked with the 'damn, I hope that doesn't explode!' thought in my mind.

jk

[m-dtech]

had a lightened mini 998cc flywheel come through the bulkhead and come close to my head.

never gonna put an a lightened flywheel on a car again.

[jaistanley]

Isn't it machined cast iron flywheels that normally cause this though?

I'd have thought the aluminium racing flywheels available would have a large safety margin built into them by design.

When you machine a flywheel (lighten it) you are cutting through all of the grain structure of the material, with cast iron this allow cracks to easily propogate under the cyclic loading from the engine. The aluminium ones I have seen have more material on them and have a very smoothe finish. I cant see them letting go on my 7500 rpm road engine if they arent letting go on 8-9000 rpm race engines (force on the flywheel is proportional to the square of rotational speed so goes up in an x^2 fashion, ie twice the speed is 4 times the force etc).

I dont think I'd fit a lightened wheel to my car but I'd fit an aluminium wheel designed for the purpose.

Jai

[yamoda]

Asked around and found someone who knows the answer. Fella that builds V8's for the strip, he reckons lightening an iron flywheel is a no-no unless you know exactly where to remove the metal and it isnt always the obvious places. It can cause weak points and in rare cases (Usually on an unbalanced or badly balanced flywheel and clutch assembly) can crack, even rarer it will grenade itself!! Ally flywheels dont usually have this problem if they come from a reputable source.