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Join Date: Nov 2008
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light Weight Flywheel

I came across "Light Weight Flywheel" claimed to be 50% lighter and partially made of aluminium for the 930 Turbo. Previously I have great success with a light weight flywheel on a E-type Jaguar with a straight 6 4.2litre engine. It just bring the car alive and the RPM revs so much faster. I was just wondering what would be the results if it was installed in a 930 Turbo? Has anybody have great results with it?

Cheers

Heung
Old 12-02-2008, 03:48 PM
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There have been several discussions posted on this topic, here as well as on Rennlist. Probably just as many differing opinions as well. But I think the general consensus is that the 930 has a heavy flywheel by design, to accommodate the turbo's inherent lag and the engine's relatively low compression ratio.

Yes, a lighter flywheel will allow quicker revs to build and probably would be more appreciated on a normally aspirated engine. But the 930 needs some time for the boost to build in tandem with the rpm's, so the benefit you may get with a lighter flywheel won't necessarily be in the form of faster power delivery. The proper amount of boost needs to be available when the rpm's reach their optimum power band. I suppose a person could play with different turbos with quicker spool-up to keep pace with the rpm's, but might sacrifice top end power in the long run. Also, the heavier flywheel is there to provide rotational mass, to keep things going (torque) when starting out (helps with the lower CR).

Hard to explain (I've surely butchered it) but Stephen at IA has commented on this in the past...perhaps he's listening today?
Old 12-02-2008, 04:16 PM
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Heung

Welcome to the board. I noticed that was you're first post. You need at some point to show us a few pictures of your car to properly introduce yourself.

Regarding the flywheel, I had looked into this a few months ago and in addition to what Mark said above it can also make it rough on initial take off. When you let out the clutch it tends to be more quick and rough from what i have heard. This may have been coupled with an aftermarket (sticker) clutch as well, but I'm sure someone will chime in.

What year is your car, how long have you owned it, etc. We need info!!!

Thanks,
Bryan
Old 12-02-2008, 05:05 PM
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Only downside is it's easier to stall the engine when letting out the clutch quickly at low revs with a lighter flywheel because the low compression 930 engine is so weak at low speeds.
Other than that the driving experience and quicker revving is the same as other engines.

There's lots of hearsay on this subject...

You can use the stock flywheel and put in a lightweight and stronger KEP pressure plate with stock sachs spring center clutch disc and have a real nice non grabby/non chattering clutch that can handle more torque than the stock one.
...and remove ALOT of weight at the same time.

It is not recommended to use a lightweight flywheel and lighterweight KEP pressure plate on a street car. It would be too light with little inertia and difficult during stop and go driving, but for a racecar its OK.
Old 12-03-2008, 09:20 AM
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I'm a big fan of lightweight flywheels, but I think my RSR flywheel and KEP clutch is too light. I'd stick with a stock flywheel and aluminum KEP pressure plate.
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Old 12-03-2008, 01:39 PM
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Quote:
Originally Posted by JFairman View Post
Only downside is it's easier to stall the engine when letting out the clutch quickly at low revs with a lighter flywheel because the low compression 930 engine is so weak at low speeds.
Other than that the driving experience and quicker revving is the same as other engines.

There's lots of hearsay on this subject...

You can use the stock flywheel and put in a lightweight and stronger KEP pressure plate with stock sachs spring center clutch disc and have a real nice non grabby/non chattering clutch that can handle more torque than the stock one.
...and remove ALOT of weight at the same time.

It is not recommended to use a lightweight flywheel and lighterweight KEP pressure plate on a street car. It would be too light with little inertia and difficult during stop and go driving, but for a racecar its OK.
Yeah, I went down that slope and figured the best compromise was to do just as JF described: Went with a KEP stage 1 pressure plate (much lighter than the stock plate and higher torgue handling ability), spring centered Sachs disc, and just left the stock flywheel in place (after resurfacing it). We dropped some weight...didn't effect my starting out any, but did give a somewhat quicker response. I think it's only the guys that go hog-wild on weight reduction in the clutch arena are the ones that quickly find the limits of driveability.
Old 12-03-2008, 06:41 PM
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Hi to All,

Thanks for to all who responded and gold worth information. I will get some photos posted once I get the car back from the paint shop. I lives in Kuala Lumpur in Malaysia. We drives on the right hand side. I previously own a 1977 2.7 911 Targa which I have sold and then bought a Euro 1981 928S with 300HP which I still have with me. I acquired the 930 a Euro 1985 few months ago and has been working on it. Nothing much on the engine, except the ignition problem that keep dieing on me once I push it hard. Finally trace down to the coil and numerous Ignition CD changed with no results. Very dirty interior that took a long time to clean as the previous owner dismantled the Air con Compressor and drove with windows down all the time. Managed to get it all back to shape and sent for painting on the bumpers and front bonnet due to stone chips and poor paint job from the last respray. I managed to drive it briefly and with a straight flow exhaust, it pull very strong at about 3500 to about 5500. after that it runs out of breath. I have a 1.0 bar spring but have not install it yet. I don't know if that will inproved the upper end.

Cheers

Heung
Old 12-04-2008, 07:17 AM
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I have a alum RSR type flywheel and clutch on my 930, my car pulls faster than a stock SC from a stop after some boost goodbye of course, the advantages are the car revs up and down fast like a race car as well, I think its important to have other mods as well such as exhaust to get the most out of it. it knocks a good 15 lbs of rotational mass off the crank definately worth it

I have no problem with the clutch from standstill stalling ever, really makes the motor spin up
fast
Old 12-04-2008, 02:42 PM
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