Author Topic: Machine shop wouldnt lighten my M20 flywheel (Read 6068 times)

JoeDellio · « **on:** August 11, 2009, 08:32:01 PM »

I have the stock 19lb flywheel. I told the shop I wanted 4mm shaved off the back and then whatever it took on the front to be able to balance it easily.
I want to take 4mm off the back first because I dont want to have to use the spacer, and Ive read that 3mm needs taken off and then Ive also read 6mm needs taken off, so Im gonna play it safe and shoot low for 4mm. If it hits the block Ill then grind the block.

Anyways, they told me itd be hard to balance, and that its a lot of weight to take off. I told him if he could get it down to 16lbs and balanced that would be great. They didnt want anything to do with it.

To my knowledge, this is possible and shouldnt be a problem.

rob_e30 · « **Reply #1 on:** August 11, 2009, 08:54:09 PM »

We have a 12.5# (IIRC) M20 flywheel.

JoeDellio · « **Reply #2 on:** August 12, 2009, 06:20:45 PM »

Anybody know what 5mm off the back and 3mm in the front would give me weight wise? I want to take at least 5mm off the back to clear the block and then go 3mm in the front to even it out a little bit to balancing will be easier. (the ring in the back has half the surface area of the front)

I cant get a hold of anybody whos actually lightened the M20 FW, I just dont want to take too much off.

strypt · « **Reply #3 on:** August 13, 2009, 01:41:46 AM »

This is what I've done to my previous M20 FW (not my fw in the pictures but it looked exactly the same), weight is 3.8 kg (8.4 lbs). I used it together with a stronger pressure plate for some 20'000 km on the street+track, after that I sold the car to a guy who used it in a racing series for two seasons and it was with a high revving engine (8k+ rpm). No problems with balancing it or fatigue.

http://www.e30.se/Bonje/svanghjul/svanghjul.JPG
http://www.e30.se/Bonje/svanghjul/svanghjul2.JPG

detoxed · « **Reply #4 on:** August 13, 2009, 09:39:23 AM »

Has anyone given any thought of putting together a kit for this conversion i.e. the COP conversion package offered?

JoeDellio · « **Reply #5 on:** August 13, 2009, 02:25:55 PM »

Quote from: strypt;76794

This is what I've done to my previous M20 FW (not my fw in the pictures but it looked exactly the same), weight is 3.8 kg (8.4 lbs). I used it together with a stronger pressure plate for some 20'000 km on the street+track, after that I sold the car to a guy who used it in a racing series for two seasons and it was with a high revving engine (8k+ rpm). No problems with balancing it or fatigue.

http://www.e30.se/Bonje/svanghjul/svanghjul.JPG
http://www.e30.se/Bonje/svanghjul/svanghjul2.JPG

I didnt know lightening involved all that extra cutting, I thought they just shaved off the face?

strypt · « **Reply #6 on:** August 13, 2009, 02:58:35 PM »

You can lighten it just as much or little as you want

my point was just to show you what you can do. You don't have to do the cutting, I did it just to loose that extra weight. I guess the "normal" way is to just shave some off the back. Typically you don't shave anything off the face towards the clutch to avoid the need of a spacer to have the pressure plate in the right position.

tjts1 · « **Reply #7 on:** August 13, 2009, 03:42:22 PM »

If you decide to drive like a fool, dump the clutch at 7000rpm and the machined flywheel takes out your legs, the shop is liable. Sounds ridiculous? It happens. Find another shop.

JoeDellio · « **Reply #8 on:** August 13, 2009, 08:24:59 PM »

I dropped the M20 flywheel off at a speed shop today. I am having them cut the back section completely off, but Im still gonna use the 3mm M42 flywheel spacer behind the FW so that I can take 3mm off the face of the flywheel and still keep my clutch travel the same. And then of course Im having the flywheel it balanced with my pressure plate.

I said screw the lightening. Itd be way too much money for too little power, and then possibly have driveability issues, especially with my A/C on. So I figured Id get the most I could out of it. I will post up the true before and after weights when I get it back; should be sometime by the end of next week.

When I install this I am gonna try to take pics as I go along and do a little write up for the E36, Im sure its not gonna really be any different from the E30 install though.

strypt · « **Reply #9 on:** August 14, 2009, 01:13:36 AM »

Quote from: JoeDellio;76824

Itd be way too much money for too little power

You don't gain ANY power at all

But the car will be a little bit quicker in the lower gears because of less moments of inertia for the engine.

JoeDellio · « **Reply #10 on:** August 14, 2009, 05:08:16 PM »

Quote from: strypt;76836

You don't gain ANY power at all But the car will be a little bit quicker in the lower gears because of less moments of inertia for the engine.

Gaining WHP to me is gaining power. Look at it however you choose.

3bvert · « **Reply #11 on:** August 14, 2009, 05:53:57 PM »

not knowing a better way to say this.....but will it also make the engine have less inertia when you take the foot off the gas in 1st gear

example: I live on a grvel road about 1 mile before hitting pavement. the firt 1/2 is rough and I cant take it out of first gear, I have to creep so slow that the speedo does not even move, but when I take my foot off the pedal , its almost like I hit the brakes
it seither that or really lug it in 2nd

3bvert · « **Reply #12 on:** August 14, 2009, 05:56:41 PM »

Quote from: tjts1;76818

If you decide to drive like a fool, dump the clutch at 7000rpm and the machined flywheel takes out your legs, the shop is liable. Sounds ridiculous? It happens. Find another shop.

the pic ( not that exact one) used to be very common sight in the muscle car days too

romkasponka · « **Reply #13 on:** August 15, 2009, 10:32:57 AM »

mine 5,3kg flywheel...
I am running it 2 years with 7200 rpm sometimes... With 0,5 mm preload for clutch.