How much can you take off the Flywheel

[terrybullwon]

Quick question guys,
Any body know if theres a limit?

Looks like you can not get alot off

Maybe i should go the alloy route...?


Cheers James

[4WheelDrifter]

IIRC Aelred got a 3B flywheel down to ~6kg.
Alloy/ Steel? It depends what you are going to use the car for James. My car will still be used mainly on the road, so I'm sticking with a lightened steel flywheel.

[terrybullwon]

IIRC Aelred got a 3B flywheel down to ~6kg.
Alloy/ Steel? It depends what you are going to use the car for James. My car will still be used mainly on the road, so I'm sticking with a lightened steel flywheel.

Cheers Stu,

I must remember to wiegh it

6kg you say :mischeif:

[4WheelDrifter]

I've found mcandmar's post about flywheel and pulley weights here.

This post by Aelred is also here.

[DJones]

I think you will find the RR & 200 20v turbo cars use a flywheel that is even lighter it would mean putting a spigot bearing in the crank though as it starts life slimmer and the gearbox comes forward.

Aelred and i lightened mine it started life in a RR its now basicaly 10mm thick which ever section you look at if that makes sense....

This was lighter than the 3b one he refers to in his post but cant remeber what it weighed...

I have a spare RR flywheel i can take pictures of if it helps..

[terrybullwon]

I've found mcandmar's post about flywheel and pulley weights here.

This post by Aelred is also here.

Jedi

Marks findings

3B flywheel 10.5kg
7A flywheel 11kg
ABY flywheel 14kg
3B pulley 4.26kg
7A pulley 4.3kg
ABY pulley 5kg

Some very good reading in there to.

[terrybullwon]

And another quote from Aelred

I lost 4.5kg on a 3B one, It could have been used as a Freezbie

[NoNonsense]

6kg for the 3B unit sounds very reasonable to me. I've done the same and used a 3B one on other non-3B projects to get the lighter weight.

[Acidburn]

Take it this is to get quicker response from the engine? does it have any adverse affects like warpage?

[Jon441cc]

6kg that is light


Is the stock 3B Flywheel Zero balanced ?

[S2_Dave]

Take it this is to get quicker response from the engine? does it have any adverse affects like warpage?

I have a lightened 3B flywheel and suffered from flywheel clatter. It bothered me a bit at first, but it context it was minor and now doesn't bother me at all. Revs climbed noticeably quicker.

[Acidburn]

Flywheel clatter? take it thats like a rattling noise, never heard of it?

Is this anything like the noise 3b's with the 5 speed have when they pull away or at low revs?

[SteveH]

Flywheel clatter? take it thats like a rattling noise, never heard of it?

Is this anything like the noise 3b's with the 5 speed have when they pull away or at low revs?

If the the noise you are detecting is a rattle below 2,000rpm, it's likely to be worn input shaft bearings on the 3B box. Usual for the 5 speed box once they have done 100,000+ miles.

[Acidburn]

Sounds about right as every 3b/20v 7a 5 speed i've heard has had over this sort of milage and had the same noise.

The only car I have not heard it on was my coupe quattro which was fine and that was only just over the 100k mark.

[S2_Dave]

Flywheel clatter? take it thats like a rattling noise, never heard of it?

Is this anything like the noise 3b's with the 5 speed have when they pull away or at low revs?

Yeah, a bit like a rattling noise. I did loads of reading on it at the time, but it was a while back so my recollection might not be spot on. The engine vibrates (something to do with the number of cylinders and the rpm) and with less mass in the flywheel these vibrations can become noticeable. A BMW tuner did a lot of research to find the mass that could be removed without introducing flywheel clatter. For the earlier attempt, where they took too much material off, the use of an alternative gearbox oil concoction reduced up to 90% of the clatter. Increasing idle speed would change the frequency of the vibrations and there's a point when the clatter stops (for me it is around 1000rpm).