Flywheel Wieght Reduction?

[dkerley03]

I have a stock single mass flywheel for my Getrag 260 swap into my 1988 325is. I found a performance Engine Machine shop that will lighten and balance my flywheel for $150. They are very well respected and skilled, I am not worried about that. My question is will I gain much over a stock flywheel, will I need to be aware of creating any problems in reliability? In general more guidance is appreciated. My flywheel 1985 325e, I the matching trans, clutch, pressure plate, etc..

[Dillinger]

I have heard that 8.5 lbs is the absolute minimum on an M20 I don't know what happens if you go below that though.

[erik325i]

I have heard that 8.5 lbs is the absolute minimum on an M20 I don't know what happens if you go below that though.

Down to 8.5 from a stock flywheel? That's what most e30 aluminum flywheels weigh.
Most guys shave it down to about 12 lbs.
As long as the shop knows what they're doing and don't tank off too much material, it'll be fine.

Erik

[Dillinger]

Down to 8.5 from a stock flywheel? That's what most e30 aluminum flywheels weigh.
Most guys shave it down to about 12 lbs.
As long as the shop knows what they're doing and don't tank off too much material, it'll be fine.

Erik

Not what I'm meaning. 8.5 lbs is minimum for the engine is what I hear, but like I said I don't know why maybe the crank will break or something.

[rThor432]

^^Yeah most guys take the stock flywheel down to about 12 lbs., which was standard for the early 320/323i flywheels. The 12 lb. flywheel will give you no problems with reliability and such.

The biggest gain I've seen with all of my light flywheels is the deceleration when downshifting. They also rev a bit more freely, of course, than the stock 17-28 lb. flywheels.

$150 for that service sounds about right. That's a little bit more than you might pay for a 320i/323i flywheel if you can find one, but it saves you the trouble of having to look.

[E30_fiend]

^^Yeah most guys take the stock flywheel down to about 12 lbs., which was standard for the early 320/323i flywheels. The 12 lb. flywheel will give you no problems with reliability and such.

The biggest gain I've seen with all of my light flywheels is the deceleration when downshifting. They also rev a bit more freely, of course, than the stock 17-28 lb. flywheels.

$150 for that service sounds about right. That's a little bit more than you might pay for a 320i/323i flywheel if you can find one, but it saves you the trouble of having to look.

a 320i flywheel will fit the getrag 260? how much does it weight in total? Im asking cuz I have a 320i sitting at my shop as we speak.





Taylor

[rThor432]

Yeah it'll fit just fine. I think you might need to check into the clutch/pp/to bearing combo (you should need all 320i/323i components). It's the same flywheel just turned down because the 320i/323i M20's had a heavy balancer on the front of the motor instead of just having the heavy flywheel behind it.

Weighs 12.75 lbs. according to the UPS postal scales at Mitch M's shop.

This is, of course, M20 E30 320i/323i cars.

[E30_fiend]

hmmm so would it even really be worth it??

[erik325i]

hmmm so would it even really be worth it??

The "worth" of a mod is up to you. I'd say a light flywheel is definitely worth it. There's little I hate more when driving than a heavy flywheel.
Others don't care about slow revs, so for them it's probably not worth it.

[Stephen]

Taylor, i get your old flywheel to fuck with

[Liam]

Worth it?

Kind of depends on what you are after in performance gains and what you are willing to sacrifice / trade for it.

A lighter flywheel will spin up faster but it will also spin down faster (not a desirable trait for long track or street use).

A good weight is right about 13lbs for an M20B25 (16lbs for an M42*) for all around performance and drive-ability.

*4 cylinder engines need the weight to carry the power pulses through.

[rThor432]

There's little I hate more when driving than a heavy flywheel.

I agree.

Swapping from a dual mass flywheel in my eta to a single mass was a night and day difference. That was just from a 28 lb. to a 21 lb flywheel (weighed all of the E30 flywheels one day).

My 318is went from a 28 lb. dual mass to an 8 lb. single mass, and my S52 eta went from a 28 lb. to a 11 lb. flywheel. It's one of the best modifications you can do to a car, in my opinion of course.

Like I said, my favorite improvement of the light flywheel over the heavy stock part is the engine braking. It really helps not to have all of that reciprocating mass. Of course, theoretically more reciprocating mass would put less effort on the motor when you are cruising at constant speed, but when you are actually driving the thing how it is meant to be driven that isnt something you should concern yourself with.

[dkerley03]

Balancer on auto M20B25?

because the 320i/323i M20's had a heavy balancer on the front of the motor instead of just having the heavy flywheel behind it.

Weighs 12.75 lbs. according to the UPS postal scales at Mitch M's shop.

This is, of course, M20 E30 320i/323i cars.

That bring up a question i had, is there a balancer on a auto M20B25? If so, do i need to remove it?

Thanks
Dennis

[dkerley03]

Improvements I want

Worth it?

Kind of depends on what you are after in performance gains and what you are willing to sacrifice / trade for it.

A lighter flywheel will spin up faster but it will also spin down faster (not a desirable trait for long track or street use).

A good weight is right about 13lbs for an M20B25 (16lbs for an M42*) for all around performance and drive-ability.

I believe the fast spin up and additional engine braking is what i want for my driving in the mountains of Eastern mountains of Kentucky and Tennessee.

[samurai7]

I agree.

My 318is went from a 28 lb. dual mass to an 8 lb. single mass, and my S52 eta went from a 28 lb. to a 11 lb. flywheel. It's one of the best modifications you can do to a car, in my opinion of course.

rThor432, are you experiencing any gear lash/rattle/noise due to your 8 lb. single mass flywheel on the m42?