Dual Mass Flywheel .vs. Lightweight Flywheel--What Performance Differences Do You See - The Unofficial BMW M5 Messageboard (m5board.com)

Anita · 13th January 2004, 04:32

I was at a local car club meeting the other night at Kelly-Moss (Hey, I've got sound posey whenever possible so you all think I know a little bit about what I'm talking about!) and I was talking to one of the Porsche techs about my M5 clutch and its replacement. He told me when I had my clutch replaced I should have had a lightweight flywheel installed in place of the dual weight flywheel that comes stock on my car. He said I could get quicker times during high speed driving events. And he said the main handling difference I would notice would be when shifting during around town driving--I would have to be more precise. I think I'm I quoting him correctly, I did have a beer to drink.

Has anyone ever replaced their flywheel with a lightweight one? What brand? What differences in times/driving performance, if any, did you notice?

Thanks for any ideas/advice on this!

ELEVENS · 13th January 2004, 05:05

Quote:

Originally Posted by Anita

.... I think I'm I quoting him correctly, I did have a beer to drink....

Anita,

If you would have consumed several beers instead of just one, you'd be certain of what he said (or at least you *think* you understood him)

Sorry I don't have anything constructive to contribute, just being goofy tonight

FAST 5 · 13th January 2004, 06:44

To my knowledge, DINAN has two different versions of the lightened flywheel. It appears as though, people opt. to get the stage 1 flywheel over the stage 2, due to the higher noise level which comes from stage 2 flywheel.
Robert

stever · 13th January 2004, 08:27

Quote:

Originally Posted by FAST 5

To my knowledge, DINAN has two different versions of the lightened flywheel. It appears as though, people opt. to get the stage 1 flywheel over the stage 2, due to the higher noise level which comes from stage 2 flywheel.
Robert

there are quite a few posts of single mass vs. dual mass flywheel -- i put in the Dinan stage 1 lightweight dual mass with clutch replacement and can sometimes maybe notice a difference. this is not high in my list of up-grade priorities

MIB · 13th January 2004, 11:16

Hey A,

I have a single mass flywheel. Don't go too light as the Beast requiries weight to launch it. Its O.K. for a lightweight P car, but our porky beasts, need a little weight.

That said, the dual mas is incredibly heavy. Instead of going for a lightweight alloy one which usually flys apart, at super insane rpm's and is illegal on a drag strip, I had mine customed out of a special steel. Super strong.

I think (10/45) don't quote me on that number, I had more than a few.

Just changing the flywheel really isn't going to produce any large changes.

In for a penny , in for a pound. Clucth, Pressure plate and flywheel all work as one.

Change one, and you really should change all three and remove all the problems forever.

Once the Flexi Dual mass piece of Rubbish is gone, you can then increase clamping pressure. The dual mass is so weak, bmw only use 2,600 pounds clamp. The dual mass can't handle anymore. Get rid of it, go back to a solid single mass, and I have increased clamping pressure to 4,300+ pounds of clamp. That aint slipping for no man, once hooked up.

My 5 button carbotic clucth is super street able and will handle any track situation and all mods. Problem GONE.

I can launch from any rpm. The only thing that burns is the tyres.

I can bark the wheels when hitting fourth on the quarter mile.

I love it. It is a small price to pay to roll over noise at idle. I will get around to raising the idle, as this quietens it right down.

If I am stopped at the lights, and want to let the clutch out, I just hold a light pressure on the accelarator to bring the revs upto 800 and the noise is gone.

But it doesn't bother you inside the car. Its those dam pedestrians giving you a funny look. If it isn't a long stop, I just keep the clutch held in and it is silent.

Anyone who is a track monster, the noise is nothing .

Its loud from outside the car, but Track people know its just rollover noise. It lets everyone know that this beast is not stock.

Lscman · 13th January 2004, 15:29

The MIB solution is the only one I've seen that looks suitable for a M5. Other setups are too light and result in terrible noise that's poorly suited to a Corvette, let alone a $75K saloon. Lightweight flywheels are a cool upgrade that lots of people "want", but you won't see significantly improved lap times. The gains are probably on the order of 0.1s a lap...or less, unless you're a real good heel & toe driver. Personally, I would not degrade the streetability of my car chasing down such gains.

RRoberts · 13th January 2004, 16:51

Anita:

I am probably one of the few M5 owners who have had recent experience with both the Dinan Stage 2 (single mass) and "Stage 1-like" (cut-down BMW dual mass) flywheels. This was all occasioned by the need to install an upgraded clutch following severe slippage experienced at RA with my S2 equipped car. I am using the Sachs Race Engineering pressure plate and disc originally intended for the E46 M3. This clutch has the same dimensions as the stock unit, but is not self-adjusting for engagement point and the Sachs disc will not fit on the stock flywheel without minor machine work to reduce the height of the annular raised boss near the crank flange bolt circle.

The weights of the flywheel/clutch assembly work out as follows:

Stock (dual mass) 52 lbs.
"Stage 1" (dual mass) 44 lbs.
Stage 2 (single mass) 25 lbs.

The reduction in rotational inertia (what resists engine acceleration) will be somewhat greater than the weight reductions shown above, due to the fact that flywheel diameter is also reduced.

As far as driving with the two systems, I would offer the following observations:

General: The improvement in engine acceleration response is noticeable, obviously more so with the Stage 2 setup. This is useful to the driver mainly in the lower gears. The advantage of reduced rotational inertia is largely neutralized, IMHO, by the considerable mass of the M5 and the modest rear axle ratio.

Stage 2 (single mass) flywheel: The Dinan unit is, for my purposes, incredibly noisy. The noise at idle is well documented and more than I expected. However the noise at low speed (1500-2500 rpm) when creeping around in 2nd and 3rd gear is much worse - quite loud and sounds like the transmission is about to fall out. This behavior is totally out of character with the refinement of the E39 M5, also IMHO, and is why I changed to a different flywheel a short time later. Two other issues with the Dinan Stage 2 (or similar aluminum) flywheel deserve mention. First, the very low rotational inertia makes it quite (very) easy to stall the engine on start-up from a stop. Also the steel insert construction is very intolerant of clutch slippage; put a lot of heat into the steel insert and it will permanently "pucker up" like a tufted mattress around the attaching bolts. This effectively reduces the contact area for the disc, making subsequent slippage more likely. This did not happen to me, but I have seen it elsewhere. I would absolutely not recommend using the stock M5 clutch with a steel insert/aluminum flywheel. Mark's (MIB) custom steel single mass flywheel obviously overcomes these last 2 issues, and possibly his use of a sprung center clutch disc reduces the noise.

"Stage 1" cut-down dual mass flywheel: I am presently quite pleased with the combination of the Sachs pressure plate and clutch on this flywheel (I had the original stock flywheel machined and re-balanced by local shops). Engine response is noticeably (if slightly) better, clutch engagement is smooth in daily driving, and did I say it is QUIET. It also locks up with authority. I also second the opinions of others who have observed that shifting is smoother with this flywheel (engine decelerates a little more quickly between shifts). Concern has been raised over the durability of the stock dual-mass flywheel in serious performance applications - specifically the leakage of oil from the dual mass absorber. Anecdotal evidence seems common in the Porsche community. We will see how this goes, and also how durable and slip resistant the Sachs clutch is over time. It is not expensive, compared to a custom unit, and not especially difficult to purchase another stock flywheel and have the machine work done if failures occur at sufficiently widespread intervals - in exchange for the silence and driveability advantages. This last is obviously my personal trade-off, for a car that is primarily street driven and sees the track only a few times a year.

In terms of aftermarket parts, it looks like UUC is getting ready to release an aluminum/steel insert flywheel similar to Dinan's Stage 2, and have found a sprung center clutch disc (from Sachs) that will fit. It is not yet clear (to me at least) which pressure plate they intend to use, whether custom or off-the-shelf, as their other clutch upgrades seem to be applying rxisting BMW parts to lower-rated engines (e.g., M5 pressure plate to E46 M3). A sprung center clutch disc may make the lightweight single mass flywheel acceptably quiet, but a higher clamping force pressure plate will be an absolute must with the composite flywheel.

Hope this helps.

Regards, Dick Roberts

MPressed · 13th January 2004, 17:55

Anita,

I've been talking to UUC Motorwerks and they've been testing their LWF for the past couple of months. They've built a LWF/Clutch combination that's supposed to have groundbreaking innovations. There is supposed to be no rattles that is commonly associated with a LWF. I need to give them a call to day to see their progress.

MIB · 14th January 2004, 00:03

Quote:

Originally Posted by RRoberts

Stage 2 (single mass) flywheel: The Dinan unit is, for my purposes, incredibly noisy. The noise at idle is well documented and more than I expected. However the noise at low speed (1500-2500 rpm) when creeping around in 2nd and 3rd gear is much worse - quite loud and sounds like the transmission is about to fall out. This behavior is totally out of character with the refinement of the E39 M5, also IMHO, and is why I changed to a different flywheel a short time later. Two other issues with the Dinan Stage 2 (or similar aluminum) flywheel deserve mention. First, the very low rotational inertia makes it quite (very) easy to stall the engine on start-up from a stop. Also the steel insert construction is very intolerant of clutch slippage; put a lot of heat into the steel insert and it will permanently "pucker up" like a tufted mattress around the attaching bolts. This effectively reduces the contact area for the disc, making subsequent slippage more likely. This did not happen to me, but I have seen it elsewhere. I would absolutely not recommend using the stock M5 clutch with a steel insert/aluminum flywheel. Mark's (MIB) custom steel single mass flywheel obviously overcomes these last 2 issues, and possibly his use of a sprung center clutch disc reduces the noise.

In terms of aftermarket parts, it looks like UUC is getting ready to release an aluminum/steel insert flywheel similar to Dinan's Stage 2, and have found a sprung center clutch disc (from Sachs) that will fit. It is not yet clear (to me at least) which pressure plate they intend to use, whether custom or off-the-shelf, as their other clutch upgrades seem to be applying rxisting BMW parts to lower-rated engines (e.g., M5 pressure plate to E46 M3). A sprung center clutch disc may make the lightweight single mass flywheel acceptably quiet, but a higher clamping force pressure plate will be an absolute must with the composite flywheel.

Hope this helps.

Regards, Dick Roberts

Hey Dick,

Yes my sprung centre made puttering around acceptable. I do not get any noise above 1,000 rpm.

The main time is just at idle. You can't here it from inside the car, but you most definitly can from outside.

But its only at idle with the clutch out. So if I keep the clutch in, at idle its perfectly quiet. I still haven't raised my idle limit yet, but that will make it right.

I do it all the time at lights if there are pedestrians about. I apply a light throttle and bring the rpm upto 800. That reduces the noise by around 80% to where it is acceptable.

At 900 it is almost completely gone. and by 1,000 it is totally gone. But now I have a decent clutch and pressure plate, I can launch with revs before clutch. So if I take off at 1,200 it is totally smooth and silent.

To show you streetability of this settup, I can in fact take off with no revs at all. Just start letting the clutch out, however once all the way out, when you apply throttle and you are under the 1,000 rpm, I do get that rattle you soke about with your S2 Setup. But it is only at insanely Low RPM. So the sprung centred clutch really did do a lot in controlling the noise. It didn't totally eliminate it, but it went along way to making it acceptable.

RRoberts · 14th January 2004, 00:12

Quote:

Originally Posted by MIB

Hey Dick,

Just start letting the clutch out, however once all the way out, when you apply throttle and you are under the 1,000 rpm, I do get that rattle you soke about with your S2 Setup. But it is only at insanely Low RPM. So the sprung centred clutch really did do a lot in controlling the noise. It didn't totally eliminate it, but it went along way to making it acceptable.

Mark:

Thanks for the feedback. I expect the heavier flywheel is a big help in this regard. Did you measure the weight of your setup? The Dinan Stage 2 flywheel weighs about 12 lbs., and the clutch & pressure plare weigh about 13 lbs., for a 25 lb. total.

Regards, Dick Roberts