[CTDrifter]

After going PS2 I was getting repeatable misfires whenever over 20psi (~500hp) and switched to a SMF with 550i clutch. The car ran great and I haven't had a single misfire since but the NHV is almost unbearable... the chatter at idle isn't that bad, the worst part is light acceleration when cruising at a lower RPM.

I wonder if my problem is due to running a solid flywheel with a solid friction disk (550i). If I were to switch to a SPEC clutch with sprung friction disk would it make a noticeable difference in NHV? Does anyone have first hand experience with this?

[E36M3]

If removing the DMF with its internal dampening springs that absorption mechanism must be replaced with a sprung hub disc when going to a SMF. If the absorption mechanism is not substituted with a sprung hub disc you will end up with the gear rattle as the crankshaft loads and unloads as each cylinder fires and then goes to an exhaust stroke. A quick check of factory stick shifts that are single mass flywheel designed will demonstrate this is engineered in to avoid the NVH issues you are having.

Bottom line: a sprung hub disc will solve your issue.

Be sure to check your flywheel surface before trying to bed in a new disc. I'd recommend your disc and pressure plate be a match set to avoid clamping pressure, fulcrum point and disc thickness not being engineered as a system.

[Jeff@TopGearSolutions]

A sprung clutch would help.

So the rattle noise at idle isn't what you're talking about.

Are you getting noise, vibration or both?

[CTDrifter]

Thanks E36 but understand all of that which is why I asked if anyone had experience with the two types of clutches on the SMF.

The rattle at idle isn't too bad and I'm pretty sure that will be prevalent even with a spring clutch.

The worst is accelerating in higher gears around 2.5k rpm. There's a very noticeable roar inside the car which is completely gone with the DMF. There's no real vibration I can fell in controls but overall it sounds bad.

[Logicoeur]

Originally Posted by CTDrifter

Thanks E36 but understand all of that which is why I asked if anyone had experience with the two types of clutches on the SMF.

The rattle at idle isn't too bad and I'm pretty sure that will be prevalent even with a spring clutch.

The worst is accelerating in higher gears around 2.5k rpm. There's a very noticeable roar inside the car which is completely gone with the DMF. There's no real vibration I can fell in controls but overall it sounds bad.

The reason so many cars come with DMF, and/or sprung clutches, is to reduce the nvh you've reintroduced. Removing those attributes introduces nvh back into the system. It's quite clear.

Both will reduce the nvh, but the DMF will remove more than the sprung clutch. However, I'm assuming you changed to clutch to prevent slipping with the added power of the PS2, so go sprung clutch instead. You still succeed in lowering the rotational inertia, reduce your horrible nvh, and get the added clamping force you were likely looking for.

[CTDrifter]

Thanks, I actually switched to 550i clutch when I started slipping and that held the power fine at 24psi but I was plagued with misfires around 6k RPM. I switched to SMF and it completely resolved the misfire issue.

I'm sure a spring clutch with SMF will be better than a non spring setup, debating if the extra power is worth all the work.

[Logicoeur]

It will be worth it. You can sell the 550i clutch to recoup the costs.