Video animation of how a Dual Mass Flywheel works...
 

Not sure what other cars use this but I know the Getrag in the Supra does... its meant to reduce NVH from the engine/trans... and going to an aftermarket solid flywheel will result in chattering and noise.
Anyway, just thought it was interested to see the breakdown like this so if you're interested in learning something check it out.

Dual Mass Flywheel Vid:
http://www.youtube.com/watch?v=YnaXB8q3uzQ

thats pretty cool! Excuse my ignorance but what would be the prupose for this flywheel, drivetrain shock?

Ive always wondered what that was, its supposedly offered in a subaru trans. ive been staring at a diagram on my wall since feburary that excludes the dual mass flywheel and never knew what it meant.

I am pretty sure my car has one

if I understand it right, a car with a dual mass (or sprung) flywheel uses a solid hub clutch. A traditional flywheel uses a sprung hub clutch.

as far as I know all 5-speed WRXs have a standard solid flywheel

Really? I've never seen or heard about it in subies... Legacy model option maybe?

I believe the DMF's main function is to remove NVH (noise, vibration, harshness), and is also designed as part of the damping system on the rotating assembly.

Its a print out from a mitchell repair guide and it lists all the parts in the tranny as a side veiw. It says this exactly.


Pointing at 1st sub gear.

1st driven sub gear (except models with dual mass flywheel)

that was a really cool video! i like it i wonder if there is one for my lt1 :D

just a big complex heavy dampener i guess. ill bet it will lose you a good few HP too. a solid flywheel would probly be a good upgrade for a car that comes stock with one of these. i doubt it would be too detrimental

A lot of manual transmissions, including some of the best, have inherent gear rattle due to the optimum gear clearances, shaft loading, etc. So when the engine vibrations are transmitted through this type of transmission, you hear rattles and vibrations which are often deemed unacceptable in a street car. The dual mass flywheel is a transmission vibration damper, similar to a crank damper pulley hanging off the front of most crankshafts. The Getrag tranny used in the MkIV 6 speed Supra, as well as many Porsches and other cars, is quite rattle prone so they use this type of flywheel to dampen out noises.

IMO the noises are not otherwise harmful and they don't really bother me, so I got a lightweight flywheel which does allow some gear rattle to be heard under some conditions, sometimes at idle, sometimes not, but it goes away as you approach and get over 2000rpm. The typical LWFW frees up about 10 to 15whp. Here's a nice writeup of the Luk dual mass found in many cars including the Supra 6sp:

http://www.mkiv.com/techarticles/luk...eel/index.html