I have been perusing the service manual and I have discovered that the Speed version of the 3 (not the NA ones) has a "Dual Mass" flywheel. I did some searching around to see what this means, and I thought I would share what I found. The flywheel is actually made in two parts, each one with some significant amount of inertial weight; the two parts are connected with compression springs. One part is bolted to the end of the crank and the other part carries the clutch connecting to the transmission. The clutch disk does not have the usual springs in the hub, this function is taken over by the springs internal to the flywheel. The effect is to add some controlled drive line lash, with inertia and springs to dampen the effect. The function is much like the "cush drive" on a motorcycle.
The reasoning behind all this is to reduce the shock loads of the high power of the engine from trashing your transmission and diff, as well as smooth out clutch engagement chatter. These are commonly installed on large diesel motors, as well as high end sports cars such as Porsche and BMW.
A downside of this implementation is that there are more parts to go wrong, and if you need to replace your clutch, you almost certainly need to replace the flywheel too, which adds significantly to the cost of a clutch job. The Dual Mass Flywheel cannot be resurfaced, it must be replaced if the friction face is scored or hot-spotted. The flywheel is likely to cost something like $1200 in addition to the clutch itself and the labor to put it in.
The bottom line is that this is a pretty nice setup that should perform very well, but don't abuse it because it's going to be expensive to fix.
One other thought I had is that the Dual Mass flywheel may add to wheel hop as it stores the energy from a hard launch, releases it when the wheels break free, and stores it again when traction is regained. This increases the energy transfer reinforcing the stick-slip oscillation of wheel hop.
The reasoning behind all this is to reduce the shock loads of the high power of the engine from trashing your transmission and diff, as well as smooth out clutch engagement chatter. These are commonly installed on large diesel motors, as well as high end sports cars such as Porsche and BMW.
A downside of this implementation is that there are more parts to go wrong, and if you need to replace your clutch, you almost certainly need to replace the flywheel too, which adds significantly to the cost of a clutch job. The Dual Mass Flywheel cannot be resurfaced, it must be replaced if the friction face is scored or hot-spotted. The flywheel is likely to cost something like $1200 in addition to the clutch itself and the labor to put it in.
The bottom line is that this is a pretty nice setup that should perform very well, but don't abuse it because it's going to be expensive to fix.
One other thought I had is that the Dual Mass flywheel may add to wheel hop as it stores the energy from a hard launch, releases it when the wheels break free, and stores it again when traction is regained. This increases the energy transfer reinforcing the stick-slip oscillation of wheel hop.
