vanster

As I am about to have my S4 flywheel turned I am wondering
is the S4 lighter than the DD flywheel.???
Is this the only adaptation to change from a single to a DD?
Painted lettering on my flywheel it says Ebay 928 S4. Why can't PO's just leave things alone?

Rob Edwards

The S4 flwheel weighs slightly more 'cause it has the timing ring cast into it, while the 80-86 flywheels don't. Here's an 85-86 flywheel (with an S4 timing ring fitted to it, to work with S4 brains):



Vs. an S4 flywheel with the integral teeth. The difference can't be more than a pound or 2.





Flywheel machining spec:

Mike Simard

No 928 flywheels themselves weigh much. It's the PP assembly that is freakishly heavy. The whole S4 setup is just awful.
Using an early DD setup transforms the car by making the engine feel nimble. It's one of the best things to do to an S4 IMO. You do have to add the timing ring and drill a dowel hole though, Rob's picture looks like a fixture for doing just that, and a noble use of a kitchen cutting block too!

Rob Edwards

FWIW, S4 flywheel with ~100K miles of wear = 4802 grams.

vanster

How much work is it to return to a DD and is it worth it?

Mike Simard

So you have a 1980 that someone fitted an S4 clutch to? It might be best to call 928Intl and have them send everything including the arm and even slave or you may wind up chasing down odd parts for mixing.
In theory a DD should just bolt up.

Maybe you can find someone that had trouble adjusting a DD and wants the simplicity of a single.