porcho heat

I've searched and come up with this:

Fidanza doesn't make a 944S2 application.
and
SPEC was considering a 944S2 lightweight flywheel.

Just wondering if anyone has any more information or any companys producing a l/w flywheel for the S2, because I'm going to need to buy a flywheel, might as well buy a lightweight one if I can.

Thanks

bgiere

Have the stock flywheel machined...I am not certain about the S2, but I know you can safely macine 9 pounds from the 8V version....Steinel's had offered to machine one for me.

Fishey

There isn't a lightweight flywheel avalible for the S2..

eohrnberger

What's the downside to lightening the flywheel?

There must be one, as why else would Porsche engineers put that much weight on a stock one?

993944S2

One downside is the car will not idle well.

Don

Matt O.

I have talked with SPEC and an S2 LW FW is in production.

Stay tuned to their website or call them.

-Matt

Matt O.

The revs die down rather quickly so you must shift quick to keep the power up. I would guess alot of it has to do with ease of driving and gas mileage.

993944S2

What is the web site for Spec?

82-928/89-S2

I've never experienced this myself but I know about the theory behind it.

Unless you need to accelerate quicker while the car is already in motion, then a lighter flywheel will reduce your rotational inertia. It provides almost no benefit to take weight out of the center; most of the weight should be removed from the outermost diameter.

The problems with this I see are:

The flywheel acts to absorb vibration between the engine and the drive train. By reducing the rotational inertia of the flywheel you will allow more engine vibration into the drive train. You will also change the natural frequency of the crankshaft which will move your engine harmonics to a different frequency which could possibly superimpose with other vibrations being generated by the car.

My guess is the Porsche engineers tried to tune the flywheel to have the engine/car frequencies cancel each other out at rpm ranges that the motor was in the most. The motor mounts also play a part in the transmission of frequency through the car and I would guess that they would also be affected by a lighter flywheel.

Your launch from a dead stop will also suffer. You will need to drag the clutch more at a higher rpm to get it to move off the line. You may also find that you have more clutch chatter off the line, as it's much easier for the engine to stall without the added inertia.

Thermal expansions are another issue, as the thinner portions of the flywheel will have a tendency to heat up and cool off faster than the rest of the flywheel. This could cause the flywheel to distort when changing temperature causing mating issues between the clutch disk and flywheel.

I can tell you this; Porsche went out of their way big time to reduce engine rotational inertia as much as they could. The reason these cars have such a short timing belt life is because they used the absolute minimum timing belt pulley diameter on the crank shaft (minimum number of teeth engaged that they could get away with) to reduce rotational inertia so the car would accelerate quickly.

If you are using the car on the highway a lot then I would definitely leave the flywheel alone.

Just some food for thought. I would try to find someone who's done it and get their feedback before I did any alterations.

Hope this helps

porcho heat

Anyone have any info on the rough price to get a flywheel machined, then?

Thanks for all the info, I'll be digesting it for a while.