Hi guys, I need your technical help.

I have a 997.1 Turbo and did a complete rebuild of the car.
I am using a single mass flywheel combined with a sachs clutch
- clutch disc 881864001098
- clutch cover assembly 883082999764

I have the following problems:

1. Really loud noise in neutral but also within gears combined with bad vibrations
2. While engaging the clutch the engine revs around 2000rpm stuck like driving up a hill for a very short moment.
3. I think the noise is louder when the car is hot to warm and sometimes it is
gone especially when i start the car in the morning
4. I drove only two days and about 80km. I think the noise gots worse over the day and while driving I had really bad vibrations as well. 2 days later i did 5 meters in the garage and the noise was gone.
5. The gearbox is out now, but i couldn't find anything at all

- I am using release bearing with sachs number
"3151227002" Is this the wrong one maybe?
- did i need other parts for this conversion?
- Is the 997 GT2RS bearing and tube the correct one for me?
944 116 080 001 and 950 116 813 30. Maybe i did a failure here, because I am using the one from sachs (3151227002) and the original tube from the turbo
- Would you guys keep the single mass
- I am using the solid evoms gearbox mounts (the softer ones) and the RSS
engines mounts as well. Is this maybe the wrong choice
together with the single mass flywheel, should I go back to OEM???
- Would you keep the single mass flywheel or should I go back
to the OEM dual mass one with sachs race clutch?
- Concerning the stucking revs. It is possible to have axial crankshaft movement
while pressing the clutch and the crank is pulling against a wall in the
crankcase???
- Could it maybe be also the gearbox? But why vibrations in neutral then?


Thanks a lot for your help in advance!!!
Regards
David

 

You're using a single mass flywheel along with a rigid hub disc (meant to be used with a dual-mass flywheel), which is the major cause of the noise. At idle and lower RPM, the crankshaft is not really moving at a constant speed--it is constantly speeding up and slowing down, three times every revolution, due to cylinders compressing and firing. When this happens, it can cause the gears in the transmission to clatter against each other. At higher RPM it smooths out a bit due to inertia, but at idle and under 3000rpm or so, it can be quite noisy. A sprung clutch disc or dual mass flywheel help to absorb these vibrations, which is easier on the gears and much quieter as well. Also, I can't speak well to a totally rigid clutch/flywheel setup, but with a single mass flywheel and sprung disc (or dual mass flywheel and rigid disc), the noise is harder on the driver than it is on the transmission.

Your situation is also not helped by the upgraded transmission mount, which even on the softer durometers is known to transmit noise from the transmission case to the unibody, even with the stock clutch. It's a worthwhile upgrade for a track car, but for a street car the noise is often a little much.

Switching over to a sprung hub disc and back to the stock transmission mount should greatly reduce the noise. You will still get some gear clatter at idle and at lower RPM, but it is an acceptable level and most people get used to it.

 

Cool, thanks a lot for your technical advice!

Some questions:
- could you help me a bit, because I am german
- "rigid hub disc" means sinter metal disc or just without springs so single mass?
- "sprung hub disc" means dual mass flywheel, correct?

So I should to the following:

- switch back to dual mass combined with sachs race clutch
- switch back to original trans mount

You wrote "you will still get some gear clatter at idle and at lower RPM"
- this noise comes from? shouldn't it be gone with the dual mass and be like OEM system?

Thanks a lot for your help I really appreciate

 

Could you please give a short and final advice.
- would be very kind and helpful

Thanks again
David

 

Rigid disc means the clutch disc doesn't have any springs built into its hub. With a street clutch, you want some member of your clutch/flywheel assembly to have some kind of torsional give to it--either a dual mass flywheel, or a sprung hub disc.

Take a look at the pictures shown in our Stage 1 kit: http://www.evoms.com/EVOMS_Stage_1_C...clu996ttl1.htm. The picture on the left is for the stock flywheel; the flywheel has give to it so we use a rigid clutch disc. The other two pictures are the clutch kits for a lightweight aluminum or lightweight steel flywheel; notice the clutch discs in those pictures have four springs arranged around their hub, giving some cushion to the drivetrain as the flywheel is now rigid.

Your alternatives are to keep the single mass flywheel, and purchase a sprung hub disc; or to do as you've said and use your current Sachs Sport clutch with the stock dual mass flywheel. The first option will have some noise, but will be quieter than what you have now. The second option will be as quiet as it was stock.

In either case, going back to the stock transmission mount will reduce the amount of sound transmitted into the car.

Sam

 

Okay thanks

I have some other questions:

- for sure i will change to the oem trans mount

- is the weight difference between Single and dual mass flywheel a big performance difference?

- would a dual mass system survive a high power vtg setup and how long approx.?

- why are you guys using the Single mass flywheel together with the Sprung hub disc instead of just using the parts like the Sachs Kit is doing?

Best regards
David

 

You're experiencing typical issues with a single mass flywheel. Not worth the hassle on these cars.

Get a Sachs "Stage 2.5" clutch with an OEM dual mass flywheel and call it a day.

 

You can definitely notice a difference in how freely the engine revs, and how the car accelerates due to the loss of inertia, especially in the lower gears.

We run them in many of our EVT775 cars, which put down around 650ft-lb to the wheels. I have not heard of a single failure due to power in a car like that. I would venture to say that the stock flywheel is as good for as much power as you'd want to run through a stock-style single plate clutch.

We put together our own clutch kits with Sachs and OEM Porsche parts because we felt they worked better in those combinations, meaning they engage smoother, have less pedal effort, hold the power we're looking for, and don't make as much noise as the Sachs kits.

 

Is the release bearing for single and dual mass flywheel the same part number?

I am a bit confused how to compensate the missing length from the missing dual mass flywheel.

I am using:

94411608001 - release bearing
95011681330 - "support tube"

 

Depending on which flywheel you're using, the difference is made up in the thickness of the single mass flywheel, or by the arms on the release bearing. I sent you a PM to get more information, let me know back .

Sam