Hi guys,

I'm new to the 997TT. I have an 07 with GT3076 Garrett turbos and other mods taking it to about 700rwhp. A couple weeks ago I was out for a brisk drive and noticed the power steering stopped working and clutch was hard.

Serpentine belt was loose. My shop told me the pulley pin was moving around in the pre-drilled hole in the crankshaft. He said if you are on boost and you let off the gas while in gear it can cause a backlash that can do this.

He replaced the pin, pulley and all was well. Well I'm getting the same symptoms today. When I stopped accelerating I recall pressing the clutch then braking and not just closing the throttle. Here are my questions:

1) Are these cars this delicate? I always thought they were super tough... Is this a known thing that you can't just let off the gas while accelerating hard in a gear? Never had such a restriction before.

2) Do you guys have any suggestions to keep this from happening that I might suggest to my mechanic?

thank you in advance!

 

Never heard of that issue on any forum and have never seen it personally?? And lots of guys are making that kind of HP or a lot more....still never seen that or heard of it.

Good luck,
DC

 

Mechanic said that with high hp/boost cars he has seen it where if you let off gas after being WOT while staying in gear you create a backlash. I had not ever heard this. But after WOT in a 1st and 2nd I noticed serpentine belt symptoms like no power steering, clutch and rising temperature.

But why would accelerating hard for a quick few seconds then stopping cause this?

 

I had the same problem 6 months back.
get protomotive pulley with pin and ur problem solved.

I think the cause of it from power shifting.

 

Spoke to Porsche tech.

He said he has seen this primarily on GT3's due to higher compression. He also said this happens when folks go to a lightweight flywheel instead of the stock dual-mass one. And mine does have a lightweight flywheel.

Do you guys think I need to go to the stock flywheel and perhaps even consider a stock GT2 clutch instead of this hyper sensitive stage 3 Clutchmasters that I have now?

 

It's funny because it happened to me at the track two weeks ago and my problem was worse than yours. My crank pulley pin was broke and pulley came loose while I was driving at the track! Luckily I didn't get any damage other than pulley and broken pin. I towed my car to a local Porsche shop and they were able to take the broken pin out. Yes I have a GT3RS lightweight flywheel. Did a research and found the solution. This is one of the product features.

"The critical feature of our crank pulley is the increased surface area where the pulley mounts to the crankshaft. Our design increases this mounting area by more than two times which distributes the contact load of the pulley over a larger area and eliminates the possibility of the pulley spinning loose, even at higher than stock RPM levels."

 

Thank you SWC. So which pulley does your quote refer to? We are going with Promotive which also apparently has two holes to bolt it to the crankshaft as well.

 

Evolution Motorsport. BBI makes lightweight and underdrive pulley as well.

 

We offer this, which was developed to combat the problem you encountered: http://www.evoms.com/EVOMS_Lightweig..._p/epk-gt2.htm. The crank pulley moving around is a common problem on high horsepower and/or high RPM cars.

Whereas the stock pulley relies on the pin/keyway and the small friction surface on the end of the crank snout to hold the pulley in place, we designed our pulley to incorporate a collar that utilizes the entire available crankshaft snout as a mounting surface and support to keep the pulley locked in place. To do this it installs with a light press fit, requiring the pulley to be heated prior to installation along with the use of an installation tool and bolt. It works very well; the pin becomes basically superficial and is only really there to line up the pulley--just as it should be. You can read more about the features and engineering of the pulley at the link. It's also much lighter and has a mild underdrive compared to the stock pulley, which both contribute to give a measureable increase in power to the wheels without causing issues with overheating, lack of A/C or P/S, etc. at idle.

Sam