Kevin

I have had some conversation with KKK with regards to the heat issues and what design issues might be changed in the next generation of units. I will post an interesting email.......

Concerning your question about the bearing housings used in the K24 turbos
of the 993 and 996 GT2, I have talked to our responsible project manager. He
had the following info which might be interesting for you:

We haven't had any complaints about increased oil carbon build-up in the new
bearing housing so far. Indeed the new bearing housing insulates the piston
ring and turbine end bearing areas better from the turbine heat than the old
one.
However, due to a reduction of the overall oil flow rate per minute in the
996 engine, the cooling effect that the oil provides for the turbos is
probably somewhat reduced. This might lead to oil carbonization especially
if the exhaust gas temperature is higher than normal when the engine has
been upgraded. Moreover, the turbos are located in a position where they
don't get a lot of airstream.
A solution for this thermical constraint could be to remove the stock heat
shields, which are mounted to the turbo/exhaust system, and replace them
with self-made heat shields mounted to the vehicle body, leaving more space
around the turbos. Additional air baffles to direct airstream onto the
turbos would be the optimum solution. BTW: the main function of these heat
shields is to protect the tyres(!).

If you have any further questions concerning this or other issues, please
don't hesitate to contact me.
Thanks for your help in advance, and have a nice weekend!

krish

Thanks for the post Kevin . Very interesting !

cheers,
kris
'97 993tt
'89 535I
'00 Mit Evo6

Kevin

The next question is... Who wants to redesign the turbine housing heat shields...?

viperbob

"IF" I owned a 996TT, then I may be inclined to tackle such a project. As such, why can't someone just follow the 996TT lead and spray liquid nitrogen over the intercoolers, and then direct this air to the Turbo. Problem solved, right?

So do I understand from this that there is no issue on the 993TT side as far as overheating??? Lord I don't even have a muffler next to the turbo any longer I would think there would be enough airflow.

Thanks Kevin.

Kevin

viperbob;

It does concern our cars. We have the heat shield on the turbine housing and share the same bearing housing's. However on the K24's there is more oiling added for cooling, but not enough.

viperbob

The only shielding near my turbos is between them and the motor. Now I have a huge hole behind the tires where the mufflers use to sit which should allow of free flow of air past the turbos. Am I missing another shield somewhere that you are describing.

Thanks Kevin.

Joe@Fabspeed

Kevin
why not just eliminate the heat shields all together along with the stupid engine undertray. On all Clubrace/DE 993TT and 996TTs I havent seen any issues even in ARIZONA in July/August.
Joe Fab

Kevin

Joe;

Your on the right track.....

A solution for this thermical constraint could be to remove the stock heat
shields, which are mounted to the turbo/exhaust system, and replace them
with self-made heat shields mounted to the vehicle body, leaving more space
around the turbos. Additional air baffles to direct airstream onto the
turbos would be the optimum solution. BTW: the main function of these heat
shields is to protect the tyres(!).

I think that we would be better served to ceramic coat our turbine housings. When we ceraminc coat our housings we also do the large inner part of the exhaust side of the housing, along with the outside. by doing the inside we keep the heat inside and pass it through to the cats. There is a post on the 996TT board that shows a dyno run and the housing glowing white. We do not want the heat to transfer to the tires/rims...

Q

thanks for the informative read Kevin

Does anyone have a photo of 996 turbos insitu ?
here is the 993 heat shield...

viperbob

OK, now this all makes sense. When I first bought the car, I took it immediately to the Racers Group for some work which included swapping in a set of Porsche Motorsports K24s. And now there are no shields on the turbos. So I guess Kevin has some extra shields laying around his garage. Not surprising I didn't get all the take off parts back. Had the same problem with my engine and transmission covers, my PSS9 wrenches (twice), clamps for holding on the cats, and lugnuts. Most of the stuff they eventually found in their shop or someone elses. So too this list I add turbo shields.

OK then, I should be pretty well set as they are already gone (permanently).

KRA993tt

Bob

That is usually an extra charge out east. And then you need to by new parts as the old ones were no longer up to spec.