CincyScott

I'm in the process of porting and polishing my headers (mainly just cleaning up welds -- the 997tt's are SO much cleaner than my 993tt's were) and have seen where others have ceramic coated the outside of them. I'm aware of why you do NOT want to do the inside because of chipping or whatever getting into the turbos, but is it worthwhile to do the outside apart from looks?

Pros, cons? Thanks for any opinions.

jem7v

Keeps heat down I believe. Also it keeps things looking nice.

Dennis C

It will help reduce heat in the engine compartment as mentioned above. How much will it really mater? Not sure. In fact, it may actually direct more heat into the turbos... I have no idea. I know that sport bike guys like to coat their exhausts with ceramic. I had ceramic coated mufflers on my 996.

CincyScott

Yeah, that's where I'm stuck, Dennis. If the exhaust gasses retain their heat, they'll flow to the turbo faster with more velocity theoretically reducing lag. BUT, at the risk of more heat to the turbo, like you mention, is it a) worth it or b) inconsequential.

512bb

I thought the bigger issue was the heat concentration where the header bolts to the block - stainless steel vs. aluminum? I have seen turbos being wrapped to keep the hot side hotter (and the engine compartment cooler), but have not seen headers powder coated.

Hopefully someone with real knowledge will chime in.

Macster

If they were *NOT* coated to begin with I do not think I would coat them.

While the coating may help in some way reduce engine compartment temperatures I'm not sure the benefit would be all the much. I note my 2003 Turbo's engine compartment fan runs all the time the engine is on and this works to force the heat -- and including that from the exhaust system -- down and out of the engine compartment.

I assume (?!) the 997 Turbo engine compartment fan likewise runs all the time the engine is on.

Any reduction in engine compartment heat from coated headers really then is made redundant from the active heat control of the engine compartment fan.

The other concern could be the extra heat the turbo's would be subjected too. I'm not sure this would be all that much but while I do not have a problem with the turbos receiving the heat they do from factory exhaust headers I would not want to increase their heat load either.

Igooz

Heat loss = energy loss in a turbo system. So if you can transfer more heat due to better insulation from thermal coating the more energy you get to the turbo. Is it measurable or negligible, I am guessing that in your case negligible. Unless you are optimizing the whole system for every ounce...so IMHO, it would be for cosmetic purposes. I do like the ceramic coated looks, and for a couple of hundred bucks they do dress up the (under) engine.

Macster, from my experience the fan in the 996TT and 996GT2 came on more frequently and for longer duration than in both 997TT and the 997GT2. Not sure about the reasons other than perhaps different cooling system, or fan algorithms, or air flow?

Macster

Along with transferring more heat (from better insulation) to the turbos comes more wear and tear on the turbos.

The turbos operate at a pretty high temperature to begin with. It was Porsche that was the first automaker to offer variable vane turbos for gasoline engines. These were used in diesels but diesel engines subject the turbos to lower heat loads.

Porsche solved the heat problem but that doesn't meant the sky is the limit and one can dump even more heat to the turbos without consequences.

Thus my philosophy is if the headers were *NOT* coated to begin with, from the factory, I would not coat them.

In the case of aftermarket headers if the header maker supplies them coated I'd use them coated, or if the maker recommends they be coated, then I'd coat them. The header maker may have resorted to using thinner walled metal to cut weight and the coating helps the headers stay as hot as the stock headers would be.

As for the engine compartment fan running less in the 997 Turbo or the 997 GT2, I suspect there is better air flow through engine compartment -- my understanding is just about every next generation car Porsche makes improvements to the aerodynamics of the car for not only improved stability at speed -- cause generally top speed goes up -- but also for improved cooling without the need to resort to more/larger/heavier radiators which would add weight to the car, with more weight affecting the car's fuel mileage and CO2 emissions, or more powerful fans, which would increase the parasitic load on the engine and affect fuel consumption and CO2 emissions.

Also, in the 997 Turbo and 997 GT2 the turbos are water cooled (and have better oil flow/cooling too boot). This I think helps cut down on the heat load that needs to be dealt with by the engine compartment fans.

For some further info on the 997 Turbo's improvements, view the details at this link:

http://press.porsche.com/vehicles/08...Coupe_Long.pdf

Kevin

Here is a good thread on porting and ceramic coating the 996TT headers.. Please note that the factory headers are double jacketed. The ceramic coating works in keeping the heat energy that is in the exhaust combustion stream and focusing it to the turbine wheel. It works very well with the factory shorty headers.

https://rennlist.com/forums/996-turb...tt-owners.html

Post 25 has the uploaded pictures.

A few quick notes: The 997TT KO4 bearing housings is water-cooled. Keeping the car running for 15 to 30 seconds allows the excess heat in the turbine section to cool. The water-cooling and coolant pump takes care of the rest.

The Porsche 997TT was NOT the first VNT turbocharger. The 1984 Dodge Daytona/Shelby had the first VNT manufactured by Garrett!

Macster

Do you have any info on the merits/success of ceramic coating 997 Turbo headers?

My info is only the 1990 Dodge Daytona/Shelby C/S Competition Package model received the VNT turbo and this was present for only one year. Only around 36 cars were produced.

The 1990 C/S Competition Package was carried over as well, and also featured some significant changes. The 90 C/S Competition Package featured a new transmission as well, the A568 5 speed, which replaced the A555 5 speed. As in 1989, the C/S Competition Package was available only with the manual transmission. Most importantly, this was the first and only year for the 2.2 Turbo IV VNT. The variable nozzle turbo, first introduced on the 1989 Shelby CSX, was brought to the mass market for 1990. While the VNT was a technological marvel, it was not a huge sales success, and Chrysler pulled the plug on the engine after one model year.

No doubt the 1990 new car price of over $13K for a fwd 3 door hatch back Dodge played a role in the car's lack of success. (The engine is rumored to be quite robust and capable of big HP if properly modified.)

While the Dodge did have this VNT turbo technology before Porsche in a gasoline engine -- and I was unaware of this or I would have mentioned it and thanks for bringing to my attention -- Porsche was successful at it if selling way more than 36 cars with this technology present and I might add utilizing VNT turbos on an engine that makes over double the HP the Dodge/Shelby engine made (174hp) is an accepted clear indication of success.

Kevin

I base the facts that most people know that the 996TT headers are used on the 997TT.

Yes, I have tested the results on the track and have datalogged the improvements. Is it substancial (no) is it a improvement (yes) > The turbochargers are spooling up 350 RPM's sooner.

Do I want to ceramic coat headers> No, I hate doing them. Do I feel better running ceramic coated headers Yes.... Is porting them and removing/smoothing the weld and port more important Yes.. The nice thing about black ceramic headers is the appearance or corrosion protection that is offered.

Side note: Never ceramic coat the inside tubing or primaries. The coating will chip off and knick/damage the turbine wheels.