on a TT or not pls ??????????????

 

In our opinion, no. We tried 3 different designs and made no improvements over stock.

Same results on the GT3.

The 997S was a different story. We did gain some power with headers.

 

you probably will lose HP. stock headers are pretty hard to beat.

 

Unless you go to bigger turbos etc... use your money elsewhere

 

Do headers make a difference? It depends!

The collector on the OEM exhaust manifold is poorly designed.



The gases flowing through the outside tubes collide at the junction of the three tubes, rather than making a smooth transition via a properly designed collector. That being said, the poor design of the OEM collector does not cause a meaningful restriction on stock HP cars, nor mildly modified cars, but rather, only on higher hp cars.

The OEM manifold also has a relatively narrow diameter primary tube. Narrower primary tubes generally keep the gases hotter, and produce more velocity, which can translate to quicker spooling, but may ultimately restrict airflow. Wider primary tubes generally permit greater airflow, but do not keep the gases as hot and decrease velocity, and may cause lag. Again, the OEM diameter primary tube does not cause a meaningful restriction on stock and mildly modified cars. Therefore, using a larger diameter after-market header on a stock or mildly modified car may be detrimental, as it will not meaningfully increase power, but may delay spooling of the turbos. On the other hand, with higher hp cars, the OEM diameter primary tube will restrict airflow and reduce power, and an after-market header with a larger diameter primary tube will make more power.

Based on the foregoing, those tuners that offer after-market headers with superior collectors and larger diameter primary tubes (including RUF, PSI, 9ff, TTP, IA, EVO MS, SG, etc.) do not use them on their entry level packages. Rather, most tuners only suggest headers on higher HP cars, where the OEM collector and smaller diameter primary tube cause a meaningful restriction.

When properly used, after-market headers have been documented to increase power on higher hp 996TTs. Stephen from IA experienced a tremendous power increase, confirmed by dyno testing, when he installed after-marker headers. Dyno results on Xico’s car showed 30 more hp with an after-market header, as compared to a ported and polished OEM manifold. 9ff and TTP claim dyno results showing 20 more hp with their particular headers. I am not familiar with the results of RUF’s testing, but I am confident they confirmed better performance before using after-market headers for their higher hp cars.

The following is a great article regarding header theory: http://www.burnsstainless.com/TechA...ory/theory.html .

Craig

 

re: collision of outer tubes, I'm guessing that no two
cylinders on any one side have their exhaust valves
open at any one time so there's not really any
trouble in that regard.
Joe

 

Whats considered as higher hp tt's? Stage 4 ?

 

I believe the wrong question was asked. A better question would be what parts in order of cost give the best bang for the buck. Anyone into power realizes as you go up the power ladder the cost per hp drastically increases.

Properly designed (not all headers are properly designed) and properly installed (motor tuned for them) headers make power ........... period.

It is expensive way past the actual cost of the headers and installation. I wouldn't start to consider them until exceeding 600 hp.

 

port ur stock headers with a dremmel and and get them coated(outside only) all for under $160 a pair.
and ur done.

 

MARKSKI

what kind of bit do I need to port my headers and where can I get it from?

TIA

Jags

 

This will give you the info you need LINK

 

Kevins pics in rennlist is exactly what im talking about.

 

Porting OEM headers is an improvement, but it will NOT give you the same results as a quality after-market header with a superior collector and larger diameter primary tube. Xico obtained 30 more hp on a dyno with after-market headers as compared to ported, polished OEM headers -- 30 more hp! Stephen from IA also experienced significant hp gains when switching to an after-market header (I think he was previously using a ported, polished OEM manifold).

Porting the headers merely improves the airflow at the flanges -- its does nothing to improve airflow within the manifold, beyond the limited area accessible to a grinder bit. I am not knocking ported, polished OEM manifolds. To the contrary, I used a set for over a year, and I think they are the best option for mildly modified cars which do not need the additional airflow achieved by a superior collector and larger diameter primary tube. Porting the OEM manifold has the added benefit of not adversely impacting turbo spooling. However, higher hp cars will benefit from after-market headers that achieve improved airflow throughout the manifold (as opposed to only at the flanges).

With regard to coating the headers, this can be done to any manifold, whether stock, ported stock, or after-market. I previously coated my ported OEM manifold, and subsequently coated my after-market EVO MS headers. The actual performance gains achieved by coating headers are probably minimal, but its cheap enough, so what the hell.

Craig

 

 

Headers, headers and more headers....thread