Project Porsche 991 GT3 RS: Dundon Motorsports Headers and Exhaust System

by Mike Kojima


It's tricky to attempt to improve the engine performance of a supercar, especially when its one that puts out 125 hp per liter like the Porsche GT3 RS does. When it comes to NA power, only the Porsche 918 hypercar and the Ferrari 458 Speciale have more punch per liter. With its screaming 8800 rpm redline, titanium internals and a sky-high 13:1 compression ratio, there isn't a whole lot more that can be done without serious engineering, beyond what most tuners can do.

But, leave it to us to try. One possible thing that can be improved is the stock exhaust system. Although the stock exhaust manifolds are pretty decent headers, and the stock exhaust system can be pretty low backpressure in its sport mode, we felt that there is some power to be made by fiddling with it.

Enter Charles Dundon of Dundon Motorsports. We have known Charles for years and even collaborated with him in the making of the most powerful SR20DE header on the market. A couple of examples of these can be found on the Dog Car race Sentras that are sitting in the MotoIQ megashop.

Charles is a fabricator extraordinaire and a really smart, analytical guy to boot. Seeing that there was little market for an exotic Sentra SE-R header, Charles decided to go where the money was and make stuff for the Porsche GT3. So when we got a GT3 of our own, Charles was one of the first guys we called. If anyone could extract more power out of a hypertuned, high strung motor it would be him.


The Dundon Motorsports headers are works of art. They are tig welded from 321 thin wall stainless steel. 321 has better high-temperature properties than the more common 304, and thus can be made thinner for less weight. The CNC cut individual exhaust port flanges are also very light.

Since Porshe was so hardcore in making the RS light that it has a hood sticker instead of an emblem, carbon reinforced thin urethane skins for the bumpers, lots of carbon body panels, a magnesium roof, and thinner glass, lighter is good!


The headers have very smooth and straight bends for less internal turbulence. They are also V-banded for quick assembly and disassembly. 

The headers and exhaust are modular, and the high flow cats that come with the exhaust can be quickly swapped out for race pipes for track use. The quick release V-band clamps that hold everything together come in handy for that. The headers, cats, and side deletes being modular can be used with the stock muffler. 

You can also get a look at the exquisite back purged tig welds here that are present throughout the whole system in this photo. 


One of the secrets of the additional power the Dundon Motorsports headers make is the use of a merged collector. 

A merged collector brings all of the headers primary terminations into a smoothly blended collector.  Merged collectors can use larger diameter primaries for more peak power while not losing any- sometimes gaining bottom end and midrange power at the same time. 

The collector is attached with slip flanges and held together with springs so the whole header can move around and expand and contract with heat cycles. This assures a long service life without cracking even with thin tubing.



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Monday, March 05, 2018 5:41 AM
Looks very well done, but begs me to question, why stainless and not titanium or inconel? I assume cost on a car like this shouldnt be an issue. I mean, lots of time and thinking were invested on making this car as light as possible, titanium exhaust systems are fairly low tech and becoming common.

PS. 125HP per liter is amazing, and as mentioned only 2 other CAR N/A motors make more, but motorcycles are making 200hp/Liter.
Mike Kojima
Mike Kojimalink
Monday, March 05, 2018 8:42 AM
Due to the exhaust breaking harmonics this engine makes, the main thing is corrosion strength at high temps which rules out ti since the stock exhaust is prone to breakage and the difficulty in forming sheet inconel.
Dan DeRosia
Dan DeRosialink
Monday, March 05, 2018 10:42 AM
Cost is always something of an issue - I've read commentary from NASCAR teams that they couldn't justify inconel headers. And if you're doing things thick enough where the exhaust isn't a life cycled part, there's not going to be much weight difference between 321 and titanium if you have a welder good enough to deal with thin tubing.
Monday, March 05, 2018 12:03 PM
Yup can disagree with those points. Thanks for the replies.
Monday, March 05, 2018 12:04 PM
PJS link
Saturday, March 10, 2018 7:23 AM
I have a dundon set up made out of inconel - he can do it
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