Here is what a merged collector looks like on the inside. All of the exhaust primaries are smoothly tapered and blended together with maximum flow and minimal turbulence.  

The stock Porsche collector is simply a dump box for the primaries. We feel that this is where much of the power gains over stock are made. The Dundon header also has larger in diameter and longer primaries than stock as well. The Porsche headers are shorter for better packaging to allow for bigger cats and the secondary side mufflers. 


The Dundon Motorsports system is held together with high-quality stainless V-band clamps. This speeds assembly and disassembly of the modular exhaust system allowing quick reconfiguration from street to race versions of the exhaust. 

We will be testing the street version of the Dundon Motorsports exhaust. The main difference is that the street version has a pair of high flow cats.

The only performance difference is that the race system has a few more hp in a narrow area between 5000 and 5500 rpm. This is because the front of the cat brick interferes with wave propagation at this rpm. Since you hardly see that RPM when driving the car hard with its close ratio PPK 7-speed transmission, the slight narrow power dip is unnoticeable to the driver. 


The cat has a tig welded 304 stainless body, but the tubing is 321. The welds are quite clean and awesome looking.

Bungs for all four 02 sensors are placed before and after the cat. 


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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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