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Discussion Starter · #1 ·
Which would give the most performance out of a stock '07 2.7L? I've only been thinkin' about cat-back as the first mod, but just started to think about headers. Wasn't sure which would be best. I know most people do cat-back first. I don't know if this is mostly for sound, or if it's because a cat-back system with stock headers offers better performance than aftermarket headers with the stock exhaust.

Also, can anyone direct me to a sound clip of a stock exhaust with aftermarket headers?
 

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Going from 4 to 2 cats makes a difference. It does not matter that much which two cats you remove. Removing the 2nd to via an exhaust swaps typically causes drone. Removing the first two (headers) requires re flash that will keep the CEL from coming on.

I tried three exhausts, and ended up running catless headers with the stock exhaust and SRP to keep CEL off. In a dyno forum I document my progression of mods, and you can compare gains and more importantly torque curves between them.

This was on a 3.4, on a 2.7 - I do not know, but guess would be similar.
 

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Discussion Starter · #3 ·
Going from 4 to 2 cats makes a difference. It does not matter that much which two cats you remove. Removing the 2nd to via an exhaust swaps typically causes drone. Removing the first two (headers) requires re flash that will keep the CEL from coming on.

I tried three exhausts, and ended up running catless headers with the stock exhaust and SRP to keep CEL off. In a dyno forum I document my progression of mods, and you can compare gains and more importantly torque curves between them.

This was on a 3.4, on a 2.7 - I do not know, but guess would be similar.
Thanks. I just read your thread with the dyno results for the different setups on your car. That's an impressive gain and good comparison.

Do you by chance have a sound clip? If not, would you mind makin' one? :)
 

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I am happy to make a sound clip for you... but realistically it maye take me few weeks to get to it. But will see what I can do.
 

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Discussion Starter · #5 ·
Not in a huge hurry, so whenever is good for you. I appreciate it.
 

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I recently put Cargraphic headers with cats on my 2.7 with a PSE. I did not dyno it before hand to compare and say with any certainty that there was a performance increase, but it "feels" like there is. The sound is significantly better than the stock headers, not louder, but a better quality of sound. The Cargraphic headers are long tube equal length headers which probably contributes to the better sound quality. Also I have not had a check engine light go on in the 2 weeks with them on the car. I did record exhaust prior to the change and will do an after soon and post it.

Randall
 

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You would also have to take into account the warranty which may be compromised by changing headers
 

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My car is almost out of warranty (6 mo) and is very low mileage, so I am not too worried about that. But I plan to keep the original headers to swap just in case anything were to happen. I do know that changing something like that will not void the entire warranty.

Randall
 

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Do you by chance have a sound clip? If not, would you mind makin' one? :)
I am happy to make a sound clip for you... but realistically it maye take me few weeks to get to it. But will see what I can do.
Tomasz and I met up with other NW region members yesterday and while others were on the dyno we had some time to take video of his car. Here is what Fabspeed catless headers sound like with the OEM Exhaust:

 

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Discussion Starter · #11 ·
Thanks for that video! I like the way that sounds, and it looks like some good numbers were made also.

What tips are those?
 

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Porsche RS60 exhaust tips. Which is more than tips, it connects the two mufflers bit differently. More like the Dream 1 system.

If you want to read up more on the topic of headers, please see my post here:

http://www.planet-9.com/porsche-dyno-charts/45814-cat-less-headers-dyno-comparisons.html

And quote from Dinan:

Headers have become very popular in recent years because they make substantial power gains. The real reason they gain power has more to do with eliminating the front catalyst that is built into the header than the header itself. Modern M Cars have very high quality well tuned headers but to meet the emissions standards, there are four catalysts, two in the header and two more in the center exhaust section. The two three-way catalysts on the header are monitored by secondary O2 sensors to report catalyst efficiency to the ECU. There are two more catalysts mounted under the floor before the resonator and are not monitored by the O2 sensors for catalyst efficiency. The front catalyst mounted on the header are usually twice as restrictive as the rear catalyst and are as close to the engine as necessary to light off cold to improve exhaust emissions on cold start.

Tomasz
 
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