07 MS6 CPE Austenite HP Gain?

[Thor Hammer]

All the damned exhaust threads talk about sound. Very little discussion about actual performance benefit. I just bought a CPE Austenite Dual Cat Back.

Did I waste my money? Or is there really a power benefit once my custom tune is done?

I have a TIP, ETS TMIC, M2 Catless DP, HPFP, OCC, AEM CAI, Cobb OTS map (Will be going to Freektune soon) and that's about it. No overboost issues ever. No smoky K04.

Will it be loud as fuck or tolerable? Since I have a DP that is catless? As long as it does not sound ricer, and ACTUALLY makes more power once custom tune is done I am satisfied. If the CBE will not add useable TQ/HP I am going to return it.

coming from racebikes aftermarket exhaust and tune made a huge difference.

I don't know why but my stock exhaust piping is dented to shit. Previous owner had no answer as to why.

[Thor Hammer]

Nevermind my question. Its been beat to death. I found so many posts on exhaust its insane. Finally came across some intelligent information rather than opinion!

Will brand X sound good? How will it sound? Will it get me laid? Will people hear it and think I am cool? and on and on.....

When modding the stock exhaust, you effect the turbo spool time, allowing power to kick in harder much sooner in the power band.

To put this in perspective, with a full turboback exhaust, you've basically shifted the entire stock powerband 750 rpm sooner. That's huge.

(Though I love CP-E products, I am using these graphs to help explain the effects of exhaust mods regardless of manufacturer)

One of the fundamental problems with dynographs, is that most people don't know how to read them. They look for two numbers. Peak torque, and peak horsepower. These are the numbers you should be paying the LEAST attention to. They tell you very little about what the mod is doing, other then at peak rpm's.

What IS the most important part of a dyno graph? The AREA between the stock and modded graphs. It's this space that is most important, and tells us exactly what is happening to the car.



This is the area you should be looking for on ALL dyno graphs. This is the most important change. The area tells you how much the overall gain effected the car...if it hurt the car at some rpm ranges, if it only works in the upper rpm range, if the mod is fantastic and effects the entire powerband, etc. Tons of info in between the graphs! It's here you can also figure out the "max" gains of a mod (largest gap between curves). The max gain is usually where the butt dyno records it's highest reading .


Lets take a closer look at these graphs shall we?



This is a cut section of the torque graph. I cropped this to allow everyone to concentrate on the angle of the line. Note that the modded line is roughly 75 degrees, while the stock line is roughly 40 degrees. This is a MAJOR change. The aftermarket exhaust is allowing the turbo to spool faster, causing torque to increase much sharper. (Huge butt dyno change, pushed back into the seats gain)

This is a major change in power output, and as such, causes the car to reach stock peak torque BY 2750 rpm!!! (instead of 4200rpm). By 4750 rpm, the turboback car is producing over 40 ft/lbs more torque then the stock car. So not only is the car reaching stock torque levels over 1500 rpm sooner, but it's utterly blowing away the stock car around 5k rpm. Max gains are close to 45 ft/lbs. (To put that in perspective, you can spend about 2k USD on a Mazda6 and still not get that kinda of torque gain).



Now lets look at a cropped version of the HP graph. Look closely...the powerband has shifted to the left. In this example, you're making the same horsepower at roughly 750 rpm's sooner now. You are making the same power at 4k rpm, that you used to make at 5250k rpm! You reach the stock power output at 4750 rpm, as you were (stock) at 5500 rpm. Max gain's are close to 35 whp.

Dyno's really should be presented in another way. They really need to have...

1) Peak Horsepower
2) Peak Torque
3) Min and Max Torque Differences
4) Min and Max HP Differences
5) Shaded or crosshatch between the area of the two graphs
6) Some sort of number (area between two graphs) giving you a rough estimate of the power gain across the entire rpm range.

Without that information, we all have to step back and very carefully look at the graphs to see what's really happening.

Ill be keeping my exhaust. If it doesn't work out, Ill sell it on here and someone will get a killer deal.

Should I be worried about boost spikes at all? I have none at the moment with my cat-less DP.