Ok, I've swapped the stock Coupe exhaust with Stillen's "Dual Catback w/Xpipe exhaust".

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Images & Dynos:
Screamin' Daemon Stillen Exhaust Swap Album

Sounds:
Stock Exhaust
Stillen Exhaust

Interpretations:
First, the only Dyno graph that needs explanation is the 2nd one which shows my "Run 2" baseline graph and my "Run 8" Stillen graph. Assuming a 20% loss due to an AT drivetrain, the "Run 2" baseline graph implies a "flywheel" hp of 273.25hp (calculated from the 218.6 rwhp). The "Run 8" Stillen graph implies a "flywheel" hp of 285.375hp (calculated from the 228.3 rwhp). The graph shows a delta of 9.7rwhp. This calculates to a "flywheel" hp gain of 12.125hp. Note that the hp from the Stillen exhaust was just leveling off at ~6200rpm compared to the "drop off" of the baseline hp starting at ~6200rpm.

Unfortunately, the "Run 8" Stillen graph does include the torque from the "flash" of the AT. The way I understand it, "flash" is normally ignored as it is an anomaly caused by the run-up of the "flywheel" side of the T/C that occurs before the "transmission" side of the T/C begins to respond. Instead, you have to look at the torque graph itself to determine the max torque. The "Run 2" baseline torque was 218.4lb/ft (273lb/ft at the "flywheel"). The "Run 8" Stillen torque was ~221lb/ft (276.25lb/ft at the "flywheel"). Note that, contrary to popular fears, there was no torque loss. Instead there was a minor gain with a slower "drop off" at the higher rpms.

Impressions:
First, the sound is definitely different. The sound of the Stillen exhaust while driving is going to take some time getting use to the difference from the stock exhaust. From the inside, the Stillen exhaust is dead silent when at idle or when the engine is under a very light load. Unfortunately there is a significant "drone" at ~3500rpm. This is bad for me as this is the rpm for my usual cruising speed of 70mph. It does however, go quiet again at 80mph. Hopefully the "drone" will disappear as the exhaust gets "burnt" in.

The change in the engine response was surprising. The engine revs up faster than before. This is good. But the real surprise is that the engine now revs <font color=red>down</font color=red> at a much higher rate than before. No more waiting for the rpms to drop. I can actually "blip" the engine by tapping the throttle. Yes, this is not important for a 5AT Coupe. But if the 6MT Coupes have the "slow" rev down rate like the 5AT, these higher rev up/down rates should make shifts smoother.

"Seat of the pants" shows a definite increase in quickness off the line and a faster response to changes in the throttle input.

To sum it up, "works for me".

Screamin' Daemon - L5AT

 

Hi,
I have the same feelings.about the Stillen system..I do not like the new sound, but I do like the performance. Does anyone have any ideas on how to quieten it up a little? I wondered about insulating it somehow, or changing the resonators. I could live with a couple of horsepower loss for a stock interior sound.
Alan

 

WOW! Absolutely stunning. 228 to the wheels. Nice

 

i dont know what happen with you and the dyno but with the stock exhaust i dynoed at 235 to the wheels and i have the dyno to prove it. all i did to it was take out the cat and install test piped. mines is auto too.

 

Exactly !!!! you took the cat out and ran a straight pipe.... the cat losses a lot of power, removing it helps quite a bit, although highly illegal.

Ivory Pearl - 6MT - Sedan

 

I dont know about that Dan modern day cats are very very effiecent and cause a very minimal amount of flow restriction. I think what we have here is a case of inaccurate dyno testing. Yes you will gain something by removing the cats but its more like in the single ditch gains.

 

It's not inaccurate dyno testing.

I actually had total of four baseline dyno runs done by two separate tuners.

The huge torque I saw on the first two baseline runs made me suspicious of the dyno tests so I went to another tuner four days later.

The second tuner's 2 (actually 3) dyno runs seemed more in line with expectations regarding the max torque. He also explained to me that no cars come off the line with hp and ft/lb numbers that match the published numbers. Each car is an individual, not a clone. Some may have higher numbers and others lower. Mine happen to be lower (by about 10hp).

When I went to the second tuner to get the exhaust installed and dynoed, he was able to reproduce the ridiculous torque numbers on 4 out of 5 runs (baseline run #2 and Stillen run #8 are used for the comparison chart). This is when he explained the concept of "flash" torque numbers for AT dyno runs. As you can see by the 2 "Turbo Tune" runs and one of the "Carolina Auto Master" runs, there is a huge spike in the torque when you floor the accelerator. The CAM tuner was able to reproduce this spike by starting the recording <font color=red>before</font color=red> flooring the pedal. When he and I did the baseline runs at CAM, I was in the drivers seat. This meant that he would start the recording <font color=red>after</font color=red> I'd floored the accelerator thereby missing the torque spike.

Baseline graph #1 - Max of 215.8hp and 252.8lb/ft:



Baseline graph #2 - Max of 218.6hp and 218.4lb/ft:



Stillen graph - Max of 228.3hp and 255.0lb/ft:



Screamin' Daemon - L5AT

 

suprhulk,

what gear did you dyno in? 3rd? or 4th?

thanks,
rob

 

My Coupe is a 5AT so it was dynoed in 4th gear.

Screamin' Daemon - L5AT