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Krozi · 12-14-2011, 05:48 PM

I've been kinda planning on writing a little review on the exhaust...I figure this will do the job.
Ok here we go performance-wise...

Before the GTM Exhaust I got my car dyno'd at a Mobile Dynojet and put down 335whp/250wt. A few months later I got my car dyno'd again at a different shop, also on a dynojet. This time I put down 380whp/267wt.

These results kind of baffled me since I gained 45whp but only 17wt.
I honestly do not think I gained 45whp from the exhaust, but gaining only 17wt also didn't make sense to me. I think the reason for this inflated whp gain could definitely be dyno conditions and correction factor. The runs on the mobile dynojet yielded pretty low results. This was possibly due to the laughable little fan they had set up and the 1.00 STD Correction Factor they used. The other dynojet I went to after I got the GTM installed had a much better fan and used a 1.00 SAE Correction Factor.

Since the whp numbers were so high, I was expecting the wt numbers to be much higher also. Unfortunately the wt was only 17wt higher than stock. There are two factors I think I can attribute this too... First is that the Mobile Dyno used 3rd gear in their pulls, and the other Dyno used 4th gear. The second is the fact that RPi uses a Dyno Dynamics Dyno to measure gains instead of a Dynojet. So either those 2 factors have something to do with it, or the exhaust simply doesn't make the torque gains. But I think that the difference in gear choice might have caused this.

I would have really preferred to use the same dyno to measure the power difference...unfortunately this wasn't the case...so I don't know how credible the numbers are.

Sound wise, yes, it is a REALLY loud exhaust. But it sounds insanely awesome

A very, very aggressive and vicious sound! At the same time it does have very considerable drone. On the highway it's not terrible, and cruising around 60mph isn't bad either. Where you really notice the drone is in varying traffic speeds and slow speeds.

That being said, I do daily drive the car with the GTM exhaust and I'm able to deal with it. I am looking to quiet it down a bit though...to do this I'm going to install the OEM x-pipe with the Turner Test pipes primary cat delete. That should tame down the exhaust a bit

I'm probably going to flip-flop between these two exhaust setups often cause I'll miss the insane sound hahah

12-14-2011, 05:48 PM	#10
Krozi Colonel 167 Rep 2,736 Posts Drives: 2008 E92 ///M3 Alpine White Join Date: Oct 2009 Location: SoFla - Bonita Springs iTrader: (24)	I've been kinda planning on writing a little review on the exhaust...I figure this will do the job. Ok here we go performance-wise... Before the GTM Exhaust I got my car dyno'd at a Mobile Dynojet and put down 335whp/250wt. A few months later I got my car dyno'd again at a different shop, also on a dynojet. This time I put down 380whp/267wt. These results kind of baffled me since I gained 45whp but only 17wt. I honestly do not think I gained 45whp from the exhaust, but gaining only 17wt also didn't make sense to me. I think the reason for this inflated whp gain could definitely be dyno conditions and correction factor. The runs on the mobile dynojet yielded pretty low results. This was possibly due to the laughable little fan they had set up and the 1.00 STD Correction Factor they used. The other dynojet I went to after I got the GTM installed had a much better fan and used a 1.00 SAE Correction Factor. Since the whp numbers were so high, I was expecting the wt numbers to be much higher also. Unfortunately the wt was only 17wt higher than stock. There are two factors I think I can attribute this too... First is that the Mobile Dyno used 3rd gear in their pulls, and the other Dyno used 4th gear. The second is the fact that RPi uses a Dyno Dynamics Dyno to measure gains instead of a Dynojet. So either those 2 factors have something to do with it, or the exhaust simply doesn't make the torque gains. But I think that the difference in gear choice might have caused this. I would have really preferred to use the same dyno to measure the power difference...unfortunately this wasn't the case...so I don't know how credible the numbers are. Sound wise, yes, it is a REALLY loud exhaust. But it sounds insanely awesome A very, very aggressive and vicious sound! At the same time it does have very considerable drone. On the highway it's not terrible, and cruising around 60mph isn't bad either. Where you really notice the drone is in varying traffic speeds and slow speeds. That being said, I do daily drive the car with the GTM exhaust and I'm able to deal with it. I am looking to quiet it down a bit though...to do this I'm going to install the OEM x-pipe with the Turner Test pipes primary cat delete. That should tame down the exhaust a bit I'm probably going to flip-flop between these two exhaust setups often cause I'll miss the insane sound hahah __________________ 2008 E92 ///M3 Alpine White//Fox Red//6MT// Florida Bimmer - Join us on FaceBook! Last edited by Krozi; 12-14-2011 at 07:29 PM..
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