Picked up a 2015 GT3 a few months ago. It came with an IPE aftermarket exhaust -- 200 cell headers direct to a valved cat-back system. No side mufflers.

I noticed a huge seat-of-the-pants difference when the PSE opened up and I thought it would be interesting to quantify the difference to see the accuracy of my butt-dyno.

I installed a remote control device to manual close and open the valves on this exhaust system. Closed is pretty docile, mostly engine noise, no drone. Open is quite loud, sounds great on the track but is too loud for the street.

Turns out my butt dyno is pretty good. Below is a graph of 3rd gear, full throttle 25 - 100 MPH runs at the same location, same evening, same conditions. RPMs are from about 2200 - 8700.

Blue lines are with the valves in fully closed position the entire run. Red lines are with the valves fully open the entire run.

X axis is time (seconds). Y axis is speed (MPH).

The runs started at about 20 MPH and ended about 105 MPH. The data in the chart only goes from 25 - 100 so that any initial hesitation/throttle response issues are avoided. TPS is 100% throughout the run.

Data is exported from my AiM Solo DL and is 20 Hz.



I have the OEM center muffler and will install that once I have valved side bypass pipes here, hopefully later this week.

Very interesting how bad the torque/power is when the valves are closed in this system. It'll be interesting to see how the factory center compares open vs closed.

I should note that I don't know if my car has a tune. Thinking of having my dealer reset the ECU (to remove the tune) just in case it does.

 

Just for kicks, here's are 4th gear runs from 50 to 110. These two runs are in the same location but this location differs from the 3rd gear runs shown above.

RPMs are from ~3400 to ~5100.