Well I got a chance to get the DP installed today at my buddies shop. When I got there we pulled it up on the Dynojet dyno and got the car all strapped in. (Side note: The wideband 02 was not reading probperly, we couldn't get the torque to register properly and the printer was out of ink. :( Unfortuntely, the dyno graph only shows HP and MPH.)
Mod & Tune info
As in my sig, I have the 3.3 MPS, FWI, VS Cam, PEMs, 180*, TR6iX@.60 and the stock DP. My tune (via my PowrTuner) for the car is fuel tweaked with stock timing table. (I never bumped timing because I've had trouble tuning out my KR issues at WOT.)
Before DP Install
We did 3 "before" pulls in 2nd gear. The second pull was dropped because the car downshifted to 1st. The results of 1 & 3 are as follows:
* Pull 1(blue): 232.5whp. I had the normal KR issues (4* spike with 1-3* during WOT.)
* Pull 3(red): 230.3whp. Again more WOT KR. The KR is evident by the dip in the power curve at 80-85mph.
Installation of the DP
We let the car cool for about 20 minutes and my buddy Steve began removing the stock DP while I sat and watched.
The 4 nuts that hold the DP to the cat were rusted pretty good. Steve used a torch to heat them up and they zipped right off...no broken studs.
Install of the new pipe was easy as cake. It lined right up and bolted in fine. We were lucky enough that the gasket on square flange was able to be reused. Started the car up...no exhsut leaks. WooHoo!
After DP Install
We strapped the car down again on the dyno and let it idle for about 5 minutes to let it warm back up to operating temp. (I did this to ensure it was just as warm as the first 2 pulls.) We did 2 "after" pulls in 2nd gear. The results of pulls 4 & 5 are as follows:
* Pull 4(green): 242.3whp. I had gotten small blips of KR (< 1*) @WOT, but it looks like my steady 2-4* KR issues are gone! Notice the HP increase across the entire power band with it peaking around +10-11whp.
* Pull 5(purple): 243.2whp. Again reduced WOT KR. The dip in the power curve at 80-85mph is gone and has smoothed out. Again, a constant HP increase across the entire powerband.
Well I hope this helps provide some concrete evident that a 3" DP is an effective supporting mod. It allows the engine to breathe better allowing it to make more HP and reduce KR. I'm very happy with the results. It was really nice to be able to do "before" and "after" pulls to see what a mod provides.
In the coming weeks, I'll be working on getting the Bonne tuned with dropping down to a 3.2 pulley (maybe a 3.1) and dialing in some more timing. I feel pretty confident 13s are just around the corner.
Here'* today'* dyno graph: