93egSLEEPER

Hey guys/gals just looking for some info. and opinions/answers on the topic at hand. A little background to this is I rebuilt a GSR, took it in for dyno tuning open header and the tuner told me he wouldnt touch my unless it had an exhaust on it. he said it throws off the tune too much. I found this strange since I had him tune my LSV turbo open downpipe. So I connected my Apexi WS2 and got it on the dyno. It made 174whp 128tq. I had thought it would be a bit higher...about 10whp higher.

82mm GSR block
GSR crank, rods and PR3 pistons (11.4:1)
B16 head w/ 00' ITR cams on S2 gears
Stock TB & IM
RMF narrow header (2.5' collector)
Yowaii SS intake
Magnaflow hi-flow cat
Apexi WS2 catback
B16 tranny w/ streetlite flywheel

I have done some searching and many people have been saying the WS2 exhaust with its 2.25" pipe is restrictive and causes major powerloss at high RPM (which I saw) and w/o it people were seeing 8-12whp gains. My cams stopped making power at 8k (I have seen graphs with them making power to 8500 numerous times) and dropped power from 8k to 8.5k

Heres my issue: I do plan on taking this car to the track and I know open header I will have better performance. Should I re-tune it w/ the exhaust off or will it GREATLY hurt me to run an open header tune on an exhaust bearing car for a daily grind?
Any input on this greatly appreciated and anyone with Info. on the WS2 reducing performance chime in as well.

Thanks,
Andy

juda7

I would say ONLY tune it open header if you are going to trailer/tow to the track.
The car will run either too rich or too lean for the ECU.
Now if no trailer/tow then redo your exhaust to 2.5 from the collector and eliminate resinators. Since you already have a high flow cat (2.5" I'm thinking) then connect everything to a Magna Flow or whatever you like 2.5" in/out muffler.
Here's a pic of my setup (3 " setup though) Should make more power on the dyno due to higher exhaust flow.

93egSLEEPER

Im staying away from a different exhaust because I dont want more noise. The cops in my area give modified exhaust tickets daily.

It will be trailered to the track in MOST cases so I can put my slicks on at home and adjust the coilovers etc.

I was considering a piggyback so i could run 2 tunes on my ecu and switch it back and forth.

juda7

In that case go with the open header tune.