I did not like my exhaust because it was built for headers when I had the supercharger. The turbo only uses one of the two 3" pipes. I am going to buil a new front y-pipe after the downpipe to use one 3" pipe on each side of the tranny. I started building the rear part first. It is finished from the transmission to the rear axle. I welded a tempopary 4" pipe after thr rear axle but it is going to be replaced by two 3" free flow mufflers in the near future.
Tho old exhaust:
The new:
I went to the same track yesterday with the new exhaust in place and some sticky tires.
In the first run I used too much throttle when staged so the car moved forward with locked front tires and I redlighted. The transmission computer shift at 5800 rpm but ther is a minimum time between shifts that is set to 1.5 sec. That has never been a problem before but as you hear the engine runs on the rev limiter for a moment before shifting to third. I have to reduce that time now.
http://www.joby.se/video/joby/2008-08-13_1.mpg
The secon run was against a Chevelle SS with a stick shift and a healthy 396 bigblock.
Now I used a microswitch to reduce the MSD RPM-limit to 3000 rpm during stage. Full brake, full trottle and the microswitch. At green light I released the brake and microswitch. That was too much for this track and you hear the tires screaming almost half the track. The the rev limiter again before shifting to third.
http://www.joby.se/video/joby/2008-08-13_2.mpg
The third run was my best and against the only car that ran similar times. A 1923 Ford with a big roots supercharger, big tires and only 860 kg, The Corvette is almost twice as heavy.
This time I used a bit less throttle while in stage.
I ran 7.094 sec, 170.40 km/h and 60ft 1.820 sec.
http://www.joby.se/video/joby/2008-08-13_3.mpg
The fourth run was against the same rod but my start was not as good as the third run but I catched up with him at the end.
http://www.joby.se/video/joby/2008-08-13_4.mpg
On a 1/4 mile that rod would be way behind.
All exhaust still go thru about 1 meter of 3" pipe, but it is better than it was.
With a new front y-pipe and dual 3" there should be much less restriction after the turbo.