1990 928 S4
I went to Bauer Porsche in Oakland where Tom has his dyno set up and installed the X-Pipe.
I did 4 preliminary baseline runs so I knew what I started with. The max baseline run was 386.1 rwph/343.3 ft-lbs with 6.1 psi boost. I tightened the s/c belt between each run to try and get the boost up, but even with the new tensioning spring completely compressed, the max stayed at 6.1.
We then installed the X-Pipe (no cats) and did 3 more runs. This time the max was 405.9 rwhp/366.6 ft-lbs with 6.7 psi boost. Not as much as I had hoped. Also I don't know why the boost when up, and was that the reason for the additional 20 rwhp.
Lastly we installed the Random Tech Cats and made 3 more runs. Again the numbers went up, much to my surprise. I had thought the cats would have dropped the power. Anyway the max was 437.8 rwhp/382.3 ft-lbs and the peek boost went up to 8.9. I don't know wnat to make of it. This is the power I was looking for, but I don't know why it happened this way.
(solid line with cats, dashed line without)
The low and midrange was higher without the cats, but the top end was higher with cats. The boost chart was also strange for the run with the cats.
Boost chart (red and green lines with cats, blue without)
I did put cats on for the final run. That's what was amazing about all this was that I got more rwhp (and boost) with the cats.
Tom made me some slip on pipes that I can switch to before the race.
Of course now I might not use them... I'll have to do some more testing.... As for how the car feels, I didn't get a chance to do much in the car last night. The car is really loud now, so I think I'll have to add a muffler of some type before driving too much on the streets.
I want to thank Tom Cloutier for all his hard work making the x-pipe and running the dnyo, and Bauer Porsche for letting me use there lifts and tools.
Copyright 2007, George A Suennen