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3,047 Posts
Discussion Starter · #1 ·

The 91 cam one was my car dynoed in July right after I put in the 91 intake
cam. I lost some torque immediately after (stock 98 cam gave me 124 ft-lbs)
but I gained it back several hundred miles later SOTP by the computer
learning the cam.

All turbo hp and All turbo torque are the three exhaust configurations.
DYNORUN.008 is with full exhuast (Stroker's 2.5" downpipe, stock cat, stock
catback). DYNORUN.011 is with the exhaust uncapped in front of the cat, so
just that 2.5" downpipe. pic of it here:
DYNORUN.012 is no exhaust, just uncapped at the turbo elbow thing, like

You notice how the 008 and 011 hp curves die right at 5.5k to 6k RPM, then
just kinda stutter around til redline? We think it was because of this:
Mike Jez's wonderful $250 downpipe.
Eric was kind enough to die grind
that restriction away. Didn't get to dyno it after that though. Anyone else

So that proves how much the stock catback sucks for turbo cars.
over 30hp and almost 20ft-lbs on my car right now.

And finally here's before and after the turbo (full exhaust on both)

Going back to the torque curves, it looks like turbos need SOME backpressure
to keep torque going. Just having the 2.5" downpipe really helped mid range
torque in comparison with no downpipe. I'm sure if the downpipe didn't have
that silly restriction it would have made more torque at the top end over
the no downpipe run.

I also notice I make more torque at the ultra low end of the RPM band with
the full exhaust.

Also the downpipe only seemed to be doing better on power upto 5.5k than no
exhaust. The reason again no exhaust was better at the top end was probably
because of that restriction.

I still like this one the best. It's like two different cars!

Comments? Analysis? Questions?

Oh, and here are general pics of the dyno day in Nashville, TN.

3,047 Posts
Discussion Starter · #2 ·
We have 4 mpg videos of the dyno session too.

First one is me having NO traction in ANY gear do it being constantly
raining the past weekend. The rest of the videos are obvious. Very good
quality. VERY LOUD too. The video sound doesn't do it justice at all. The no
downpipe and downpipe only ones were ear bleeding loud.

2,463 Posts
Damn. I feel all envious and stuff.

Could that dip at 6k be related to your wastegate (I think i'm using the right term, or is it the bypass valve, or are those the same thing)?
Or has that thing started working earlier?

You said you noticed you make more ultra low rpm torque with the stock exhaust. I dont see it. It looks to me like no downpipe had the best low and top end, while downpipe only had the best midrange. Too bad you didn't re-dyno with the retriction filed away.
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