AWD Turbo Parts and Performance

Marc S – Racing / Comparison with Eric Lu’s 95 GSX – First Race

This weekend Eric (“EricATCA”) and I got together to compare 95’s.
(He has a T25 turbo with upgraded compressor wheel (Super 60)
& since I am in the market for a performance turbo, I wanted to see
how it ran). Eric’s a great guy, and it was a fun afternoon.
The performance results are somewhat surprising…

Here’s a description of the 2 cars-

Eric’s 95 GSX                              My 95 GSX
————-                                  ———
K&N FIPK                                  K&N FIPK
Nology Hotwires                         Magnecor 8.5mm wires
Trust 2.5″ Exhaust                        RSR 3″ Exhaust
HRC Intercooler pipe upgrade     Imagine Motors Intercooler pipe upgrade
Test pipe                                      Stock catalytic converter
Buschur 2.5″ down pipe                 Stock down pipe
EVC (was set at 16psi)                Stock (no boost control)
T25 w/ Super60 compressor        Stock T25

I really expected Eric’s car to leave me behind. The test pipe &
downpipe should have made a nice difference (25+ hp?), not to mention
consistent & higher boost from the EVC, and a bigger turbo flowing
cooler air.

The results though?… I was usually 1-2 car lengths ahead for the
duration of each race! The pattern was as follows- as soon as we
both stomped on it (almost all races were done from a roll)
my car would pull a little ahead. My smaller compressor wheel got into
boost a little earlier, enough to give me a car length usually. At
“upper midrange” we were around even, at upper revs Eric would start
to pull a little. When we hit second gear, it was “1st gear all over.”
I’d pull a little further on him initially and pretty much manage to hold
most of my gains. Towards the higher rev range he’d probably close a
little distance. We took it to the top of third gear once or twice,
but the results were still pretty much the same, the nose of his car
was behind my bumper from a few feet to 1.5 car lengths.

I should mention that also having been in his car as a passenger,
it definitely pulls a harder than my car from 4500rpm on up. I think
with a little better shifting the races would have been closer. But
that would mean 2 cars dead even when one has more mods..

Now, trying to sort out the why’s… Clearly a performance downpipe and
a test pipe give better performance and were helping him. Though the
EVC probably helped a bit as well (a little more boost + wastegate
held closed longer) for simplicity’s sake I’ll ignore any gains the
EVC should have been giving his car. That leaves: the Trust 2.5″
exhaust vs. my 3″ RSR exhaust, the HRC Intercooler pipe upgrade vs.
the Imagine Motors upgrade, and the upgraded T25 vs the stock T25.

I figure the RSR 3″ had to have helped me for some of that. We both
noted that in addition to the difference in pipe diameter, the Trust
exhaust has a relatively sharp bend near the muffler, and necks down
to 2 1/4″ where it meets the test pipe, whereas the RSR is very straight
throughout, and necks down to 2.5″

Intercooler pipe upgrade… I don’t feel as comfortable making any
claims here other than that the HRC upgrade only upgrades the area
from the intercooler up to the blow off valve, whereas the Imagine
Motors upgrade continues up from the blow off valve to the throttle body,
and replaces the stock throttle body elbow (which has a nasty sharp
edge/kink inside it) with a bigger/smoother elbow.

Eric & I felt that the T25 made the big difference. Upgrading
the compressor-side-only meant more lag, and because the exhaust side
stayed stock, it probably had too much backpressure building up there.
At the least the turbine wheel needs to be clipped. More likely the
turbine wheel needs to be upgraded as well. I’m unsure on whether
the compressor wheel shouldn’t be downsized as well to perhaps a
standard 60 wheel.

Eric will be upgrading the exhaust side of his turbo soon, with a bigger
turbine wheel and a clip. We’ll get together again and see exactly how
it affects things. Though I’m looking to upgrade a few items on my car,
I’m going to hold off until we can do this comparison. It’s important
to see what works and what doesn’t. I’m hopeful (and I’m sure Eric is
as well) that when his new turbo goes on and we meet again, that his
car will soundly take mine when we race. I’d hate to think that a
TD05 is the -only- way to go. I’d like to keep the T25 if possible
for the sake of warranty. So far all my mods are ok with my dealer,
but putting on a different turbo would probably change all that.

(Thanks again Eric!)

-Marc

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