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TurboKraft TurboKraft is offline
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Join Date: Mar 2005
Location: Phoenix, AZ
Posts: 2,542
911st -- we just shipped a 0.63A/R to a customer with a pretty normally modded 1987 3.3L (B&B headers, custom 3" open muffler muffler, B&B IC, 964 camshafts).
He had a K29#11, found it too lazy and got our GT35RE package with a 0.82A/R turbine. Faster spool up than his old turbo, and loved it.
But not responsive enough for his taste and how he likes to drive the car. So he just switched to the 0.63A/R turbine and he likes it even more.
I'll ask him to please quantify the change, ex: "in 3rd gear it now reaches X psi at Y rpm instead of Z rpm."

Turbine A/R comparison for you on a different car:

3.5L 930 with EFI. The prior builder had fitted EFI and a "GT3040R" (GT3082R) with a 1.06A/R turbine housing. The big housing was likely to overcome the backpressure of the too small GT30R turbine wheel.
0.8bar boost by 3500rpm (restrictive single outlet B&B muffler didn't help), peak torque at 4,750rpm, peak power at 5,700rpm.
Switched to a smaller 0.82A/R turbine housing:
0.8bar by 3,250rpm, peak torque and peak power happened at pretty much the same rpms, but a loss of 18tq and 17hp.
So a smaller A/R turbine helped response but hurt peak figures at this boost pressure.

At 17psi on 100-octane (that ECU's HIGH setting), it gave up 35tq and 21hp, and still the same . So the turbine housing becomes a restriction at higher boost where more flow is needed.

(Wish we had been allowed to switch it to a better sized turbo...)

And no, no EBP readings on either the old C2T EFI (first car we converted to AEM EFI) or that 3.5L.
Chris Carroll
TurboKraft, Inc.
Tel. 480.969.0911
email: -
Old 10-14-2010, 05:29 PM
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