Which turbo to use on TB42?

[Andrei84]

I'm putting a turbo on my gq tb42. So I need to know which one is the best suited for low down torque and spools early in the rev range say 2000rpm. As a side note I only want to run 8-10psi with a top mount cooler. I have done the search thing but can't find clear answers. Few people go with the chinese made t3t4. Also what do the A/R numbers mean? And what's the best? I'm not chasing huge power maybe 150kw at the wheels on 33" max. Thanks in advance.

[YNOT]

A popular choice is the Garrett GT35/40 off a Falcon XR6 turbo.
I'll explain the A/R bit later.

Tony

[YNOT]

Copied from "turbobygarrett" website;

The A/R parameter has different effects on the compressor and turbine performance, as outlined below.

Compressor A/R - Compressor performance is comparatively insensitive to changes in A/R. Larger A/R housings are sometimes used to optimize performance of low boost applications, and smaller A/R are used for high boost applications. However, as this influence of A/R on compressor performance is minor.

Turbine A/R - Turbine performance is greatly affected by changing the A/R of the housing, as it is used to adjust the flow capacity of the turbine. Using a smaller A/R will increase the exhaust gas velocity into the turbine wheel. This provides increased turbine power at lower engine speeds, resulting in a quicker boost rise. However, a small A/R also causes the flow to enter the wheel more tangentially, which reduces the ultimate flow capacity of the turbine wheel. This will tend to increase exhaust backpressure and hence reduce the engine's ability to "breathe" effectively at high RPM, adversely affecting peak engine power.

Conversely, using a larger A/R will lower exhaust gas velocity, and delay boost rise. The flow in a larger A/R housing enters the wheel in a more radial fashion, increasing the wheel's effective flow capacity, resulting in lower backpressure and better power at higher engine speeds.

Tony

[Andrei84]

Cool. Thanks for that info. Now what would be the better A/R on turbine (hot side?) ie .063 0.84 or 1.06?

[YNOT]

For good low end response the .063 would seem the better choice but I'm no expert on the matter.

Tony