Turbo Selection for 350-450hp (thinking T-61), opinions pls

[Bernardd]

Look Here

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[300guy]

Interesting details:

Stage 5: Minor diameter (in. 2.439) Major Diameter (in. 2.798)
O trim: Minor diameter (in. 2.296) Major Diameter (in. 2.922)
P trim: Minor diameter (in. 2.544) Major Diameter (in. 2.922)

Ratio of Minor diameter / Major diameter

Stage 3: .87
Stage 5: .87
O Trim: .78
P Trim: .87

I wonder what has more of an effect on back-pressure (turbine) – trim or minor diameter (exducer)?

What turbine is better for 15-20 psi high flow (as in… high RPM)? O or Stage 5?

I’m also considering a T-58 (smallest T-series compressor).. I think this compressor is also known by the name TO4S – anyone know anything about this one?

[Jason84NA2T]

300guy wrote:
I wonder what has more of an effect on back-pressure (turbine) – trim or minor diameter (exducer)?

What turbine is better for 15-20 psi high flow (as in… high RPM)? O or Stage 5?

I’m also considering a T-58 (smallest T-series compressor).. I think this compressor is also known by the name TO4S – anyone know anything about this one?

Minor diameter, according to what I've read. I don't think the T58 is a T04S, because the T04S is also know as the 60-1. In practice, most people apparently notice no difference between O-trim and stage 5 turbine wheels (unless the turbine housing is different), while the P trim offers slightly more flow over either one. I think the T66 or T04R compressor paired with a P trim turbine is the way to go. The real decision is in the turbine housing which is available in .58 .69 or .81 and tangential or on center style. On center would be probably easier to install and make an O2 elbow for, and probably a little cheaper. This combination will get you to about 600bhp and streetable spool with the smaller ar housings.

But don't take my word for it.

[300guy]

Good info - thanks Jason.

The thing is, I'd have to build a new motor to handle anything more than 400hp-500hp (because I've got stock pistons and connecting rods), and I'd also need a new clutch. So that means I dont need to boost more than about 20-22psi.

This is why I'm leaning towards a slightly smaller turbo... but I want something thats gonna breath well in the high rpm range.

.81 a/r T58/T3 Stage 5

The reasoning behind the Stage 5 instead of the O trim is that:
O trim ans Stage 5 are supposed to flow about the same
Stage 5 is slightly smaller major diameter - so it would require less energy to spool
Stage 5 has the same [minor diameter/major diameter] ratio as the p-trim, stage 1 and stage 3 wheels... because that ratio is more common, it might be better

Now I just need to get a price on one - I'm going to phone Peak Boost or http://www.cheapturbo.com.

Any suggestions of other places?

[300guy]

I'm very conserned that the compressor could surge on the T58/T61/T66 - the way I read the maps... if the turbo spools at a low rpm (say around 3500) then its in the surge zone.

Now I'm thinking GT35R on the cold side, and T3 stage 5 on the hot side.

Jason - have you had a GT35R on one of your Z's? Anyone else? How did you like it? What was the power like on the top end?

[SATAN]

I speak from experience

T-66 compressor
P-trim turbine
.81 A/R hot side.

Works great, no surge, very good power.

GT35 is a nice turbo too I guess.