1slowhatch

iTrader: (8)

Just found a great deal on T4 or T6 new Garrett GT4202 turbo. I have an LQ4 (6.0) going in a Foxbody. I believe the turbo measures 74mm comp, 88 turbine. It comes standard T6 flange, or for $200 more you can get a T4 with 1.15ar or 1.25.

I'm thinking of running the T4 with 1.15 ar. My question is.. will this end up being too small for a stock 6.0? Should I get the larger ar turbine housing? My goal is 650-700 rwhp through a 4l80e.

1slowhatch

iTrader: (8)

Here are the dimensions for the GT4202 I pulled off the website:
Compressor Specs:

Inducer = 74.3mm
Exducer = 102.3mm
Trim = 53
AR = 0.60

Turbine Specs:

Wheel dia = 82mm
Trim = 84
AR = 1.01, 1.15, 1.28, 1.44

These specs look very close to a standard S475 if I'm looking at it right...? Looks like most S475 are 74.7mm compressor inducer, 100mm inducer, 88?mm exhaust wheel, available in similar T4 or T6 housings.

Sales@Tick

iTrader: (3)

I'd go 1.25 AR.

toytech93

iTrader: (2)

T6 with 2.5" hotside

1slowhatch

iTrader: (8)

the 1.25 T4 housing? I think standard T6 is is around 1.2ish? I assume the "choking" point of this turbo would be the relatively small turbine wheel? Does the larger A/R help?

Sales@Tick

iTrader: (3)

I'd go with the T6 housing. Anytime you can decrease back pressure on a turbo engine it will always make more power and spool faster from my experience.

66Chevellelq4

This is not me questioning your expertise, but isn't it pressure that drives the turbine in the first place? Wouldn't added pressure decrease spool time, but then obviously make less power up top? What you said seems backwards, but then again, you're the cam//turbo expert haha

DavidBoren

Exhaust pressure drives the turbine. Back pressure is pretty much excess pressure building up when you are creating more exhaust pressure than the turbo can effectively use. A bigger exhaust housing can use more exhaust pressure before it starts to "pile up" creating back pressure.

Having a properly matched system is what decreases spool time and makes power.