[Peralvr4]

I am wondering if there is anyway to predict when I will be able to see close to full boost, This will be my deciding factor for choosing which gtk,

I have a built dart block 2L, ported gsr head, flows high 200cfm's
and am looking for around mid/high 500's fwhp, car will be mid/hi 20psi, on meth, the two turbo's i have to decide between are, 550 and 650, the only reference I have is a 2.4l can spool a gtk500 at 4200, so less displacement I might be able to spool a 500 at 5000rpm but I have no idea how to guess on the two I want, I am really leaning toward 650 because it's a vband. Please any help would be greatly appreciated.

[Robert]

Originally Posted by Peralvr4

I am wondering if there is anyway to predict when I will be able to see close to full boost, This will be my deciding factor for choosing which gtk,

I have a built dart block 2L, ported gsr head, flows high 200cfm's
and am looking for around mid/high 500's fwhp, car will be mid/hi 20psi, on meth, the two turbo's i have to decide between are, 550 and 650, the only reference I have is a 2.4l can spool a gtk500 at 4200, so less displacement I might be able to spool a 500 at 5000rpm but I have no idea how to guess on the two I want, I am really leaning toward 650 because it's a vband. Please any help would be greatly appreciated.

Its difficult to product boost threshold on any car with that much extensive work. If you have an idea of what your current or prior turbo did I might be able to give you a guesstimate if things haven't changed.

[Peralvr4]

Gt35 did 430whp at 26psi and spooled at about 5100rpm

[Robert]

Originally Posted by Peralvr4

Gt35 did 430whp at 26psi and spooled at about 5100rpm

The GT-K 550 uses the closest turbine wheel to the GT35R. The GT-K 550 uses an F1 version of the Stage 5 T3 turbine which is very comparable in non-F1 form to the GT35 turbine section. With the F1 wheel though you should see a little faster spool up. The GT-K 500 uses one size smaller then that turbine (F1 Stage 3 turbine) so its spool up would be faster even then the GT-K 550. The compressors are the same between the 500 and 550 so personally I would opt for the 500. Especially since you already have a reference to it.

[Peralvr4]

How much bigger is the 650?

[Robert]

Originally Posted by Peralvr4

How much bigger is the 650?

The GT-K 500 and 550 use a GTK61 compressor which is roughly a 61mm compressor wheel. The GT-K 650 uses an HP66 compressor which is a 66mm compressor wheel. Turbine wise the GT-K 650 uses an F1 P trim T4 turbine which is quite a bit bigger then a F1 Stage 3 T3 or F1 Stage 5 T3.