If I were Looking at a Garrett unit for the GS400.

I need it to spool around 2K rpm or lower if possible and still push 800rwhp comfortably. I dont know anyting about the Garrett line and so this is why I need some guidance. I figure ballbearings will be required but I dont know for sure.

Currently have turbonetics T04e T62-1 P trim. It spools around 2800-2900rpm

 

You are going to need something in the neighborhood of a 72mm turbo to get 800whp comfortably. That is not going to spool at 2000 rpm. You arent going to find anything that is going to give you 800whp and spool that early. It is a trade off, big peak hp OR quick spool.

Edit- Just noticed you said a Gs400. I still doubt you will find something to spool that early. It would be better than a 6cyl but asking for 2k or lower is alot to ask IMO. If you go on the Garrett website the should have a listing of what their turbo's flow. from that you can determine approx. hp capabilities on your motor.

 

I figure I could get somewhere around 2k because the current turbo is spooling around 2800 so if I were to just change to ball bearings that should get me 500rpm lower, with just that one change.

Everything on the Garrett site is geared toward the 6 cylinder motors. but I have emailed them for some reccomendations.

 

T62 P-trim is considered a small turbo. You will not loose 500 rpms in spool just by going to the ball bearing turbo that small, maybe 200 rpms. You could also try a smaller A/R, but than you will be loosing the top end power.
There is always a trade off and no magic when comes to turbos.

 

Ignition retard will help spool with less rpm in staging, but I dont know how it would effect these cars. Also there are exhaust housings where they have the split tangential (sp?) housing. One side stays blocked to keep the spool fast, and when a certain psi is reached it opens to allow more flow. So it can act like a .5? durring spool and a .9? when open. But thats big $. Its been a while since Ive seen it so that info is off of memory.

 

i think your confusing twin scroll turbos with variable vane turbos.

 

Yeah, Variable Vane Turbos are what I was thinking of. Thanks Some guys on turbomustangs.com were messing around with making exhaust housings with electric butterflys (electric exhaust cutout style). They could change AR with a push of a button. Some said you could hook up a a map sensor to a switch and have the motor control when it opened.

 

A tangential housing will help with spool but not that much. If you want wuick spool and 800whp comfortably your best bet would be running a large turbo with nitrous on a rpm switch to spool it up.