GM TH400 in a T88 Supra: Issues

[GN138]

Hello all,

My buddy has a '95 Supra with a GM TH400, 3800 Stall, T88 turbo, fully built engine/ head, etc...

He's just got it off the dyno and is hitting around 708HP to the wheels, still not fully tuned, running lower boost (25psi) and not running his nitrous yet.

Issue: While @ the track, when trying to build boost, his car pegs @ 2000rpm and launches crappy.

His first run @ the track was a 15.?? @ 120mph.

He used a small 30-40 shot and got down to 14.3 @ 120mph.

This track is @ 5800ft above sea level and he running ET Streets and skinnies in the front. Full cage. Car does a hell of a burn out and then once he pulls to the line and tries to build boost he says it only gets him to 2000rpm and when he launches he gets a tiny bit of spin and it takes forever for his turbo to finally kick in @ 5500rpm.

If we take it on the street and start from 2nd gear (higher rpms) the car lights up the ET's and hauls booty.

Thinks it's an issue with the torque convertor. Would a transbrake help at all?

Thanks!

 

[John Wilde]

I can see a couple problems:

-88MM Turbo is big for a small motor and automatic.
-The stall is way to low for the turbo and that engines power band. I would think about 5000 would be a good start
-You will need a transbrake for sure!
- Make sure that you are not getting exhaust or tire smoke
in the turbo when trying to spool.

This car sound like it should be really cool once the bugs are working out!

 

[GN138]

Thanks John!

I'm pretty clueless about imports but the 3800 seemed to small and evidently it's not working 100% anyway.

I'll pass your info on to him. Thanks again!

 

[Crazy87GN]

if he needs a diff t400 tranny i have one for sale with less than 1,000 miles on it

 

[86brick]

Is this a GReddy T88 turbo?? If so it is NOT a true 88mm (comp wheel) turbo...... There are not many Supra guys I know of running a true 88mm turbo, so I would guess it is a GReddy T88 which is actually a 72 or 74mm turbo..... Just thought I'd throw that bit of info in here..... Also, you may want to post this on www.supraforums.com because I'm sure they could probably help him out.... Sounds like there could be a problem with the converter, but it could be a lot of things.....

 

[John Wilde]

Originally posted by GN138
Thanks John!

I'm pretty clueless about imports but the 3800 seemed to small and evidently it's not working 100% anyway.

I'll pass your info on to him. Thanks again!

A couple of my friends that run a 88MM turbo on a 274CI Motor
use close to a 5000 stall.

 

[John Wilde]

Originally posted by 86brick
Is this a GReddy T88 turbo?? If so it is NOT a true 88mm (comp wheel) turbo...... There are not many Supra guys I know of running a true 88mm turbo, so I would guess it is a GReddy T88 which is actually a 72 or 74mm turbo..... Just thought I'd throw that bit of info in here..... Also, you may want to post this on www.supraforums.com because I'm sure they could probably help him out.... Sounds like there could be a problem with the converter, but it could be a lot of things.....

Steve,

We have a big GT4X on a supra out here.
I think it is in the 8XMM Range. It has a
5inch ported shroud cover.
I will let you know more as I find out!

 

[86brick]

Originally posted by John Wilde
Steve,

We have a big GT4X on a supra out here.
I think it is in the 8XMM Range. It has a
5inch ported shroud cover.
I will let you know more as I find out!

Yup there is one down here that was built by the Scranton brothers that has been terrorizing the streets lately.... Last I heard it had one of the big GT series turbos + spray and made 1200hp at the rear wheels I'm pretty sure it is a 6-speed car and he's not looking to go from a dig (he wants to go from a roll)....

 

[KEVINS]

Originally posted by 86brick
Also, you may want to post this on www.supraforums.com because I'm sure they could probably help him out....

Ditto.. They should know what to do...

ks

 

[John Wilde]

Originally posted by 86brick
Yup there is one down here that was built by the Scranton brothers that has been terrorizing the streets lately.... Last I heard it had one of the big GT series turbos + spray and made 1200hp at the rear wheels I'm pretty sure it is a 6-speed car and he's not looking to go from a dig (he wants to go from a roll)....

Steve,

Let me know about this one when you find out!

 

[86brick]

Originally posted by John Wilde
Steve,

Let me know about this one when you find out!

Will do! Actually it might be a Turbonetics thumper now that I think about it.... I know somebody posted pictures of it when it was at this NMRA race where they had a dyno and it put down 940rwhp with a mild tune without the spray..... I'll see if I can find pics for you.....

 

[86brick]

John, there are pictures of the Supra I'm talking about in this thread.....

http://www.supraforums.com/forum/showthread.php?threadid=177458&highlight=scranton+brothers+supra