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PT88-47H or GT4788

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Old May 11, 2013 | 04:53 PM
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Default PT88-47H or GT4788

Hey there..

Users/expert help and opinion is needed..
I have only 2 options to go on the turbo
1- GT4788, AR is 1.08
2- PT88-47H, AR is 0.96

Firebird, TH400 tranny
408 lsx short block
CNC'd Ls3 heads (Compression is 9.2)

which one will be the best for my engine, Am shooting for 900rwhp

Thanks and appreciate your feedback
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Old May 11, 2013 | 06:06 PM
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Ill go with the PT88, lots of people love how they spool on 408s. Very nice turbo for those cubes.
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Old May 11, 2013 | 06:10 PM
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The pt 8847 is rated at 1475 hp t4
The gt 4788 is rated roughly at 1400~ hp t6
My pt spools from 0-29 psi in roughly .8 seconds with the th400.
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Old May 11, 2013 | 06:47 PM
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The PT 8847 is much more compact than the GT-4788. A PT 8847 uses the small PT88 housings and stuffs the GT-4788 wheels in it. So it's basically a PT88 with the newer style wheels in it. Obviously the same wheels in a larger compressor housing will flow more air. Precision also makes a 4788 I believe which uses the larger housings. Honestly on a 408 I'd skip both those units and go straight to a GT50 or GT55 series exhaust side.
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Old May 11, 2013 | 06:49 PM
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Those are the same wheels in different housings

The pt8847 uses the tiny H compressor cover, and a custom cast precision .96 t4 exhaust housing

Same housings and size as the standard pt88 other than the pt88 being a little longer since it uses the TV bearing housing



The gt4788 is in the full size (huge) compressor cover, and uses the standard t6 exhaust housing


The fullsize 4788 will make more power, more efficiently
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Old May 11, 2013 | 06:50 PM
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Treed me
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Old May 11, 2013 | 06:54 PM
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As 383 said if you have room there is no reason to be using the pt8847.

You would be much happier with a gt50 or 55 turbines that motor

Its the same physical size as the 4788 so no difference there
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Old May 11, 2013 | 08:41 PM
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Originally Posted by rotary1307cc
As 383 said if you have room there is no reason to be using the pt8847.

You would be much happier with a gt50 or 55 turbines that motor

Its the same physical size as the 4788 so no difference there
I wish i could go with the GT50 but i cant
I have already paid for the shop to purchase one of the above.
So, for my 408 and ls3 heads you guys suggest to go with the GT4788
How much should i expect from the GT4788 and my motor?
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Old May 11, 2013 | 08:45 PM
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Originally Posted by rotary1307cc
Those are the same wheels in different housings

The pt8847 uses the tiny H compressor cover, and a custom cast precision .96 t4 exhaust housing

Same housings and size as the standard pt88 other than the pt88 being a little longer since it uses the TV bearing housing



The gt4788 is in the full size (huge) compressor cover, and uses the standard t6 exhaust housing


The fullsize 4788 will make more power, more efficiently
How is the efficiency/spooling and lag with the 4788 on my motor?
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Old May 11, 2013 | 08:48 PM
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Originally Posted by FasTimeSS
The pt 8847 is rated at 1475 hp t4
The gt 4788 is rated roughly at 1400~ hp t6
My pt spools from 0-29 psi in roughly .8 seconds with the th400.
So you are saying that the t88-47 will produce more power than the GT4788?
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Old May 12, 2013 | 08:30 AM
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Come on guys, I need to figure out which way to go
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Old May 12, 2013 | 08:34 AM
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Between those two as said is a no brainer. The fullsize gt4788 if you can fit it

It will be very responsive on your motor/trans combo
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Old May 12, 2013 | 09:32 AM
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4788 hands down! Full size T6 will flow more air and not choke your motor like the little PT unit.
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Old May 12, 2013 | 10:20 AM
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Originally Posted by z0vette
Come on guys, I need to figure out which way to go
You made three posts in 7 minutes, pushy. It's already been said between the two. The 4788
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Old May 12, 2013 | 10:33 AM
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Forums= people will have different opinions soo dont expect a straight answer.
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Old May 12, 2013 | 01:28 PM
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Neither, the smallest I would do is a GT50 sized turbo.
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Old May 12, 2013 | 03:20 PM
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Originally Posted by Nitroused383
The PT 8847 is much more compact than the GT-4788. A PT 8847 uses the small PT88 housings and stuffs the GT-4788 wheels in it. So it's basically a PT88 with the newer style wheels in it. Obviously the same wheels in a larger compressor housing will flow more air. Precision also makes a 4788 I believe which uses the larger housings. Honestly on a 408 I'd skip both those units and go straight to a GT50 or GT55 series exhaust side.


I agree , Specially with stalled auto.
I'm going with GT4788 T6 1.08 on 370-408ci 6 speed trans and I'm thinking GT50
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Old May 12, 2013 | 05:31 PM
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Originally Posted by Cam72aro
You made three posts in 7 minutes, pushy. It's already been said between the two. The 4788
Lol, i didnt know we have a time keeper here ;-) just kidding..
The thing is that i wanna know how efficient is this turbo on my car. Am not going to use a stalled convertor
How would it spool/response
Am gonna hit my goal with that 4788?
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Old May 12, 2013 | 06:27 PM
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What are your plans for the car other than 900rwhp? You can't expect more answers without giving more details.

Will the 4788 make the power? Yes
Will the 88-47 make the power? Maybe. You will for sure run out of steam fast I. The rpm range.

Is this a car that is going to see the track often? If yes, or only a track car and those are the only choices it would be the 4788. HOWEVER, I would get a 1.23 or 1.39 housing for it!
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Old May 12, 2013 | 07:31 PM
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Originally Posted by z0vette
Lol, i didnt know we have a time keeper here ;-) just kidding..
The thing is that i wanna know how efficient is this turbo on my car. Am not going to use a stalled convertor
How would it spool/response
Am gonna hit my goal with that 4788?
No worries.

You are not going to run a higher stall? Why not? A stock converter will die quickly. A 3200-3600 converter will be essential in turbo spool, without it the car won't get into the power band and spool. My car has a 3600 in it, when I nail it in 3rd on the freeway it flashes and goes into boost instantly. The motor will lift the heads before you run out of turbo. That turbo is a little small for that motor, but with that spool will be earlier. It might not make as much power past a certain rpm but will more than meet your goals.
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