Gt4788
PTE once rebuild a t4 88 for me like 5 times before we came to the mutual agreement that it was being over spun, pushed too hard, and failing. Alot of times there are fine lines to where a combo is happy or not and right or not and sometimes hard to get there without a long talk about a combination. Then there are people who have been there and done that and post up the results and nobody listens. I cant count how many times Dr turbo has posted that the 47-88 is too small for the larger ls crowd. I also posted my thoughts in this thread and I have a 47-88 on a 5.3l....which should be on the happier side of displacement for that turbo.
But I still don't understand why both Percision and Garrett would tell me to stick with the 4788. And yet this 4788 seems to be a big issue. Not just on this thread but many others. But talk to the ppl that make turbos like stated above and they are know issue. Then you see someone like tinkerd with a 408ci do as well as he done. Makes someone like me an konceptracin somewhat confused. 
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
Topdon ONE vs. Artidiag 800 BT2: Which is the Diagnostic Tablet For You?
Pouria Savadkouei
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine
Verdad Gallardo
7 Most Reliable High-Performance Engines GM Has Ever Built
Verdad Gallardo
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin
Verdad Gallardo
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo Yes on the A4 and no on being limited to a 88mm. I bought the 4788 bb and based the rest of my build around it. Fraser at AES based my CI on the turbo and my goals. Which is how I ended up with the 410ci. I had also spoke to Shawn at ERL before I spoke to Fraser at AES and he was going to do a LS6 427ci with my 4788 T6 A/R 1.23 bb turbo.
A lot of the 1200whp cars I see with that turbo are sbf and supras. The ls motors flow a lot of air compared to older sbf and sbc. I know it suckcs that you bought a nice turbo and built your combo around it but I think you will choak it. I had a 80mm that I was told would do 1100 flywheel. Well even after going from a 1.10 ar to a 1.25 and from a 83mm to 87mm turbine its still choaked out. 13 lbs boost was just under 1.5 back pressure and I'm a 9.0 compression 365. Now I'm redoing my whole turbo kit with a new turbo. I thought about the gt4788 and I still may do it if I find a deal on one. But if you want 1200 wheel then ide look in to a 91mm compressor and some thing with a 100mm range turbine
A lot of the 1200whp cars I see with that turbo are sbf and supras. The ls motors flow a lot of air compared to older sbf and sbc. I know it suckcs that you bought a nice turbo and built your combo around it but I think you will choak it. I had a 80mm that I was told would do 1100 flywheel. Well even after going from a 1.10 ar to a 1.25 and from a 83mm to 87mm turbine its still choaked out. 13 lbs boost was just under 1.5 back pressure and I'm a 9.0 compression 365. Now I'm redoing my whole turbo kit with a new turbo. I thought about the gt4788 and I still may do it if I find a deal on one. But if you want 1200 wheel then ide look in to a 91mm compressor and some thing with a 100mm range turbine
I only comment on what I know and what I know is that the PT88 is too small for my mild 370 and the GT4788 is very similar. Does it work? Yes. But it's not optimized. I can feel it lay over at about 6K RPM. I got a buddy with a Fox Mustang with a 331ci SBF and he was having the same problem. He got his to 8.6's in the 1/4 at about 300-400 lower raceweight. He recently upgraded to a T4 GT5088 from Forced Inductions. It has the same exact PT88 exhaust housing with it bored out a little to accept the bigger wheel and ran a 8.4 his first time out with a soft 1.34 60'.
So if the Pt88 is too small for my mild 370 street car, then it will only choke a 408 more. Here's the thing though. The 88mm will be enough to overpower the street. It's enough on the 370 and it's certainly going to be enough for a 408 but it's not optimized. What Black mentioned above is the correct way to do a street combo with an 88. The 5.3 or even a 4.8 should be perfect and will be far more reliable.
So if the Pt88 is too small for my mild 370 street car, then it will only choke a 408 more. Here's the thing though. The 88mm will be enough to overpower the street. It's enough on the 370 and it's certainly going to be enough for a 408 but it's not optimized. What Black mentioned above is the correct way to do a street combo with an 88. The 5.3 or even a 4.8 should be perfect and will be far more reliable.
But I still don't understand why both Percision and Garrett would tell me to stick with the 4788. And yet this 4788 seems to be a big issue. Not just on this thread but many others. But talk to the ppl that make turbos like stated above and they are know issue. Then you see someone like tinkerd with a 408ci do as well as he done. Makes someone like me an konceptracin somewhat confused.
They asked me what my goals was first and I said about 1200hp to the wheels. ET's around mid to high 8's. They asked me is this a street/track car. I said yes. They said more street than track or more track than street. I said 70% street and 30% track. They asked what CI. I told them 410.
They asked me what my goals was first and I said about 1200hp to the wheels. ET's around mid to high 8's. They asked me is this a street/track car. I said yes. They said more street than track or more track than street. I said 70% street and 30% track. They asked what CI. I told them 410.
Thread Starter
Launching!
Joined: Jan 2011
Posts: 250
Likes: 0
From: vegas
What a/r can u suggest for the 91.5 infact what is the difference between the 91 and 91.5? Any one know? I would rather have more room to grow in a bigger turbo instead of needing to buy a new one ... But def don't want the car to fall on it's face or feel like it's dying out after 6k