Louis

iTrader: (7)

Thats 20 hp/lb of boost, which is on the other side of the map, yes, but still efficient to some degree. On most apps, we like to see 25hp/lb of boost when we are in the meat of the compressor map.

IAT delta and backpressure would really tell us if we were out of turbine, but with out knowing what those two numbers are, we can only speculate.

bad6as

iTrader: (17)

Right I've been looking into doing a gt4788 on my 365. Looking for 1200 flywheel.

Ricky Bobby

It's a 96 ar with a g trim wheel clipped in a 4788 housing , Reed at works turbo built it it made 1030 rwhp thru a 4l80 at 18 psi no timing so when we add boost and timing maybe some race gas it's on

98Z28CobraKiller

iTrader: (17)

I wouldn't build a 408 for this turbo. If the build is done, then I'd do a GT5591 with a smallest T6 housing.

koolrayz

iTrader: (26)

This is what I ran on my first setup a 410 with a GT5591 and the 1.00 ar.
If you look at garrets site the GT55 with the 1.00 ar flows the same # per hr as the 4788 with the 1.39ar. Thats why I said he should use the bigger housing. If you are clipping the wheel then you're compairing apples to oranges

craig382ci

iTrader: (5)

Hey Los its been awhile since I've got to talk to you! Did you look at the link I put up on TINKERD dyno? He don't hit full boost until 4500RPM's and that's with a A/R .96 on the GT4788 408ci. How will the GT55 compare in your opinion on it coming into/hitting full boost at? I am interest to know what you think. You have been very helpful in the past for me. You and Josh@KY-Turbo is about the only 2 on here that I go too for opinions/advice.

craig382ci

iTrader: (5)

I understand what you're say. Watching TINKERD dyno pulls and the street ones. I would think if he went to a bigger A/R that it would have him going over 4500RPM's before hitting full boost. Mine is the same turbo but with BB and a 1.23 A/R. It will be a few months before mine will be ready for the test.

I called Percision and Garrett both! I got the same answer from both places. What they told me was "building a drag car only, then things would be different." Being that I am not building a drag/track only car they said "keep what you have, any bigger and you are going to run into more lag than you want" I don't want to be hitting 5000RPMs before my car hits full boost and I hope that don't happen. But if it does then I will just change the housing out.

I hope that whatever you choose to go with konceptracin it will perform just like you want it to. Good luck to us both LOL.

WS6HUMMER

iTrader: (19)

I was all set on a GT5588 turbo until a friend of mine got one (Exile), its awesome on the track but very extreme. On the street the thing takes forever to spool & the new converter to make the turbo work right slips so much that the trans temps go sky high when you try to drive it on the street. He talked me out of a GT55 & into the GT4788. FWIW

konceptracin

Yeah luck is what I'm praying for.....lol the main reason I wanted to go with the gt4788 is the price ... You can't beat it! And then after seeing the 800 on 15 psi I thought that was the way to go... I know there are other factors but how much hp is really needed to run a 8.99-9.5 pass?

konceptracin

If tinkerd had a open thread about his build and his 408 with the gt4788 .96 a/r everyone would suggest something different....because it just don't sound right......but look at the results.....makes good power to me!

koolrayz

iTrader: (26)

I thought the OP said he wanted max effort? If it is a street car that you want to stab from a roll and be at near instant full boost then thats a different story

craig382ci

iTrader: (5)

That is just what I was told or one of the things that Percision and Garrett told me about. I was like you with the GT55 or even bigger. The first one to warn me was Josh@KY-Turbo. But I had read so many different things that I was just so confused. That is when I just said "call Percision and Garrett to see what they would tell me". It should have been enough when Josh told me. But.....you know how it goes.

craig382ci

iTrader: (5)

Well I totally missed that. My bad. Then I suggest you get a trans brake and get the GT55. Got to have the trans brake to help build your boost up off the line for max performance. I am sure others will have more input to help you get it coming off the line with the right amount. What are you using for a boost controller?

konceptracin

I have a aem and I plan on getting there boost solenoid.... The bigger the turbo gets from the gt4788 I worrie about pushing water! So I'm not sure what to do

bad6as

iTrader: (17)

Gt88 is another choice. Same compressor wheel as a gt4788. Slightly lower flowing compressor cover. And the turbine is 2mm bigger but a slightly older design.
Over all its a slightly lower flowing unit as the gt4788. But the overall package is smaller and the prices are a lot cheaper. A few board members have it and made over 1k wheel. Good data too as far as boost vs. hp. On A 347 and a 408

Professor_speed

iTrader: (8)

High back pressure is going to make it push water easier.

GT5088 is something $100 more GT4788

Go bigger turbine before running a clipped wheel imo. It helps but Its not all about turbine flow, turbine leverage will make a big difference too.

Try to buy a turbo with an A/R that is in the middle of the range so that you can tailor it to your combo after it is running if need be. buying the smallest wheel and largest A/R leaves you no where to go if you need more flow and vice versa.

craig382ci

iTrader: (5)

How much boost do you plan on running? I had my block and heads modified to take a 1/2" head bolts. That is what a lot of ppl are doing. That and having your block and heads O-ringed. But I could not afford all that.

The best boost controller that you can get is the AMS 1000. That is what I got for mine. But it is like $1000. But with all the option of what it can do with it's worth it.

Get up with Josh@KY-Turbo and he will tell you what you need. What is your budget for the build? These build can run high fast. Most ppl that does a complete build and do it right with the best parts over $40,000 easy. Like what trans are you going to use? What rear end? What are you going to do with the suspension? ECT.! Don't go and buy the cheapest parts. You will save yourself a lot of money by doing it right the first time around. You have to look at every point on the car. It has to be built to handle the high HP. You can have all the HP in the world but if you can't put it to the ground then you have spent a lot of money on a engine for nothing.

konceptracin

I will start with 15 and then hope to get up to 20 .... Well see what happens the 1/2 " head studs what's all involved with that ? Can it be done if my roating assembly Is already installed? What needs to be done to the heads?.....and I have no plans on buying the cheapest parts but trying to not buy the most expensive because your right it will cost me more in the long run! We should look in to that gt5088....

konceptracin

Craig what head gaskets you going to run?

konceptracin

I talked with AES and
They didn't think the 1/2 studs
Were worth doing in my set
Up they suggest giving the ls9 head gasket and the arp hardwear a shot!