2004 996TT with the following mods:

GT28 turbos
Imagine Auto Stage 4 clutch
Maxspeed headers
Maxspeed exhaust
Maxspeed diverter valves
V-flow intake
EVO turbo intakes (from air filter to turbos)
EVO IC's
EVO silicone hoses
Speedtech 75mm Y-pipe with 70mm silicone hoses from IC to Y-pipe
75mm throttle body
75mm intake plenum
60cc injectors
Imagine Auto ECU flash

I love the setup, but I have struggled for 2 years to get this thing to run right. I could not control the boost, first too much (1.6 bar), then too little (.8 bar which take forever to build up to). I have tweaked the wastegates and got it to build boost much quicker (.8-1.0 bar by 3.5k RPM), and hold at about 1.1 bar. But in lower RPM's it will jump up to 1.5-1.6 bar which scares me. I think it's the small 16G housings on my GT28 hybrids. I also think with my mods they are holding me back from making a lot more power. I also am not happy with my tune; it is jerky at lower RPM's and just isn't tuned like I would hope it would be. Lastly, I now have a CEL with a several codes relating to a vacuum leak and other things.

So I have decided to ditch the GT28's and go with something else. I want to retain as much of the parts I have on there now as possible. What will bolt right up?

Also, I'm thinking about just shipping it to a tuner and having them put on the new turbos. Any recommendations?

Thanks in advance!

Colby

 

Yep, you should ditch the GT28's this way ...

 

alpha 28s second best thing to ur turbos now. fast spool up w/endless power up top. u should call EVOMS. MY CAR IS RUNNING FASTER THAN EVER WITH THESE TURBOS.
sorry to hear u have problems for 2 years now. how can u stand that? i admire ur patient

 

I dont get you... your first sentence says - I love this set up.... your second to last says Im not happy....

first of all you need to get the car check out by someone that knows these set ups... is everything hooked up right.. no boost/vacuum leaks... then start from scratch... just from looking at your mods... your all over the board... mixing and matching... then your gt28s. are probably the 6 year old gt28/K16s with a 1 bar Wg spring... your probably running Giac program and your overboosting causing limp mode(.6 bar)... etc etc etc... if you lived closer I would look at the car..

 

its not the turbos causing your issues it is more then likely the wastegates which are crappy, and your tune but on top of that your likely to have a boost leak from what you describe.

the closest tuners to you would be Switzer(ohio) and Markski(uses Protomotive Flash's), with Todd Knighton from Protomotive just down in Arkansas and any of them could sort out your issues. a little further and you could send the car to EPL they do some good tunes/installs

if your wanting to ditch the turbos definitely a Alpha28/30 would be the way to go, just depends on what you want more street car or more highway car.

 

We have a very similar setup except for the tune. My boost hits 1.3 as soon as I floor it and stays there until redline. I don't see 1.5 or 1.6. And, I can control the boost pretty well just by how much gas I'm giving her.

Instead of switching the turbos, you may want to work on the tune. But then it sounds like you are finding an excuse to go bigger. Good Luck.

 

That's not right either.... you should not have to drive part throttle to get less boost...
Temps have something to do with it... Wgs as well... I have been saying this for a long time.. It is hard to keep the 1 bar WG springs under control via the ecu... when it gets cold they overboost and cause limp mode on some tunes...

Thank God there are EBC... this never happens... no over/under boosting....

 

MARKSKI,
With respect (as always), we don't always drive our car in full boost, right? If I don't use the throttle to control that, what would I use? EBC can control over boost, but can it really control under boost?
Thanks

 

Of course it does. That's what a ebc is for.
Most I not all of the higher hp p cars run them.
Now it's not for everyone. Also u cam control the boost via ecu but with aftermarket springs and changing conditions its not always that easy.
Do u recall how a many gius purchased the aftermarket wg kits and complained about going to limp mode? Overboosting? Etc. An ebc is one one of being in control. But its not for everyone.
Markski

 

Your talking about controlling the boost with throttle position, we dont tune like that. So in theory your saying if i got a tune for 1.4 bar on race gas if u drive 80% throttle Then you can run pump gas and 1.0 bar boost, Negative Ghost Rider

when someone says they cant control the boost like the original poster is referring too he cant keep the boost consistent with a Boost controller (the stock DME/ECU has one). The turbos should Spool and possibly for a split second spike 1-2psi max above the desired boost level depending on the way your controlling the boost mechanical versus Electronic, and then settle to desired level so 1.0bar tune might spike to 1.1. This event can happen faster then the guages can read so you may not even know it happened.

so that means either the boost solenoid is Fubar, there is a leak or something is wrong with the waste gate diaphram or the adjustment of the gates. and if all of that is in order the fuel/timing(the Tune) delivery is out of wack causing the computer to go into limp mode.

you guys are talking two different things, apples dont = Oranges

 

I'm not quite there with the higher hp cars (I'll never be with the Tip), so EBC never came into mind. It is truly an asset to have you on this board to guide us, thanks.
Eugene

 

Didn't mean to confuse anyone, all I meant was the GT28s are quite linear (with the right tune) and boost can easily be held anywhere between 0.0-1.3 (for me). I was trying to tell the OP... the problem is mostly not the turbos.

 

Call us Colby! You bought a tune over a year ago that you still haven loaded. I would love to help you work through this.

 

I love the setup as a whole (no turbo lag, etc), the boost control is the only issue. You are good; GT28/K16 w/ 1bar WG, GIAC tune (all parts bought from Stephan Kaspar, installed by a local shop), stock ECU boost control, although I have a Profec B in there but couldn't get it to control the boost either, so I went back to stock.

Chicago isn't too far from me; I'm in Indianapolis. I was prepared to ship the car somewhere to get it right. I can drive it to Chicago, spend the weekend up there, drive home with my fiancee and come back when it's done. If you're interested in working on it, let's definitely talk.

Colby

 

Tony, LOL that's because I never got to the point that you could help! As you recall, when I got your tune it was because the car was only making .6-.8 bar and GIAC was of no help. The data I sent you showed no boost intervention from the ECU, so the issue was hardware. I spent another year messing with it and finally figured it out by tightening down on the WG preload to get it to make more boost. Your tune surely will help, but with the boost leak, I'm not sure the hoses and BOV's are right, and other hardware issues I think they needed to be sorted out so we're tuning a car that's "right".

Colby