Problems with T4 Gt91??? wont make more than 6psi!!
#1
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Guys, it was at the dyno shop all day today trying to get my car tuned. it would never make over 6psi on the wastegate alone, even with a 17lb spring. here is my setup:
408ci
gt91 w/ T4 .96 a/r from forced inductions (he said it flows plenty for my motor)
turbosmart pro-gate 50mm wastegate with 17lbs of spring pressure
AEM boost controller
So we tried every combination of boost controller settings and nothing worked... I was on the phone with turbosmart most of the day, and judging by the tests they had me do, it seems like the WG is fine. we pressure tested the cold side, and there were no leaks. The motor runs great, and is making good power for the boost level that its at. by cranking up the boost controller, we could get the boost into the low teens, but the controller was MAXED OUT.
the only thing left is the turbo... when I got the T4 flange, i noticed that the clearance between the turbine blades and the inside of the wheel was pretty large. I also have the t6 flange and the clearance is MUCH MUCH less. it is a very tight tolerance between the housing and wheel on the T6 housing. I asked jose@forcedinductions about this and he said that the T4 was fine. Im worried that there might be a little too much clearance, causing the turbo to spool slowly. The tuner kept telling me how slow the turbo was spooling.
I remember reading a thread about someone who got a bad exhaust housing, but i cant remember the details. does anyone have any input or advice on this??
408ci
gt91 w/ T4 .96 a/r from forced inductions (he said it flows plenty for my motor)
turbosmart pro-gate 50mm wastegate with 17lbs of spring pressure
AEM boost controller
So we tried every combination of boost controller settings and nothing worked... I was on the phone with turbosmart most of the day, and judging by the tests they had me do, it seems like the WG is fine. we pressure tested the cold side, and there were no leaks. The motor runs great, and is making good power for the boost level that its at. by cranking up the boost controller, we could get the boost into the low teens, but the controller was MAXED OUT.
the only thing left is the turbo... when I got the T4 flange, i noticed that the clearance between the turbine blades and the inside of the wheel was pretty large. I also have the t6 flange and the clearance is MUCH MUCH less. it is a very tight tolerance between the housing and wheel on the T6 housing. I asked jose@forcedinductions about this and he said that the T4 was fine. Im worried that there might be a little too much clearance, causing the turbo to spool slowly. The tuner kept telling me how slow the turbo was spooling.
I remember reading a thread about someone who got a bad exhaust housing, but i cant remember the details. does anyone have any input or advice on this??
Last edited by KILLER-LS1; 09-21-2011 at 10:42 PM.
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#10
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That GT91 will easily make more then 6psi...lol. Block the gate and BOV and see what she does. Just becareful cause it will boost to hell and back. The other thing is, I would definitely think about switching later to a T6. A T4 housing will work, but it simply won't flow what a T6 will.
#12
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I have the same thing going on. Makes about 8psi off an 11lbs spring,max out the aem controller and I get 11psi. My tuner thinks back pressure on my comp 80/79 with a 1.32ar housing. I'm not sure whats going on.
#13
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Mine has seen 22lbs on a 404 with t4 gt91. Theres something else going on cause mine would def make more boost just havent tried. I plan on swithching to the t6 sometime soon.
#15
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I just did a test. I drove the car WITHOUT the boost reference lines hooked up. it made 15lbs until I let off the gas. I talked to turbosmart and they think that there must be a ton of backpressure forcing the valve open. They are going to sell me a bigger spring to help me keep it shut.
Dr. Turbo, does this seem accurate? Im just surprised if thats true because you guys recommended that I get the T4.
#20
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hmm i have the AEM controller too.
I just did a test. I drove the car WITHOUT the boost reference lines hooked up. it made 15lbs until I let off the gas. I talked to turbosmart and they think that there must be a ton of backpressure forcing the valve open. They are going to sell me a bigger spring to help me keep it shut.
Dr. Turbo, does this seem accurate? Im just surprised if thats true because you guys recommended that I get the T4.
I just did a test. I drove the car WITHOUT the boost reference lines hooked up. it made 15lbs until I let off the gas. I talked to turbosmart and they think that there must be a ton of backpressure forcing the valve open. They are going to sell me a bigger spring to help me keep it shut.
Dr. Turbo, does this seem accurate? Im just surprised if thats true because you guys recommended that I get the T4.