T28 not performing as advertised

[Tom Sawyer]

Well I finally got this thing properly installed and ran it at 12 psi for a bit (a week). Was running great so I thought I'd bump it to 15 and see if that was fuel cut territory. Ran great on a second gear pull so I left it there. Went out on the highway, nailed it in third...near instant 15 psi, rock solid. That was until I got to about 6000 RPM and it began falling to 10 psi, JUST LIKE MY FAWKIN T25. So I did it again to see if my eyes were deceiving me. Same thing, 10 psi by redline. I was told I could hold over 20 psi to redline no problem but it can't even hold 15. I'm really hoping something is wrong with the install or this particular turbo. We took it slow and spent a whole weekend on it so nothing should be wrong. If any of you have suggestions as to what I might do please post them. I'm making a call to AGP tomorrow and if I need to upgrade, I'm going to be just a bit upset (biggest understatement of the century).

Tom

 

[Turbo Guru]

The AGP T-28 that I just installed on my 98 GSX is performing very well (considering I haven't installed my downpipe and fuel upgrades yet.) I am able to hold 15psi all the way to redline with a Hallman MBC. I am not sure of the problem you are having, but I will say that I have not had any problems so far.

Joe

 

[DSMJim]

I would check to see if your boost controller is working properly first. Second check for air leaks in your intercooler system, then later on check to see if you have any exhaust leaks before the turbo.

Something is stoping the turbo from spooling hard, either the wastegate is opening before it should or the air is leaking out of the intercooler pipes somewhere. Have a look at those.

 

[McGruffAWD]

More then likely its a leak somewhere. Check all your connections.

 

[SPEEDY]

I can relate to this situation. I'm currently running 22 psi on my FP ported Big28, and I have noticed lately that my boost drops to 20 psi at the top of third. I have went over the car several times retightening everything to check for leaks. The car runs very strong even though the boost falls a little. I'm still happy with my purchase regardless.

 

[Tevenor]

Please tell me you don't the T28 installed on car that still has the stock 2G BOV.

 

[98TsiAWD]

Originally posted by Tevenor
Please tell me you don't the T28 installed on car that still has the stock 2G BOV.

Heres from his mod list:

"Brode UIC Pipe, Turbo XS RBV"

So its not that, but that was a good thought to think of that it could possibly be

 

[SPEEDY]

I'm thinking my problem has to do with me using a 1g bov, Duh! The 1g bov will only hold about 18 to 20 psi without being crushed or modified in some way. I completely forgot all about that.

 

[Tevenor]

Originally posted by SPEEDY
I'm thinking my problem has to do with me using a 1g bov, Duh! The 1g bov will only hold about 18 to 20 psi without being crushed or modified in some way. I completely forgot all about that.

Explain my 24 psi on an uncrushed 1G BOV then. Like most things, test you parts to know what they are capable of. Some 2G BOV's hold 14-15psi. Some 1G's hold 24 psi. Don't assume anything.

 

[Tom Sawyer]

All right. I gotta drive this thing back down to college tonight. Hopefully I won't have any chance to race, I don't wanna get killed with my new turbo in....I was undefeated on the T25, . On a side note, what would be the best method to find the leak? Thanks fellas.

Tom

 

[Turbo Guru]

Originally posted by Tom Sawyer
On a side note, what would be the best method to find the leak? Thanks fellas.

Tom

There is a recipe for a boost leak detector on www.vfaq.com

Joe

 

[SPEEDY]

Originally posted by Tevenor


Explain my 24 psi on an uncrushed 1G BOV then. Like most things, test you parts to know what they are capable of. Some 2G BOV's hold 14-15psi. Some 1G's hold 24 psi. Don't assume anything. [/QUOTE I agree... my 1g bov seems to be holding around 20 to 22 psi so far. It just seems to drop off to 20 psi from 22 psi right at redline at the top of third.

 

[Violater101]

Well, its not very hard to crush the BOV anyhow...just stick it in a vice and have a pressure gauge hooked up to it and you can see how much boost it will hold if memory serves me correct.

 

[larryd]

are you guys all sure that you are holding boost up around 22psi and its dropping off, or is it possibly spiking to 22psi and then leveling off.. i see that as more of a possability and I had that issue with my Big28

 

[Violater101]

Thats a possibility and a good point. Have you checked by just seeing what kind of boost the turbo holds with the bc out of the equation?

I seriously think in Tom's case that something has to be hooked up wrong.

 

[Turbo]

If everything after your second checkover
still seems to be hooked up right , you might want to take a pressure tester (I use a bycycle pump that has an air pressure gauge on it ) & hook it up to your
wastegate accuator & apply pressure to it &
see what your wastegate accuator is starting to open @ (when you see the accuator rod start to move) .If the accuator is opening prematuraly it can do\cause the things that you are describing. Hope that helps ya out .
You want to try & check everything before you go through the chore of pulling your turbo off again.
Wade

 

[Tom Sawyer]

Wade,
I appreciate your insight. Clearly explained and everything. I'll make sure to add you to my list when considering purchases for my 6-bolt project.

Tom

 

[SPEEDY]

Originally posted by larryd
are you guys all sure that you are holding boost up around 22psi and its dropping off, or is it possibly spiking to 22psi and then leveling off.. i see that as more of a possability and I had that issue with my Big28

That must be what's happening to me then Larry. I guess I'm really just running 20 psi, and not 22 psi, cause 20 psi is where it levels off at. I think I'm going to crank the boost up a couple more psi and see what happens. If this is the case, I wonder if spiking to 24 psi is cutting it to close with to much Cylinder head pressure, and having the possibility of blowing a head gasket.

 

[taylorspl]

All of you with the "fall off" problems are you running MBC's or EBC's?

 

[SPEEDY]

Originally posted by taylorspl
All of you with the "fall off" problems are you running MBC's or EBC's?

I'm currently using a MBC.

 

[Turbo]

I just hope you find that it IS something wrong other than your turbo. I can't think of anything more inconvienent/ unmotivating
than spending 3\4 k on your pride & joy only to .... well.... I know I'd be upset to just from my own personal experiences in the past. I didn't always work where I currently work ya know.

Even if it is your new turbocharger, you should be in good hands with Ben & Kevin at
AGP turbochargers.

Keep us posted.
Wade

 

[crashed97tsi]

Originally posted by Turbo
If everything after your second checkover
still seems to be hooked up right , you might want to take a pressure tester (I use a bycycle pump that has an air pressure gauge on it ) & hook it up to your
wastegate accuator & apply pressure to it &
see what your wastegate accuator is starting to open @ (when you see the accuator rod start to move) .If the accuator is opening prematuraly it can do\cause the things that you are describing. Hope that helps ya out .
You want to try & check everything before you go through the chore of pulling your turbo off again.
Wade

sorry to bring up an old thread, but can this work the other way too. The reason I'm asking is because I got the T-28 and I'm having creep problems. I'm almost positive it's the o2 housing but we were having soem problems with the wastgate actuator too.

 

[Silent2g]

Originally posted by SPEEDY

Originally posted by Tevenor


Explain my 24 psi on an uncrushed 1G BOV then. Like most things, test you parts to know what they are capable of. Some 2G BOV's hold 14-15psi. Some 1G's hold 24 psi. Don't assume anything. [/QUOTE I agree... my 1g bov seems to be holding around 20 to 22 psi so far. It just seems to drop off to 20 psi from 22 psi right at redline at the top of third.

my stock uncrushed, unmodded 1g bov has held 24-25 psi all the way to 6k.

every car is different.

 

[DCJ98GST]

Originally posted by crashed97tsi



sorry to bring up an old thread, but can this work the other way too. The reason I'm asking is because I got the T-28 and I'm having creep problems. I'm almost positive it's the o2 housing but we were having soem problems with the wastgate actuator too.

Which T-28 did you get? AGP, FP?

Never mind saw your profile. Its the AGP version

 

[crashed97tsi]

Yeah it's an agp t-28 ported. The turbo should be fine. I'm gonna start to port out the stock o2 tonight. The car was in an accident and the wastegate got a little bashed up. We had to bend the wastegate bracket so the arm could clear it but it didn't help any. I was just wondering if maybe the actuator isn't opening the wastegate enough or at the right psi. Right now i have my mbc backed out to the last thread so it shouldn't be hitting 15 psi.