2G T25 won't hit "full boost"

[smills1840]

So after filling up with Shell premium the other day (I doubt that's relevant), I noticed that no matter what I try, I can't get my stock t25 to hit "full boost". I put quotes around full boost because I don't have a boost gauge yet, so I'm still using the stock one. Trust me, I know it shouldn't even be considered a boost gauge, but I haven't bought a real one yet.

Anyway, I can rev this bi*** out to 7000 RPMs in any gear and it still won't reach the top of the boost gauge. I can also definitely feel that it isn't pulling as strong as it used to.

This is a completely stock 2g dsm, with the exceptions of the dump tube mod and a 3" cat back.

I've done a BLT, with no leaks.

I've checked my wastegate, and it moves freely. Even if the wastegate actuator is stuck, it's stuck in the closed position so it should let me build full boost and beyond.

From what I can tell, there aren't any exhaust leaks pre-turbo. There is one post turbo, but it's not bad and it's always been like that (long before this problem started)

I've checked all vacuum lines and the MAF connector, all good to go.

I've run it with and without the BCS, still no good.

The only thing I haven't done is pull my exhaust/downpipe off and see if it's clogged.


I cannot think of anything else that would be causing this. Do you guys have any ideas?

 

[Bud92gsx]

Well your t25 is not going to hold x amount of boost at 7k rpm.

What is considered "full boost" on a t25?

 

[AngelOfPassion]

There is no way to know if your t25 is hitting 12-14psi with the stock gauge. Unless you get a real boost gauge you will never know. The stock gauge is just controlled by the ecu, not actual pressure. I don't think it ever reaches the top of the gauge anyways.

 

[Paintballaa5]

More than likely just some boost leaks.

And there's really no reason to redline the t25..

 

[donniekak]

More than likely just some boost leaks.

And there's really no reason to redline the t25..

Boost leaks will make the stock gauge read higher.

 

[AngelOfPassion]

Boost leaks will make the stock gauge read higher.

So maybe he had some boost leaks that he has now fixed? And the gauge is reading properly now... haha

 

[kleenf4i]

i just went throught this same issue with my car.pull the intake pipe from the turbo and check for shaft play, up,down and side to side. +1 for the boost gauge not being accurate on the cluster. My cluster gauge tops out right at 14 psi.I know this becasuse I have a mechanical boost gauge as well. so if the stock gauge is getting to 3/4 to the top. I would say that its doing just fine in theory.However like stated before. there is no way to telll the exact amount of boost by that cluster gauge.

 

[AngelOfPassion]

i just went throught this same issue with my car.pull the intake pipe from the turbo and check for shaft play, up,down and side to side. +1 for the boost gauge not being accurate on the cluster. My cluster gauge tops out right at 14 psi.I know this becasuse I have a mechanical boost gauge as well. so if the stock gauge is getting to 3/4 to the top. I would say that its doing just fine in theory.However like stated before. there is no way to telll the exact amount of boost by that cluster gauge.

Dude. How do you have 134 tech posts in less than a month? On here all day?

 

[smills1840]

I checked for shaft play, and there is a tiny amount of side to side play. No in and out play.

I should have been more clear in my first post. I don't really care what my max PSI is with the t25. I can feel that something is not right with the car. It's not pulling as hard as it usually does.

I also know that the stock boost gauge is a waste of space on the dash. But I know for a fact that I used to easily be able to peg it at the top when pulling, and now I can't.

Thanks for the replies!

 

[kleenf4i]

Dude. How do you have 134 tech posts in less than a month? On here all day?

. basically. im working for myself right now so im on here to lear and get help myself. I was wondering when someone was going to ask that question. plus I like to help people( the best iam able).

boot leak is the #1 culprit for this. I learned this the hard way over severall hours of painstaking, beating my head against the wall. If not a boost leak, then possible waste gate. For one, and i mean one run unhook the vacuum to the waste gate and go do a pull. report back with the info. Did it change anything?

 

[99ECLIPSEGSXDSM]

You really need a boost gauge. Like stated you don't know if your getting "full boost" (should be 11-12psi) with out one. How many times have you drove the car since you filled up?

 

[Dsmkauai]

Check for vacuum/boost leaks, also check the wastgate and all components to ensure they are moving freely.

 

[DSMnoobsause]

Could also be fuel quality. They usualy put more ethanol in the gas close to fall/winter time.

 

[Diamond Star Werks]

Wanna do something fun? Turn your stock bov around backwards. 2g bov's are know to leak. If it is leaking back through the intake this will stop it.

 

[Diamond Star Werks]

Like this

 

[Jesse2012]

I've never seen the stock gauge all the way up, even when my autometer gauge is reading 15 pounds. The purpose of that gauge isn't to measure pressure, it's just to tell you that its in boost basically

 

[kleenf4i]

I've never seen the stock gauge all the way up, even when my autometer gauge is reading 15 pounds. The purpose of that gauge isn't to measure pressure, it's just to tell you that its in boost basically

Mine hits the top..just saying.

 

[DSMnoobsause]

Mine hits the top..just saying.

Just goes to show how accurate the stock guages are.

 

[kleenf4i]

Yeah About as accurate as Iam hitting the bulls on the dart board after drinking a keg.

 

[smills1840]

Mine definitely, 110% positive that my stock gauge hit the top when I floored it. Like I said, I couldn't care less about the gauge. I can definitely feel something is different.

I checked the wastegate, and it moves freely. I'm not sure about the actuator, should it be able to move freely with the car off? Like I said before, even if it is stuck, it's stuck in the closed position so I should be building too much boost if anything.

I also unhooked the vacuum line to the wastegate, and it still didn't change anything.

 

[kleenf4i]

then there are two things left. boost leak. or your compressor is not spinning in sync with the turbine. The cause of this is a loose nut on the (inlet) turbine side or broken shaft.
yes you should be able to pull the wastegate actuator with a little force with the car off.Also, yes, if you unhooked the vacuum line, it should hit about 20psi at 5k rpm. I was convinced I didnt have a boost leak, but it turned out I did. I was having the same exact issue. you can always bypass the intercooler and you will quickly find out if you have a boost leak. I now have a hard time not spinning the tires in the first 3 gears. That never happened before I found my boost leak.

 

[AngelOfPassion]

I agree. Are you positive there are no boost leaks?

I guess the T25 could be on its way out the door. But in my experience they usually just break. Night and day not a slow death.

It could be timing/fuel related. But you would need a WB or something to log with in order to tell.

 

[Diamond Star Werks]

Bov.

 

[boblong6]

what grade of gas did you use cause if you use like 87 it wont work properly

 

[kleenf4i]

I really hope 87 was not put into the tank!