Slow building boost

[andrewjscott]

I know somewhere on this fourm theres got to be an answer, but searching turned up 500 results, most of which had nothing to do with problem diagnosis. I just finished a rebuild and everything went really well, except now I can barly build boost. I get maybe 3-4 psi and it takes forever to get there. Any ideas where to start looking?

 

[oldman]

1. Exhaust leaks before o2 housing.

2. Actuator arm disconnected or flapper not fully closed.

3. Boost leaks.

4. Defective turbo.

 

[andrewjscott]

no exhaust leak before o2 housing.

Actuator arm is defiantly connected, but how to I check that it is closed?
No major leaks, I haven't done a leakdown test, but i would think I could hear a leak that big, and it sounds like its running smooth

turbo was fine when I took it off....don't think it could have become defective while sittin on the shelf.

So I'm thinking its the actuator arm.....Do I just pull the arm off and let it fall shut, and if the arm is holding the flapper open, how do I adjust it?

 

[ddavisaf]

You'll take the o2 housing off so that you can see the flapper. You'll be able to tell if it's fully closed when you look at it.
Check for shaft play on the turbo. Side to side and up and down.

 

[andrewjscott]

the actuator arm is definatly holding the flapper open, about 1/2 way.....how do i make it so that it will close?

 

[oldman]

the actuator arm is definatly holding the flapper open, about 1/2 way.....how do i make it so that it will close?

If you're saying with arm re-attached the flapper is open half way, then you need a new actuator assuming you still have the T25.

 

[ddavisaf]

When you take the arm off the flapper, is it able to shut completely?

 

[andrewjscott]

its a 91 w/ a 14B. Will i still need a new wastegate? When I take the arm off the flapper will shut completely. It was fine before the rebuild, what could have happened?

 

[ddavisaf]

Yeah, you will have to replace the wastegate. The spring went out is all. It happens. Keep in mind that the newest 14b is still 10 years old (stock). They just get old.

 

[andrewjscott]

well damnit...oh well, guess it's off to the junkies. For the time being, should I just run with the arm disconnected?

 

[ddavisaf]

well damnit...oh well, guess it's off to the junkies. For the time being, should I just run with the arm disconnected?

I wouldn't really recommend it. Your boost will hit 20+ before you know it and that could cause alot of damage to your engine. I would keep it connected and run the 3-4 lbs of boost for now until you get the new wastegate.

 

[oldman]

I wouldn't really recommend it. Your boost will hit 20+ before you know it and that could cause alot of damage to your engine. I would keep it connected and run the 3-4 lbs of boost for now until you get the new wastegate.

No, leaving the arm off will result in little or no boost, not out of control boost. If the flapper is open half way with the arm attached, there is probably no difference between arm being on or off.

 

[andrewjscott]

Yeah, you will have to replace the wastegate. The spring went out is all. It happens. Keep in mind that the newest 14b is still 10 years old (stock). They just get old.

I went out and pulled on the arm....its tough but i can pull it out a bit, it looks like the arm is just a little too long. Can I just cut and reweld the arm first....see if that'll work?

 

[laserspeeddemon]

Don't do that. And don't get a used one.

The reason the arm is stuck open is because the its old and rusted. So what use is it to go out and get one from a junkyard, that will be just as old and rusted out.

 

[andrewjscott]

but its not old and rusted....at least it doesn't look like it. It actually looks very clean for being 14 years old. When I pull it out, its nice and stiff. All i did to the turbo was unbolt it, it sat in a shop for a little while, and then bolt it back on. I don't know how something went from working great to old and rusty in a month of non-use.

 

[ddavisaf]

No, leaving the arm off will result in little or no boost, not out of control boost. If the flapper is open half way with the arm attached, there is probably no difference between arm being on or off.

I guess the 20+ boost pegs are for when the wastegate actuator freezes the flapper on the o2 housing then?

 

[oldman]

I guess the 20+ boost pegs are for when the wastegate actuator freezes the flapper on the o2 housing then?

You will get all out boost if you leave the acuator nipple open but the arm attached, no pressure signals are being sent to the actuator.

Can I just cut and reweld the arm first....see if that'll work?

That will work if it's done right but at the same time it will create new problems like boost creep because the arm is no longer long enough to open the flapper sufficiently.

 

[ddavisaf]

You will get all out boost if you leave the acuator nipple open but the arm attached, no pressure signals are being sent to the actuator.

That's what I was thinking of! Thank ya.

 

[andrewjscott]

That will work if it's done right but at the same time it will create new problems like boost creep because the arm is no longer long enough to open the flapper sufficiently.

Well, I'll fiddle with it tomarrow. If i can't get it to work, i'll try rewelding it..worth a shot, especially if I have to get a new one...I'll just monitor my boost.

 

[oldman]

Well, I'll fiddle with it tomarrow. If i can't get it to work, i'll try rewelding it..worth a shot, especially if I have to get a new one...I'll just monitor my boost.

Instead of cut and weld, try shimming the actuator mounting points on the compressor housing with multiple washers but this will only work if the gap isn't too large. Good luck.

 

[andrewjscott]

I shimmed it and it works fine...I have a feeling the mounting bracket got a little bent along the way. Thanks, oldman.

 

[oldman]

You're welcome.

 

[tselling]

I am having the same problem with my car, which is a 90 gst, so i am going to try and follow what u do. Have you had time to fix your probelm? I know the spring is gone on mine too. The question that i want to ask everyone, and to save money for the both of us, can the spring be replaced for a small fee or do you have to buy a whole new wastegate or stock exhaust manifold with one in it?

P.S I am a newbie to the whole dsm world but learning a lot from this site. I plan on rebuilding the one that i have back to factory specs so i will be learning a lot from it and will have a lot of questions and answers.

 

[andrewjscott]

well, my spring seemed to be in good shape, so I dunno if my experience will help. I shimmed the backet and it worked, i got boost just fine, but it was creeping pretty bad. turns out the wastegate wasn't opening enough. The whole bracket seems a little cockeyed, so I have to tinker a little more with it.

 

[oldman]

well, my spring seemed to be in good shape, so I dunno if my experience will help. I shimmed the backet and it worked, i got boost just fine, but it was creeping pretty bad. turns out the wastegate wasn't opening enough. The whole bracket seems a little cockeyed, so I have to tinker a little more with it.

I told you boost creep might come into play. The best way to deal with this is to find a used 14b/16g actuator, I found one for $10 and it worked fine.