Car won't boost over 11-12 psi

[wvturbo2]

I turned the boost controller way up and it still won't let the car boost over 11-12 psi. What could the problem be ?

 

[oldman]

With all my idle problems I never thought of this. My vacuum reading is at 10hg when it should be at 20. I am running on one line and not using the J Pipe. Also I have idle probles. Could this be the problem?

Tapping the BOV line with a ball and spring MBC will not effect your vacuum reading, however it will still have negative effects. Here is what I posted on another thread on why tapping the BOV line is a no no.

1. BOV line was previously thought to be better and more accurate because it's the pressure the engine sees when in reality it doesn't matter because boost gauge is already measuring manifold pressure regardless where you reference your MBC.

2. Long route vs short route, increased chance of boost spike.

3. Turbo protection. In a case of developed boost leaks in your intake tract, tapping BOV line will result in turbo spinning out of control while boost gauge till maintains full boost. Where as a compressor source will open wategate sooner while registering pressure drop on your boost gauge.

4. This is the most important one. Tapping your BOV line will result in a slightly opened BOV under WOT because of pressure bleed through the MBC's wastegate pressure relief hole. The situation gets worse when using a bleeder type like the TurboXS units because it's also a vacuum leak which can lead to idle surge as well as compressor surge.

As for your vacuum problem, perform a boost leak test, check your timing marks and compression.

 

[evogst97]

Tapping the BOV line with a ball and spring MBC will not effect your vacuum reading, however it will still have negative effects. Here is what I posted on another thread on why tapping the BOV line is a no no.



As for your vacuum problem, perform a boost leak test, check your timing marks and compression.

I did a boost leak test and had no leaks. I still need to do one from the throttle body at least thats what I've been told. Do I do the test from the elbow or have to take the throttle body off? I checked the timing and its right on. Compression is 175 on all four.

As for the bov line I will do the J-pipe drill tap thing. I've been sick this whole week which has made it harder to work on the car.

 

[romeen]

That is correct for ball and spring type MBCs, the more you turn it in, the higher the pressure of the spring, the higher the boost level. A bleeder type like the TurboXS Standard on the other hand is opposite, the more you turn it in, the smaller the bleeder hole, the lower the boost. The more you turn it out, the larger the bleeder hole, the more boost.

That makes sense. Thanks.

 

[StR8sPo0Ln]

Should i run a new line for the bov line, since it was t fitted to use the mbc. Or can i just go out and buy a female to female adapter and reuse the line that is there already.

 

[romeen]

I did a boost leak test and had no leaks. I still need to do one from the throttle body at least thats what I've been told. Do I do the test from the elbow or have to take the throttle body off? I checked the timing and its right on. Compression is 175 on all four.

As for the bov line I will do the J-pipe drill tap thing. I've been sick this whole week which has made it harder to work on the car.

You don't need to remove your TB, that would be more work than necessary for a boost leak test. Leave your TB elbow attached so you can have something to couple your boost leak tester to. Personally I just do my boost leak tests from the turbo compressor inlet although there is some debate to the wisdom of this since some air may get past the seals when the motor is not running. You really only need to start from the TB and work your way back if you suspect a possible intake obstruction, although it may help isolate a leak that you just can't seem to find. Did you use soapy water during your last test?

 

[evogst97]

You don't need to remove your TB, that would be more work than necessary for a boost leak test. Leave your TB elbow attached so you can have something to couple your boost leak tester to. Personally I just do my boost leak tests from the turbo compressor inlet although there is some debate to the wisdom of this since some air may get past the seals when the motor is not running. You really only need to start from the TB and work your way back if you suspect a possible intake obstruction, although it may help isolate a leak that you just can't seem to find. Did you use soapy water during your last test?

I used soapy water but didnt get any leaks when I do the BLT from the turbo but havent tried from the TB. Is it possible for my vacuum to be at 10-15HG without any leaks?

 

[Talesin]

Did you open the throttle while testing, with the engine warm, and move the crank so no valves are overlapping (ie: air pressure goes out through the cylinder, and out the exhaust)? Don't know if there's still a path from the turbo inlet to the cylinders with the car (and ISC) shut off, and the TB plate closed. A vacuum leak will happen after the throttle body... either on the manifold-side TB gasket, manifold->head gasket, somewhere in the manifold itself (in the event of a crack, unlikely as it might be), or the valves.
Personally, I'm riding around with 15in/Hg in the morning because I have a funky valve/lifter combo that apparently refuses to seal while it's on the car, but closes just fine when the head is off on a workbench. After the first time I boost, something seats and I get a full ~20in/Hg for the rest of the day.

Altitude can also play a part.. I'm normally at sea level, but when I pop up to about 6,000ft I only ever see about 14in/Hg at best, and around 9 if I let the car sit too long.

 

[evogst97]

Did you open the throttle while testing, with the engine warm, and move the crank so no valves are overlapping (ie: air pressure goes out through the cylinder, and out the exhaust)? Don't know if there's still a path from the turbo inlet to the cylinders with the car (and ISC) shut off, and the TB plate closed. A vacuum leak will happen after the throttle body... either on the manifold-side TB gasket, manifold->head gasket, somewhere in the manifold itself (in the event of a crack, unlikely as it might be), or the valves.
Personally, I'm riding around with 15in/Hg in the morning because I have a funky valve/lifter combo that apparently refuses to seal while it's on the car, but closes just fine when the head is off on a workbench. After the first time I boost, something seats and I get a full ~20in/Hg for the rest of the day.

Altitude can also play a part.. I'm normally at sea level, but when I pop up to about 6,000ft I only ever see about 14in/Hg at best, and around 9 if I let the car sit too long.

You mean push down on the gas pedal? I didnt do that. Ill try it. I'm gonna go through the idle surge checklist on http://www.dsm.org/how-tos/tttt/tttt3.html. I just thought it was convenient it happened right after a cylinder head job.