Boost Drops to 6 psi....No leaks

[bigbro6785]

Well yesterday I fixed the last of my boost leaks, did another test and have none. But I still have the same problem, when I make a run at WOT my boost will go up to 10 psi, but once i get to 4500 rpms it drops to 6 psi. And it doesnt drop slowly, it instantly drops down. Any suggestions on what the problem can be? Thanks

 

[Loewen21]

Sounds like something to do with your actuator, opening too early/too much

 

[bigbro6785]

thats what i was thinking. I was planning on clamping off the supply to the actuator and seeing if that does it (just gotta keep an eye on the boost). Ill let you know how that works out.

 

[oncehuman]

what kind of controller you running? also how many miles do you have? if you have high mileage like me, now this is just a possibility nothing else, your exhasut turbo blades could be wearing out. assuming you still have stock turbo. also have you checked your bov if its seating ok no leaks there?

 

[bigbro6785]

The car has 95k miles on it, but the people i bought the car from said the turbo was re-built at 90k miles (its the stock t-25, stock actuator, no MBC). No leaks in the system at all, just fixed the last of them. Upgraded to a 1g bov.

 

[bigbro6785]

Just a little update. I disconnected my actuator and took the car out for a run. I didnt want to over boost so I feather the gas at WOT, but it held 15 psi to almost redline. So im assuming that the actuator was the cause of my problem. I still dont understand why the boost drops at a certain RPM. Even in 4th or 5th gear, it will hold 10-11 psi until it gets to 4500rpm (which gets there slower in those gears), then it drops instantly. Seems strange to me. What do you guys think?

 

[StR8sPo0Ln]

I would have to say, that i think your waste gate is blowing open. Try adjusting the arm on the actuator. A friend of mine had to do the same, and that fixed his problem.

 

[bigbro6785]

I ordered a MBC so maybe that will help. How would I adjust the arm on the actuator?

 

[romeen]

The WGA arm is not adjustable.

You may have a faulty boost control solenoid. You can try bypassing it by running a vacuum line from the compressor nipple directly to the WGA (don't route it through the BCS). If it does the exact same thing then that may be it. Unless it has something to do with the ECU control of the BCS. Either way, the MBC you ordered should fix the problem.

It's also possible that your WGA is just worn out. I've actually never seen this happen. But it's just a diaphragm under spring tension so I suppose it is possible.

 

[bigbro6785]

Just an update. I installed my MBC and now the boost doesnt drop down like it use to. So im assuming that the BCS was the problem. Now my problem is the car runs at 12 psi in 1st, and 16psi in 2nd+. Haha. A new problem always arises once i fix another. But incase anyone has the same problem I did, try getting a MBC.

 

[kenamond]

Just an update. I installed my MBC and now the boost doesnt drop down like it use to. So im assuming that the BCS was the problem. Now my problem is the car runs at 12 psi in 1st, and 16psi in 2nd+. Haha. A new problem always arises once i fix another. But incase anyone has the same problem I did, try getting a MBC.

I'd highly recommend a logger if you're pushing 16psi on a T25 with stock fuel.

 

[bigbro6785]

Ya that is gonna be my next mod. I dropped the boost down to 13-14 psi (dont remember which one), so I should be fine.