Car:
- EVO IX

Problem:
- Noticed less power.
- Boost gauge shows slightly reduced peak boost and it instantly (within 50rpm of boost peak) drops to 15spi as opposed to tapering off while making my way towards reline.

Diagnosis:
- Suspected boost leak.
- Pressurized system between turbo and intake manifold: unable to pressurize.
- removed diverter valve and plugged opening: system pressured to 25 psi & held
- re-attached diverter valve, held hand under opening that goes to turbo (return). Tried to re-pressurize system: unable to, all boost leaking out of diverter valve.

Assumption:
- improper testing of diverter valve (I did nothing with the vacuum hose nipple - it was at atmospheric pressure)
- defective diverter valve

Question:
- Do I need to do anything with the vacuum input to the diverter valve to test it ar can it be left at atmospheric pressure?
- at what psi should the diverter valve stop holding boost and start to open/leak with and without input to vacuum nipple.
- Anything else I should check/test regarding my boost problem?

Thanks.

 

This might actually be my issue, im wondering the same.

 

I just tried running some pressure into the vacuum nipple and it seemed to hold some of the pressure in the piping. Problem is that i don't know how much psi I was putting into the nipple and was able to get the system up to only ~10 psi before my hack setup started to leak or pop the valve completely open. I have to figure out how to properly test the diverter valve out of the car.... anyone know?

 

The bov needs the same psi going to the nipple and the IC pipe side to work right .

With no psi on the nipple side it will leak .

How is your tester set up ?

Is the TB hose still on the TB or is the TB hose pluged ?

 

Thanks.... My setup was not 100%. I need to redo it. But I thought the valve should be able to hold at least 6-14 psi without any input to the vacuum nipple. This is based on results of testing various valves here: http://dv.mistertam.com/

I'll try to do a rig that inputs the same psi into the valve and into the vacuum nipple....

 

The reason i was asking about the TB hose is b/c if you keep the TB hose on it pressurizes the Intake Mani , psi gauge in the car and the nippel side of the bov .
So that way the bov stay closed and you can read psi from the gauge in the car ......But I found it works best when the motor is warmed up with #1@TDC.

 

I always just leave the nipple on the BOV connected to the signal line coming from the intake Mani. I put my tester on the turbo inlet and leave everything else connected. I can watch my boost gauge in the car to see what pressure I am at. This way the BOV operates as it would when normally installed. I don’t know why you are trying to give a different PSI to the signal line on the BOV.

 

What are you using to pressurize the system? If you have a leak like you describe then any hand/foot operated pump won't do the job. I hope you have an air compressor with around 5 gal.

 

I had the valve out of the car and trying to use 2 different hand pumps to pressurize it one of which had no gauge.

 

Ok, I build a little test rig, same PSI input to vacuum nipple now as the valve. See pic.

It does not hold pressure too well. If I pump up to ~25-20 psi, air leaks out almost as fast as I put it in. I assume that it should be able to hold 20 psi without issues for at least a few secs. At ~15-10 psi, the leaking is slower, but it eventually all leaks out within ~10 secs.

Can anyone repeat this test with a good valve and post your results?

This seems to be consistent with my car's behavior. I guess I'll have to buy a new valve... can't be bothered with dealing with warranty, too much aggravation from past experiences...

 

I have a valve like your and a plastic one, I will test them this weekend and tell you what I find. What parts did you use to build your tester?

 

1" ID hose
clamps
1" diameter PVC pipe end cap
valve stem
brass vacuum nipple
vacuum line
silicone gasket maker
zip tie

Total cost was under $10.

 

I stoped at Home depot and picked up the parts, tomorrow I will get the vaccum line, I will test this weekend