Boost Leak/pressure Tester

[Shoujiki]

Hey guys,

So i made up a boost leak tester as per another thread I came across. Pod filter adapter, pvc end cap and air compressor tyre valve.

Worked great! I had 5 leaks I identified. At the beginning it wouldn't hold pressure for more than 1 second. Now raising it to 5 psi, it will hold for at least 15-20 seconds, slowly dropping off.

I can still hear 1 air leak. It's coming from down near the exhaust/back of the engine. I've checked all the hoses at the top and they seem to be ok, soapy water shows no bubbles.

My question is, is it normal for it to taper off boost within that time? Could the noise i'm hearing be the air coming from engine out into the dump pipe? Doesn't sound muffled, but it's the only thing I can think of.

Cheers

[Hanaldo]

Try putting the car in gear and rocking it forward and back to turn the engine slightly. You may have a couple of valves in overlap which is bleeding air off.

[SargeRX8]

I noticed I have air seeping up through the oil filler cap. I can hear the air hissing out from there. Its a nismo cap. Anyone know where I can buy the stock one? Also is that normal?

How do you get all th valves to be shut? Whats the most pressure you test with? Some people online say no more than 8psi but thats retarded since my turbo applies up to 20psi to the walls.

[Shoujiki]

Ok i'll try that, i figured it might have been something like that.

I'm testing with 5-6psi, really no need to go anymore as you'll hear air hissing at that pressure. 5 psi is a lot of pressure.

My thinking was also, using this type of testing, your applying positive pressure to the "intake" side of the turbo, which normally is sucking. So that means the MAF and all that is seeing positive pressure. Which isn't a normal thing for it. I'd be weary about applying 20psi to it.

Edited September 9, 2013 by Shoujiki

[SargeRX8]

People run these mafs after the turbo in big boost setups. She'll be fine but as you said it generally isnt necessary. The only vacuum point is the intake pipe to afm to air filter. The rest of the intake goes under pressure.

[Shoujiki]

Yeah that is true. When i'm pumping it up with 5psi, the intake hose is expanding! Quite funny to watch. Interestingly i had to reseal the MAF top with silicon as it was leaking too!

So i tried the gear/push thing, doesn't seem to change it. Same exact hiss, same area. How fast should the pressure drop off once it's at 5-6 psi?

[Dave.TAS]

A good setup with no leaks should hold 20psi no problem, with no hiss noises. In the exhaust area, if you have a boost tee, they will make a hissing noise. It's there job to bleed off boost pressure

[Shoujiki]

Well this wont hold anything for more than say, 20-30 seconds now. It's a lot better now that i've gone through and found the other leaks. But this one is certainly letting air out.

The engine has a Greddy Profec 2 Spec B controller, i checked the solenoid connections and all seems good in that area. This hiss is coming from near the back of the motor, sort of where the boost pressure sensor is, but it doesn't seem to be that.

[SkudR33]

try getting it smoke tested - only costs around $70 i think... good thing about it is smoke comes out of any leaks so they're easy to spot!

[scotty nm35]

Bong testing costs coin, why would he need it now all the leaks are taken care of?

The small leak you have is no issue, if it is holding 5 psi for 20-30 seconds it is fine. Don't be scared to pump a little more in, I run 40psi in mine when testing, but I don't have the dodgy stock intake pipe like yours does Shoujiki.

[Hanaldo]

I agree with Scott, I'd say it's probably not an issue. What you could try though, is pumping some more pressure in there. I found that at 5psi things were generally ok, but at about 12-13psi I found a couple of vacuum hoses that were leaking from t-pieces etc. Now I generally try to get my system to its target boost pressure, which is 20psi. Just watch your pvc end cap doesn't come shooting out and crack you in the hand, mine often does

[Shoujiki]

Thanks guys for your help. Yeah smoke test seems a bit much at this stage, i don't really want to spend as such (hence me making up this great idea, thanks Hanaldo for your thread btw!).

I'll try a bit more pressure and go from there. If i really can' find it today then i'll just leave it and see how it goes. I'm curious to see how it will drive now with all these little leaks fixed. My target boost pressure is 11psi so i may try to get to that.

Yeah Scotty i think that dodgy stock pipe would explode at that pressure! It will be great to get that changed out to an alloy one. And yes i'll watch the end cap, it was that hard to get in there in the first place, and i used a hose clamp too, so hopefully it's nice and tight!

Again, thanks guys.

[scotty nm35]

I spun up a proper alloy plug with a step so the hose clamp doesn't pop off, the hose runs to a gauge and trigger setup. I can tell you, at 40psi there is not much chance of sealing all the leaks, unless you glued them perhaps. Most would say it's overkill to pump that much in, but I run nearly 3 bar at gearchange.

If you are worried about the AFM, take it out of the equation, why would you run it in the system anyway? Just remove the afm/airbox, stick the bung in, and pressurize.

[scotty nm35]

Yeah Scotty i think that dodgy stock pipe would explode at that pressure!

You would be surprised, I have shoved over 20psi into one without issue. They expand quite a bit. If it fails just hit me up for an 80mm alloy intake.

[Shoujiki]

Ok so i found the "air leak". It seems to be coming from the valve cover? I have an oil weep back there somewhere, so perhaps it's coming out of that area? If I take the oil cap off, all the pressure releases straight away. Would having a weep like that really affect the car? I guess the pressure has to go somewhere.

Took it for a quick drive and boy what a difference. It actually boosts to 0.92bar now, never done that before. And the boost ramp is so strong, really kicks you back. Also no misfire at idle with an open filter like I had before.

[Shoujiki]

Faulty PCV perhaps?

[GTSBoy]

Next idea will be to do a leakdown test on the engine itself and make sure it's not just air flying past the rings.

[Shoujiki]

Now that I think of it, because i'm pressuring part of the intake that never sees boost (ie pre turbo inlet side), i wonder if theres a hose/line connection somewhere there that's going off to the intake/valve cover area, like crankcase breather. So in normal boosting/driving conditions, there would be no boost in the valve cover area.

Edit:

Just had a look. That is indeed what the noise is. On the stock intake rubber pipe, there's 2 ports coming off it. One goes to the crankcase breather on the valve cover. The other goes to the turbo recirculation valve. So normally that pipe would never see boost pressure like that, as both ports are pre turbo, just after the MAF. I bet if i took off the hose on the breather and blocked it off, it would hold pressure.

Edited September 10, 2013 by Shoujiki

[scotty nm35]

They should still hold air pressure.

[GTSBoy]

In fact, pushing air in through the BOV connection (one of the ports) should do nothing and pushing it in through the cam breathers should overcome leakage past the rings - now that I think about it.

You could try taking the turbo inlet off completely and use a dedicated bit of 3" (or whatever size to suit your turbo) hose to connect up with. That will cut those two connections out of the loop, but will cause you other hassles (disassembly being a big one, and possibly having to block off the BOV being another).