Boost Leak Test Results

[EricDET]

I have a redtop with the factory SMIC... I made a boost leak tester today and threw it on to try it out. There doesn't seem to be any external leaking from any pipes but I could hear air rushing out somewhere. It sounds like there is air coming out of the factory BOV back into the intake pipe. At least that's where it sounds to be coming from. Is there any way to tighten the valve or does it usually do this?

PS it leaks 10 PSI down in about 8-10 seconds.

[Z U L8R]

what motor? if it's a stock sr20 or rb20 it's probably not a boost leak, the turbo's on both motors are small and as the rpms climb the boost falls off. if you had a boost leak your car would surge and buck because the air has been measured by the mass air flow sensor and if it escapes before it reaches the throttle body/intake manifold you'd have a shit load of fuel left over (since that was the fuel the ecu delivered to balance the incoming air from the turbo) and it'd studder and jerk and surge. if it boosts normally though without all that craziness then it's just the turbo's too small. as the turbo delivers a charge you can hear the air being moved through the turbo's side of the intercooler piping pretty easily. nothing abnormal there. i'm thinking that's probably the noise you're hearing. you could always unhook the bov's recirculation and then try to boost...if same results there's no leak, it's just the itty bitty t25. gl man
Dave =]

[koukimonster139]

bov shouldnt be opening until your back on vac.


might be leaking all the time tho

[EricDET]

what motor? if it's a stock sr20 or rb20 it's probably not a boost leak, the turbo's on both motors are small and as the rpms climb the boost falls off. if you had a boost leak your car would surge and buck because the air has been measured by the mass air flow sensor and if it escapes before it reaches the throttle body/intake manifold you'd have a shit load of fuel left over (since that was the fuel the ecu delivered to balance the incoming air from the turbo) and it'd studder and jerk and surge. if it boosts normally though without all that craziness then it's just the turbo's too small. as the turbo delivers a charge you can hear the air being moved through the turbo's side of the intercooler piping pretty easily. nothing abnormal there. i'm thinking that's probably the noise you're hearing. you could always unhook the bov's recirculation and then try to boost...if same results there's no leak, it's just the itty bitty t25. gl man
Dave =]
Yes it's a stock Redtop SR20...I actually had the car off and made a rubber endcap with a valvestem and put it on the end of the chargepipe and pressurized it with a compressor to ~10 psi. At that point I can hear a hissing of air escaping that is not really loud but definitely air escaping. But there doesn't seem to be air escaping from any of the charge pipes. I was under the impression that if I pressurized the system it should hold that pressure and not leak off anywhere. It sounds like when I pressurize the pipe that the hiss comes from the BOV recirculation pipe. So the turbo shouldn't theoretically have anything to do with the test. The BOV should be closed when the car is off correct??? The car stutters with the onset of boost while low in the rpm range... If I give it more than 50% throttle it will stutter at about 2500 then it goes away and acts fine. It sounds like when I'm on the throttle that the BOV starts to leak off before I actually let go of the gas... That's why I did the test to begin with.

[cotbu]

yes the stock bypass valve stays open at idle, thats normal for it too allow air to leak during your test. Oh, and that's why every one says to recirc your bov! you could cap off the BOV and its inlet on the intake pipe

[Justin Bernstein]

Are you using a boost controller? If so it may be messing with your stock wastegate which would cause the hessitation that eventually goes away when you get past a certain rpm range. Same thing happened to me. Let me know.

[statik]

what motor? if it's a stock sr20 or rb20 it's probably not a boost leak, the turbo's on both motors are small and as the rpms climb the boost falls off.

Im confused as to why you think the size of the turbo has anything to do with the ability of his intake piping to hold pressure...sounds like the stock recirc is shot, cap it off and try again.

[Z U L8R]

Im confused as to why you think the size of the turbo has anything to do with the ability of his intake piping to hold pressure...sounds like the stock recirc is shot, cap it off and try again.

because the last comment "PS it leaks 10 PSI down in about 8-10 seconds."

in his first post it doesn't say what kind of "boost leak tester" he made, or how he made it, or how it's specifically testing for leaks. nor even the motor he's got. so with not enough information, all i could do was assume the rest of the equation and offer advice in hopes of getting more information. so from the symptom he was describing....when he said it leaks down to 10psi i'm thinking he's boosting his car. i'm assuming he's got an sr20 with a t25 and he's under boost for his 8-10 seconds probably trying to run 14psi on a stock t25 on a stock sr20. which is what i did back in the day and a lot of folks do as well. so then after the couple of seconds his boost falls down to 10psi. WHY? because the stock t25's that come on rb20's or sr20's can't hold 14psi all the way to redline, they drop to 10-11psi by the time you get to 7k. that's how the turbo size matters. tha'ts why i brought it up.

ANYWHO, i agree with Cotbu up there. the stock bov may not hold 10psi without 10psi going to the top of the diaphram to assist it. if there's nothing connected to the top nipple on the bov and you have 10psi in the piping, i would think it should leak a little, that wouldn't be alarming. if you have the same 10psi to the bov that's in the pipe, then no it shouldn't leak. and that's how you'll determine whether you have a boost leak or not. does the car surge or jerk, or shutter as soon as you get 1psi of boost? if it doesn't then you may not have a boost leak. your ignition timing may be off, or you just may be expecting it to be faster than it is. more info plz, thx. good luck with it.
Dave =]

[EricDET]

Are you using a boost controller? If so it may be messing with your stock wastegate which would cause the hessitation that eventually goes away when you get past a certain rpm range. Same thing happened to me. Let me know.

No... No boost controller at all. It's on stock boost right now. I'm thinking it may be timing related now.

And Z U L8R I said I had a redtop in the first post, but I see where you are coming from with your answer.

[statik]

because the last comment "PS it leaks 10 PSI down in about 8-10 seconds."

in his first post it doesn't say what kind of "boost leak tester" he made, or how he made it, or how it's specifically testing for leaks. nor even the motor he's got. so with not enough information, all i could do was assume the rest of the equation and offer advice in hopes of getting more information. so from the symptom he was describing....when he said it leaks down to 10psi i'm thinking he's boosting his car. i'm assuming he's got an sr20 with a t25 and he's under boost for his 8-10 seconds probably trying to run 14psi on a stock t25 on a stock sr20. which is what i did back in the day and a lot of folks do as well. so then after the couple of seconds his boost falls down to 10psi. WHY? because the stock t25's that come on rb20's or sr20's can't hold 14psi all the way to redline, they drop to 10-11psi by the time you get to 7k. that's how the turbo size matters. tha'ts why i brought it up.


oh yeah, i can see how you thought turbo size would matter, im just normal and read "boost leak test" as doing a boost leak test by pressuring the intake tract, and not flooring it in 5th for 10 seconds with someone in the engine bay listening to the recirc leaking while he watches the boost fall. Just two wildly different interpretations is all, one correct, and one horribly wrong :kiss:

[Z U L8R]

blah, i can see where i adlibbed a little too much in his particular scenario and came up with what i came up with. and i see "Redtop" now that i read it again. i leaned into this equation a little off balance i admit =]

important question though. why are you testing for boost leaks? what's the car doing or not doing that you think something's wrong with it?

[EricDET]

correctly quoted below...

[EricDET]

The car stutters with the onset of boost while low in the rpm range... If I give it more than 50% throttle it will stutter at about 2500 then it goes away and acts fine. It sounds like when I'm on the throttle that the BOV starts to leak off before I actually let go of the gas... That's why I did the test to begin with.



important question though. why are you testing for boost leaks? what's the car doing or not doing that you think something's wrong with it?

I explained here why I performed the test...

[Z U L8R]

i never saw that thread though.

so have you replaced your bov then?

[EricDET]

i never saw that thread though.

so have you replaced your bov then?
I quoted that from my 2nd post in this thread.
I actually checked and adjusted the timing and it seemed to clear the problem up quite a bit. (Thanks for the suggestion ZUL8R) It holds boost dead on at 7~8 psi when I'm full throttle so I don't think it's leaking very bad if at all. Thanks for the help guys. :rawk: