EVO8LTW

iTrader: (41)

Since installing new I/C piping I've had a little bit of a boost issue. Well, it was a little issue at 18 psi. Today with the nice weather I tried upping the boost to 19-20 psi for the first time and there is obviously a boost leak or BOV problem. You know that short PSHHH sound that you get through the cone filter when the BOV releases? I get that sound on a pulsing basis at a rate of a little less than once a second when boost is over 18 psi. If you push it to 20 psi, it gets very pronounced and the boost oscillates between 18 and 20 psi and it builds and releases, builds and releases...

I'm going to build a Home Depot pressure tester and look for leaks, but does this sound like a typical boost leak or a BOV problem? I have the Buschur upper piping, so a 1G BOV.

Thanks for any guesses that might save me some diagnostic time.

Curt@MrLed

iTrader: (107)

what bov do you have..the spring could be weak,a leak or a plug in the vacuum line to the bov

EVO8LTW

iTrader: (41)

It's a 1G BOV.

Curt@MrLed

iTrader: (107)

did you try your factory one

EVO8LTW

iTrader: (41)

I can't. The 1G is flanged to the Buschur upper pipe.

evodrifter

when it hits boost (18-19-20 ish psi), does it only make the sound when the BOV vets, when it hits boost, cause it sounds like the springs weak...i have a forge VTA and it used to surge like crazy, but i put in a stiffer sping and its good....but i dont know the 1g valves...

trinydex

iTrader: (12)

hmmm doesn't buschur sell the 1g valve crushed? if he doesn't then that's what you need to do... or it could be the spring that is in yours. because i know of someone personally that is running 27 psi regularly with a crushed 1g. it sounds to be definitely your bov.

jonduke

iTrader: (2)

i dont think he crushes them ,my friend got one and we just crushed it in a vice,works great

EVO8LTW

iTrader: (41)

Why would you crush the BOV? What does that mean?

I was doing some testing tonight of this problem. It seems that the faster that it comes on boost the worse the problem. If I floor it from 2000 rpm in 3rd gear and then it gradually comes up on boost then it won't do it, or it will be very slight. But if I downshift so that I'm at 3000 rpm with no load and then floor it, the boost comes up very fast and once the boost peaks there is a huge oscillation in the boost level (like bouncing between 18 and 20 psi). If I lower the gain on the boost controller, then boost comes on slower and it isn't as bad, but then the car is slow.

The one place where I'm a little worried that I may have a leak is at the coupling between the inlet of my Buschur LIC piping and the stock FMIC. Those pieces didn't line up very well, so the coupling is a little strained. Could a boost leak there cause this sort of a on-off boost behavior?

Thanks.

EVO8LTW

iTrader: (41)

Since I'm still having issues, I want to test my car for boost leaks. I found out from a search how to build a tester. I have a few questions about how to do the test though:

(1) Can you just pressurize the system from the MAF pipe without capping off anything else?

(2) Is it better to cap off the upper I/C pipe where it enters the throttle body. That seems to be 2-1/2". I'm not sure what I can cap it with. Home Depot PVC parts jump from 2.0 inches to 3.0 inches.

(3) In order to test the BOV, do you need to separately pump pressure into the line that usually goes to the intake manifold?

(4) Does the throttle blade stay closed for the test?

(5) How important is it for the engine to be at TDC? I see mixed answers on this one.

Thanks!

MYEVO8U

iTrader: (3)

you should check out vfaq.com and dsm.org. I know the vfaq.com has an intake pressure test, but both sites have great information mainly for DSM's but stuff like this test will work for the EVO.

2MANYCARS

iTrader: (2)

Sounds like a leaking valve to me, change the spring to a stiffer one and you are all set.

timzcat

iTrader: (10)

Does anyone read first?
It's most likely not the BOV. The 1G is a good valve and it does not need to be crushed at your boost levels.

First you should make sure the flange on the upper I/C is flat and sealing well to the BOV. Sometimes the welding of that piece onto the pipe tweaks the flange a little. Second, it is probably a clamp that is not tight enough or that lower connection you already are not sure of. All that is happening is leak that requires say 18 psi to show up. Which means the leak is pressure related and most likely something not fully seated or tight.

IEXCELR8

iTrader: (6)

Boost controller going bad? Just a thought,check all claps/hoses as stated. Hope you fix the issue.

2MANYCARS

iTrader: (2)

Well, if you said the 2 pipes there didn't line up perfectly, then that's most likely your problem. These are the areas I would look into when boost is not holding:

1. Boost leak
2. BOV
3. Wastegate spring
4. MBC

Hope this helps.