I am a recent owner of an 05 evo 8 on which I have just installed a BR stage 1 kit and 255 fuel pump with the requisite dynoflash. The car also has an MR BOV installed.

My problem is that upon a standard 3rd or 4th gear pull - or any other time when really getting into the accelerator - the boost will quickly ramp up to 18-19 psi then the needle will flutter steadily and quickly (0.5 - 1 sec) down to ~12 psi and hold there. Having reviewed other related threads, I was led to test the WGA by disconnecting it from the MBC and slowly rolling into the boost. I am able to hold consistent boost - with careful throttle modulation - at ~17 psi through all of the rev range that I tested. I did not want to risk trying to hold the boost at any higher level. From a previous thread, I understood this to indicate improper MBC installation. My MBC installation is as follows: BR MBC, stock solenoid still connected (wired) and both outlets capped off, turbo outlet capped off, line from WGA to the side of the MBC, t-line from BOV line into the bottom of the MBC, intake outlet capped off.

I have not yet performed a boost leak test; I do intend to do this soon but I have not yet assembled the necessary parts (having just read about them this afternoon). I am seeking advice after performing the unconnected WGA test. Does my result indicate improper MBC installation? I do believe that my MBC is connected correctly, but please correct me if I am wrong. Would it be of any benefit to attempt to connect the MBC source to the turbo outlet instead? Are there any other tests/solutions I could attempt to further narrow down the problem?

Other possibly pertinent info: idles on startup at ~1500rpm for 1-2 min, warm idle is steady at ~17mm Hg at ~900, tends to hold revs between shifts for ~0.5 sec before dropping anytime over about ~5psi but drops normally otherwise, turning up the MBC just affects the psi at which it will spike but the boost still quickly drops.

I would appreciate any advice, suggestions, etc...

 

If your mbc was hooked up backwards, it wouldn't spike that high. So, I don't think that's your problem. Are you on stock intake? If so, check your snorkle clips.

 

I am not running the stock airbox. I have the BR airfilter from the kit attached to the stock intake pipe/hose.

 

This may help...

https://www.evolutionm.net/forums/sh...d.php?t=209640

Try hooking up the MBC between the WGA and the Turbo outlet pipe and leave the intake/vacuum lines alone.

 

I have been reading that post, great info. I did not think it would make much of a difference but I will give it a try as soon as everything cools down and I can get at the turbo again. I was unclear as to whether the small pull from the MBC to the BOV would result in total BOV opening and boost loss to wastegate level or if it would just bleed off a little until it equalized again.

 

After reading some more posts I checked the vacuum lines running to the egr valve. Both lines from the throttle body are connected along with all other connections. I do not think that the symptoms indicate a faulty egr, but is there any other test to determine whether it needs to be removed and cleaned?

 

I switched the MBC input from the BOV to the turbo outlet and the car exhibited no change. I will try and put together a boost leak tester tomorrow.

 

Is the BOV on backwards?

 

the vacum lines to the egr have nothing to do with your boost,it only will make your car run rich at idle not at wot,and the clips you dont think make much of a difference make all the diffrence in the world many people have had the same problem and this was fix,but your problem sounds a little diffrent maybe you have a boost leak,or something is not hooked up wright....by pass your boost controler with a union and see what boost youy get off of wastegate pressure...and make shure you bov is installed correctly..corect me if im wrong warrtalon?

 

He doesn't have the snorkel problem for sure, because he's using the BR intake.

I have not actually heard of a problem before where boost goes up to a normal max and then flutters down to 12psi. That's very strange.

 

I do not believe that the BOV is on backwards - it seems to exhibit normal behavior - but I am not really familiar with turbo setups. The BOV orientation is as follows: MR BOV, the arrow stamped into the body is pointing toward the connection to the intake tube, the metal hat is oriented towards the radiator/front as opposed to being oriented towards the hood/up, the vacuum tube nipple is consequently pointing towards the hood/up. Is this correct?

 

Yes, that is.

 

If the MBC and the BOV were connected correctly and neither MBC reference input changed the car's exhibited behavior, what did the results of the WGA disconnect test show me? I do not think that I understand what disconnecting the WGA exactly demostrates. Anyone care to enlighten me?

 

Just to make sure... the BOV is positioned like in the following pictures correct?

 

Yes, that is how my BOV is positioned. I was trying to look for some pictures just to be sure. Thanks for clarifying.