I recently installed a TurboXS single solenoid MBC in my 04, I am able to adjust the boost pretty easilyto about 20.5 psi w/o any extreme spiking but it still tapers almost 3 psi by redline, I double and triple checked all my vacuum lines and IC piping so I'm pretty sure that those are not the problem. The MBC is used and I have heard that they are crappy. I already ordered my Hallman Pro and Walbro fuel pump for peace of mind, but I would like to know if I could or should check anything else for the meantime. If it helps I am teeing off the BOV line for one line and the other is from the wastegate, capped the turbo nipple and stock wastegate actuator ( I think thats what its called ) "the sensor by the air filter". Anyway I capped both of those and left the electrical plug connected. Oh yeah my mods are an Injen intake w/ upper IC piping and 3" UR TBE w/ cat delete and obviously the MBC now. Thanx in advance

 

If you have the stock plastic BOV, you should replace it imemdiately, I bet that it is leaking.
I replaced it with a JDM MR one and just recently switched back (I sold the MR one) and the plastic one SUCKs!!
I can't wait for tomorrow when I install my Greddy!

Also, I had a TurboXS and with the JDM BOV, I had no problems with it. I currently used an HKS EVC EZ. Yeah, it's worth the money.

 

Might be the MBC, check again once you install the Hallman. If it still tapers, check the BOV.

 

TXS MBC's suck total ***. Mark basically refused to tune my car with mine, threw in a halman and it holds boost like a champ.

 

I got MBC goes to 22psi then tapers to 20psi ..No Problems.....

 

You never mentioned if you had a dyno flash of some sort! If you dont have a boost flash then thats for sure your issue. I had the same problem before geting custom flashed. Now i lose 1 psi from 22 down to 21 with a halman. Used to spike 19 and drop to 16 after hitting @7k rpm.

 

OK sorry I added my mods to the original post.

 

So you need a flash!! that will fix your issue. its not gonna make any difference really which MBC you have if your not flashed.

 

I guarantee you will be happier when you replace that stock POS bov.

 

Im using the stock BOV and dont have one issue FYI! That bov should handle 25 psi strong if you want it too. Im telling you with a flash is gonna be the difference maker.. do you have a flash RedUSEVO?

 

Getting an aftermarket or different BOV isnt necessary at all until your running different turbo and so forth. It looks better yes i agree, but its not NEEDED to improve any control of exhaust release.

 

This is the number one reason why aftermarket BOV's make so much off of their products.

IMHO, I have the stock BOV and I have a boost spike of around 21.5 psi initially for about a second and settles down to a rock steady 20psi. AND, it spikes different in each gear. Gear 3 and 4 spikes maximum 1.5 psi. Gear 1 and 2 about 1psi and and Gear 5 almost no spike. It is NOT due to the stock BOV. True, some stock BOV's are defective just like any OEM part, but, in general, it holds boost pretty well. There are other better mods to do then spend over $200 bucks on a shiny new BOV just on the premise that the stock BOV sucks and cannot hold boost. Plus, these numbers are from a mechanical boost guage which also has some error factors built-in.

PS I have an ECU flash as well.

Brent

 

Yep nice to see another person backing my thoughts.. although its kinda proof instead of my thoughts.. Like i said before..aftermarket bovs look cool.. thats bout it until you doing major mods past your avg bolt on. You run 25+ psi.. then sure.. go get one.. but dont waste your money on one cause its not gonna fix your issue.. the dyno flash.. even mail in flash makes huge dividends.. You'll gain 20whp regardless of you mods.. helps lean ya out and so forth. Look into DYNOFLASH @ www.dynoflash.com to see for yourself. Works awesome

 

One more thing to add...You have basically introduced more air flow from the intake and from the exhaust. Your ECU will learn to a certain extent how to deal with this MAJOR change. However, an ECU flash will definitely give you BETTER performance. The car will feel like a totally different beast with the reflash.

Also, just by the fact that you completely loosened up your exhaust (3" is VERY loose ), will cause the boost to spike a LOT more than compared to a stock exhaust setup.

Bottom Line: Spend $400 on a custom tune reflashed ECU or even LESS on mail-in flash than spend $200+ on a shiny aftermarket BOV. Believe me, this is not something magical, many, many, Evo owners have gone this path. We are just trying to help you get there faster and with less money wasted.

Brent

 

also........... LOL...... with your intake with no Reflash.. your actually losing HP not gaining.. it sounds awesome I agree first hand, but its doing you no good with just strapin it up and hoping for higher numbers!

its just an add on to previous post