so i helped a friend install his go fast bits boost contoller on his car today his other mods are a 3" catless turboback and thats it. i installed it correctly running one line to the wastegate actuator and one to the turbo nipple. it is definatly not installed backwards because there is an arrow pointed in one direction in where the directions say that this arrow points for the line to the wastegate actuator. but anyways at exactly 5500 rpm the boost drops from 20psi wich is held strong all the way to 5500 all the way to exactly 10psi and holds strong 10psi to redline. there is also a noise almost like a boost leak but i have checked all piping every hose and it isnt a boost leak. the wierd thing is that its the exact same rpm no matter what gear or how hard you are on the throttle. im assuming it has to do with the ecu or something because it is exactly the same every time in every gear and drops instantly to 10psi even though it holds 20 fine up to 5500. i know its not the boost controller or bov because i swapped the boost controller to my car and it held 21psi all the way to redline with a slight taper wich is normal. please help me out with this it is something i have never seen before or even heard of. by the way the car is an 05 if that makes any difference and we unplugged the ecu for about 20 minutes plugged it back in and it did the same thing. thanks for any help

 

did you replace all the vaccum lines when you put on the MBC? Cause if you didnt I'm almost certain there is a boost pill insert in the line to prevent any accidentals. Also Im guessing that you plugged all the lines from the boost celleniod and intake right? just a few things to make ya think about if you had'nt already

 

im guessing the boost pill in the vaccum line..

 

He should definitely not have the pill in there if he tapped into the turbo nipple. The factory line that goes to that nipple is very short and can't be reused unless the MBC is being kept inches from the turbo. But hey, you never know...are you using the stock line with the boost pill by chance?

I think this is another case of the ATTACK OF THE SNORKEL FASTENER! forum04pl, is the stock intake snorkel fastened down, or did you break the fasteners when removing it and/or decide not to fasten it back down? If the snorkel is still in place, but is not fastened down, then it is sucking up against the hood at high rpm and choking off the air intake.

If the snorkel and pill aren't the issue, then let us know how you KNOW there isn't a boost leak in the IC piping or vaccuum lines? Did you do a pressure test? That's the only way to know for sure. When I had the snorkel attack, I heard what I thought was a boost leak (loud whistle) and had a huge dropoff of boost at ~6k rpm in every gear. Since I thought it was a boost leak, I built a pressure testing device, and put my vacuum system through the ringer. I had small leaks at 3 different vaccuum connections from 16-18psi, but I had no IC leaks luckily. This wasn't really a surprise, since I had re-installed my entire IC system 5 times while trying to fix the leak, when the whole time it was just the damn snorkel.

Hopefully, the snorkel is your problem, because it's a 2-second fix and means nothing is wrong with the car...

 

the stock lines were replaced with two completely new lines and the airbox is fastened down, it hasnt been pressure tested but everything has been checked over and tightened. however im am 99% sure that it isnt a boost leak because of how exact everything is and how well it holds boost until exactly 5500rpm then drops almost intstantly to 10psi

 

I didn't say the airbox, I said the SNORKEL. Please make sure it's fastened down to the front of the engine bay with the 2 factory fasteners. You are describing the exact symptoms I had, if in fact you are hearing a "noise almost like a boost leak." I, too, was pretty certain that I had everything in the IC system buttoned down tightly, and I was right! I just didn't know about the snorkel thing...

If your snorkel is DEFINITELY fastened down, then you are somehow experiencing the exact same symptoms as I did, but it's being caused by something else. How are you sure it's not the BOV? You said you're sure because the MBC worked on your car, but that doesn't rule out HIS bov. If you're at your wit's end, try switching BOVs just to be certain. My stock BOV opened at 13psi when I did my pressure test, but it didn't caused the big 10psi boost drop at 6k rpm.

Your stock BCS is still connected and in place with the nipples capped, right?

 

what snorkle are you speakin of.. i cant think of what your reffering to

 

i have had a similar problem with my evo but i dont have the snorkel on it so i figured it was the bov leaking but i replaced that and it is still leaking.....any help would be much appreciated

 

The stock instake snorkel that feeds air from between the hood/bumper into the stock airbox. It attaches to the bumper right where the hood closes.

 

I'd need to know the exact details to help troubleshoot. Without knowing anything else, I'd say to do a pressure test of the system. That will identify any big leaks in the IC system.

 

Oh maybe thats why i dont know the snorkle thingy.. since i took my stock box off like a week after i bought my evo..

 

Ah, too bad. It works very well and doesn't cost an additional several hundred dollars...

 

i dont know if his snorkel was connected or not but i know its not the bov because we did switch with an aftermarket valve and it did the same thing, and yes the stock boost solenoid is still connected with both ends capped, i just called him to see about the snorkel so hopefully he will get back to me soon

 

bump... need some help on this because we were planning on heading to the track tomorrow

 

Can't help until you tell me about the snorkel...it's the easiest thing in the world to fix, so don't waste another breath until you make sure!