I'm having an issue with something in my car that's causing my boost under wot to fluctuate. I am tuned. Basically when I go wot it will peak at about 20 psi then drop 2-3psi then build again then drop. It's gone as far as a 5psi drop before and I feel like I'm building boost all over again. It's very annoying and you can actually feel and hear it in the car. Video attached shows it a bit. It's been worse but you get the idea.

http://youtu.be/ut2HXdEVfYw

 

Video doesn't work on iPhone but I'd say either u got a boost leak, or ur vac tank is going bad and opening ur Bpv solinoid. Do u hear it blow off when boost drops?

 

If it blows off I can't quite hear it. I definitely hear the change in pitch of the turbo.

 

U got a stock intake?

 

K&n typhoon intake. Custom hard charge piping. Tuned. Gms1 sensors. That's all I can think of at the moment

 

Well from the experience I had, I'd boost up to 15psi then boost would drop to 10 and build back up to 15 and so on. But I heard my bpv blowing off so I knew what was wrong. Bpv vac tank was bad so I bypassed it and removed it totally and been good ever since. If u are on stock intake its harder to hear so try running the line on the left of the bpv solinoid , which is ur bpv line , run it straight to the intake. Just unplug the one on the intake and plug the bpv line in. Take it for a run and see if that fixes it, if it does I'll tell u how to properly bypass the vac tank

 

Well then It may not be the vac tank, ur hear it blow off. I'd say do a boost leak test, ur probably loosing all ur boost somewhere. And yes u do usually thow a code but if had decent leaks that didn't throw codes

 

Okay quick update for everyone. I need some help. So I deleted the vac tank and my boost doesn't fluctuate anymore. I stay at a steady 20.5 psi according too my obdll scanner. And just under 20 according to my gauge. So now that that is fixed. My car started doing this thing where when I'm crusing and my vac hits about -1.5 the car doesn't know whether to blow off or hold boost and it will do this weird In Between and blow off and hold boost every second. I also noticed on my obd, it says 100% load when I'm barley accelerating. Like not even quarter throttle. Also it sounds like the bpv isn't holding boost all the way. It's hard to tell if it's leaking or if it's just my turbo spool noise. Any info will help.

Edit: I do not believ that vac tank delete is the source of the issue because I noticed the issue before but not as bad and it started happening bad since I did I launch control to scare off a focus st 😳

 

ok now that u have the obviously leaking vac tank deleted. now we move on to the next issue. how do u have ur lines hooked up now? post a pick. and may want to order a new bpv solenoid. seems like that could be bad as well. I will see if I can post a pick of how u should have it hooked up

 

this is how it should be. remove red hose from manifold port. run green hose from where it is on the bpv solenoid to manifold port. everything else stays the same. u can go under the car and totally remove vac tank if u wish. 2 10mm bolts. to do this totally right put a check valve on the green hose from bpv solenoid to manifold port. make sure the check valve is backwards so that the solenoid can only see vacuum and not boost. then it will work as it was designed to. take it for run. if u already have it like this or if u do it like I say and it still does it, then its time to replace solenoid. the do go bad. iv changed mine once already as well.