Turbo Surge! WTF?!

[Dusty_Duster]

I finally got my PCV system straightened out, and now I have TURBO SURGE. Really bad turbo surge. At any boost level, I let up off the throttle, and I get turbo surge. I still hear the BOV a little, though. It seems to be opening, but maybe not enough?

I'm not really sure what to check. Could I have done something wrong with the vacuum lines of the PCV system to cause this? I didn't even touch the BOV or its vacuum lines when I was doing the PCV system.

It's an HKS SSQ BOV, and I've had it for years with zero problems. I have a hard time believing it would just up and quit on me like this. I mean, if it's dead, it's dead, and I'll get a new one, but I don't want to buy a new BOV if this is being caused by something else.

I've tried hooking the BOV to both the port on the brake booster (where it was always located before) and directly to the intake manifold. Neither works. I've also tried removing the vacuum line between the PCV valve and the intake manifold, thinking that maybe boost was escaping backwards through the turbo, up the line from the airbox to the valve cover, and through the PCV valve and into the intake manifold. That didn't solve the problem, either.

Now, it JUST got cold out here. Could that have affected something? Or am I most likely looking at a busted BOV?

[DodgeZ]

is the BOV a real HKS, have you adjusted the BOV, what turbo do you have?

[Dusty_Duster]

is the BOV a real HKS, have you adjusted the BOV, what turbo do you have?

It is a real HKS, you cannot adjust it, and it is the stock 2.5 turbo. I never had any problems with it until now.

[Force Fed Mopar]

Found on the Supra forums:

quick question guys..
i got a HKS SSQV BOV

i was wondering whats the right setting on the adjustable screw on the back of the bov.

I think if u tighten the screw its more responsive but i aint sure how tight it should go as i dont wanna damage my turbos.

running on 14psi
fmic
zorst

it (the HKS SSQV) is there so you can adjust the tension of the spring,to suit your needs.
so if its loose/weak,you will get a peeeew very early in the rpm range,where as if its tight,it will open up at a higher rpm due to the tension,but you might get a flutter at lower rpm as it wont open enough.
so its best to experiment yourself and see when its the best for you.
maybe you want the peeeew heaps early?
Also,some bov when adjusted soft,can maybe leak at high boost pressures,but i dont think you will have that problem as your boost level is ... low

[Dusty_Duster]

Found on the Supra forums:

I'll have to check to see if that adjustment screw is on my BOV. But I don't understand why I would have this issue all of a sudden.

[OmniLuvr]

how much vacuum is your engine making at idle? when mine got down to about 14\15 i couldnt find a blow off valve that would work without surge, i tried 6 different ones, even two at one time.

[Dusty_Duster]

There is no adjustment screw on the back of my Blow-off Valve.

how much vacuum is your engine making at idle? when mine got down to about 14\15 i couldnt find a blow off valve that would work without surge, i tried 6 different ones, even two at one time.

My idle is the same now as it was before this problem. I get around 11" because there are some pretty big cams installed. That was always sufficient to make the BOV work before.

Is there any way I can test the BOV to make sure it is not the problem?

EDIT: I removed the BOV from the engine and pulled the cover off the BOV. The gasket that seals the valve looks completely fine. But I can't really look at the actual "machinery" inside the BOV.

I also remember that the BOV seemed to work fine when I first started driving it this morning, but it worked less and less, and by the time I got home, I had the terrible turbo surge I outlined above. I can still hear the BOV a little bit, though...

[Dusty_Duster]

I've listened to several video clips of the HKS SQV, and I realized that my HKS BOV has never sounded like that. It is possible that my BOV was defective from the factory and just now failed completely.

I'm planning on replacing the HKS unit with a TiAL 50 mm BOV. I've heard good things about them, and I especially like that you can change the spring to compensate for different idle vacuums. I just have to save up money, so I won't be able to drive Dusty for a while. But at least it's cold outside right now, so I wouldn't be able to drive the Duster much anyway.

However, before I spend money on a new BOV, is there anything else that could be causing this turbo surge when I lift off the throttle? The turbo boosts very well, and the engine runs great. The BOV was connected directly to manifold vacuum but still didn't work.

[tryingbe]

No, just the malfunction or lack of the BOV or CBV.

[contraption22]

Is there a check valve in your systems that is possibly not allowing the BOV to see vaccuum? The hose out of the BOV goes where?

[Dusty_Duster]

Is there a check valve in your systems that is possibly not allowing the BOV to see vaccuum? The hose out of the BOV goes where?

The hose out of the BOV goes to a port on my brake booster. My vac/boost gauge tees into that same port, so it's definitely seeing vacuum. I even tried hooking it up directly to the intake manifold, but it still didn't work.

It just stopped working all of a sudden after I finished fixing up my PCV system. My original concern was that I screwed something up someplace else, but I can't really think of anything else that could cause this.

I'm pretty sure the BOV is toast, but I just wanted to check everything else before I spend $200+ on a new TiAL BOV.

The turbo surges only after lifting off the throttle. It acts like there's no BOV at all, though you can still hear the BOV a tiny bit.

[BadAssPerformance]

It is a real HKS, you cannot adjust it, and it is the stock 2.5 turbo. I never had any problems with it until now.

The turbo surges only after lifting off the throttle. It acts like there's no BOV at all, though you can still hear the BOV a tiny bit.

Thats not turbo surge (which occurs under boost) thats more like turbo stall chugging out your air filter. So yes, it sounds like the BOV is not opening much. Check the vacuum line for kinks, leaks. Is it going straight to the plenum, shorter the better. Also, how much boost are you running> Some BOV barely open with low boost... probably why the make them adjustable?

[Dusty_Duster]

Thats not turbo surge (which occurs under boost) thats more like turbo stall chugging out your air filter. So yes, it sounds like the BOV is not opening much. Check the vacuum line for kinks, leaks. Is it going straight to the plenum, shorter the better. Also, how much boost are you running> Some BOV barely open with low boost... probably why the make them adjustable?

12 psi of boost. The HKS is supposed to operate under all boost levels (and it used to), but it just stopped working the other day. (It was actually kind of gradual; it worked fine when I pulled out of the garage, and by the time I got back home (~15 minutes later), it didn't work at all.)

[contraption22]

Can you manually apply pressure and vacuum to the valve to see if it's moving?

[Dusty_Duster]

Can you manually apply pressure and vacuum to the valve to see if it's moving?

How would I do that? In order for the BOV to open, there needs to be pressure on the charge pipe and vacuum on the rear of the valve, right?

[Force Fed Mopar]

I was think that BOV's are generally open even w/o pressure in the pipe, but maybe that's just stock ones. The Bosch/Saab BOV on my Shelby Z is always open at idle.

[t3rse]

New SSQVs do not have adjustment screws. They are closed at idle as well. Try running the vac line directly to the manifold first.

[Dusty_Duster]

New SSQVs do not have adjustment screws. They are closed at idle as well. Try running the vac line directly to the manifold first.

Already tried it. Didn't help.

[22shelby]

i need to either,A. go buy a Mighty Vac tester kit or B. go rent one... for u to figure this out ur going to need the diagnostic tools for this. being a Might Vac. if u dont know what one is google it. u shoud be able find one for less than 50 bucks. this will tell u wether ur BOV is working or not

u deff have some kind of a Vac leak (from the manifold to the BOV).

get urself the Vac tester and test it on the BOV if the BOV is bad it will leak off the vac that u apply very rapidly, immeditly. if the BOV is good, the vac applyed will hold where u pump it up to.
then put it away snuggly back into ur tool box and thank me later... one of the best diagnostic tool to have!

[Murphy]

usually you can suck on the line hard enough to make a difference, you mgiht nopt be able to open it, but you should be able to feel the plunger is easier to move with your finger.

If you really want I could lend ya a DSM BOV to test it out. I might be going by hagerstown this weekend, LMK