Weird "Pssh" noise when I lift off Throttle

[mcglsr2]

Hey guys, back with another question. I've pretty much put my car back to stock for the time being - it's an 87 CSX. I am NOT currently running a BOV. I do have a cone filter on the compressor intake.

So here's the issue: the car drives fine, but I step on it, it builds boost, and all is right with the world. When I left off the gas, I hear a "pssssh pssh psh" noise. As I said, no BOV. Also, I don't think the turbo is surging. It has never surged before that I know of. Boost is about 12 or so right now. So not that high.

I was thinking it's a leak in the intake or something, as the throttle body closes and boost has no wear to go, it's leaking out from someplace. The car idles at about 15" vac. I don't hear any escaping boost while I'm on the gas - I only hear it after a left off.

I know this is pretty vague, and I'll probably get a "check your hoses" answer. Which is fine, and something I need to do for sure. I was just wondering if anyone else has had this issue and knew of a particular place I should start.

Thanks in advance!

[turbodaytona87]

Not familiar with the CSXs, is this a blow through setup?

[contraption22]

It's probably surge.

[cordes]

It's probably surge.

Almost a certainty.

Also, Scott, it is good to see you back on the board.

[BadAssPerformance]

Yes, with a cone filter its the sound of your intake chage (boost psi) getting shoved back thru your turbo when the throttle closes.

[prepared]

Agreed...

Pshhh Pshh Psh is definitely compressor surge. LOL, but I can hear it as I read that! Getting a BOV will eliminate the surge.

[mcglsr2]

Thanks for the replies!

Almost a certainty.

Also, Scott, it is good to see you back on the board.

Thanks, it's been a looong time - long enough to see that there is now a "new" tuner we have available, the MP Tuner. I'll have to start reading up on that

Agreed...

Pshhh Pshh Psh is definitely compressor surge. LOL, but I can hear it as I read that! Getting a BOV will eliminate the surge.

Okay, regarding the surge. So this may very well be the issue. However, I have ran the car for quite a while with a cone filter, but am only now hearing this. Also, I have run the car with a BOV - I still hear it. I hear the BOV sound, and then I'll hear the "Pssssh pssh psh." I then took the BOV off to "simplify" the plumbing in an attempt to isolate the noise.

Sooo, not saying it isn't surge, but it didn't go away when I was using a BOV...

Some additional info that I should have mentioned - I am running a ported exhaust man., TU 3" sv and a 3" exhaust with no cat.

[22shelby]

your BOV isnt either adjusted properly os its not working, what kind of bov is???

[prepared]

Also, what IC do you have? What piping?

The total volume of air in the IC and piping has to evacuate through the BOV before surging back to the compressor. More piping or larger IC means more air that has to be evacuated. Is the BOV big enough?

[mcglsr2]

your BOV isnt either adjusted properly os its not working, what kind of bov is???

It's an HKS SSQV. There really isn't any adjustments that need to be made. I also have an unmodded mitsu that I could try. The HKS is new. The mitsu I've run for several years now. So I can try the mitsu - and if I still hear that noise, then it's got to be something else (as in I didn't hear that noise with the mitsu before).

Also, what IC do you have? What piping?

The total volume of air in the IC and piping has to evacuate through the BOV before surging back to the compressor. More piping or larger IC means more air that has to be evacuated. Is the BOV big enough?

Stock TII IC in stock location. Stock 2-1/4 piping. Running at about 12 psi right now.

[TonaKid62]

i heard the same thing you are hearing now on my 89 daytona but it was so quiet that most of my friends didnt even hear it. i now have and HKS ssqv and it went away, but then again the bov could be covering up the noise. lol

[mcglsr2]

Alright, now I'm confused. When I got home, I put the mitsu BOV on the car and went for a drive, and damned if the Pssh Psh noise went away. I'm pretty sure it went away and not that the BOV was covering it up.

So this means it is indeed compressor surge?

Next, I need to try it again with the SSQV BOV. And if I hear that stupid noise, that means the SSQV is not venting the boost fast enough? Assuming that is indeed the case - does that even make sense? It's a way better BOV than the mitsu one, and it's dual staged. How can it not be lifting fast enough? Anybody with experience here using this BOV?

[OmniLuvr]

for sure compressor surge, which is bad times, is it a "REAL" hks or knock off? doesnt really matter, but what does is how much vacuum your motor is making. when my motor started to get tired it only made like 14" of vac, which wasnt enough to engauge bov fast enough or long enough. the plus with the mistu bov is that it engauges very quickly because the bov is accuated with boost and vacuum when not modified.

[cordes]

Alright, now I'm confused. When I got home, I put the mitsu BOV on the car and went for a drive, and damned if the Pssh Psh noise went away. I'm pretty sure it went away and not that the BOV was covering it up.

So this means it is indeed compressor surge?

Next, I need to try it again with the SSQV BOV. And if I hear that stupid noise, that means the SSQV is not venting the boost fast enough? Assuming that is indeed the case - does that even make sense? It's a way better BOV than the mitsu one, and it's dual staged. How can it not be lifting fast enough? Anybody with experience here using this BOV?

The SSQV is adjustable. You may need to loosen it up some so it can more freely vent to the atmosphere.

[mcglsr2]

for sure compressor surge, which is bad times, is it a "REAL" hks or knock off? doesnt really matter, but what does is how much vacuum your motor is making. when my motor started to get tired it only made like 14" of vac, which wasnt enough to engauge bov fast enough or long enough. the plus with the mistu bov is that it engauges very quickly because the bov is accuated with boost and vacuum when not modified.

It's a real one, not a knock-off. The motor is pulling about 14 to 15" vac, so maybe that's the issue? I also have a filter inline to the BOV - not sure what it's for but the instructions said to install it...

The SSQV is adjustable. You may need to loosen it up some so it can more freely vent to the atmosphere.

cordes, my man, I have not the clue on how to adjust it. I didn't think they were adjustable. I'll have to do some reading/research on that...

Edit - thinking about it, I think maybe the early ones were adjustable? This one is the version 2 of the SSQV I believe... here are some pics of it:

[cordes]

You are right. It doesn't look as though the second generation ones are adjustable. What vac source do you have it hooked up to? Perhaps a better feed would react more quickly and powerfully?

[mcglsr2]

You are right. It doesn't look as though the second generation ones are adjustable. What vac source do you have it hooked up to? Perhaps a better feed would react more quickly and powerfully?

I've got it hooked up to a vacuum block which sits between the intake manifold and brake booster. There are other feeds coming off this block - boost gauge and MBCs.

So the thought is that the BOV isn't getting enough vac? Why is it that the mitsu one works fine? Just a difference in manufacturing?

[92spiritrt]

i'm not very familiar with those bov's, but i know that the tial ones are adjustable by changing the spring. do the newer hks units possibly work the same way? if so, you may be able to put a lighter spring in to loosen it up.

[Dave]

i'm not very familiar with those bov's, but i know that the tial ones are adjustable by changing the spring. do the newer hks units possibly work the same way? if so, you may be able to put a lighter spring in to loosen it up.

Some of the earlier ones had a bolt with a jam nut that you could set the preload on the spring cup.

[mcglsr2]

Some of the earlier ones had a bolt with a jam nut that you could set the preload on the spring cup.

yah, apparently this one does not.