Help Needed! High Pitched Whining Noise When Boosting...

[pixel8r]

Hi all,

I have a '99 Stagea S2 (neo) and since I bought it back around march/april its been doing this squeal / whining noise under the bonnet when the turbo spools up. Its fairly loud too.

It seems the faster the turbo spins, the higher pitched the noise gets.

I've recently done the mod to the stock boost solenoid where you ground one of the wires so it now runs 7-8 psi boost and the higher boost means the noise now reaches a higher "note" when it maxes out.

Haven't had the turbo properly checked out but on just taking it for a test drive some people have said its probably the turbo on its way out and others have said its a leak in the factory blow off valve.

the car is completely stock and has made this noise since i bought it.

Any help as to what it is?

[Tangles]

Hi mate, Ive seen you driving that beast (down Flinders st near Wakefield Hospital), very nice and clean S2.

Umm, better take off the piping from the air filter to the turbo and check to see if the front wheel is touching the sides of the housing?

[Spammeoff]

My standard S1 does the same thing, no other side-effects it seems, but its gotta be a prob of some sort. I do have a slight exhaust leak between the head and exhaust manifold where I can see its snapped some studs off. Could be this I suppose? Doesn't sound that way, but backpressure between exhaust ports and turbine wheel must increase when boosting, hence perhaps the 'squealing' noise.

I took my air intake to turbo off to check sideplay on turbo shaft, essentially none. But I didn't really think it would be that.

Be pretty interested in some other opinions though!

[Spammeoff]

Oh and some more info, my factory BOV was leaking (but I never thought the squealing would be that) so I replaced it with a block-off plate, squealing noise didn't change. (Boost maybe climbs a bit faster.... hard to tell).

[pixel8r]

Thanks for the quick replies guys!

I just tried blocking off the blow-off valve (by unscrewing it, putting something across the hole to cover it, and then screwing it back up to seal it properly) but still the same noise.

will check the turbine wheel as soon as it cools down enough...

i guess that means my blow-off valve is ok?? i dont know that much about mechanics so this is a learning thing for me but i'm making progress.

The bov itself had a small amount of oil leaking out of it - on the end that connects to the big rubber hose - is this normal?

i really just want to find out where the issue is. if its the turbo then apparently it should still last a while and if it does pack up then i'll have to assess my options at the time.

was kind of hoping it was the bov cos thats just a simple replace job.

thanks again for the help.

[decoyslikecurves]

If you could describe it as a high pitched "whoooosh" its probably a leak. On my old laurel, where the exhaust bolted to the motor was loose and as soon as I tightened it up the noise went away.

Have a look around for leaks and check all the bolts

[munchstagea]

Been there done that! Oh such a worry, could be your turbo as a lot of people will tell you, mine was not.

See Here for my solution.

I hope you have the same issue I had as it is easy to fix. (go straight to post #26 for the solution)

Cheers

Luke

Edited July 11, 2006 by munchdesign

[pixel8r]

Thanks guys.

Looks like i've basically nailed it down to turbo - or a leak around that area...

Not up to pulling everything apart today but will definitely give that a try in the next couple weeks when i get a chance and check for loose nuts etc...

Hopefully it is just a leak. But its audible anywhere above ~1800rpm - ie. as soon as the stock turbo starts winding up.

it gets higher with the turbo, not rpm - so it will get higher and higher until the turbo hits full boost and then it stays at constant pitch.

Not really a 'whoosh' in that it doesn't go away. The noise keeps going for as long as i'm on boost. kind of annoying when going up steep hills etc.

Anyway, not much else I can try other than look for an exhaust leak or something similar.

[munchstagea]

Anyway, not much else I can try other than look for an exhaust leak or something similar.

I am tipping exhaust leak, if your turbo was on the way out it would have gone by now (maybe not), sounds just like what mine was doing though. Mine started off making noise only when booted and then it happened lower and lower in the range until it sounded like yours is.

It is a bit of stuffing around getting the pipes off and on and the heat shield is a pain if you need to take that off (I think you do) but theres not much you can stuff up, getting to those bolts and getting them tight (for a start anyway).

Cheers

Luke

[pixel8r]

Thanks Luke!

I really hope you're right

will have a look on the weekend.

actually the thing that made me look into it was that I heard (yes 'heard') another stagea go past as I was walking to my car from work - and it sounded awesome. I love the sound of turbo + engine combined. When I heard it I thought 'I wish my stagea sounded that good!'.

Out of interest it was a silver stagea s1 heading west along greenhill rd, eastwood area...

[darrinspencer]

I had the same problem on my r33

Turned out to be a loose turbo to exhaust manifold

Had to change the gaskit as part of it had blown out from the turbo being loose.

Fitted a new gaskit and new lock nuts, problem fixed.

[Ska]

Ummm also I thought that without a BOV venting the pressure when it does, that pressure goes back down and causes your turbo to effectively "cut" the air, where is spins forward then reveres then forward again, producing that horrible "flutter" noise which is popular with ricers.

BOV are there for a purpose, I would think long and hard about leaving it off. Also do a bit of searching abut this subject, it has been discussed lots of times, mainly in the Forced Induction section.

Just reading that you guys have "blocked off" where the BOV used to me sent shivvers down my spine..................

[Spammeoff]

Ummm also I thought that without a BOV venting the pressure when it does, that pressure goes back down and causes your turbo to effectively "cut" the air, where is spins forward then reveres then forward again, producing that horrible "flutter" noise which is popular with ricers.

BOV are there for a purpose, I would think long and hard about leaving it off. Also do a bit of searching abut this subject, it has been discussed lots of times, mainly in the Forced Induction section.

Just reading that you guys have "blocked off" where the BOV used to me sent shivvers down my spine..................

I've had my BOV blocked off for a while. When I discovered it leaking I preferred that to loosing boost. And yes the air flutter noise everytime you back off from boost is very noticeable, but didn't concern me.

What was a problem though was that with no BOV the car was stalling when you backed off after loading the engine. Problem could be reproduced everytime if you stalled up the auto using a quick stab on the gas, then backing off completely, the engine would stall. Became a problem when entering tight round-abouts off the gas and turned quite sharp, the power-steering load would stall the motor, and you nearly go up the curb etc.

Putting the BOV back on eliminated the prob altogether, but I'm not clear on why no BOV caused this. Will investigate. Maybe I had a vacuum leak when I removed the BOV.

[Ska]

Yeah that is because the stock bov vents the pressure back into the intake before the turbo, and the ECU is expecting that and richens the fuel and because there is no air it floods it and stalls?

Well at least that is what I understand from reading all the threads on this specific issue, it has been argued to death on SAu, just do a quick search, make a couple of cups of coffee and start reading

[Ska]

On my old r33 I wanted the "whoosh" sound, so dissconnected the plumback, not the bov just the plumbback and had this stalling issue. That is when I went searching, and found the answer above.

[66yostagea]

I've had my BOV blocked off for a while. When I discovered it leaking I preferred that to loosing boost. And yes the air flutter noise everytime you back off from boost is very noticeable, but didn't concern me.

What was a problem though was that with no BOV the car was stalling when you backed off after loading the engine. Problem could be reproduced everytime if you stalled up the auto using a quick stab on the gas, then backing off completely, the engine would stall. Became a problem when entering tight round-abouts off the gas and turned quite sharp, the power-steering load would stall the motor, and you nearly go up the curb etc.

Putting the BOV back on eliminated the prob altogether, but I'm not clear on why no BOV caused this. Will investigate. Maybe I had a vacuum leak when I removed the BOV.

The first time I drove the S1 it stalled in exactly the same way,but turning into a servo. I thought it was low on fuel. Then it was ok, next day it did it twice more but has not done it since. The bov could have been stuck due to time since given a good run.

[Spammeoff]

The first time I drove the S1 it stalled in exactly the same way,but turning into a servo. I thought it was low on fuel. Then it was ok, next day it did it twice more but has not done it since. The bov could have been stuck due to time since given a good run.

Remembering my car doesn't stall with stock bov on, only with the blanking plate. I haven't seen a good explanation, or figured out yet for myself, the physics of why the blanking plate might make it stall.

[darrinspencer]

Remembering my car doesn't stall with stock bov on, only with the blanking plate. I haven't seen a good explanation, or figured out yet for myself, the physics of why the blanking plate might make it stall.

Ska is correct I believe

If you have a look at you blowoff valve when it is off the car, on the underside there is a small hole approx 2-3mm diameter

This allows a constant bleed of air back thru the inlet. The factory ECU is expecting it. When you blank it off, or fit an aftermarket blowoff valve, you get the stall problem

Fitting a SAFC or new ECU can fix this problem, as you can turn the system not to allow for the constant bleed of air.

You can test this theory, by refitting your factory blowoff valve, but put a bit of electrical tape across the little hole and see what happens.

Let us know if still stalls

[Spammeoff]

Ska is correct I believe

If you have a look at you blowoff valve when it is off the car, on the underside there is a small hole approx 2-3mm diameter

This allows a constant bleed of air back thru the inlet. The factory ECU is expecting it. When you blank it off, or fit an aftermarket blowoff valve, you get the stall problem

Fitting a SAFC or new ECU can fix this problem, as you can turn the system not to allow for the constant bleed of air.

You can test this theory, by refitting your factory blowoff valve, but put a bit of electrical tape across the little hole and see what happens.

Let us know if still stalls

Great explanation Darrin thanks! I will check that out tonight then. Couldn't find that info elsewhere actually, the small hole bit that is. I'm about to go for the Jaycar DFA so maybe I can sort it out then.

So just to straighten this out in my mind... the vacuum present at the vacuum line on the BOV, is sucking air through that little hole, and essentially bypassing the butterfly. I take it thats what you mean? The only other place for air to be going would be on the recirc path back to the post-afm turbo intake point, and I couldn't see why that would effect idle/stalling.

So maybe I'll modify my blanking plate for that operation eh? Still not happy with a leaky bov.

[Ska]

OK here is a pick of my old r33, notice the plumbback is still attached:

And now here are pics of what I did:

Basically I undid the hose clamps either side and removed the rubber hose and then I put a bit of metal across the open end of the BOV to make a nice WHOOOSH sound and sealed the plumbback side with some duct tape.

Unfortunatly anything under about 2,000 rmp it used to just die in the arse and stall.

So the BOV is still there and it was doing it's job, but the vented air was not making it back into the intake and therefore the fuel was being pumped to compensate for it and hey presto stall!