I am 95% sure that the "wheeeee" sound is the wastegate opening once you hit full boost. It may be a perfectly normal sound.
The turbo works by taking exhaust gas pressure and volume and turning that into intake pressure and volume. If there is too much exhaust gas pressure and volume to sustain a constant intake pressure, a wastegate will redirect some of the exhaust around the turbine and directly into the exhaust. This creates a direct path of high pressure exhaust from the valves into the exhaust.
Boost creep is when the wastegate can not direct enough gas around the turbine and boost increases uncontrolled.
A boost spike is when the wastegate does not react fast enough to redirect gas around the turbine and a short duration high boost condition occurs.
I know it is "late" for this thread, but I wanted to weigh-in on this too.
My GXP Auto is EXTREMELY quiet under FULL acceleration compared to any other car I have driven. I DID match / exceed the magazine numbers (14.05 quarter) and there is NO loud whistling / screetching noice. I concur, the ONLY noise is a whistle from the BOV at shifts. All else is easily identified as "normal" noise. Any squeeling you hear is a PROBLEM!!
__________________
Ernie Guzman Pontiac in Houston are liars and profiteers!!
Power Train Mods Are Done!!! Dejon CAI, Dejon IC Pipes, EDAL, Magnaflow 3" cat-back
Misc. Mods: WindRestrictor 2, stubby, de-badged, engine cover painted, garage door opener, headlights smoked, egg yolks gone, Garmin Nuvi 660, custom trailer hitch, upolstering
To Do: Calipers painted, Back mud flaps, ECM tune? Boost Controller?
Remembered reading this thread and thought I'd come pipe in now.
I'm hearing a slight wheeee noise as I build boost also. It's not very loud and I don't recall if it's been there since I got the car, but there is a noise as boost builds. It gets louder the more boost the car is making. Then I shift and I get the BOV slight whoosh and it goes away till I build boost again in the next gear. In general I've only been able to build 14~15 psi of boost, but I've seen it peak as high as 17 psi then drop. I don't know if that's because of the current colder temps or what.
It's a pretty low noise from inside the cabin, but it's still there. Having never owned a turbo car before I was unsure if I should be hearing anything at all as it builds boost. I mean I would assume as the turbo is building boost you might hear it whine as it accelerates or the sound of far more air being sucked in faster.
I'll try to focus on the noise some so I can describe it better.
__________________
Save the Kappa!
A grassroots movement to save the Kappa platform based cars.
It's not just a car, it's a lifestyle and a community.
NASSOA (TM)
Founding Member - Communications Chair
All this talk about the various possible ways of turbo venting are Greek to me. What isn't is the presence (or absence) of sound. What has been described in the original post is not normal. I have 2500 miles on mine now, and make regular red-line runs through the gears (quite sweet, BTW ). Under full throttle acceleration you can barely here any turbo whine. When I shift gears, you can hear just a little "whistle" from the BOV. As has been mentioned in other posts, the car is spooky quiet. Other than the very slight BOV whistle at shift points, all but the highly initiated wouldn't have a clue this car is turbo charged. I've driven a few other turbo charged cars, and this one has, by far, the most quiet engine I've been in. Suggest you get your car to the dealer ASAP.....
when my father takes me for a ride in the gxp its spooky quite and spooky fast. when someone tries something he hits first second then third and there in his turbo puff dust but seriously that car is fast but you didnt hear it from me
__________________ ~~~~~~~~~~~~~~~~~~~ Pontiac builds excitement... Saturn has rethought it's image...
The time has come for the enthusiasts... NASSOA
Founding Member #49 ~~~~~~~~~~~~~~~~~~~
#1922 12/03/05
N/A Classic Solstice
Mysterious Steel/Sand w/ 6-Disc Monsoon
Conv., Pwr & Premium Pkgs A/C LSD Carpet Mats
MODS: GM CAI & CATBAck
High Pitched Whine
Turbo Spooling up/spinning. Most noticeable when you remove your airbox and any sound deadening canisters.
High Pitched Squeal
Air leak, either from the exhaust pre-turbo or pressurized intake air post-turbo.
Whoosh Sound
Blow Off Valve/Bypass Valve (same thing). Occurs on throttle close to release high pressure air that would cause the turbo to slow or reverse direction. Especially if it vents to atmosphere.
Absence of noticeable sound
Wastegate bypassing exhaust gasses. While driving, the wastegate it quite often working to maintain proper boost pressures. Makes no signifiacnt noise.
One can have a boost leak or pre turbo exhaust leak and still be able to make max boost. Problem is, the turbo will be working harder to do so.
Absence of noticeable sound
Wastegate bypassing exhaust gasses. While driving, the wastegate it quite often working to maintain proper boost pressures. Makes no signifiacnt noise.
I agree with everything above except this statement. There is a definately a change in exhaust tone when the wastegate opens. It's very audible if you know what you are listening for. The problem is that the wastegate is open for so little time during normal driving that people only hear it as part of the exhaust note. The only time the wastegate is open is when the turbo is making max boost. If you are at the track where the wastegate will be open more and for longer durations that you will start to hear the difference.
I've been working on and racing turbo cars for many years now.
Whoosh Sound
Blow Off Valve/Bypass Valve (same thing).
Actually this is an incorrect statement as well. Although they have taken the same meaning in common vernacular, they are quite different and function differently.
A bypass valve completely relieves pressure in the intake tract after the turbine when the throttle plate closes. This is to keep the turbine spinning between shifts and to prevent compressor surge which over time will destroy the turbo.
A Blow Off Valve is a (usually spring controlled) valve in the intake tract that will relieve pressure at a predetermined point. If a blow off valve is set to 10psi, the pressure in the intake tract will never exceed 10psi because the blow off valve will open to vent the excess pressure. Street cars (except for some early ones) do not use these devices but race cars do to keep the teams honest.
I agree with everything above except this statement. There is a definately a change in exhaust tone when the wastegate opens. It's very audible if you know what you are listening for. The problem is that the wastegate is open for so little time during normal driving that people only hear it as part of the exhaust note. The only time the wastegate is open is when the turbo is making max boost. If you are at the track where the wastegate will be open more and for longer durations that you will start to hear the difference.
I've been working on and racing turbo cars for many years now.
I should have been clearer... you don't hear anything from the engine compartment when the wastegate opens. I could see how you'd hear a change from the exhaust, especially an open one like on a race car... and even more so if it dumps straight out via an external wastegate instead of going back into the exhaust and through the muffler.
Actually this is an incorrect statement as well. Although they have taken the same meaning in common vernacular, they are quite different and function differently.
A bypass valve completely relieves pressure in the intake tract after the turbine when the throttle plate closes. This is to keep the turbine spinning between shifts and to prevent compressor surge which over time will destroy the turbo.
A Blow Off Valve is a (usually spring controlled) valve in the intake tract that will relieve pressure at a predetermined point. If a blow off valve is set to 10psi, the pressure in the intake tract will never exceed 10psi because the blow off valve will open to vent the excess pressure. Street cars (except for some early ones) do not use these devices but race cars do to keep the teams honest.
Hmmm... everything I can find on the 'net refers to both BOVs and Bypass Valves as relieving intake pressure when the throttle closes... although they do differentiate them by whether they send the air back between the MAF and turbo (Bypass Valve) or vent the air to atmosphere (Blow Off Valve).
That's the exact problem that I was referring to. The common vernacular and the aftermarket part manufacturers have been calling the parts the wrong names. Some of the part names are used in racing. So originally, it was either an intentional mistake to mislead consumers or an unintentional mistake by thier marketing departments. Since then, everyone else has just followed suit. Bypass valves are either recirculating or non-recirculating.
Here is a better example: A blow-off valve and a pop-off valve are the same thing. Here is an article that is written that describes how champ car engines work: http://auto.howstuffworks.com/champ-car5.htm
Quote:
The by-pass valve, blow-off valve, anti-surge valve are all intended for the same purpose;
The above was copied from Corky Bell's web site. Why would there be three names for the same part?
That's the exact problem that I was referring to. The common vernacular and the aftermarket part manufacturers have been calling the parts the wrong names. Some of the part names are used in racing. So originally, it was either an intentional mistake to mislead consumers or an unintentional mistake by thier marketing departments. Since then, everyone else has just followed suit.
Here is a better example: A blow-off valve and a pop-off valve are the same thing. Here is an article that is written that describes how champ car engines work: http://auto.howstuffworks.com/champ-car5.htm
This doesn't mention that a Blow-Off Valve is the same as a Pop Off Valve. Can you find a site equating the two? :-)
This doesn't mention that a Blow-Off Valve is the same as a Pop Off Valve. Can you find a site equating the two? :-)
Russ
I'm sure I can (I have books, remember those, that call them the same thing) but I can give you an example right now of someone calling a CBV a Pop-off valve: http://www.sfxperformance.com/parts/EDY93501.htm
Your Mustang forum reference is from someone posting in 2005. He likely got his information from other places on the 'net which have incorrect information.
You have to look back more than a decade to get the right names to these devices. Since no car has a non-recirculating bypass valve stock, it is the aftermarket driving the name change. "Blow-off valve" sounds 100x more cool than "non-recirculating bypass valve."
I'm going to assume that you want them in the correct context since I can find sooooo many sites that are incorrectly calling them the same but going on to explain them both as CBVs.
The AutoGuide.com network consists of the largest network of enthusiast-owned enthusiast-operated automotive communities.
AutoGuide.com provides the latest car reviews, auto show coverage, new car prices, and automotive news. The AutoGuide network operates more than 100 automotive forums where our users consult peers for shopping information and advice, and share opinions as a community.
when my father takes me for a ride in the gxp its spooky quite and spooky fast. when someone tries something he hits first second then third and there in his turbo puff dust 
Linear Mode
