Help me solve this mystery once and for all!

[Four Door GSR]

Well as some of you may know, I've been having this wierd high pitched squeeking/whistling type noise that seems to kick in when the car is under slight load.

Well my initial reaction was a loost belt but after trying numerous belt tensions and some belt dressing, the sound didn't change at all. So Im convinced its not the belt anymore.

Today I installed my Apex boost guage and low and behold the squeeking noise ONLY happens during the crossover from Vacuum to boost (0 psi). If I hold the throttle there, it will squeel/whistle for about 3 seconds. Im thinking something is happening there to cause this to happen. I know the bypass valve is supposed to close at that RPM, could it be possible that the valve is leaking causing it to whistle? How can I check this?

BTW, at WOT I noticed the meter pegs to 6psi then slowly creeps to alomost 8psi near redline. Just wanted to compare results with everyone else.

Any ideas are appreciated.

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Supercharged GSR Sedan
JRSC 6 psi,AEM CAI, AEM Pulley, AEM Cam gears, RSR header, Greddy PE, Field SFC-VTEC, Neuspeed Race, KYB AGX, Racing Hart C2 (3 piece).

Objects in mirror are losing.

[Holden]

I would investigate your bypass valve. Check that the butterfly vane closes completey. I don't know how you could really see this w/o major de-installation, but you check its' range of motion with your hand and compare that to what vacuum does to it.

At idle, it should be fully open. Pull its' vacuum hose off the throttle body/gooseneck and it should close completely.

My boost gauge goes right up to 8 to 8.5 if I floor it over 3-4K rpms. It does not climb as redline approaches.

I also don't get that sound you described.

96 GSR, RSR headers, stock cat, Greddy PE, 6psi JRSC.

Good luck,

Greg

[waveoff]

I get a slight whistling sound right around the vacuum to boost transition. It sounds just like the first couple of seconds of a turbo spooling up. I have never determined what it is but I have an idea. That brass nipple that is tapped into the airbox might be causing it. You know, the brass nipple that has a hose going from it to the valve cover. The air rushing by it could sort of be like when you blow air across the top of a soda bottle. I've never really been worried about the sound because it's not really that obnoxious. The sound I'm hearing may not even be the same sound you're hearing. On my car, the boost usually corresponds with whatever RPM I'm at and maxes out at 6 psi at 6k RPM's.

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Fred G.
'97 Civic EX supercharged http://www.geocities.com/motorcity/track/4059
Beech 1900D driver...2,558 shp, 10,000+ ft./lbs. tq., top speed 331 mph

[Four Door GSR]

The range of motion looks ok, but I think somethings defective inside the valve. Without taking it apart, i wont be for sure. I just might have to live with it. its pretty damn loud though.

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Supercharged GSR Sedan
JRSC 6 psi,AEM CAI, AEM Pulley, AEM Cam gears, RSR header, Greddy PE, Field SFC-VTEC, Neuspeed Race, KYB AGX, Racing Hart C2 (3 piece).

Objects in mirror are losing.

[sjoback]

I know mine whistles at changeover, especially loud with the AEM. wasn't noticeable before.

at least your bypass doesn't chatter like mine. good thing I can't really hear it now with an exhaust system.

[Encino Man]

If you idle screw is too tight it will make a high pitched squeek at "slight" load. is it doing this at 1/4 throttle anywhere in the RPM range?

[Four Door GSR]

Only exactly during the switchover from vac to boost. You're right it usually happens at 1/4 throttle. I'll check the screw.

[Turismo]

I also get this whistle at part throttle.
Mine also wasn't audible until I put the AEM CAI on it. I think it's inherent.

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'96 JRSC GSR Sedan (Black Currant Pearl)
AEM CAI / PMS / J&S Safeguard / Vortech Fuel Rail / Autometer Boost/Vac, Fuel Pressure (Dual Pillar), EGT (in glovebox for now) / Walbro HO Pump / Billstien Shocks / H&R OE Sports / Skunk2 Rear Swaybar / 3pc DC Sports Tie Bars / Bridgestone RE-71 Potenzas

[Four Door GSR]

Im convinced its the bypass valve, but im surprised its that loud in my car. I havent heard anyone compain about it. You can hear it even with the radio on.

I noticed it whitstles on the way down too from boost to vacuum.

Oh well, just have to deal with it I guess.

[JRCivic]

It is not uncommon for the "Fast rush of air" passing through the small crack around the nearly closed butterfly of the bypass valve just as it is transitioning to boost WILL whistle... some people just seem to recreate this condition more than others... mine does it all of the time. If the noise changes slightly in pitch as it is about to quit, it is the bypass valve. If not, you will need to investigate further.


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'93 Civic Si H/B with B18C1, JRSC @ 8psi
Best 1320: 12.68 at 110 mph