XStylus

My car has developed a rather interesting chirp or tweet sound when it hits max boost.

Here's the situation:

Within the first fifteen minutes of driving, any time my car hits a boost level over 15, the turbo starts chirping or tweeting.

It's very audible initially, but as the engine gets hotter, the tweeting when hitting high boost becomes less and less audible, until eventually it becomes inaudible.

And before anyone asks, yes, I do let the engine warm up properly before driving.

She's still under warranty, so I took her to the dealer. They replaced the turbo and did a smoke test to check for leaks, and found none. Took it on a test run after I received the car back, but the tweet is still there, loud as ever. Took it right back to the dealer, who re-confirmed the problem and expressed proper apologies for missing it, but they're still trying to find the cause.

Anyone got any thoughts on what the problem is?

Sox-Fan

iTrader: (7)

Bypass valve would be where I'd look first. That exactly describes what my Forge was doing for a little bit until I removed it and serviced it. I don't fully understand how the things work, I just know that cleaning and lubing it fixed it. You might find otherwise because I'm assuming you're on the stocker, which is a different design and not servicerable but nonetheless, check there.

mofofernando

iTrader: (3)

Do you let your car get up to operating temp before hitting full boost?

Sox-Fan

iTrader: (7)

It's extremely rare for me to hit full boost when not at the track, so yes.

tomj77

iTrader: (2)

mine makes a air going through an empty can sound, all started when i took the thing off there turbo that conects the hose to the valve cover. after i put it back in it makes that sound now, cant figure out why. id have to buy a new one to see if that helps

XStylus

Dealership just called, they say they've traced the problem to be the Intake Manifold. We'll see when I get the car back.

SSlobalt

It's extremely rare for me to hit full boost any less than 5 times per day.

gotboost?17

iTrader: (46)

my stock made like a raddle snake noise, now im onto the forge tho

XStylus

Got 'er back from the dealer. Yep, it was the exhaust manifold. It was warped by .010" and, was allowing just enough exhaust to blow through that it acted like a reed, and that's where the repetitive chirp came from.

SSlobalt

So, once it warmed up, after 15 minutes, that gap was closed by expansion? I wonder how they figured that one out?

XStylus

They tried a number of rather amusing things, actually, none of which worked so well. One involved some sort of fancy stethoscope or microphone thing that they could insert inside the exhaust system as the car was running. Must've been funny to see how they were listening to it while driving at full boost. I'd have thought they'd put the car on a roller and let er' rip, but nope, they said it was all road testing. Guess they were lucky there were no cops around.

Ultimately though, how they figured it out was simple, and the tech kinda facepalmed for not noticing it sooner. He just happened to see some carbon deposits on the edge seal of the exhaust manifold. They took the manifold off, measured it, and sure enough there was a slight warp. They machined it out so it was straight, mounted it back in, and it runs beautifully now.