My friend just called me, his 87 GN is making a nasty ticking noise that he says doesn't increase with engine speed. I know ever since he's had the car, he'd punch it, the turbo would kick in, it'd sit ya back, then, when he let out of it, there was a loud fluttering noise from under the hood. He dismissed it as a loose heat shield...I say nay. He says all of a sudden, the car isn't running right, and he then described the ticking I just mentioned. Could it be blowoff valve? Is this common? He thinks he cratered his turbo, but he's kinda stupid when it comes to cars. I've just never even stuck my head under the hood of a car with a turbo, let alone a badass GN (except when I changed his brake pads and front rotors, but that's not technically under the hood is it?) Any way, any help would be appreciated.

Kelly Shull

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If you've gotta fix it, fix it better than stock.

 

the noise your hearing is the turbo winding down. normal noise. the turbo spins past 100k when your boosting and is still spinning and producing boost when the throttle plate closes. the air is released because the wastegate thinks it a good idea since it has a ton of boost between the turbo and throttle body when you are boosting hard and let up. this release is the noise your hearing most likely.

 

Close, but not quite. Wastegate releases exhaust gases into exhaust system during acceleration. Bypass valve releases boost pressure from intercooler pipes during deceleration. Because the GN has no bypass valve, excess boost pressure is reversed through the turbo and out the air cleaner, which goes "phttphttphttphttphtt". This is not good, and can cause shorter bearing life. If he is hearing rattles or clicking, his turbo is checking out...

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1989 Formula, 383", DFI, Mini-Ram, S-Trim Vortech, blah, blah...
Best ET: 10.796 @ 125.8 mph

TURBO 406 PROJECT STARTED!!!

Other expensive hobby: assault weapons/shooting sports

Employed at:
Hahn Racecraft
Accel EMIC/DFI Tuning
Turbosystems & Custom EFI

Member of Midwest F-Body Association
http://www.mfba.org

 

well, the loud fluttering noise that you have been passing off as a heat shield is completely normal... its the wastegate letting out excess pressure after its not needed.

the only real thing that comes to mind that would make a ticking noise mght be a fuel pump... if its bad maybe.... guess you could check it!

steve

 

You want to ask that question and any others about the GN to Frank Baber "Dr. Turbo" at Performance Pontiac in Portsmouth, VA... He is "The MAN" when it comes to the GN.... His # is 757-488-3500 and ask for him, tell him I sent you, you won't be disappointed. Good luck to you.

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Kevin Irving
85 Trans Am WS-6, 305 TPI, custom burned '86 PROM with '87 "165"ECM, Accel Supercoil & 8.8 Wires, MSD 6AL, Aluminum Driveshaft, TB Coolant Bypass, Ported Plenum, Modified MAF, Cyclone Fuel Pump, JET Airfoil

Veiw my car at: http://www.geocities.com/transam85tpi/TransAm.html

 

Hey my brother is getting a GN engine in pieces soon. Can I tell him you sent us if we have a problem too?
Thanks
Corry

BTW, the GN engine will most likely be getting a bigger turbo then going into a fiero (Yes lots of work to beef up the suspesion, get stronger tranny, etc, but hell, it's gonna be a street legal go-kart!)

 

Thanks, Kevin, I'll give him a call. Nobody here can seem to agree on whether it's good or not, but you all seem to think it's normal. Probably the turbo goin out then huh? I'll give Frank a call tomorrow and ask him what he thinks.

Thanks again guys.

Kelly

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If you've gotta fix it, fix it better than stock.

 

Sure Corry... I talked to Frank yesterday and he said he doesn't mind answering your guy's questions.... call him, he'll be more than happy to talk to you guys... he can build these engines in his sleep.

Kevin

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Kevin Irving
85 Trans Am WS-6, 305 TPI, custom burned '86 PROM with '87 "165"ECM, Accel Supercoil & 8.8 Wires, MSD 6AL, Aluminum Driveshaft, TB Coolant Bypass, Ported Plenum, Modified MAF, Cyclone Fuel Pump, JET Airfoil

Veiw my car at: http://www.geocities.com/transam85tpi/TransAm.html

 

So what happened? I have a GN too!