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Old 11-15-2001, 09:06 AM   #1
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Help with tuning and Tial wastegate

Hi everyone,
I have run into a problem today when getting my car tuned. Car is a Nissan Skyline R33-25T Stright Six Turbo. Reason I was getting my car tuned was that I have upgraded to a 300ZX AFM from the Skyline one. And installed a smaller exhaust housing for my Garret GT30 turbo. Everything else being the same.

I am running a Tial wastegate.

On the dyno run I loose power when the car reachs around 0.6~0.7 bar boost and anywhere around 4000~5000 rpm. It sounds like its mis-firing and gets all rich with black smoke coming out the tail pipe. So during the day I replaced the plugs, at first we gapped the plugs to .028 then .020 thou without any luck, then we tried replacing the coil packs... no luck. After I got home I borrow from friends car a working "Igniter / Amperifer" that sits on top of the valley cover and tried that in my car without luck. Because I can rev the car on the road all the way to redline as long as I keep the boost low.... E.g 0.2~0.3 Bars. So then I suspect its the Wastegate or the boost control system.

FYI - I am running a Apexi PowerFC with the boost control kit. And a Tial wastegate

So I changed boost settings on the PowerFC without any effect to the problem, I then disconnected the blue silcon hose from the boost control valve and it made no difference too. I then tried using another boost control valve from another car that I know its working .... no luck either. So now I suspect its the wastegate that is not working, since I don't have much experience with wastegates can someone tell me what to check for and how? Like procedure of taking it apart if it requires servicing.? Attached is a photo of the setup. Yellow hose goes to pipes after the turbo. And Blue hose goes to the Boost control valve.

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Old 11-15-2001, 12:33 PM   #2
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If you've installed a smaller diameter exhaust pipe to the turbo, which I understand from your post, the turbo should spin faster than stock. Your ECM could be sending extra gas to the engine while the blowoff valve is preventing extra air from entering. That would explain the black smoke. I'd look for info on the RPM of the turbo vs. the engine RPM for a stock motor and compare what you're experiencing. Hope this helps.
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