Boost psi questions - Diesel Truck Forum -
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post #1 of 3 (permalink) Old 11-12-2007, 10:51 PM Thread Starter
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Boost psi questions

I have a 99 with a quadzilla 120/325 on "3", 75/150 nozzles, straight pipe, intake and adjustable boost elbow with no adjustment left. I read everywhere that boost shouldn't go over around 25psi? or so with a stock turbo. When i have the quad off i can hit and hold 32 like nothing and with the quad on i have seen 40 before the egt gauge is pegged and I have to let off. Why? Is this dangerous? Is the wastegate bad?
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post #2 of 3 (permalink) Old 11-13-2007, 07:30 AM
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35psi is fine for a stock turbo. After that there is no additional power from more boost, its just hotter air. Back the elbow down a little to see 35 max. If the wastegate isn't opening then its bad.
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post #3 of 3 (permalink) Old 11-13-2007, 07:40 AM
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Once you start getting into the higher boost levels you are really asking a lot of that charger. They pretty much run out of their map at around 32-35 psi and stop being efficient, like K20 said, they start pushing hot air, which reduces power, and raises EGT's. As far as it being really dangerous, if it were to come apart it could do some serious damage. I push mine to around 40psi occasionally, and took the one on my 12v up to 48psi from time to time, and they were fine. However, I would say I was really pushing my luck.

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