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Old 05-16-2008, 01:23 AM   #21 (permalink)
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Originally Posted by JohnnyGrey View Post
John, how are you certain you're in open loop, is the O2 unplugged? I tried doing this on my Cavalier, but the variation in AFR was too wild to run reliably for any length of time. I would advise against slowing down your pump. If it produces less pressure than the regulator needs to open, the fuel supply line will slow to a crawl and the return line will stop. Depending on the design of your pump, it may be cooled by the fuel that runs past it, which will not be much if you go below regulator pressure. Try finding an adjustable fuel pressure regulator instead.

Be careful if you do this, because you will have leaned out your WOT mixture as well. If you need a sudden burst of acceleration, you could cause severe detonation. My car stays in closed loop at around 16.5:1, but if I stomp it, open loop is still around 12.5:1, so I can still get full power out of my engine safely.
I unplugged the 02 signal from the ECU but still monitor it with my DVM. seems to be leaning much better now. still throws my mileage computer for a loop, cause it uses pulse width to calculate fuel flow. but it was off anyway cause i don't think it counts miles when the injector pwr is cut during engine braking.

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