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911nut 911nut is offline
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Join Date: May 2001
Location: Michigan
Posts: 2,513
Originally Posted by spoke View Post
One thing I don't understand with the WUR is how at cold temps with the fuel pressure lower the engine runs richer. I would think that higher pressure would mean more fuel.
Remember that we are talking about control pressure, not fuel pressure being supplied to the injectors.
Control pressure is in fact using fuel flow to apply a force to the top of the metering piston in the fuel distributor. This force acts as a counterforce to the air metering plate that's being pushed on by the air that's rushing into the intake tract (the air metering plate is connected to the metering piston in a pivot arrangement). The two opposing forces dictate the position of the metering piston in it's chamber in the fuel distributor. The piston has a tiny slit in it that allows fuel to flow to the six chambers in the fuel distributor. Less counterforce allows the air metering plate to move lower in it's housing for a given air flow, lifting the piston at the other end and exposing more of the slit in the piston to the chambers, increasing fuel flow to the injectors.
Paul B.
'91 964 Turbo
Port matched, SC cams, K27/K29 turbo, Roush Performance custom headers w/Tial MV-S dual wastegates, Rarlyl8 muffler, LWFW, GT2 clutch & PP, BL wur, factory RS shifter, RS mounts, FVD timing mod, Big Reds, - 210 lb
Old 10-30-2014, 01:37 PM
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