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JFairman JFairman is offline
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Join Date: Jul 2006
Location: S. Florida
Posts: 7,129
Hey JBL, you're 100% correct lol

and, from a post above your's...

"The fuel head piston moves farther up the chamber as control pressure rises and allows more fuel to flow."

Isn't it the other way around....?

Control pressure from the WUR is pushing down on the top of the fuel head piston which when moving downwards covers up more and more of the metering slits in the cylinder wall letting less fuel through to go to the injectors.
The air flow metering plate through it's lever and linkage is pushing up on the fuel head piston from the bottom. So, more airflow then pushes the piston upwards exposing more of the metering slits and letting more fuel go to the injectors.
The position of the fuel head piston is a balance between the force on the bottom of the piston from the air flow meter and the force or fuel pressure on the top of the piston which is being governed by the control pressure regulator or WUR.

The WUR or control pressure regulator is regulating that pressure on the top of the piston by simply bleeding it off and letting return to the fuel tank. The amount it does that is defined by ambient temperature when cold, and then heater element and engine block temperature when warming up, and in a turbo's WUR the boost pressure routed to a diaphram in the bottom of the WUR when the turbo spools up. This one lowers control pressure when you are on boost letting the piston rise because the airflow meter is really pushing up on it now which finally sends more fuel to the injectors.

Last edited by JFairman; 06-04-2008 at 01:29 PM..
Old 06-04-2008, 05:34 AM
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