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lucittm lucittm is offline
Manassas, VA
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Join Date: Apr 2007
Posts: 1,211
My book lists these pressures associated with the CIS:
System Pressure - from the fuel pump and regulated by the line pressure regulator (91-94 psi).
Control Pressure - determined by the WUR (engine warm, above 68* F 62-68 psi).
Residual Pressure - maintained in the closed system after engine shutoff (23 psi after 10 min).

If you mean charging pressure as related to control pressure, there are two values, cold and warm. Warm is 65 +/- 3 psi and cold depends on the ambient temp. For example, at 32* F the control pressure will be 29 psi. At 68* F the control pressure will be 39-46 psi. At 104* F the control pressure will be 58-65 psi. These were just three random temps taken from the graph, but you can see the cold control pressure is based on ambient (sea level) temp.

The way this works is the control pressure pushes down less on the control plunger in the fuel head to allow more fuel to reach the injectors when the engine is cold (more of the system pressure is used). As the engine warms up, the control pressure increases and this higher pressure pushes down harder on the control plunger allowing less fuel to reach the injectors (less system pressure is used because it has to overcome the control pressure).

Did that help?

1991 964 Polar Silver Metallic Turbo Coupe

Last edited by lucittm; 07-10-2011 at 10:16 AM..
Old 07-10-2011, 10:00 AM
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