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89 930.
 
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Question Charging pressure in shop manual

In my shop manual is shows (25-16c) a graph with two measurements.
one is without charging pressure and one is without. Can someone tell me what charging press is?

Its the only fuel system graph with two. 1989 930.
It appears i have the 930/68 engine type.

Thank-you

Old 07-08-2011, 07:11 AM
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No one know's?
Old 07-09-2011, 04:31 PM
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I don't understand what "charging pressure" is.
Is that system fuel pressure?
Old 07-10-2011, 07:53 AM
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Yes, it's the pressures for the WUR. There is 2 ranges for my year??

Last edited by Benny771; 07-10-2011 at 08:58 AM..
Old 07-10-2011, 07:57 AM
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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?

Mark
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Last edited by lucittm; 07-10-2011 at 10:16 AM..
Old 07-10-2011, 10:00 AM
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Thx Mark,
still a little confused. It sorta looks like with charge is it plugged in?
And not plugged in is without charge.

By plugged in, i mean the WUR?

Can anyone clarify? See graph:

Old 07-31-2011, 04:12 PM
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I think charge pressure refers to the .5 bar pressure applied at the wur for testing. Just a guess.
Old 07-31-2011, 05:13 PM
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Know one know's this? I just need to confirm that my car is set right at 24degrees 2.4 bar.
Old 08-01-2011, 03:53 PM
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Quote:
Originally Posted by e170drvr View Post
I think charge pressure refers to the .5 bar pressure applied at the wur for testing. Just a guess.
I believe that is the correct answer. "Charge pressure" is the result on the control pressure when the WUR sees air pressure indicative of a boost situation. This is confirm that you are getting proper enrichening when boost is present.

The only way to test it would be to hook up an external regulated source of air pressure to the WUR (you'll find a small vacuum/pressure hose connected to the lower left hand side of the WUR). You would have to pop that hose off and connect an external source to it...then pressurize and see the impact on control pressures.

I think that's correct....somebody tell me I'm wrong, I'm all ears.
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Old 08-01-2011, 07:07 PM
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no corrections, im guessing your right...
Old 08-02-2011, 06:07 PM
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Quote:
Originally Posted by Benny771 View Post
no corrections, im guessing your right...
I'll second that... Makes sense Mark...

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Old 08-04-2011, 04:03 AM
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