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Power steering pressure physics?

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Old 03-09-2016, 05:31 PM
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Default Power steering pressure physics?

What's up guys. So I work on cars for a living and am my taking ASE certs one by one. I have just recently passed my A4 test which is suspension and steering a few weeks back. Currently, I have starting reading my study guide for Heating and A/C. It states that when the refrigerant moves through the orifice tube, pressure decreases. I am familiar with main line pressure in an auto trans working the same. Fluid moves through restriction: main line pressure decreases. Then why (and I answered the question correct on the test even though I didn't really get it) does having a restriction in a power steering pressure hose result in an INCREASE in fluid pressure? Kind of contradicts there. Why? I'm sure there is engineer-brainiacs somewhere in here that could explain this a bit better. Thanks! Sorry kind of odd question but I have faith in ls1 tech it is an automotive related hahaha
Old 03-09-2016, 05:53 PM
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"when the refrigerant moves through the orifice tube, pressure decreases". After the orifice tube,pressure IS decreased. That reduced pressure volume is expanding and requires BTU to do it(expand),it takes heat from whatever it contacts,that's the cold side of AC.
"having a restriction in a power steering pressure hose result in an INCREASE in fluid pressure". Yes,before the restriction.
Old 03-10-2016, 07:22 AM
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Originally Posted by TransAmFever90
It states that when the refrigerant moves through the orifice tube, pressure decreases.
The pressure doesn't actually physically "decrease" until the refrigerant exits the restriction in the middle of the orifice tube part and the gas can expand:




The difference with a hydraulic or P/S system is that when you go in to a more restrictive pipe, the fluid stays in that restriction (there's no expansion chamber on the other side) and it doesn't get a chance to expand.



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