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Old 14th September 2019, 10:28   #1
macafee2
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Default clutch master, how many psi?

how many psi (pounds per square inch) of pressure is there, between the clutch fluid and seals in the clutch master cylinder when the clutch pedal is fully pressed down, I assume this is when there is maximum pressure.

If that's not when at maximum pressure (psi) then can you tell me what the maximum psi is?

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Old 14th September 2019, 14:54   #2
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The hydraulic pressure in the clutch system depends on the clutch diaphragm spring tension and its degree of deflection. It will vary somewhat between engines. I doubt you'll find a figure, but will be maximum near full deflection (pedal fully down). If you really need to know, I think you'll have to install a pressure gauge in the line to the slave.


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Old 14th September 2019, 15:12   #3
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Originally Posted by T-Cut View Post
The hydraulic pressure in the clutch system depends on the clutch diaphragm spring tension and its degree of deflection. It will vary somewhat between engines. I doubt you'll find a figure, but will be maximum near full deflection (pedal fully down). If you really need to know, I think you'll have to install a pressure gauge in the line to the slave.


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cheers TC, at a guess, have you any idea what I should expect?
I could not begin to guess, my life does not depend on knowing

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Old 14th September 2019, 19:31   #4
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Quote:
Originally Posted by macafee2 View Post
how many psi (pounds per square inch) of pressure is there, between the clutch fluid and seals in the clutch master cylinder when the clutch pedal is fully pressed down, I assume this is when there is maximum pressure.

If that's not when at maximum pressure (psi) then can you tell me what the maximum psi is?

macafee2
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Old 14th September 2019, 19:39   #5
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Its a bit like saying, how much pressure does it take to push a pea across a dining table...

As much as it needs, the pressure differs when it comes up against resistance, so as already said, it depends on the type of engine, age of pressure the plate and the conditon of the slave & fluid.
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Old 14th September 2019, 20:26   #6
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I've got a feeling that you are the first person to ever ask that question since the owners club first began.----
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Old 14th September 2019, 21:06   #7
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cheers TC, at a guess, have you any idea what I should expect?
I could not begin to guess, my life does not depend on knowing
EDIT: A bit of Googling will get you anywhere.
This article: https://x-engineer.org/automotive-en...uation-system/


- suggests the typical car clutch operates at around 50Bar, which is about 750psi.


TC

Last edited by T-Cut; 14th September 2019 at 21:13..
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Old 14th September 2019, 21:38   #8
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WOW!
Gives me a bit more respect for the humble slave cylinder.
Yet another system on a car that operates under very harsh conditions.
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Old 15th September 2019, 08:30   #9
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Wow! High pressure indeed! Which leads me to believe that my theory of the failure of the Taz* metal cylinders was due to the failure of the seals between the brass cylinder liner and the outer alloy casing. They were tiny, circular section seals (similar to watch caseback seals) . That sort of pressure would eventually force fluid past them and out via the pushrod end. If they had been pressure seals (ie tapered profile) the pressure would force the seal into the outer wall to retain the fluid, rather than seep past it.



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Old 15th September 2019, 15:27   #10
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as said, wow. I would never has expected it to be so high and considering the clutch pedal can be pushed down my hand I would have thought more the 20-30psi range.

see, this is why I cant guess.
thank you T-cut very kind of you to have searched

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