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Is it possible to reduce the effectiveness of hydraulic power steering?
Would you reduce the gearing of the pump,, or would a reduction in the pipe work do it?
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I can't speak for your particular car, but every pump I've seen uses a sprung pressure valve, similar to that used in a engine oil pump. You can usually shim it up or down to change the pressure and thus the assistance. Changing the belt to reduce the pump speed would just mean the pump wouldn't be able to make pressure at idle but would still give the full pressure at higher revs.
Most systems have a acceptable range of pressures, so there is probably some room for adjustment within the existing parameters without any risk.
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Annoyingly, it's usually a little more complicated than that. There is a sprung relief valve that sets the maximum pressure, but there's other gubbins going on in there with a sliding shuttle and a tapered orifice as well. Changing the sprung relief valve spring would help though.
This video does a great job of explaining what's happening in them:
I managed to find springs compatible with my LUK LF30 from flexosprings.co.uk, but it did take some measurement of the original springs to get their rate and free length. What pump do you have?
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usually the amount of assist is controlled by the stiffness of the torsion bar in the steering rack, this determines how much the control valve opens for given torque to the steering wheel. You could fit an external relief valve (between the high pressure line and reservoir to drop the line pressure which would help but mean the steering efforts at parking speeds rise.
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Thanks all, no particular car in mind, just wondering atm
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It's a whole mess of factors, between the overpressure spring, the torsion bar stiffness, the orifice/venturi and the shuttle spring. The only thing that's easy to adjust is the overpressure spring.
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Jun 11, 2022 21:33:16 GMT
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Thinking whilst typing:
First idea: Presumably the more modern electric power steering pumps have a similar valve setup- but perhaps a small modern car doesn’t require the same pressure in the system, so if you ditched the mechanical pump on your retro car and plumbed in an electric pump from a small modern car, perhaps it would result in less power assistance?
Second idea: various Mercs (and no doubt others) used to have adjustable power steering, with what basically looked like a dimmer switch on the dash to adjust the level of assistance. Could that pump/valve/however it works be integrated into a different car I wonder?
Cheers
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Jun 12, 2022 21:58:39 GMT
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Peugeot 106s/Citroen Saxos have electric power steering pumps that pressurise a regular hydraulic rack. Run at about 80 bar which is lower than a lot of newer stuff that runs 120-130. Might be worth a look.
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