Need some help with electro-hydraulic power steering

[AtomicRooster]

Hello!

I just need some info from someone more knowledgeable. Obviously electro hydraulic PAS is your average PAS but with an electric pump rather than the one run off a pulley on the engine. With electric power steering you can adjust the assistance using a potentiometer, but am i right in assuming that if you were to adjust the electic pump speed on the hybrid systems you would get the same effect?

I want to run PAS on my Rover P6, the constantly running traditional version you get on p6's fitted with factory power steering is by all accounts completely lacking in any feel at all, therefore i want a modified version with adjustable assistance.

This is doable on a lot of classics using the fully electric Corsa B/C rack modified to fit to the rack of the car of choice, only thing is, on a P6, the rack is really close to the dash top, which is metal and welded into the car, and the corsa B & C steering motors are massive and i don't think it'd fit. That, and the internal rack is pretty short so i don't think id be able to fit it in.

Therefore, if i can use a V8 PAS box, and an electric pump with speed adjustment to adjust the assistance, then that would be winner. But i need to know of that'd work or not, if not, might have to fit a leccy motor somehow, or cope with no assistance adjustment.

Cheers all!

[Rich]

I have a feeling if you vary the power on the more simple ehpas pumps it will possibly just stall if it drops too low? I may be wrong. some cars may have variable ehpas fitted, maybe vauxhalls, but I imagine the pump will be harder to get to operate due to the control systems, whereas for example the saxo ehpas is just 2 big wires.

[usedabused]

To vary the power produced by the hydraulic power source you would use an adjustable flow regulator in the hydraulic lines.

[dickdasterdley]

Jul 25, 2014 7:43:44 GMT usedabused said:

To vary the power produced by the hydraulic power source you would use an adjustable flow regulator in the hydraulic lines.

This is the best way...you would use something like a needle valve and a tank return...dead easy!

[AtomicRooster]

So if i was to adjust the level of flow as described, would this lower the assistance?

If so, fabulous. I was going to use an electric pump anyway because my P6 is a 4cyl and its a pain in the back end to try and fit the pump drive, much easier to whack an electric saxo motor in there or similar.

[usedabused]

Just remember flow and pressure are completely different but by reducing flow you can slow things down without affecting pressure.

To be honest once you start combining different hydraulic systems the brain requirements can spiyrel out of control it might work it might not it depends on all sorts of things.

I'd concentrate on finding one system that will work as one rather than blending different systems together.....

[AtomicRooster]

The saxo motor is a tried and tested method with the 4cyl p6's, i just wanted to be able to alter the assistance level.

[mdh]

The editor of ppc mag did this in his v8 crapri with a Merc a class pump.

Iirc there's some sort of doohickey you can buy that senses your speed and adjusts the assistance accordingly.

[2woody]

adjusting it hydraulically isn't relly feasible I'm afraid.

you see, the pump has to be able to supply a "normal running pressure" and a higher "I'm moving the steering wheel" pressure and a super-high "I've reached full lock" pressure.

If you were to dump some of the pressure back to tank during normal running, then it would no longer be able to provide the higher pressures for steering movements.

conventional steering pumps have a flow-sensitive valve in them, capable of providing all of these pressures according to the flow being demanded of them

your best bet is to find a pump from another vehicle already outfitted to provide lower pressures.

also, check the rack high-presssure inlet to see if there's a separate feedback-reducing valve inserted