lighter power steering?

[CamperVanBeethoven]

Thinking about Robbie's suggestion........................................
If I was designing a pump I would incorporate some sort of pressure bypass valve to prevent excess pressure blowing the seals out. Like if you were spinning the pump abnormally fast by redlining a petrol engine due to a stuck throttle.
So, by putting a larger pulley on the steering pump you might be asking for trouble.
Discuss.

If I was designing said pump I'd make it give adequate flow at way below normal idle (say, 500 rpm) and have a max design spec of, say 10,000 rpm (way past what a normal engine would rev).

[knighty1981]

aren't most (almost all) hydraulic pumps constant flow pumps ?

so they shift the same amount of oil per rev no matter what ?
(as long as you're not overloading it, it's not worn out etc.)

what makes the pressure is the restriction you have on the output / at the end of the output hose / the piston at the end of that hose / whatever ?

[CamperVanBeethoven]

aren't most (almost all) hydraulic pumps constant flow pumps ?

so they shift the same amount of oil per rev no matter what ?
(as long as you're not overloading it, it's not worn out etc.)

what makes the pressure is the restriction you have on the output / at the end of the output hose / the piston at the end of that hose / whatever ?

Dunno, I am no expert, I was just thinking from the design point of an engineer given the brief ... 'make this pump as cheap to manufacture as possible given reasonable parameters and to work on both diesel and petrol engines'

[knighty1981]

wasn't really directed at you, more the posts about pressure

as long as the pump is working ok, it should be good for loads more pressure than power steering needs ?

[CamperVanBeethoven]

How hard is it to fit power steering to a Mk5 anyway? I guess all I need are:

- Pump
- Hoses
- PS fluid reservoir
- Suitable steering rack
- Bigger serpentine belt

[robbie.cee]

If it helps i retro fitted a saxo electric pas pump to my old mk5 and used 10mm compression fitting from plumbers merchant to join the 2 steel high pressure hoses.
Worked a treat cos i destroyed pas bracket drag racing and liked the extra horses i got from not driving the pump hence went electric.
Had a kill switch (due to annoying squeek from the motor) so i could drive with pas off and turned on for manoeuvres when needed.

[Luke]

yeah most pumps will have an internal pressure relief valve so the pump builds up to a set pressure then as it spins faster all that happens is it bypasses more fluid internally and keeps the same pressure

if you adjusted the pressure relief valve (if its possible i have no idea) then you would in theory have lighter steering but at a higher pressure it may leak easier etc.

[Aardvark]

So my theoretical design including an internal bypass valve could be sound. I've never opened one up to see what is inside. So Luke's comment does make sense. Screw around with that valve at your own risk.

[Luke]

Screw around with that valve at your own risk.

yeah thats the idea

[Jim Archer]

aren't most (almost all) hydraulic pumps constant flow pumps ?

so they shift the same amount of oil per rev no matter what ?
(as long as you're not overloading it, it's not worn out etc.)

what makes the pressure is the restriction you have on the output / at the end of the output hose / the piston at the end of that hose / whatever ?

They are positive displacement, so the thing that controls the flow is how fast the pump is operating. The pressure is governed internally by way of a blow-off relief valve, the flow then by hose diameter and size of rack piston/displacement.

Spinning the pump faster or slower won't change the operating pressure of the system - unless slower means the flow drops below that required to maintain the pressure in the system. Or faster means the pump intake becomes 'orifice restricted' - the hole is too small to flow the required amount.

To change the 'weight' at the wheel you either raise the system pressure, or fit a rack with bigger diameter piston with a pump that can cope with the flow requirements.

Jim

[vanfox]

In addition to your list of parts:

- Pump
Mounting bracket and bolts.
- Hoses
- PS fluid reservoir * and mounting bracket*
- Suitable steering rack *and bolts*
PAS belt is separate and check you have a dual belt engine pulley.

- Bigger serpentine belt. No.