I'm not sure exactly how it works but it is undeniable to anyone who has driven a 928 without the PS pump belt installed. At cruising speeds - say 3000rpm plus there is no discernable difference without the PS. Conversely at parking speeds and low engine revs the effect of the PS is to make the steering wheel turnable as opposed to not.

All I can think (and I am not an hydraulic pump expert) is that the pump is designed for optimum pressure/flow at about 1000 engine rpm and that pressure/flow just reduce somehow above that. - Designed to deliberately cavitate at higher rpm ?

 

I will buy RPM sensitive and not speed sensitive as far as the assist.

I put power steering on my old hot rod Chevelle and it went from being ok to drive at triple digit speeds to being very twitchy, but you could turn it at parking lot speeds.

 

bigger steering wheel?

 

Excessive caster could be the cause of your heavy steering as well - I have very stiff steering due to well-out-of-spec caster, which is not an adjustable suspension setting. I've been told lots of reasons why this is (none of them convincing), and that I would have to rebuild the suspension to fix it.

Can any of you suspension gurus (or even the slightly-more-knowledgeable mortals among us) comment on this?

 

You can change the caster on a 928.

 

Ok Greg, I'll bite...

HOW??

 

By adjusting the eccentrics at the ball joint.
Part of every alignment on a 928.

 

Look at 44-4 in the WSM.
They have a good picture of them.

 

Gaz,

If your suspension won't adjust to where it's within spec, you may have bent or otherwise damaged parts. As Greg says, the suspension on the 928 is completely adjustable/tunable.

My initial answer to the OP was going to be 'step on the gas!' It gets real easy to steer in no time.

So to sum up:

For pre 1991 928s the only option for making your car easier to steer at parking lot speeds is either:

A) Hit the weight room or
B) Get a 100bar PS pump, and a 91+ steering rack (Porsche rebuilt rather than ZF?).

Is there anything else needed? (all hoses and fittings can handle the higher output or should they be upgraded as well?)

 

Well look at that! Thank you Greg!

The 928 owner/tracker/mechanic that told me that my camber was not adjustable has some 'splainin' to do!! Maybe the message from him was that it's at the limit of its adjustment? In any event, I'll have it redone and re-evaluate the steering.

 

Also Gaz,

I would recommend researching the effects of high caster, and low caster. I think you have it backwards.

 

Put more air in the front tires, run stock wheels with correct offsets and stock size tires (the avitar shows wheels near the fenders), you might also change pulley sizes for more low RPM assist....as noted run less caster.

 

The power steering reservoir in my '86.5 was empty, again, so I dumped a whole bottle of Lucas 'treacle' in there. Leakage has pretty much stopped, and I was surprised that the power steering assist improved, also.

 

Are you sure about that? I read up on the terms and the math here, and they say "If the caster is equal but too positive, the steering will be heavy and the steering wheel may kick when you hit a bump."

 

Does anybody have a later model rack they can take apart? I am thinking about moding my early rack to have a softer torshon spring. I can just take a wack at it, but I would love to have an example to work by. I'd love to able to drive the car at low speeds with one hand.