rexpontius

Hi all,

I love my 86.5 but one thing I would really like is a little more power steering assist. Like most 928s I have driven, my 928 has pretty heavy steering (despite the narrow 205 front tires I have on it now, it's even worse with the 225s).

This makes it feel like a heavy car which is not really the case.

So I looked around the internet and found that similar ZF steering pumps are used in many cars amongst BMWs, MBs and also Alfa Romeos.

These pumps have similar dimensions but run higher pressures (100-120 bar).

So I was wondering if anyone tried to fit a pump with more pressure to a 928?

I have two weeks holidays now, so I could go to a breakers yard and get a pump for little money and try to fit it.

But of course I am interested to know if anyone else ever tried it and what the results where.

Cheers

Hilton

What offset are your front wheels? Lower than stock offsets makes the steering heavier in my experience.

The later 928's (91 onwards from memory) have a higher pressure pump too, and lost the restrictor on the pressure line. However they also have a slightly different rack, so not sure about just swapping on a higher pressure pump without changing other bits.

rexpontius

I have ET55 (summer) and ET60 (winter) wheels, so well within OK range. Both steer heavy though :-)

I guess I will just try another pump and see what happens :-)

The Fixer

I removed the power assist altogether in my '83 and once
the fluid is removed it steers with little effort.

It finally feels like a Porsche to me now.

I love it without power assist and would never put it back.

rexpontius

Each to his own off course, but I would really like to have it with power steering :-) I use it as a comfortable cruiser not as a hardcore sportscar.

Chuck Schreiber

Put higher bar pump on my 79, lightened it up a bit around town.
No difference at cruising speed.

rexpontius

That is exactly what I would be looking for, lighter steering around town, but stil enough 'feel' on the highway.

What pressure pump did you mount?

Jerry Feather

I found a guy some time ago who is/was rebuilding the basic 75 BAR pumps to put out about 110 or 120, don't remember which. The price wasn't too high as I recall; and I think his name was Griffiths or similar. I also seem to recall that he had felt insulted in some way so he quit participating in this forum. I can't remember how I found him, but it might have been on eBay.

Yes, I know -- a lot of CRS here.

rexpontius

I think it should be pretty easy to make the original pump put out more pressure, as I understand it is just a spring/ball operated pressure relief valve.

But these ZF pumps look very similar so I will check if another pump fits, so I do not risk damaging my original pump.

Will keep you guys posted :-)

Chuck Schreiber

Been a while since I did it. IIRC, stock was 85bar. I went with a 100bar which at the time Griffiths sold.

As others said above, it sounds like you could have someone build one to 100bar spec. In that case, I'd grab a used one from Mark Anderson and take it to be rebuilt, that way you have minimal downtime.

littleball_s4

I had the same urge some years ago. After some track days and use, I think my arms are stronger and I don't need lighter steering anymore.

Anyhow, the way I understand power steering, the crucial part to make it lighter is inside the rack, the servo-valve.

The higher the pressure, the more the maximum force the steering will give you. But you never use maximum force everyday. You don't need maximum force, you need more force sooner.

The restrictor increase the effort when you try to move the steer really fast. Not the right part to solve the problem, either. I think the part to tweak/rebuild/replace/investigate is the rack.

rexpontius

Hmm you make me doubt to put on the higher pressure pump.. I guess I should consider upgrading to a GTS rack as well...?

Thanks

terry gt

91 and up different rack and pump

Randy V

You can increase PS assist by replacing the high pressure line with a larger diameter size and remove the in-line restrictor while at it.

Any hydraulic hose specialty shop can reuse the end fittings and build you a new line.

I did this on my previous 1979 convertible 928 and the improvement was quite apparent.

waynestrutt

Is it volume or pressure to make the steering lighter? A larger hose would allow more volume but lower the pressure.What about a smaller pulley on the pump? I am presently trying to rebuild mine but cannot find a puller to remove the pulley. Does anyone know where I can obtain one?