Electric power steering pump conversion

[oil pan 4]

I have been driving my 3/4 ton suburban around with no power steering for the last few days trying to get a feeling for it.
Its no fun especially in parking lots.

To get some help I am initially going to try to install a hydraulic power unit. These are about as cheap as trying to put a clutch on the Saginaw that may not even work.
They appear to weigh less than a cast iron pump and clutch.
They are also the same price or cheaper and easier to get than the OEM take off electric power steering pumps people like to repurpose for applications like this (old MR2 pumps).

Best part about the HPU compared to an automotive OEM take off, there are no proprietary hydraulic fittings. The HPUs will always use NPT or common straight threaded hydraulic fittings.

First go will be with a hydraulic power unit. They move about 1.3 to 1.5 GPM up to 2500psi. That is about half the flow of a Saginaw pump at idle.
Will it work? I don't know. I think its time to find out.
The HPU motor and pump are physically bigger than the electric power steering pumps pulled from Japanese cars. So if size matters then it should work to some degree.

Since I already know what happens when you feed a recirculating ball steering box 2,500 to 3,000 psi of unregulated pressure, so I am also going to get a pressure regulator.(The wrong pumps got sent to supply from the manufacture, with no built in regulator it blew a recirculating ball pump to pieces.)
The recirculating ball type steering box on the weapons load trucks I work on call for 850psi +/- 50psi or 875psi +/-25psi depending on which steering box it has. I figure that sub 900psi number is good starting point.
The 1.3gpm of that HPU should not be able to reach 2500psi with a relatively gigantic recirculating ball steering box attached to it but I would rather not find out the hard way.

If that doesn't work I will try something else.

Power steering delete - EcoModder
New wiki page:
http://ecomodder.com/wiki/index.php/...ic_conversions
Still working on it.

[oil pan 4]

I have a 12 volt hydraulic power unit rated for 1.3GPM and 2,500psi and a used 125 to 1,000psi hydraulic relief valve on their way.

[Ecky]

How hard would it be to retrofit an existing electric power steering rack? Seems silly to retain a system that uses fluid, if you can avoid it.

[oil pan 4]

I am not even going to try an electric rack.
Difficulty would be extreme. It would take a lot of money and time to get it working. Then it still may not even work correctly.
As far as I know all the OEMs are still sticking with hydraulic steering on heavy duty applications.
Most of the OEMs have had major recalls on their electric assist steering that they put in small cars.

Recirculating ball gives a greater mechanical advantage and is easier to maintain. This is why it is still found on trucks and utility vehicles.

Just because something is new does not always mean its better.

[spacemanspif]

Sorry if I missed it in your older threads but have you tried a lower ratio manual box out of a S10 or older car that came manual. I'm guessing that bolt pattern is the same on all boxes or that the frame can be drilled to accommodate. You'd probably have to reuse your old pitman arm since the suburban probably has different geometry than a smaller car but it may be manageable.

[oil pan 4]

There are manual steering boxes available for 9th generation 3/4 ton suburban and chevy/GMC trucks. I already located them. They are around $200.
I am trying to keep power steering for situations such as:
Driving off road
Fighting cross winds
Backing up a trailer
Driving on real uneven road
When my wife drives it

The manual boxes have ratios around 25:1 where power steering boxes have between 12 and 15 to 1.

[oil pan 4]

Looks like new toys will be arriving Monday.

I have read some more on some of the auto cross web sites where guys crank up the Saginaw P1 relief pressure to as high as 1,500psi.
They want smooth, responsive and easy steering. Being able to whip the steering wheel back and forth as easily as if the other end is stuck in a jar of mayo on a cloud and being able to turn it off or use it as much as I need is very tempting.
It just costs a lot. Realistically for a clutched pump, and big GPM hydraulic relief valve is $900. So that's why I am not likely going to do that.

[darcane]

Some electric assist uses an electric motor on the steering shaft under the dash. It's getting popular as a clean retrofit on classic cars.

$100 Power Steering? Yes you can. Use Column Electric Power Assist System (EPAS) ! - Ford Muscle Forums : Ford Muscle Cars Tech Forum

Then you would keep your steering box, have electric power assist, and no hydraulics.

[oil pan 4]

It takes so much force to turn that suburban steering wheel that I don't think simply installing an electric assist from a car would cut it.
Maybe if it would work if I had the manual box with roughly double the mechanical advantage.

[oil pan 4]

I got the hydraulic power unit in early.
The motor has disastrous duty cycle, up to 1 minute on 3 to 4 minutes off. Which sux.
The pump uses size -4 ORB, -4 SAE, -4 straight cut O-ring.
The power steering box should use 18x1.5mm O-ring sealed.
To connect the pump to the steering box I ordered an 18x1.5mm to -6AN adaptor and a -4 ORB to -6AN adaptor.