Electrohydraulic Power Steering

[t vago]

It works!

I had to modify the wiring a bit to accommodate the electrical parts I have on hand. The PS unit controls a normal 30 amp automotive relay, which then switches a Toyota PS solenoid relay. That controls 50 amp power to the PS unit.

It was a bit of fun to make the pressure hose from -6an braided stainless steel hose. I could use the return hose with no modification.

The steering feels normal when the PS unit is running, even with the engine turned off.

The system has been flushed of most of the old fluid, and has been bled. I still have to connect up the VSS signal. I will probably leave the IDUP and the EFI signals alone for now, since the engine computer should be able to compensate for an increase in electrical demand caused by the PS unit, and the PS unit powers up by itself.

[t vago]

Two more things of note:

You can find the Toyota FSM for the 2000 MR2 here -> Index of /car/Toyota/mr2 spyder/Repair Information/Repair Manual/05 - Diagnostics

For the Dodge, be sure to either reconnect the stock power steering pressure switch to its electrical connector, or jumper the two connector terminals together. Otherwise, the Dodge engine computer thinks the power steering is under load, and will throw a P0551 code with a CEL when you drive above 40 MPH.

[oil pan 4]

Well done.
I was thinking about using one of those but I was not sure if that P/S pump designed for a rack on a little car would work on a 3/4 ton chevy recirculating ball P/S system. Because I could find no pressure and flow numbers.
Does the Dakota P/S us recirculating ball or is it rack and pinion?

[t vago]

Originally Posted by oil pan 4

Well done.
I was thinking about using one of those but I was not sure if that P/S pump designed for a rack on a little car would work on a 3/4 ton chevy recirculating ball P/S system. Because I could find no pressure and flow numbers.
Does the Dakota P/S us recirculating ball or is it rack and pinion?

Thanks!

Forgot to mention that the power steering unit got installed into the Durango. I figured that, since we were travelling to Oiho in the Durango anyway to go visit family, and that I'd have a lot of time on my hands while there, and while the Durango has approximately the same engine as the Dakota, I might as well test the installation on the Durango.

I don't know exactly what the flow numbers are, but I can tell you that at idle, and with 16 fluid ounces of fluid in the reservoir, the pump will empty out its reservoir through the gear in about 3 seconds. That works out to approximately 2.5 gpm. I didn't really accurately measure the time, though, so YMMV. The MR2 manual states the pump should develop at least 711 psig at full lock. Other than that, there's not a whole lot of information on the intertubes about this pump.

Both the Dakota and the Durango use rack and pinion steering. I would think that your recirc ball setup would perhaps feel slightly sluggish with this pump. I know that the Durango occasionally has a slight amount of lag, usually when coming to a stop after decelerating. It may have something to do with the fact that the Durango (and the Dakota) outputs a VSS that is 8000 pulses per mile, and the the pump only expects 4000 pulses per mile.

[oil pan 4]

For recirculating ball 700psi is enough.
The hydraulic power unit I use is 2.4gpm at a maximum of 1,400psi.

[t vago]

I can also tell you this much, now: The pump puts out pressure in excess of the 1000 psig rating of the braided stainless pressure hose I fabbed up. The hose burst about 3 inches away from the pump outlet, and sprayed fluid all over the front of the engine. It occurred as my wife was negotiating a parking lot. Time to find a better hose...

[Xist]

Good luck!

[Ardent]

Made-To-Order Hydraulic Hose Assemblies

[t vago]

Originally Posted by Ardent

Made-To-Order Hydraulic Hose Assemblies

Funny you should mention that!

I had DiscountHydraulicHose.com fabricate a hose for me. It's a 3 foot length of 3/8 inch SAE 100R12 hose that's good for pressures up to 4000 psig, and temperatures up to 100 C. One end has a flareless compression fitting to tie into the existing tube, and the other end has a 3/8 JIC fitting which is compatible with the -6AN banjo adapter on the pump itself. It cost me a hair over $40, with shipping extra.

Ordered the hose Wednesday night, got it today, and installed it just now. The Durango power steering works again!

Now to go about making that Arduino-based adapter... I think I figured out how to pull diagnostic codes from the pump computer.

[Ardent]

Originally Posted by t vago

Funny you should mention that!

Ha!

Originally Posted by t vago

Now to go about making that Arduino-based adapter... I think I figured out how to pull diagnostic codes from the pump computer.

Do keep us informed.