Toyota MR-S Electric power steering pump conversion
To make space for the Rotrex I needed to ditch the PS pump. I tried driving the car without PS by just looping the lines but didn’t like it at all. 225 R888 and agressive wheel alignment is too much drama without the aid of PS and simply ruined the driving experience both on the road and track. I’m sure it would be a little better by doing a proper depowering but PS is needed imho.
The solution for my misery is electric power steering pump, or a Electro-Hydraulic Power Steering, since we are still pumping fluid into the hydraulic steering rack.
I did some research on the interwebs and found the MR2 pump to be popular in the EV community.
The 3rd-gen MR-S pump is especially desirable as it got the reservoir, control unit and pump in one compact unit complete with rubber mounts.
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</div><div class="separator" style="clear: both; text-align: left;">I got almost all my info from this page: http://www.diyelectriccar.com/forums/showthread.php/power-steering-using-toyota-mr2-ehps-19505.html </div><div class="separator" style="clear: both; text-align: left;">You need to register to see pics. In case the pics or info disappears I’ll host them on my Picasa account as well:</div><div class="separator" style="clear: both; text-align: center;">
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I was afraid the long lines would affect flow/pressure but it worked out fine. I reused the stock trans cooler.
For the pressure line I initially wanted to use AN braided lines and fittings but read something about the pump pressure spikes of 1000psi.
I ended up using a super heavy duty hydraulic 10mm ID hose from the local Tess with steel 10x10 banjo bolts and hydraulic fittings good for 5K psi. Would AN work ? Probably, but this was actually cheaper and the SS lines had a rubber lining which meant better protection for other parts. Routing the lines and wires took ages. For return line I used plain rubber fuel line hose.
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</div><div class="separator" style="clear: both; text-align: left;">Wiring up the pump was easy with the available schematics. I used a 40 amp relay kit from Summit meant for fuel pumps complete with relay and a circuit breaker. </div><div class="separator" style="clear: both; text-align: left;">I also run a wire from the VSS signal of the ECU to the VSS terminal on the controller.</div><div class="separator" style="clear: both; text-align: left;">This seems to work very well. I can hear the pump goes idle when the car goes past ~ 10km/t and the steering PS input is a lot less at speed.</div><div class="separator" style="clear: both; text-align: left;">The pump has internal sensors that detects steering input via pressure so there is no need for steering rack sensors as used on the older MR2 mk 1/2. It will also work without VSS signal but will user a longer time to idle down when you stop and goes into speed. </div>
If I should do it again I would have used thicker lines as I can feel some hesitation in extreme steering action on autox events. The diameter I used are the same as stock MR-S but those lines are probably less than 50cm. The whole kit ended up costing quite a lot as I needed to buy a new reservoar and also bought the plugs and pigtails new from Toyota. A Opel guy told me that newer Open Corsa or similar has a neat little EHPS pump that shuld fit even better.
I friend of mine managed to mount the pump on his 400whp NBFL down low in front/under the generator with some complicated bracketeering. Check out his thread on mt.net for details: http://www.miataturbo.net/showpost.php?p=714835&postcount=132
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