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Default Power Steering using Toyota MR2 EHPS pump

Many EV conversions have to deal with Power Steering decision. If you decided to keep PS and looking how to drive PS pump, consider this all-in-one solution brought to you by Toyota engineers. Toyota MR2 has EHPS ( Electric Hydraulic Power Steering ) in which pump is driven by its own electric motor instead of pulley hanging off the main engine like most ICE cars do. First generation of MR2 had separate fluid tank, motor/pump assembly and controller, some EVers took motor/pump and wired it directly to 12V or via various switching circuits designed to keep the pump off while driving straight or at high speed to save power.

However, 3rd generation of MR2 also called Spyder has a single pump assembly combining motor, pump, fluid tank and controller, making it very attractive option for EV community.

To the best of my knowledge you are looking for 2000-2005 ( maybe some other years, I'm not sure ) EHPS pump from Toyota MR2 Spyder, call your local junk yards or check this one online http://car-part.com . The pump looks like this:

DSC_2071.jpg

To wire it use schematics below. If you don't have proper harnesses you can either solder directly or create your own connectors for each pin. I personally created connectors and then filled harnesses with caulk to keep wires in place. It can be removed later if needed.

PS_Pump_1.jpg PS_Pump_2.jpg

Although 50 Amp relay is stated, I couldn't find one so I used typical 40 Amp automotive relay, my testing shows that it doesn't actually reach 50 Amp current anyway.

You can wire VSS signal from your car to make the pump turn itself off at higher speeds, but I couldn't manage that because my Miata has unusual VSS signal. Even without VSS, the pump runs idle at 4 Amps until you actually turn the steering wheel, so the power wasted is very minimal.

You'd have to find a way to connect PS Pressure line from the pump to your car's rack and return line from the rack back to the pump. Return line is easy, just use 3/8 hose and clamps. As for pressure line, if you are lucky you can fit one from other Toyota models, if not, you can make custom one from separately purchased fittings and the pressure hose, I have seen those on Ebay and online shops like this one http://www.summitracing.com/

Hope this helps, feel free to update this Wiki with more details, my main goal was to publish schematics and wiring, I am not very good with hydraulics, maybe someone can add details on making custom pressure hose.

Here are the Toyota part#'s for the electrical Connectors: These part#'s get the Plastic part only, The metal pin wiring parts are sold separately. Maybe someone can add the part#'s for those.
Part#'s Large connector 90980-12068
Middle connector 90980-10897
Small end connector 90980-10942

There are two part numbers for the wiring. They come with the plugs, rubber seals, & about 6 inches of wire. At $6.55/ea they aren't cheap for what you get, but they are made to fit.

Three pigtails for the small & middle connectors P/N: 82998-12440
Two pigtails for the large connector P/N: 82998-12500



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Contributors: BWH, dimitri, slimdigits, Thaniel
Created by dimitri, 08-27-2008 at 11:42 AM
Last edited by BWH, 10-31-2010 at 08:13 AM
65 Comments , 114065 Views
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Old 09-02-2008, 09:26 AM
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Default Re: Power Steering using Toyota MR2 EHPS pump

Very nice, dimitri!
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Old 09-08-2008, 06:01 PM
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Default Re: Power Steering using Toyota MR2 EHPS pump

Very nice indeed!

How does this work out of you? How much power do you think it actually draws?
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Old 09-12-2008, 02:03 AM
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Default Re: Power Steering using Toyota MR2 EHPS pump

Whooah! that was awesome man!!!
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Old 09-12-2008, 08:22 AM
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Default Re: Power Steering using Toyota MR2 EHPS pump

Thank you gentlmen.

Very helpful information!
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Old 09-26-2008, 06:42 PM
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Default Re: Power Steering using Toyota MR2 EHPS pump

Dimitri,

While hooking up my pump I found a small yet important mistake in your diagram. The ground that feeds the relay from pin five on the middle plug (pump) is actually the bottom left pin instead of the bottom right. The pin that you indicate is actually pin 8.

Thanks for the great work!!




Ben in SC
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Old 09-26-2008, 07:00 PM
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Default Re: Power Steering using Toyota MR2 EHPS pump

Ben,

look at original pinout from Toyota on the other picture, pin 5 is under pin 1, and pin 8 is diagonal from 1. My wiring diagram is a mirror image because I am showing harness on the pump, not the connector, but still 5 is under 1.

And I don't think my pump would be working if I had it wrong...
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Old 09-26-2008, 07:19 PM
TelnetManta TelnetManta is offline
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Default Re: Power Steering using Toyota MR2 EHPS pump

You're right about the pin numbers. My mistake. But, I have ground on pin 8, 5 doesnt give me any connectivity to ground. I dunno but thats how mines working and thought I would point it out for other.

Still just awesome work, Dimitri.


Ben
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Old 09-27-2008, 06:02 AM
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Default Re: Power Steering using Toyota MR2 EHPS pump

Ben,

you missed the point of this connection, its not supposed to be ground, its a control line from controller to relay. If it was ground then relay would be always on, then you don't even need the relay, just apply power constantly.

Using this line controller has ability to shut off power to the motor completely by raising this line, for whatever reason ( protection, overheat, speed signal, etc. ). Under normal condition and during the start this line is low, which allows relay to trip. If you are checking continuity by ohmmeter, do not expect this line to be ground, its not supposed to be.

Just try and connect everything as it states on diagram, I promise that relay will trip and pump will spin.
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Old 09-27-2008, 09:21 AM
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Default Re: Power Steering using Toyota MR2 EHPS pump

Okay, I guess I really need some help. Hope your around this morning.

I hooked everything up per your drawing (assuming I understand the relay symbols) and I cant get it to work.

Heres a breakdown:

Relay pin 85 to 12V
Relay Pin 86 to pump pin 5
Relay Pin 87 to 12V
Relay Pin 30 to pump Pin1 (next to gnd)

Pump pin 5 to switched 12V
Pump pin 2 to ground



Am I anywhere close? It seems that I never get the relay to close with the relay switch side ground connected to pin 5. I'm hoping that I have something wrong. As I mentioned earlier, and I understand what I was doing wrong, I can get the relay to close by connecting to pin 8 as it is directly tied to ground.


Thanks!!!
Ben
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