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  1. #1
    4th Gen
    Join Date
    Dec 2008

    Electric-hydraulic power steering pump conversion

    Well due to the recent success with my electric power steering pump conversion, I figured I would finally do a write up.

    I must admit, I am Really happy with the results. The system works really well!

    Ill give a bit of background history first as to why I performed the conversion. Basically I was after a cleaner look in the bay and to reduce the amount of drag on the crank by removing rotation mass. A standard mechanical pump can reduce the amount of horsepowers you have by around 8hp or so in a straight line to around 15hp full lock. now these were pulled from research performed on a civic (iirc) and lets face it, preludes are not as lite as civics.But 8 HORSES!?! ID love to have those 8 or so extra horses, especially since i don't have the balancer shaft delete.

    The electic power steering system will take a whopping 0.5hp just through electrical load (+/- 1 hp). Now i call that a win. Don't you?

    Some details.
    The pump I used is a toyota MR2 spyder pump (2000+) You can use previous versions and also I have seen that quite a few people have used holden astra pumps as well. The Toyota pumps are a little more expensive but I went with them because they are a brushless (stepper?) motor, and they are one of the least electrically drawing pumps.
    Which brings me onto the electrical side of things.

    Standard prelude alternators are around the 90-95amp mark (4th gen, although I am using a 5th gen alternator in mine i believe and i think they are the same rating). It is hard to determine if the alternator is fine with it as I only have old (like 20+year old alternators) But it appears to be handling it ok at the moment. I will be able to clarify at a later date.
    The MR2 power steering pump runs off a 50 amp circuit in its natural environment.
    BUT - it has been seen to never reach near that. I'm currently running a 40amp relay and 40 amp fuse and it has never blown either.

    Electric Power steering pump. (in this case the mr2 spyder pump) roughly 300 for the one i used from the wreckers.
    Associated plugs. (make sure you get the three plugs that go into the pump with about 20cm of length for wiring)
    Modified high pressure line (I had my standard one modified at pirtec for like 60-80 dollarbucks from memory)
    Relay (in this case i used a 40amp Solid State Relay) ~$50 from jaycar
    Various Wiring (for the main line i used some car amplifier wiring with a inline 40 amp fuse and just some smaller wiring for the trigger)
    Fuses (as mentioned above I used a 40amp fuse and a 7.5amp for the trigger)
    Mounts ( I fabbed my own)
    Power steering fluid
    Some sort of plan as to where you are going to put the pump

    Optional Parts:
    Custom Cap ( I had to use one due to the positioning of the pump. Basically I'm silly and didn't confirm clearance with the skunk2 intake manifold)
    Standard reservoir (once again mostly due to my inability to measure and prepare. But it allowed me to run the standard ps cooler which i intended to from the start)

    Ok on to the steps

    Now first and foremost. Location location location.
    You've gotta sort out where you gonna place it yo.
    Due to my oh so perty bay -_-, I wanted mine in the most convenient of places (not convenient at all, I have have to fix the cap or check plugs or the pump, i have to take the intake off :/)
    BUT, that allowed me to simply have the high pressure line shortened and the new fitting crimped on. (note to all that want to ask about the sensor that is in the high pressure line, It is there just to tell the motor to increase RPM when turning if the RMP drops. So its not needed with the electro/hydraulic setup)

    Once you have decided where to place the pump, now its time to start creating some mounts. I would give you a detailed write up about mine, but it will be different for each setup. My mounts are made of mild steel ( i think). the front one is welded to the subfram and the other two are actually just bolted to standard bolt spots in the bay. Make sure you keep the rubber mounts that are in the pump already as they will reduce vibrations and I've also seen that they can help the pump be isolated from the rest of the car.

    Once you have the pump mounted and you are happy with its positioning, you can then either move onto the wiring or the plumbing. I personally went for the plumbing as it would allow me to test the pump once the wiring was in place.

    The plumbing.
    Ok so for this part there is a couple of things you need to keep in mind. Especially for 4th gens. I believe 5th gens will be pretty similar and I have heard that 3rd gens are as well. 4th gen racks have The main high pressure line in, then a return to the reservoir which then goes to the cooler and then returns to the rack. PLUS there is another return that comes out of the VSS unit on the gearbox (i believe it assist the steering at low speeds and lessens the strength at higher speeds). So this means that if you are to use the standard MR2 reservoir without a cooler, you will need to have a y piece fitting so you can then run a line from the return to reservoir to the lines that run into the VSS. If you are to use a cooler in the system, basically the same process except you will need to put a cooler in that line that runs from the y piece to the VSS.

    However, if you are to use the standard reservoir, It acts as the why piece. It has a return fitting into it already and a fitting for it to exit the reservoir to the cooler. BUT, you will need to create some sort of cap on top of the Pump (like I have) with a decent size fitting and line to allow the reservoir to supply the cap with enough fluid to keep it full at all times.

    If you wish to bypass the VSS, you can loop the lines but make sure you leave some fluid in it. Also if you wish to still have something controlling the strength of the power steering at higher speeds, the mr2 (and also many other pumps) have a speed input that allows the pump to control that itself. I have not got mine hooked up at the moment. but its running so good at the moment i dont know if i want to touch it. It is very possible i may want to in the future though. Only thing stopping me at the moment is the fact that I will need to get the correct voltages that the VSS puts out and what voltages the pump will look for to make sure they will be able to talk to each other (not hard, I'm just lazy).

    Now another thing to remember in turns of fluid and and plumbing (and i learned this one the hard way) Is pressure/air movement. Next time you are topping up your PS fluid or even just looking at the system yourself, Have a look at the lids for the reservoir. They are designed to allow for movement within the system. The mr2 cap has a diaphragm in it which moves with this pressure movement and the prelude cap has rings that run around the sealing area that have channels for air movement. The first setup I had did not incorporate this type of cap and essentially tried to create higher pressures in the lines/areas that were supposed to be low pressure which in turn forced leaks. And leaks are not fun no good as it allows the pump to suck air. But that was quickly sorted with the addition of the standard prelude reservoir.

    Now we can move onto wiring...yay.... haha I racked my brain for hours over this one. And then i started to think more simple and BOOM. It didnt turn out to be that hard. If you have done any sort of wiring before, you will be fine. The most useful diagram for this part is included in this write up. Basically its as simple as this. thick wire going into the relay (input) with a 40 amp fuse, thick wire going out (load/output) to the thick wire for the pump. Thin wire going into the relay with a 7.5amp fuse (input/trigger), thin wire coming out to the trigger for the pump. Ive run my wiring independently from the rest of the car so that in case the motor wont start or whatever, i can flick a switch and have easy seamless power steering while i push the car around haha (interesting logic i know). And the last wire is one that you can chose to run to the VSS or not. It should be a purple color for the mr2 pump from memory

    Once the wiring is complete, BOOM, you now have electro/hydraulic power steering. Feel free to flick the switch or turn the key depending on how you have it set up and be amazed at how many extra horses you have, and make sure that when you arrive to any meet or anyones house, you pop the bonnet to show off your amazing skills and super cool new PS system.

    enjoy folk.

    Apologies for not including pictures at this stage. My computer is not allowing me too. I will post some pics up very soon!!
    Last edited by 5h4d0w; 13th February 2016 at 07:31 PM.

  2. #2
    Junior Member Zane's Avatar
    5th Gen
    Join Date
    Dec 2015
    New South Wales
    Very interested to see pics! Thanks for the detailed thread

  3. #3
    PA Janitor Bob's Avatar
    3rd Gen
    Si 4WS - B Spec
    Join Date
    Jan 2006
    Western Australia
    Awesome. Added to the quick reference guide.

  4. #4
    4th Gen
    Join Date
    Dec 2008
    sorry guys. still trying to work on the pics. the site just doesn't like me

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