Electric Power steering <Toyota MR2 Pump>

[jjbmwm5]

I work at a company that makes custom power steering rack and pinion kits for just about any old hot rod worth having. Recently a customer asked me if I had any electronic power steering pumps and I said nope never really heard of any of them. Being that I am curious as all get out I found one and plan to do the swap on my Merkur. The information for the swap I found on a scion website for t/c's the guy who originally wrote this up did an excellent job.

SPECIAL PROJECTS MOTOR SPORTS
Electro-Hydraulic Power steering conversion:
This is not an original idea… Credit goes to Derek from Hondata who did the swap before me. I acknowledge many of his findings and quotes.

This outlines the adaptation and fitting of a Toyota MRII Electric Power Steering unit to our DC2 Integra Racecars. This system uses an electric motor to drive a hydraulic pump which in turn provides hydraulic pressure to the conventional Honda power steering rack. We have refined this swap and we will be producing a complete bolt on kit in the near future.

The reason for this swap is twofold: (A) to reduce the Horsepower drag from the engine driven power steering pump. On an engine Dyno the stock DC5 ps pump and rack uses 8.5 hp peak, while in a straight ahead position. On a lower powered B series the loss was 5 hp peak. The power loss from EHPS is between 0.25 and 0.75 hp (via the alternator), depending on steering load.
And (B) The reason I wanted the power steering at all is that after over thirty years of International Touring Car Racing, I have found it is faster around a race track than with manual steering. The lap times of a high powered front wheel drive racecar with a lot of castor, will improve if driver fatigue is reduced. Call it old age if you like, but I prefer to finish an event not feeling like I have just survived the fight of my life.
Note that this form of electric power steering is not the same as EPS, as used in the S2000 and EP3 Honda Civic, which used an electric motor directly on the steering rack, with no hydraulic fluid involved.

Disclaimer:
This information is provided for those interested in performing the same installation as me. I have tried the vehicle at race speed, it works, and I am completely happy with the results. If you do want to perform the swap, all the information I have is on this page – And will be provided in step by step detail with a purchased conversion kit. If you are not mechanically or electrically competent, then this swap is not for you.

The Conversion:
The main component is the motor/pump assembly. We used the motor/pump from an early ‘92-‘93 MR2, which used old technology (brushed DC motor, vane oil pump) which was perfect for our purpose. These are available for around $150-$200 used.
The pump has a pressure adjustment screw, so matching the pressure to the rack requirements is quite easy.
(See Pic. 5)
All you need:
1 - Good Used Toyota MRII Pump.
1 - High pressure hydraulic line with Dash - 6 female fittings on either end. 1 Straight and 1 90 degree bend.
1- Fabricated bracket to mount the pump.
1 - Dash -8 Low pressure fluid line with Dash -8 Female fittings on either end.
1 - 1/2” or Dash -8 Low pressure fluid line from Pump to reservoir.
2 - ½”to 3/4” Hose Clamps for low pressure line from Pump to reservoir.
1 - Fitting Dash -6 Male to 16mm x 1.5
1 - Fitting Dash -6 Male to 14mm x 1.5
1 - Fitting Dash -8 Male to 16mm x 1.5
1 - 80 AMP Circuit Breaker
8 Gauge wire. Soldering equipment and wire ends

Hydraulics:
After we had decided on the best place to locate the electric pump- We laser cut a stout 3/16” bracket that bolts under the Top Control Arm nuts on the top side of the Strut and allows the pump to be suspended alongside the strut tower. In our case as we are K-20 powered, the left side afforded the most room. However, with a B series engine, the right side will be better. (See Pic 1)
We then mounted an after market fluid reservoir on the fire wall taking care that the lowest point of the reservoir was above the electric pump. (See Pic. 2) The hydraulics is fairly straight forward. The pump outlet was a 16mm thread with a 10 mm hard line, and the steering rack was a 14mm thread with 8mm hard line. (See Pic 3)
Rather than use the hard line which was too hard to bend and shape, I went to a Hydraulic hose specialist and had a flexible high pressure hose made up with the correct fittings on either end. I used A -6 Male to 16mm x 1.5 adaptor into the high pressure Pump outlet, and a -6 Male to 14mm x 1.5 adaptor into the Steering Rack pressure outlet. I have fitted this system to both my US Spec. Integra and my JDM Right hand drive car, so make sure you double check your Fluid line lengths before you get them made up.
The pump suction side used a hose fitting which was identical size to the Honda fluid reservoir, so no problem finding some hydraulic low pressure hose for the Pump to the reservoir.
By holding the pump assembly in a vise, using a large Crescent Wrench you can carefully rotate the pressed in - low pressure hose fitting so it points at a 90 angle to the vertical pump when mounted, according to where you position your reservoir.(See Pic 3)
For the low pressure return line from the steering rack, I used a -8 Male to 16mm x1.5 adaptor. I made up a -8 braided hose with -8 Female fittings on each end to connect the low pressure Steering rack outlet to the -8 Male fitting on the inlet of the reservoir. (See Pic. 4)
As the complete systems fluid capacity is almost double that of the OEM Power Steering system, so far I have not found the need to run an oil cooler.
We filled the system with Motul fluid and powered up the pump. A little bit noisy… but hey, it is a race car. After two bottles of fluid and working the steering vigorously from left to right to bleed the system I was happy to see that none of the fittings had leaked.

Electrics:
The wiring of the pump was easy.
There are two sets of wires coming out of the pump. The lighter gauge wires & plug we discarded. I think they are something to do with turning the pump on after engine start up in the stock Toyota MRII configuration?
There are two thick wires in one connector - one red and one black. You must remember that the pump draws a lot of current (allow for 60 amps), so you need heavy duty wiring. All the parts are commonly available from most automotive electrical suppliers. We used 8 gauge wires with an 80 amp circuit breaker. We mounted the Circuit Breaker beside the shifter so it is within easy reach of the driver so if he wishes, he can turn it on and off, but for a street car you would probably need to also use a high power relay to switch the Steering pump motor on after the engine is started. I don’t want to get too carried away as my electronics knowledge is very basic…
The pump draws 15A with no steering input, and 30-50A when turning the wheel quickly.

The Test:
It worked pretty well driving around the yard and down the street. The real test would be at the track. So off to California Speedway for the SCCA Cal Club first round of Honda Cup January 27& 28 2007
So apart from telling lots of lies about the racing and how the older I get, the faster I was … All I can say is… Fantastic! It works beautifully, one of the most worthwhile modifications I have ever done! This will be a standard fixture in every one of my Race cars from now on."

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...so yeah. seems easy enough. just need an mr2 pump and some odds and ends. thinking about just using one of my high side outputs from my aem and a relay. just wondering if anyone has done this on a tc yet? also, im trying to find a good source on how to do an electric water pump conversion. so if anyone has any info on that, please speak up

[jjbmwm5]

pictures wont trans late here so here is the link
http://www.scionlife.com/forums/showthread.php?t=195962

[DPDISXR4Ti]

Interesting stuff. I'm quite sure nobody has tried this with a Merkur - looks like you get to go first!

Doing a quick search on eBay, it looks like '91 - '95 MR2 is all the same - this is the "newer" rounded body style - hard to believe that first came out over 20 years ago now, but I digress...

I hate using eBay links, but here's one that shows the pump and all the ancillary electronics...
http://www.ebay.com/itm/91-92-93-94-MR2 ... 22&vxp=mtr

But from the looks of your post above, when retrofitting to an alternate platform, a less "intelligent" approach is taken and the pump is just left running at all times and you skip the fancy-shmancy controls. On the stock factory configuration, it would appear that the pump can be throttled back or even shut off entirely when driving straight at highway speed. In fact, here's someone that adapted the factory stuff to an alternate platform, making it a more involved project...
http://www.evalbum.com/tech/mr2_powersteering.html

And here's someone who documented putting one into a RX7...
http://www.norotors.com/index.php?topic=9817.0

If you go ahead with this (and please do ), go ahead and start a project thread on it in the photo/project section.

[DSPXR4ti]

Well I think I'm going to try this also but first I'm going to check on the weight of both PS units and see if it's worth it. Thank you Brad for getting the year of the Mr2. going to check on all the parts today.

Ben

[DPDISXR4Ti]

Well I think I'm going to try this also but first I'm going to check on the weight of both PS units

I suspect the weight is a wash between the two. The benefit is in the reduced parasitic power draw.

[aviatorpa23]

" reduced parasitic power draw" Yep, Ya gotta watch them Parasites!!! Give them a few HP and they will try for more...... On a more serious note - some of the new car evaluations/wriite-ups say that "road feel" is lost with the electronics. Don't know, but I do like how the XR4TI translates the road conditions as manufactured!

[DPDISXR4Ti]

On a more serious note - some of the new car evaluations/wriite-ups say that "road feel" is lost with the electronics.

That's an entirely different type of steering system - no hydraulics involved. With the MR2 setup, you shouldn't notice much of a change at all - same steering rack and column driven by hydraulics - just a different means of powering the pump.

[DSPXR4ti]

On a more serious note - some of the new car evaluations/wriite-ups say that "road feel" is lost with the electronics.

That's an entirely different type of steering system - no hydraulics involved. With the MR2 setup, you shouldn't notice much of a change at all - same steering rack and column driven by hydraulics - just a different means of powering the pump.

And the mr2 power steering pump is adjustable, so maybe you'll get a better feel, thats what I'm hoping for and if it doesn't weigh less, I could mount it lower in the car then stock.

Ben

[Rocky's Wrench]

I'm pretty sure some whack job in Seth Efrica did this 40 odd years ago...



In this...

[Mike McCreight]

Ickcellent.
I heard "Seth Efrica" in the voice of my favourite international reporter!

[John Brennan]

So, we keep the leaky pump and hoses and add an electric motor and some gadgetry, to save... what, in terms of hp?

[Rocky's Wrench]

So, we keep the leaky pump and hoses and add an electric motor and some gadgetry, to save... what, in terms of hp?

Probably 2 or 3 HP, and the "added weight" is where these cars needed it, never mind
that the pump is constant pressure, no belt to throw/break. KISS principle at work...

[hEaT]

Probably 2 or 3 HP, and the "added weight" is where these cars needed it, never mind
that the pump is constant pressure, no belt to throw/break. KISS principle at work...

If we want KISS, manual steering all the way. Love mine (converted power rack).

I looked into this swap and when I was looking to ditch my belt-driven pump and the biggest headache was controlling pump pressure to not over-assist at speed. If you successful combat that, it's a great swap. Check forums for electric car conversions. This is really popular for them.

[jjbmwm5]

Gain over an older style pump is about hp 8-10 on a dyno from what I've read(-.75 hp under max load to alternator). I just had my company rebuild my Xr rack and I'am actually going to be using the Electric power steering pump from a 1995 mr2 that I sourced from a back woods junk yard. I have the comp and the related wiring for it I wanna make it work with pressure sensitive steering as well. This is probably going to take me awhile as I am redoing a couple of vehicles trying to make extra scratch for my wedding in May. The unit its self weighs about that of the original pump and bracket,possibly lighter, I plan to mount mine just to the right of where the stock pump would be. Also I am relocating my alternator to the ac side this all stems from some work Ive been doing with some kids a virginia tech for their electric Jetta they are making. I originally suggested the use an in line system my company makes but after researching this popped up and my merkur gears started churning.

[jjbmwm5]

Also not much of much of a danger of over assist with a pump that runs at 700 psi- 900 at lock