ChargerBill

Has anyone installed an electric power steering pump?

Electric power steering pumps aren't all that common yet, thus few models of vehicles come with an electrical power steering pump from the factory. One car that does use an electric power steering pump is the second generation Toyota MR2. These cars utilize a power steering pump that consists of a 12 volt motor and hydraulic pump head in one self-contained unit.
Also in the power steering system is a small reservoir which holds about a pint of fluid.
The following is some info about the electrical side of the new power steering system. The MR2 pump head runs off of the 12 volt system. However, it is no small load to the electrical system as it can pull up to 75-80 amps @ 12 volts when the steering wheel is turned close to a stop. It of course pulls less power when the wheel is centered because mechanical load on the pump is reduced. To handle the switching of this load I had to use a heavy duty relay. The relay I ended up using is a 75 amp power relay made by Bosch. this relay is triggered by the ignition switch, so the pump runs anytime the Jeep is on. Also, I used an 80 amp, automatically-resetting circuit breaker as the means of circuit protection for the pump.
I get a lot of questions regarding the specific parts I used to control my electro-hydraulic power steering pump. To clarify, the power steering pump is controlled either full on or off by a power relay and its circuit is protected by a high-current circuit breaker.

The relay I used is pictured above. It is a SPST (Single Pole, Single Throw) relay with 75-Amp rated contacts and a 12-volt coil. The manufacturer is Bosch and the part number is 0 332 002 156. Note that this relay has integral parallel and series diodes to help control the voltage spikes from shutting off the pump motor. A relay without integral diodes could've been used, but would have required the installation of at least one external "freewheeling" diode to prolong the life of the relay.

The circuit breaker is part of the HI-AMP line manufactured by Buss. It is an 80-Amp rated, self-resetting circuit breaker, Buss part number 181080F. I feel that it is important to have a self-resetting breaker in this application because sudden and prolonged loss of power steering could create a safety hazard if you aren't expecting it. The self-resetting breaker helps to avoid this situation because it will attempt to reset even if the output is shorted... and while this could create problems in itself, I belive this would be the lesser of two evils.
As a final convenience I used a small gray type Anderson connector to connect the wires coming out of the pump head to the pump relay. I found this was a smart idea because I can now easily connect/disconnect the pump (of course!)

As a last note, the MR2 Power steering pump has an extra four-wire wiring harness coming out of it. This harness originally connected to a computer on the MR2 which varied the speed (through Pulse Width Modulation) of the pump in relation to the vehicle speed. This makes sense because the pump really never needs to run at full speed while the vehicle is moving since once the tires are rolling, less force is required to steer. At this time I haven't connected these wires to anything, but in the future I plan to make a PWM controller circuit for the pump.

Link details below:
http://driveev.com/jeepev/convpgs/psteer.php

peterc005

Interesting. Subscribed.

oil pan 4

iTrader: (1)

http://ecomodder.com/wiki/index.php/...teering_delete

There are links to pump clutch pullies at the bottem of the page.

The P/S is costing you at least 2hp.

I think the simplest way to do it would be clutch it.

ChargerBill

Very cool!

ibmtech

iTrader: (1)

Even though I kinda think that is a neat idea, What would be the major advantage of it except for performance, and what would it cost to replace if something went wrong.. ?

ChargerBill

I just think it's cool...

Z28ricer

iTrader: (2)

2HP ?

Give up a bunch of money, and nearly all of your electrical power for 2HP ?

80A is no sneeze, i'd at the VERY minimum be running a 140A alternator with that.

How many HP in parasitic drag is it for an alternator to produce 80A ?

ChargerBill

Interesting that the Toyota MR2 has a 90 amp alternator.
Guess it shouldn't work eitheir...



www.autozone.com
Part Number:13238Weight:12.0 lbs Warranty:Limited Lifetime
Notes:90 Amp alternator* Power steering *

ibmtech

iTrader: (1)

I never new it existed.. A little before it's time with a different outlook on life. About what year was that Toyota ?

ChargerBill

3rd line down on the first post.