This is from my website http://www.hondata.com/racecar/ps.htm
Electro-Hydraulic Power Steering conversion
This outlines a swap which I have performed which uses an electric motor to drive a hydraulic pump to provide pressure for a conventional power steering rack.
The reasoning behind this swap is to reduce the power loss from the power steering pump. On an engine dyno we measured the stock DC5 ps pump and rack using 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.
The reasoning behind the necessity for power steering at all is that simply put it is faster around a race track than manual steering. A high powered front wheel drive with a lot of castor benefits from reduced driver fatigue, a much better rack ratio and more precise steering.
Note that this form of electric power steering is not the same as EPS, as used in the S2000 and EP3 Civic, which used an electric motor directly on the steering rack, with no fluid involved.
Disclaimer
This information is provided in case someone is interested is performing the same swap as me. I have not tried the vehicle at race speed as yet, but every indication is that it will work. If you do want to perform the swap, all the information I have is on this page - don't hassle me for any more. 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. At first I tried a motor/pump from a late model Mazda 3, but found that the motor used was a stepper motor with integrated control electronics, and the adaptation of the electronics was beyond my timeframe. Next I tried a motor/pump from an early 90s MR2, which used old technology (brushed DC motor, vane oil pump) which was perfect. These are available for around $100 used.
The pump has a pressure adjustment screw, so matching the pressure to the rack requirements should be possible.
Hydraulics
The hydraulics was 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. Fortunately 8mm is very close to 5/16 and 10mm is very close to 3/8, but then size mismatch was a problem. In the end I flared 5/16 stainless hose to 3/8 on the motor outlet end, then put an inverse flare on it and used a Honda 16mm nut from another ps rack.
The pump suction side used a hose fitting which was identical size to the Honda fluid reservoir, so connecting the two was a matter of finding a hose with the necessary convolutions. In the end I joined two hoses.
The rack return line was a 16mm thread with a 10mm line. I used the original Honda 16mm nut and 3/8 aluminum hard line, running the line to an aluminum cooler in the front of the car and then back to the fluid reservoir.
After a lot of bending and flaring I put some fluid in and powered the pump on. After two bottles of fluid and working the steering 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 thick wires in one connector - one red and one black. The only trick is to remember that the pump draws a lot of current (allow for 60 amps), so you need heavy duty wiring. Fortunately with high powered car stereos being common, all the parts of commonly available. I used 8 gauge wire with a 80 amp circuit breaker but for a street car you would need to also use a high power relay to switch the motor on after then engine is started.
The pump draws 15A with no steering input, and 30-50A when turning the wheel quickly.
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Acid Test
It works pretty well parking, but we'll have to wait until the first race test to see if this project was successful. The pump is fairly noisy, but this is not a problem in a race car.
Photos
Electric motor and pump.
![Image]()
Top view of pump with fluid reservoir.
![Image]()
Power steering oil cooler.
![Image]()
Update 1 : Wired the pump properly with 8 gauge wire and a circuit breaker. The pump is very loud. Could be because I mounted the pump to the wirewall with no rubber.
Update 2: Road tested. The steering feeling is good. The pump is about as loud as the engine when cruising. Tried with success to vary the pressure via the adjustment screw in the pump. The motor nor pump did not get hot - the cooler might not be necessary.
Electro-Hydraulic Power Steering conversion
This outlines a swap which I have performed which uses an electric motor to drive a hydraulic pump to provide pressure for a conventional power steering rack.
The reasoning behind this swap is to reduce the power loss from the power steering pump. On an engine dyno we measured the stock DC5 ps pump and rack using 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.
The reasoning behind the necessity for power steering at all is that simply put it is faster around a race track than manual steering. A high powered front wheel drive with a lot of castor benefits from reduced driver fatigue, a much better rack ratio and more precise steering.
Note that this form of electric power steering is not the same as EPS, as used in the S2000 and EP3 Civic, which used an electric motor directly on the steering rack, with no fluid involved.
Disclaimer
This information is provided in case someone is interested is performing the same swap as me. I have not tried the vehicle at race speed as yet, but every indication is that it will work. If you do want to perform the swap, all the information I have is on this page - don't hassle me for any more. 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. At first I tried a motor/pump from a late model Mazda 3, but found that the motor used was a stepper motor with integrated control electronics, and the adaptation of the electronics was beyond my timeframe. Next I tried a motor/pump from an early 90s MR2, which used old technology (brushed DC motor, vane oil pump) which was perfect. These are available for around $100 used.
The pump has a pressure adjustment screw, so matching the pressure to the rack requirements should be possible.
Hydraulics
The hydraulics was 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. Fortunately 8mm is very close to 5/16 and 10mm is very close to 3/8, but then size mismatch was a problem. In the end I flared 5/16 stainless hose to 3/8 on the motor outlet end, then put an inverse flare on it and used a Honda 16mm nut from another ps rack.
The pump suction side used a hose fitting which was identical size to the Honda fluid reservoir, so connecting the two was a matter of finding a hose with the necessary convolutions. In the end I joined two hoses.
The rack return line was a 16mm thread with a 10mm line. I used the original Honda 16mm nut and 3/8 aluminum hard line, running the line to an aluminum cooler in the front of the car and then back to the fluid reservoir.
After a lot of bending and flaring I put some fluid in and powered the pump on. After two bottles of fluid and working the steering 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 thick wires in one connector - one red and one black. The only trick is to remember that the pump draws a lot of current (allow for 60 amps), so you need heavy duty wiring. Fortunately with high powered car stereos being common, all the parts of commonly available. I used 8 gauge wire with a 80 amp circuit breaker but for a street car you would need to also use a high power relay to switch the motor on after then engine is started.
The pump draws 15A with no steering input, and 30-50A when turning the wheel quickly.
Â
Acid Test
It works pretty well parking, but we'll have to wait until the first race test to see if this project was successful. The pump is fairly noisy, but this is not a problem in a race car.
Photos
Electric motor and pump.
Top view of pump with fluid reservoir.
Power steering oil cooler.
Update 1 : Wired the pump properly with 8 gauge wire and a circuit breaker. The pump is very loud. Could be because I mounted the pump to the wirewall with no rubber.
Update 2: Road tested. The steering feeling is good. The pump is about as loud as the engine when cruising. Tried with success to vary the pressure via the adjustment screw in the pump. The motor nor pump did not get hot - the cooler might not be necessary.
