Honda / Acura K20a K24a Engine Forum banner

1 - 20 of 58 Posts

·
Registered
Joined
·
71 Posts
Discussion Starter #1
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.
 
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.
 

·
Registered
Joined
·
15,818 Posts
Thanks for posting that information.

On a unrelated subject have you heard any rumors about a self programming ECU that keeps looping till it calibrates itself? Is that even possible?

Thanks for any info,

Nikos
 

·
Registered
Joined
·
71 Posts
Discussion Starter #3
nikos said:
On a unrelated subject have you heard any rumors about a self programming ECU that keeps looping till it calibrates itself? Is that even possible?
No, have no heard rumours but then I try to stay away from sources of rumour. What is a 'self programming' ECU? Possibly something which uses feedback from the o2 to alter the fuel tables. Many after market ECUs do this.
 

·
GoldStar
Joined
·
2,657 Posts
Hey Rubber Chicken. I was out of the country for awhile and to totally missed this thread. I was hoping there was someway I could see those pictures of your electric hydraulic p/s pump. I am very interested in this conversion.
I tried your link with no success.
 

·
Registered
Joined
·
71 Posts
Discussion Starter #7
Ok, put the photos back for you.

Since the initial post I have road tested the car a couple of times and raced it at California Speedway. I adjusted the pressure down until I got a good steering feel at speed and I must say that this steering setup feels as good or better than the engine driven pump I used to run, but does not have to 5+ hp power loss from the pump.

The pump is noisy but on a street car you could mount it on rubber down low near the front of the car. This is where toyota mounted the pump for the MR2.

Edit: The pump runs fairly cool and may not need the cooler in the front.
 

·
Registered
Joined
·
285 Posts
Thanks for putting the pics back up :thumbsup:

i think i might try that. wouldnt the (engine driven) pump only use lots of power while turning though? so, the gains are really higher than ~5hp?
 

·
Registered
Joined
·
5 Posts
digging this up from the dead, but what relay are you guys using for this??? I used a starter relay and keep killing it. The pupmp works great, but I only get about 20 minutes drive time before my relay craps out on me.

Thanks.........
 

·
Registered
Joined
·
27 Posts
bump :up:

edit: HOW loud is it? I'm wondering if this is a viable option for a daily driver. I'd really like to do something else than what everyone else is doing, lol. besides, I don't want to notch my hood. :rolleyes:
 

·
Registered
Joined
·
1,810 Posts
Agreed, I'd love to do this. I think if you mounted it to the framerail or somewhere away from the firewall with rubber behind the mount it wouldn't be so loud, you have to remember these units ARE used in OEM cars.
 

·
Registered
Joined
·
27 Posts
haha, yeah, that's true. But not OUR OEM cars :silly:

I plan on spraying the entire inside of my car with sound deadening, and the front clip too, inside the engine bay. I'm thinking that should help with noise/heat.

Did you find the motor for the EHPS by itself? or was it still attached to the car. Wondering where I might be able to find those grommets when I'm ready. Maybe just use some rubber template :confused:
 

·
Registered
Joined
·
146 Posts
Would this eliminate the squeeking steering rack in a ep?I'm kinda confused by this post.
 

·
Registered
Joined
·
31 Posts
rsx664 said:
digging this up from the dead, but what relay are you guys using for this??? I used a starter relay and keep killing it.
Interested in the what amp relay to use. I'm collecting the parts for this and want to do it right the first time (car's my DD)...
 

·
Registered
Joined
·
289 Posts
makibaka said:
Interested in the what amp relay to use. I'm collecting the parts for this and want to do it right the first time (car's my DD)...
Doing this swap too... and for a daily driver.
I just got the same pump from a yard this weekend and plan on doing this myself; and yes, I would like to know what the best relay to use is too? If not, I'll come up with something, but if anyone knows, that would be greatly appreciated!
 

·
Registered
Joined
·
54 Posts
I've been using this setup for a few weeks now. It really is easy to install - once you get the right hi pressure line made up. Best relay to use is the one that comes with the pump.

Mine feels a bit over assisted at the moment but unsure how to adjust it - I've played with the screw at the bottom but doesnt seem to make much difference.

Anyone have any ideas?
 

·
Registered
Joined
·
289 Posts
What does the relay(s) look like from the original? When I had the MR2 PS taken out, I saw 2 black boxes near the unit, are these the ones you are talking about? There were lots of wires going to them and routing into the interior too.

Pictures if you got em, would be awesome!

Otherwise, I was thinking that some type of high powered relay would work, along with a switch to turn it off whenever you like.
 
1 - 20 of 58 Posts
Top