Honda Civic EPS conversion
 

I am working on converting my 2005 Honda Civic to EPS from the hydraulic assist that it came with. Unlike most people on this forum, my primary reason for doing this is performance and cleaning up the engine compartment more than gas mileage. I have been building this car for better performance mostly. Specs for my build will be posted soon. However, fuel efficiency was a reason to convert to EPS too.

Also, another reason that I am converting to EPS is so I don’t have to worry about getting power steering to work or getting compatible hydraulic hoses when I swap to a K20 or K24 engine in the future. So in a way, I am futureproofing for a K swap in the future.

So the first step was to find a used EPS system to install. I found an EPS rack and an EPS module from a 2004 Civic hybrid for a total of $90, which seems like a good price to me. I don’t have the wiring harness yet though.

I ended up installing the EPS rack anyways though. The install was pretty straightforward and easy except for one a couple of things: First problem is that I had no room to work with the D16Y8 intake manifold that I installed, so I had to remove the intake manifold to get it in. Second, I didn’t get the brackets that go with the new EPS rack, so it didn’t fit correctly. The passenger side of the rack had a random chunk of metal under the mounting hole, which kept the rack from sitting flat on the bracket. But once I chopped off the random chunk of metal, the rack bolted in perfectly just like the OEM rack. I will upload pictures when I get home.

However, if you choose to do this swap, I would suggest getting both brackets just in case. You could probably get away with just replacing the passenger side bracket, but I am not certain since I never tried it. For all I know, the rack might not sit straight if you replace only one bracket, so I would suggest getting them both just to be safe.

But other than that, the installation of the rack was easy. I used the OEM tie rod ends and the tie rods that came with the rack, but I am pretty sure that they are the same.

I still need to get an alignment since I aligned it by eye, but so far so good. The car drives fine with this rack. The steering is easier than it would be with the OEM rack when the assist isn’t workiing, but it is still pretty hard to turn since the electric assist isn’t connected yet.

So the last step is to connect the wiring. From my understanding all I need to connect is constant power, power when the key is on, RPM signal, VSS signal, and ground. It probably would be a good idea to connect it to the OBD also so it can be scanned for codes if there is a problem. Also, I have no idea why the control module would want an RPM signal since there is no pump running off the engine, but whatever.


So that’s where I am at right now. The rack is in, so I just need to find a wiring harness and connect it.

Anyways, that is what I am working on right now. If anyone has any questions, comments, or suggestions, feel free to post

You're not the first guy I've heard of, installing an EPS system to free up a few ponies for better performance. Decluttering the engine bay has got to be a plus, too.

What I had been seeing though was that for people looking for an off-the-shelf option, they were splicing in the business end of a Prius column to get the motor and rack. The Prius has some speed-sensitive hardware that it needs for proper function, but in a non-Prius install it defaults to a certain level of assistance so even when lobotomized it still works.

My experience in my HCH was there was a small range of deadness at the center of the steering where it gave no assistance, and beyond that it would suddenly jump in with added torque, causing a jolty ride if you weren't ready for it. I never dug into it much to try to adjust that out, I just got used to it.

Thank you. Just out of curiosity, does the EPS system work without the engine running? I know that it could, but I am not sure if it would since it needs an RPM signal.

I have heard the same thing that there is a little deadness at the center of the steering wheel, and as far as I know there is no way to adjust that. However, I have also heard that Honda updated the control module for the 2004 and 2005 models to help address that issue, although I am not sure if that is true. I do know that the part number for the control module is different though.

That is very interesting what you said about some people using a Prius steering column, that sounds like it could be a good option for someone looking to convert a car to EPS where there is no OEM option available. Another option would be an electric pump that only runs when needed, or installing a clutch on the belt driven pump so it only runs when needed. I thought about trying to find an electric pump, but I decided that it would be easier to install an OEM EPS system than to try to build something custom.

Thank you. Just out of curiosity, does the EPS system work without the engine running? I know that it could, but I am not sure if it would since it needs an RPM signal.

I have heard the same thing that there is a little deadness at the center of the steering wheel, and as far as I know there is no way to adjust that. However, I have also heard that Honda updated the control module for the 2004 and 2005 models to help address that issue, although I am not sure if that is true. I do know that the part number for the control module is different though.

That is very interesting what you said about some people using a Prius steering column, that sounds like it could be a good option for someone looking to convert a car to EPS where there is no OEM option available. Another option would be an electric pump that only runs when needed, or installing a clutch on the belt driven pump so it only runs when needed. I thought about trying to find an electric pump, but I decided that it would be easier to install an OEM EPS system than to try to build something custom.

Neat project! Following with interest.

The Civic Hybrid EPS is one of my least favorite EPS systems, but I imagine it to be the easiest swap. Insight and Fit EPS have much smaller dead zones and lighter steering, though I suppose that could have as much to do with the weight of the vehicles in question as anything.

I'm about to do a K swap in my Insight and I'll report back on how my EPS functions. From what I've gathered from others, K series tach signaling is different but EPS still works after the swap it's probably only used for some of the logic. EPS in my car works whenever the key is in the 2 position even if the engine is off.

Great info, thank you. I think that the RPM signal might only be used for error checking somehow. I say that because there are EPS trouble codes that are set based on the RPM/speed comparison. For example, "The car’s RPM is less than 500, but the car's speed is 6 MPH". Why it would care I have no idea, maybe to help verify that the VSS signal is correct.

As for the K swap you are planning on doing, that's awesome! I don't expect that you will have a problem with the EPS. The Civic EP3 comes with EPS, and people have also done EPS conversions on their RSX with no problems.

Also, I would imagine that the EPS module makes a big difference in how the steering feels and responds. I have the Civic Hybrid EPS module, but I have heard that the Civic SI EP3 module might be a better choice because it is programmed for a heavier, more sporty steering feel, where the Hybrid EPS module is programmed for a lighter, more relaxed steering feel. I have no idea if that is true, but it's what people have said.

As for the dead on center feel, I was kind of concerned that my rack would feel loose and unresponsive because it has a torque sensor on the steering input, so the shaft can be twisted a little bit in both directions without moving the tie rods. However, I can feel no additional play or deadened response at all, which I am very happy about. Actually, this rack feels better with no assist than the hydraulic rack felt when it has no oil in it or when the belt isn't on the pump.

I don't know if the Prius EPS needs an RPM input - Prii can do engine-off EV operation up to 40+mph in my Gen2. What I read was that the Prius EPS, installed in a car that was too analog to provide such info, nevertheless provided some assistance. It didn't turn up to higher assistance at low speeds like you'd expect, but some assistance is better than nothing.
I'll see if I can't dig up where I saw that and drop a link. I'm pretty sure I'm remembering it correctly.

I am almost done with the conversion. I will upload pictures as soon as I have time. I got a wiring harness from a buddy and I installed the harness. I needed to cut the harness and extend 8 wires total. I needed to extend the 6 wires for the torque sensor, as well as the 2 large cables that go to the motor. I made the wires a bit long, better to have a bit of extra length than have it too short.

Then I hooked up the VSS, RPM, and key on power to the module. I cut the harness to add the RPM and VSS wires on the car's harness rather than the engine's harness so I don't have to redo any wiring if I need to replace my engine harness again or when I K swap.

Then what I did is since I wanted to test it but I didn't have a long cable to connect the main power to the fusebox is I put an extra battery on the floor and connected the power and ground to the harness with jumper cables to test it. It worked! I didn't drive it with the assist working since I didn't have a way to power it, but it worked and it felt good.

So tomorrow I am going to get enough 8 gauge power cable to connect power to the EPS module and see how it drives. I will report back as soon as I am able to drive it with the EPS working

It's a Honda civic. Do you even need power steering?
I drive my 3/4 ton suburban with no power steering.

Define "need". I can drive it with no power steering, but it is actually pretty hard to steer when it's stopped. Like it pretty much can't be steered with one arm.

Also, if the car can't be quickly steered at a very low speed or while stopped, that is a safety hazard.

Besides, installing an EPS system is a lot cooler, more interesting, and more unique than just taking the system out :)