Honda Civic EPS conversion

[samwichse]

Gen1 HCH EPS rack... be prepared for extreme disappointment.

Hated every second of highway speed driving in that car.

[EcoCivic]

Originally Posted by samwichse

Gen1 HCH EPS rack... be prepared for extreme disappointment.

Hated every second of highway speed driving in that car.

Well hopefully it's not disappointing. But if it is, I could easily install a switch to manually shut off the assist on the highway. For that matter I could figure out a way to set it up so it disables itself above a certain speed too.

[EcoCivic]

Here is one picture. I had to chop off the random chunk of metal circled in red to bolt it in with my OEM brackets

[EcoCivic]

The installation is electrically complete. I installed a power cable from the fusebox to the module and went for a drive. The steering actually feels great to me! At low speeds the steering is extremely easy, but since the steering is speed sensitive, it feels firmer than the hydraulic system felt when the car is up to speed. It feels very predictable and responsive with no lag or deadness at all. To be honest if this wasn't my car and I didn't know that it has EPS I would not know that the system was electric from driving it. I guess Honda figured worked out the bugs in the system by 2005. That or I just got a good system

[EcoCivic]

Here's a picture of the module installed in the car. Now I just need to mount it, clean up the wiring, put the carpet back, and put the interior back together

[Piotrsko]

Might want to think about some sort of clamp mechanism to hold it on that side. Not knowing how much you cut off, it looks weak

[EcoCivic]

Originally Posted by Piotrsko

Might want to think about some sort of clamp mechanism to hold it on that side. Not knowing how much you cut off, it looks weak

Great point! However, I did not actually cut out anything structural, I just cut off the random chunk of metal under the bolt hole so it looks round like the OEM rack. Also, the OEM mounting bracket has a thick strip of metal that goes over the mounting hole for added strength. The easiest solution would have been to get OEM mounting brackets for the hybrid, but I didn't think to and by the time I realized that the brackets were different the rack was already out and I couldn't go get brackets.

[Ecky]

Really glad it worked out for you! There are a lot of Honda folks on here, and I'm certain someone else will eventually follow your lead with this swap.

For what it's worth, the EPS rack is also great for manual conversions, there's a lot less resistance than with a hydraulic rack, but there are some things you need to do to it to make it work. Simply unplugging or even unbolting the EPS motor is going to leave a stiffer than necessary manual rack because the motor connects to the rack via a worm gear. The gear turns very easily from the motor side but not the other way around. Turning the rack without the motor spinning results in a lot of resistance unless you remove the worm gear as well.

See here: https://en.m.wikipedia.org/wiki/Worm_drive

Unlike with ordinary gear trains, the direction of transmission (input shaft vs output shaft) is not reversible when using large reduction ratios. This is due to the greater friction involved between the worm and worm-wheel, and is especially prevalent when a single start (one spiral) worm is used. This can be an advantage when it is desired to eliminate any possibility of the output driving the input. If a multistart worm (multiple spirals) is used then the ratio reduces accordingly and the braking effect of a worm and worm-gear may need to be discounted, as the gear may be able to drive the worm.

Worm gear configurations in which the gear cannot drive the worm are called self-locking. Whether a worm and gear is self-locking depends on the lead angle, the pressure angle, and the coefficient of friction.

Put another way, Honda's EPS racks have a large reduction ratio and unless the worm gear is removed along with the motor, a manual conversion with these racks leaves a lot of friction and drag, similar to how looping the lines in a hydraulic rack still results in high steering effort.

Q. Why would you ever want to do a manual conversion on an electric rack which is virtually free in terms of economy?

A. Due to the above property of worm gears, relatively little steering feedback is able to get back to the steering wheel.

[EcoCivic]

Originally Posted by Ecky

Really glad it worked out for you! There are a lot of Honda folks on here, and I'm certain someone else will eventually follow your lead with this swap.

For what it's worth, the EPS rack is also great for manual conversions, there's a lot less resistance than with a hydraulic rack, but there are some things you need to do to it to make it work. Simply unplugging or even unbolting the EPS motor is going to leave a stiffer than necessary manual rack because the motor connects to the rack via a worm gear. The gear turns very easily from the motor side but not the other way around. Turning the rack without the motor spinning results in a lot of resistance unless you remove the worm gear as well.

See here: https://en.m.wikipedia.org/wiki/Worm_drive




Put another way, Honda's EPS racks have a large reduction ratio and unless the worm gear is removed along with the motor, a manual conversion with these racks leaves a lot of friction and drag, similar to how looping the lines in a hydraulic rack still results in high steering effort.

Q. Why would you ever want to do a manual conversion on an electric rack which is virtually free in terms of economy?

A. Due to the above property of worm gears, relatively little steering feedback is able to get back to the steering wheel.

That is really great information! I actually noticed that when the front tires are off the ground it is still quite hard to steer, similar to the feeling of if I was turning a hydraulic rack without the engine running. I wondered if it was drag from turning the motor, but then I remembered that the motor turned very easily when I had to take it out to get the rack in. I would say that with the front tires off the ground, the steering effort is the same as or slightly higher than with the tires on the ground and the EPS active, but definitely more drag than the OEM hydraulic rack with no oil in it.

As for converting the EPS rack to a manual rack, there is one little thing that you are forgetting: The torque sensor play. The torque sensor would introduce a little bit of play in the steering also because you are basically turning through a spring. I can't feel the play while driving, but if EPS isn't active and the car is sitting still, the play can be felt a little while turning. It isn't bad at all, it just basically feels like you are turning through a spring, but not that bad. But with EPS active, the play can not be felt at all.

But if you are going to go through the trouble of converting an EPS rack to manual for the purpose of achieving more steering feel and more precise steering, you may as well find some way to get rid of the play in the torque sensor or make a solid shaft with no torque sensor for the best possible results though.

[EcoCivic]

Oh and I answered my own question on when EPS is active. If you turn the key on without starting the engine, the EPS system does not activate, the engine has to actually be started to activate EPS. However, once you start the engine, the EPS will still work if you kill the engine as long as the key stays on the whole time. Interesting. However, for the people who like to EOC, I guess it’s a good thing that EPS still works without the engine running.