EPAS Retrofit
First of all, this is probably the best documented EPAS research thread on the internet.
https://www.vintage-mustang.com/thre...ideos.1008722/
https://www.therangerstation.com/tec...ps-conversion/
Much thanks to waid302 from the forum for all of the prior research to make my end so much easier.

From my research the top 2 widely used EPAS retrofit setup are..

1. 2002-07 Saturn Vue or 2005-06 Chevy Equinox
2. 2004-2009 Toyota Prius

#1 2002-07 Saturn Vue or 2005-06 Chevy Equinox is the unit that epowersteering/kpower industries uses for their EPAS retrofit. These units do not work on "fail-safe" mode, however, epowersteering already developed modules to activate the unit and make it a plug and play. They have a couple different styles of modules but most people uses the one with the potentiometer to control the steering assist.

#2 2004-2009 Toyota Prius unit does NOT need any additional modules for it work. This unit can work in "fail-safe" mode. When these units are in the fail-safe mode, they are turned down to about 48% of assist. This sounds pretty underwhelming, but it is more than adequate level of assist for small cars.

Acquired both units from my local junkyard for test fitting into the EG.
2005 Equinox Unit


2008 Toyota Prius Unit


Thread from above goes over many units and the difference in each unit.
But the biggest take away here is their size and motor mounting orientation.
Equinox and Prius has EPAS motor mounted in inverse of each other.


In order to clear these units, minor(?) modification is needed around the steering column.
Mid-column pivot/support will need to be removed completely to clear the unit.



I've tried to test fit both units and Equinox unit does not fit well because of the size of the unit and EPAS unit motor orientation.
When the motor is clocked to the right side, motor hits the heater core. Since my car will eventually will have ac, I’m not planning on removing the heater core.
Unit will clear if you clock the motor where the OEM fuse box is located (left side), however, you have to relocate the fuse box and the brake switch mounting.
(Sorry, no pics)

Prius unit on the other hand will clears the heater core and motor can be clocked to the right.
It is very tight, about 1/4 to 1/2 inch clearance at the most but the unit will clear the heater core, when it’s clocked to about 1 to 2 O’Clock position.


Prius unit is not a bolt on by any means, however you can install this unit without cutting the steering shaft. This also means collapsable steering column will function even after the swap. Not to mention that there is zero chance of weld failing or any shaft alignment issues. Of course there are some downside to this as well. One thing you lose is the steering column locking mechanism. Because I’m not using the civic upper column/shaft, there is no way to integrate the factory steering column lock from the ignition switch assembly. Also, Prius never had the steering column lock from the factory.

Here are the parts lists to make Prius steering column a “almost” bolt on.

• EK Steering Wheel/S2000/RSX/EP3 style steering wheel.
• EK Clock Spring
• EK Combination Switch Bracket
• DC2/Integra Power Steering Rack

Mid-mounting bracket welded up so I can have the unit pivot similar to the factory column.
Bracket provides a way to adjust the steering column tilt.
Since the motor mounting orientation is not exactly same as Prius, I welded on a tab on to Prius pivot bracket.



Bottom half of the Prius steering shaft and u-joint will bolt right up to DC2/Integra power steering rack
To make this steering column retrofit easier, I’m swapping out the subframe/crossmember with the Integra power steering rack.
Thing to note here is EG Manual Rack is 4.0 Lock to Lock VS Integra Power Rack is 3.2 Lock to Lock.
Integra racks are much quicker than the EG manual rack.
I'm actually exploring an option to retrofit an even quicker rack in the future, but.. that will be another day.

I did not weld the pinion nor painted the subframe, but those will get done at a later time when the engine comes out for the swap.
Also no front sway bar install... This is just a rush job so I can test the EPAS functionality.


With the Integra rack installed, rest of the steering column is just bolt on using the Prius lower shaft and u-joint.
Also, notice that there is some adjustment where the u-joint mount to the shaft.
I believe there was over 1/2 inch of adjustment left to make it shorter or longer.


Brake pedal clearance (I think there is even more clearance than the stock column here)


Next is the Combination Switch install.
Combination Switch mount is from EK 96-00 Civic since I am using the EK Clock spring to retain the horn and the cruise control switch. (more update on this later on my build thread)
If the turn signal trigger (white plastic piece on the inside) was swappable, there is no need to do the bracket swap but, unfortunately they are difference sizes and cannot be just swapped.
Top is the EG and bottom is the EK bracket.


Switch mounting needs to be enlarged a little.



EG combo switch bracket welded on. (ugly welds but it gets the job done)


EG column cover cut


EK combination switch, EK clock spring, EG column cover all installed


Just for a reference, this is the measurement of EG column.
About 6.25 inches from the metal bracket.


This is after, around 6 inches.


EPAS Control Module
Prius bracket removed and re-welded.


Adding M6 rivet nut and bolted up next to the clutch pedal assembly.
Plenty of unused room here for the control unit. (LOL, please don't mind the golf tee... Didn't even know that was there until the install)


Wiring it up.
All you need to provide is 12V Battery (constant), Negative Chassis ground, and 12V trigger (ignition/acc)


Does this setup clears dashboard?
Absolutely! EPAS motor doing a little peekaboo


From the side. It looks untouched!


Video of the EPAS in action.
92-95 EG Honda Civic Power Steering Retrofit using Toyota Prius Electric Power Assist Steering EPAS

Steering assist from Prius EPAS is just enough to turn the steering wheel with one hand.
It's actually rather stiff to turn with one hand while parked.

Also, another thing to mention is the Return-to-Center ability of this EPAS swap.
My steering wheel is actually NOT returning to center after a u-turn or sharp turns, and manual have to correct the steering wheel to the center.
I'm assuming it's the combination of suspension setting and my caster.
Will have to do more research on this at a later time since my car is not really road worthy yet, and still a WIP.

 

No return to center is probably the friction in back driving the worm gear in the power assist unit. First gen Insight had the same issue.

Needs a lot of castor to overcome all the friction in there.

Also kick *** job on the retrofit. Looks great in there.

 

Thanks for that!
Now that you mention it, I'm going to check up on that for sure.
Check if there are any friction/resistance and grease up all of the gears again.
I've read from other people that did Prius EPAS that their RtC works much better than the Equinox unit, so it should be possible to get this fixed...

 

Nice!! I actually did this a few years ago myself! Cool to see someone else doing it. Great info. Here’s a few pics of mine

 

@Pepe14 Just did this in the Forced Induction sub.

Really cool, I've seen EPS conversions using the MR2 motor before but never the Prius column in our chassis. I'll be using a Chase Bays PS tuck/relocation kit with mine, so keeping the stock hydraulic pump and Si rack. Have a feeling the steering will feel lighter than I'd ideally like, at some point in the future I may consider switching to a manual Integra rack and possibly a setup like this.

Thank you very much for sharing, OP! I saved this web page.

 

Nice! How’s your “return to center” ability with the EPAS swap?
I’m trying to find out if I need to add caster to get some RtC back cuz I have almost none…
Also, I noticed that you kept the metal support where the mid shaft support goes.
I had no idea the column fits with that still attached. That’s really good to know.
I initially tried with the Equinox column and that unit is MUCH bigger than the prius so I had to cut that metal support out.

Column style EPAS is really getting popular right now because of the simplistic design.
There are also no messy P/S fluid and cooler to worry about.
And also the biggest advantage is now you have the flexibility of custom rack and pinion for more customization and faster steering ratio.

EDIT: I forgot to mention that steering wheel effort is rather pretty heavy with this setup. I can turn the steering wheel with one hand but it’s not easy at all when the car is stationary.

 

I never go into this section but i think I saw your video once i finished mine on youtube.

I want to say my setup is from a 2012 prius. It definitely has a different output shaft. Seems like my motor is stronger because i can move it at a complete stop with minimal effort. Mine also bolted up to my stock civic pinion shaft.

I drove a rsx type s to compare the return to center and its almost identical if not better than the rsx

 

@kmvguy83 what did you do for the ignition switch? Great info here, thanks!

 

@kmvguy83 did you ever get your “ability to center” fixed? I noticed that you mentioned you used an Integra power steering rack. Did you “de power” the steering rack? I heard you need to remove the seal inside the rack. Not sure if you depowerd it or not and if that helps with ability to center? I definitely plan to do this EPS setup soon and would like an update on how it’s going for you.

 

I de-powered it completely. I didn't take a pic of cutting the metal seal, but here is a picture.
if you are interested in doing this, you need to cut the metal seal/ring off the rack.


My current additional mods are..
1. De-Powered rack
2. Shimmed lower control arm. whiteline kit
3. Left/Right switched upper control arm
4. Canbus module (WIP) to put the Prius EPAS on normal mode (no more fail-safe mode)

I'm expecting about 3-4 degree caster with current setup along with de-powered rack and also trying to put EPAS running on non-failsafe.

I don't have an update on how the RtC is because my car is not running yet.
I also have ABS retrofit in progress, hopefully I can get everything working soon.