wvumtnbkr
wvumtnbkr GRM+ Memberand PowerDork
5/3/23 4:08 p.m.

I would like to put a column mounted electric power steering system in my fc rx7 champcar.

 

What do I gotta do?  

 

I don't have a dashboard to worry about.  My column currently is mounted to the roll cage so I'm not worried about the extra weight.

 

What are the suggestions for the column and controller?  What's easiest?  What's cheapest?

 

What are the "gotchas"?

 

Purity isn't an issue here. The car already has more GM parts than original Mazda parts.

Olemiss540
Olemiss540 HalfDork
5/3/23 4:24 p.m.

Watching this with serious intentlyness.

GameboyRMH
GameboyRMH GRM+ Memberand MegaDork
5/3/23 4:39 p.m.

You have to choose either a unit that doesn't need any digital inputs to work (1st gen Echo/Yaris comes to mind? I think 1st-gen Prius is the same) or one where an aftermarket standalone controller is available for (there is a GM/Opel unit, don't remember which one...).

I found a list of systems that can work with no inputs here:

https://www.therangerstation.com/tech/toyota-electric-power-steering-eps-conversion/

They do still need the factory control unit to work, but these can work in isolation from the rest of the car's systems.

californiamilleghia
californiamilleghia UberDork
5/3/23 4:57 p.m.

I believe one of the Volvo guys here did one last year , 

Hopefully he will see this thread .

wvumtnbkr
wvumtnbkr GRM+ Memberand PowerDork
5/3/23 4:59 p.m.
GameboyRMH said:

You have to choose either a unit that doesn't need any digital inputs to work (1st gen Echo/Yaris comes to mind? I think 1st-gen Prius is the same) or one where an aftermarket standalone controller is available for (there is a GM/Opel unit, don't remember which one...).

I found a list of systems that can work with no inputs here:

https://www.therangerstation.com/tech/toyota-electric-power-steering-eps-conversion/

They do still need the factory control unit to work, but these can work in isolation from the rest of the car's systems.

That's a great link! Thank you!

paddygarcia
paddygarcia GRM+ Memberand Reader
5/3/23 7:02 p.m.

I might be the volvo guy, have a GM unit waiting to go into my 122.

They're conceptually simple with thr standalone controller. Mount between steering wheel and steering box, connect to the battery with a 8-10 gauge wire + 50ish amp fuse, and you're good to go. They don't draw a lot of current all the time but clearly can draw a lot when used hard. 

The GM unit has splines on either side. My job has been held up waiting to get to the fabricator to make new steering shafts with splined ends - I don't trust my own welding for steering or suspension.

The standalone controller can be had with variable or fixed boost. IIRC the GM is larger than the prius and both mount differently so you might want to plan out installation before settling on one unit or the other.

kb58
kb58 UltraDork
5/3/23 9:27 p.m.
Pete. (l33t FS)
Pete. (l33t FS) GRM+ Memberand MegaDork
5/3/23 10:17 p.m.

Paging fidelity101...

VolvoHeretic
VolvoHeretic GRM+ Memberand Dork
5/3/23 10:28 p.m.

Electric power steering + steering quickener in a Volvo 1800 will be pretty tight, probably no more room for a collapsible shaft.

Byrneon27
Byrneon27 HalfDork
5/4/23 7:26 a.m.

I'm a fan of the 02-07 VUE (Some Equinox, Torrent, and Ion) GM column, the control box is readily available, cheap, and the shafts are pretty easy to adapt to almost anything. Column length is reasonable, steering feel is good, assist is what you make of it using the aftermarket control boxes. 

www.epowersteering.com is a good resource 

collinskl1
collinskl1 GRM+ Memberand Reader
5/4/23 8:46 a.m.

I was a development engineer for a Tier 1 supplier for EPS systems for 6 years. I have little experience with aftermarket retrofits, but do have general knowledge of the systems mainly from an OE perspective.

Your mounting will need to be more robust than the factory column mount, as those brackets will now be reacting the assist torque - they don't need to be 1/4 plate, but they should be more than sheet metal.

The factory rack and pinion can be de-powered obviously, but the torsion bar in the input/pinion shaft will still be there and will give more windup to the total path between the steering wheel and the tires. Some people disassemble the gear and weld the shaft - I don't love this from a metallurgy standpoint, as that pinion also has to see the assist torque now, and it wasn't sized to do that. Others epoxy the shaft together... which can work if you use the right stuff. Not knowing the RX7s of that vintage - there may be a manual rack that could be used, but it probably would have a much slower ratio.

Not exactly the application that you're asking about, but I installed a PS unit on our side-by-side 2 years ago and it works GREAT. With the manual steering, Jennifer had trouble making tighter turns here on the property when she was driving it. I read about the aftermarket units available for the model we have and the good reviews and decided to give it a shot. It's is a total game changer! It works so well that my father-in-law envied it and I decided to put one on his SXS as well. For an 80 year old with a bad shoulder who had trouble steering his, he can easily drive it now with ease. I added a "suicide knob" to his steering wheel and u-turns are a one-arm affair since putting the unit on. 
 

The units I used is by EZ Steer and they make a universal kit which might work? I know there are kits that Legends, Dwarf and Mod-Lite cars use, so if something more robust is needed, you might look up one of those units.

Carl Heideman
Carl Heideman
5/4/23 11:18 a.m.

We put a Prius unit and a quickener on the CAM-T Falcon Wagon we built a few years ago. We initially had a 2:1 quickener but went to a 1.5:1. There is some detail about the EPS on page five of the thread. It has worked well and we plan to do this with other projects in the future.

wvumtnbkr
wvumtnbkr GRM+ Memberand PowerDork
5/4/23 11:25 a.m.

Thanks for all the info yall!

 

The steering rack in the rx7 has been depowered for years with lots of race laps.  I would think that the rack is going to see the same force as it would without power steering. Basically, it takes the same force to turn the wheels whether it is from human force, electric motor force, or a combination of the 2.

 

I want to do this as cheaply as possible.  Those kits are all rather more than I want to spend!  

 

Looks like I'm headed to the junkyard this weekend to find one of the ones that doesn't need an aftermarket controller and just has a failsafe.

 

Keep it coming yall!

Ian F (Forum Supporter)
Ian F (Forum Supporter) MegaDork
5/4/23 11:30 a.m.
VolvoHeretic said:

Electric power steering + steering quickener in a Volvo 1800 will be pretty tight, probably no more room for a collapsible shaft.

There is a ready-made kit for installing EPS into a Volvo 1800 sold by a company (EZ Steer) in the NL.  It fits under the dashboard.  I don't remember if it maintains the collapsing column.  I have one of their kits in my TR8 and it works well.  Well enough that I plan to get one for my long term 1800ES project.

A few companies on eBay sell the controller for the GM system used in the Vue/Equinox. One example for $65. Then it's mainly a matter of trusting one's welding skills to attach a EPS sourced from somewhere into your existing steering system. 

paddygarcia
paddygarcia GRM+ Memberand Reader
5/4/23 12:16 p.m.

I was going to say the same about cheap controllers. The standalone prius is provably cheapest (dont forget to grab the electronics along with the motor). With the GM column and a cheap controller (which just plugs onto the unit) I'm in for about $200. Having the shafts fabricated will probably cost more than that but I figure all in for under $500.

wspohn
wspohn SuperDork
5/4/23 1:21 p.m.

First go drive a BMW Z4 and then try a Z4M and tell us if you could put up with the difference.  Having driven both, I know I couldn't live with the electric version.

californiamilleghia
californiamilleghia UberDork
5/4/23 3:04 p.m.

Can you just put an on / off switch and only turn it on when needed .?
Mostly parking and low speed turns .....

buzzboy
buzzboy SuperDork
5/4/23 3:54 p.m.

My friend has the Vue column with the controller in his TR8. I really like that you can turn it up or down at whim. Out on track turn it down, the as you come back up in the pits set it for "one finger" mode.

GameboyRMH
GameboyRMH GRM+ Memberand MegaDork
5/4/23 4:09 p.m.
wspohn said:

First go drive a BMW Z4 and then try a Z4M and tell us if you could put up with the difference.  Having driven both, I know I couldn't live with the electric version.

Column-assist EPS has come a long way in the last decade or two. Toyobarus have column-assist EPS and the steering feels very similar to an NB Miata. If you made someone guess what kind of power steering the car had, the only hint that it wasn't hydraulic would be how quiet it is.

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