Starting on my EPAS project (Toyota junkyard swap)

[Map63Vette]

So long ago when I first bought my car it had the factory Dodge power steering. Fast forward a bit and when I did my 5.7 Hemi swap, I changed over to a standard 24:1 manual steering box as there weren't really power options at the time, and I didn't really like the finger light Dodge style power steering anyway (Borgeson was still working on their PS box back when I did my engine swap, and it was expensive). Fast forward many more years and when I got my new job I started updating my Dart more as it was becoming my go-to daily driver. I was getting tired of having to sling the wheel around multiple times in a parking lot, so I swapped over to a 16:1 manual box with the thought that I might do an EPAS setup at some point. The 16:1 box isn't too bad to drive day to day, but it can get heavy at times and one handed driving around low speed corners can get interesting (car is a stick shift as well, so one handed driving is more common). This past Christmas I got a pretty complete EPAS column setup from a Toyota, so I bought a spare Dodge column to cut up to see how I could merge the two into one.

So far I've only really taken both columns fully apart to see what I have to work with and to do some measurements to figure out how I want to graft it all together. It actually looks like it might not be all that bad to get the two stuck together, though the input shaft is going to be the main one I'm still thinking about. I'll try to get some pictures this weekend to show all the parts, but I did measure them all up the other day and try to get them into CAD so I can do some layout work and get a better idea of where I might want to cut stuff down. I went ahead and 3D scanned the motor and column mounting bracket as well just for the fun of it and it actually lays over my crude model pretty good.

The general plan at the moment is to press the inner "shift" tube (it's just a dummy tube on my column since I have a console shift setup) onto the bore of the EPAS motor as they are pretty close in diameter. I'll also need to make some kind of spacer to go between the inner shift tube and the outer column housing to make them more solid. I'll have to cut down the Toyota and Dodge input shafts and weld/join them together in some way. I can go a couple of ways on the output side depending on whether I want to keep the collapsible part of the column or not. The "cheap" plan would be to just cut down the Toyota output shaft I have and weld it to a portion of the Dodge output shaft. That would be simple and straightforward, but would mean no collapsing anymore. If I want to maintain some amount of collapsibility it looks like I can buy U-joints and a telescoping shaft from Borgeson to join the two together. Drives the cost up quite a bit, but would potentially make for a safer setup in the event of an accident.

On the electronic side, my plan is to send the actual CAN messages the controller wants to see to the EPAS module so that I get variable assist depending on speed. I hooked things up on my test bench and was reading the CAN messages off the module to see what it thought was going on, but I don't have a ton of info on those at the moment. I can see the output of the torque sensor and some status messages, but I don't know what the actual status messages mean just yet. Once I get it in the car I'll see what kind of assist I get out of it and if the factory scaling is palatable or if I want to tweak it.

So plenty of work ahead and likely something I'll take my time with as I'd like to make sure it's done well, but figured some of you might find it interesting.

 

[Map63Vette]

So here are some pictures of the columns in pieces to give an idea of how they go together.

First up is the Dodge column:

I didn't break down all the parts at the end by the steering wheel, but you can see the main upper bearing housing and then a tapered shroud under it. On a column shift car that part rotates and is connected to the shift tubes inside the column. On this column there is a single filler tube that supports the shroud, but otherwise doesn't really do anything. It does have a collapsible section in it though. The shaft goes in the middle of all of it and also has a collapsible section. The column bolts to the mounting bracket with 4 bolts, and the mounting bracket bolts to the pedal support with 3 bolts.

Next up is the Toyota column:

It's harder to tell from the pictures, but it's mostly just an upper column tube and shaft and then a lower driveshaft style setup. This column is tilt/tele though, so its' got a little more going on. The tube with the white sleeve was originally pressed on the shiny portion of the motor assembly at the base of the input shaft. The upper column slid over it and the tilt and telescoping was controlled by the little black lever. Similarly, the upper portion of the input shaft rode in the upper column and was retained with a snap ring. The lower portion is just a typical driveshaft style setup with U joints at both ends, though this one also came with a solid shaft extender piece. Unfortunately, the U joints are just barely different sizes between the Toyota and Dodge. I believe the Dodge is 3/4 and the Toyota I think is 11/16. The column attached to the dash similar to the Dodge with two bolts on the upper column housing portion and one bolt through a bracket on the motor.

The plan going forward looks something like this:

I plan to press the inner shifter tube onto the motor housing like the small plastic wrapped tube that was there originally from Toyota. Then I need to make a filler piece to press between the inner tube and the outer housing. The steering shaft itself I'm still on the fence on. I was going to try to just cut the very end of both the Toyota and Dodge shafts off and weld the Dodge end to the Toyota end to keep the slip joint. I don't really need the slip joint though, since the upper column can't collapse, so I may just cut the Toyota input shaft at the base of the splines and attach the Dodge shaft there. Need to do some measurements to see what makes the most sense. On the output side, I still haven't done enough measurements to know what I want yet. The factory Toyota slip shaft might actually be long enough with the extension I have if I can find a yoke to swap out on the steering box end. I also need to figure out how I want to attach the lower portion of the housing to the motor. My current plan is to use the mounting holes on the motor and make a bracket that would bolt where the third bolt on the factory Dodge column mounting bracket goes. Strictly speaking, I wouldn't actually need a lower column housing, though I think it's easier to keep it to fill the hole in the firewall.

Here is a section view of the parts in my CAD software to give a better idea of the assembly I have planned:

And here's my plan for mounting:

Should hopefully make some more sense as I start cutting stuff up. I'll try to get more pictures along the way.

 

[Clelan]

Looking forward to seeing how this turns out! Good luck!

Cley

 

[72bluNblu]

Definitely going to be watching this one, I have 16:1 manual steering in my Duster and while I don't have a problem with it doing something like a variable boost EPAS has definitely crossed my mind more than a few times!

 

[Map63Vette]

Definitely going to be watching this one, I have 16:1 manual steering in my Duster and while I don't have a problem with it doing something like a variable boost EPAS has definitely crossed my mind more than a few times!

The variable part was the big one for me. I like a little weight to my steering when I'm cruising along, but would appreciate a little more help at low speeds and for things like turns from a dead stop. I'll be curious to see what the factory assist "curve" looks like. Might be interesting trying to scale it in a consistent way that doesn't just jump around. I don't know if the factory assist is linear or by some kind of power, though I'm not sure if I'll be able to determine that even after the install or not. I should have torque sensor values available to me on the CAN which I could log along with me speed to build up a curve, though it might be more complex than that. Either way I've got to get it in the car first, so I've got a ways to go before I have to worry about it.

 

[Map63Vette]

I started taking some measurements on the upper column to make my first cuts to start sizing things up. The inner tube I'm still going to have to flare out on the end to press onto the motor, but it's only maybe 1 mm off, so I think I can expand it. I found a socket that's the right diameter, so my plan was to get the end as hot as I could with a torch and try to hammer it over the socket to spread it a little bit. I could potentially just heat it and press it on that way, but I think that would be too tight a fit and it might crack. The outer column was simple enough and I just cut it at the start of the mesh part. I still need to work out a spacer to join the inner tube with the column housing, but that should be pretty straightforward. I might 3D print something just for a test fit. Here's a loose test fit just setting the column over the motor. So far it's looking pretty good.

Where things got even better was on the input shaft. I was scratching my head trying to figure out how I wanted to join the two as I was a bit worried that any sleeve might not fit inside the inner tube. As it turns out, the upper Toyota input shaft that has the female splines is entirely hollow. Even better, the ID of it is a near perfect fit for the OD of the Dodge steering shaft, aside from it being fully round and the Dodge being a double D.

So at this point I think I'm just going to drill through the full assembly and put a roll pin through it, then probably do a bead of weld at the joint as well. So the weld should take most of it with the roll pin as a backup just in case. I've got ~1.25" of insertion between the two shafts, so I could even just do two roll pins and that might even be enough to hold it without any weld. Suffice to say I'm rather pleased with the way it's turning out so far.

 

[Killer6]

The variable part was the big one for me. I like a little weight to my steering when I'm cruising along, but would appreciate a little more help at low speeds and for things like turns from a dead stop. I'll be curious to see what the factory assist "curve" looks like. Might be interesting trying to scale it in a consistent way that doesn't just jump around. I don't know if the factory assist is linear or by some kind of power, though I'm not sure if I'll be able to determine that even after the install or not. I should have torque sensor values available to me on the CAN which I could log along with me speed to build up a curve, though it might be more complex than that. Either way I've got to get it in the car first, so I've got a ways to go before I have to worry about it.

I know it's a different brand, but the upper option Hyundai's had a steering wheel button which allowed the amount of assist to be selected, (3) levels were available. I believe called out as 'Sport', 'Standard', & 'Comfort'. Might investigate if Toyota had a similar feature..