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01-07-2021, 02:01 PM | #1 |
Scooby Guru
Member#: 15822
Join Date: Feb 2002
Location: TOPOHTO
Vehicle:1999 WRB GM6 2.34 LR destroker |
EPAS conversion
Ok boys and girls, I can't promise I will go through with this mod, but I will take you as far as I can get
The goal is to convert from PS to EPAS, by retrofitting Toyota Corolla 120 EPAS unit. This unit is basically power assisted steering column. Its a bit updated, but its cheap, plenty of them available, and what's most important it doesn't the EPAS ECU is not running on CAN, all newer units do which would lead to some electrical challenges later down the road. The ECU enables power assist with ignition on, and uses VSS signal to modulate steering effort - full assist on low speed (like parking), and less assist during driving. For this mod to work, EPAS ECU and special Toyota relay are needed, so I sourced all of those for ~ $100 I didn't make a pic of the unit before I started tearing it apart, but it looks like this The idea is to integrate it into the OEM steering column, create proper brackets and EPAS motor orientation so its not in a way of anything As is, it would not fit because the brackets are in wrong place, the shaft on the steering wheel side is short, and the splines won't work with Subaru steering wheels. So I knew I had to try to disassemble it to a level where I could get creative I cut of the front portion of the tube, and starting shortening the outer tube more and more until I got here: The shaft consists of different pieces that slide on together, which is perfect - I am going to try to create adapters so that in case the EPAS dies, I can just replace it with another one and reuse all adapters, so this gave me hope. Notice the U-shaped part, it slides on the shaft for a tight connection between the pieces, that's it! Its not welded or bolted, just like that The pieces itself has a heptagon shape I bought a used GC column for the sake of this experiment, here it is next to the EPAS Next, I had to take the GC column apart, pulled the C-pin out, used rubber mallet to get the shaft to slide out, easy I was expecting something more solid from a factory part to be honest... but hey, it works and I've never seen them fail Here it is from the other side, notice the hole - its for the key lock (which I intend to keep) rear portion that sticks out in the engine bay and I am out of allowed 10 images... moving to next post
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Last edited by Hyper; 01-07-2021 at 02:22 PM. |
01-07-2021, 02:01 PM | #2 |
Scooby Guru
Member#: 15822
Join Date: Feb 2002
Location: TOPOHTO
Vehicle:1999 WRB GM6 2.34 LR destroker |
front end
I also noticed a strange junction, that seemed to be just a press fit hard to see on the picture, but there are 2 little holes on the sides with something that reminded me of plastic tabs, so I thought its just plastic glue covering spot welds, so I pulled out my heatgun and starting melting it.... what happened next really shocked me, as that was not plastic, the two pieces were actually GLUED together with some epoxy or resin, the stuff you usually find on hockey sticks when you assemble them yep, its official, our steering columns are glued together and those holes are to compensate for extra glue, so that extra compound has a way to escape Oddly, the shape of the that piece resembled EPAS output shaft can it be true????.... nope. different sizes Here is the EPAS with the "toyota" steering wheel adapter, and the "subaru" adapter shaft, showing just how much longer this thing needs to be My idea is to reuse the Toyota piece that slides on the EPAS output shaft, cut it, do the same with the Subaru part and make a single piece out of it (somehow) This probably requires a mill and tig, I don't have either so will need to find someone who will be willing to do the coupling for me but I may not be seeing another solution here, any experienced machinists can chime in? Next, I need to figure out how to mate the rear part of EPAS with the the "remainder" of subaru column - EPAS uses splined shaft and a steering linkage goes over it, however this won't work because the shaft needs to be expended, another riddle that needs to be solved Last edited by Hyper; 01-07-2021 at 02:21 PM. |
01-07-2021, 02:02 PM | #3 |
Scooby Guru
Member#: 15822
Join Date: Feb 2002
Location: TOPOHTO
Vehicle:1999 WRB GM6 2.34 LR destroker |
reserved2
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01-08-2021, 12:06 PM | #4 |
Scooby Newbie
Member#: 144044
Join Date: Mar 2007
Chapter/Region:
South East
Location: Alabama
Vehicle:2006 STI OBP |
I have no idea how much torque is no the steering shaft, but I don't *think*it would be that much. Check before following the following suggestion. It look slike there is enough metal that you could file a bit off of the outside of the EPAS shaft and a bit off of the inside of the Subie shaft so that they would mate together.
Airplanes are now glued together also |
01-08-2021, 05:40 PM | #5 |
Scooby Specialist
Member#: 297799
Join Date: Oct 2011
Chapter/Region:
South East
Location: Knoxville, TN
Vehicle:2003 WRX EJ207 version 8 |
I am curious to see how this all shakes out for you. I am essentially doing the same thing but with the BRZ power steering/GR column (I want the telescoping action).
For connecting the power steering motor to the steering rack (assuming your current setup doesn't work), I would look into the BRZ/FRS steering linkage. If you need spline count/diameter measurements let me know. For connecting the p/s motor to the column, I got lucky. The GR column matches the spline/diameter of the BRZ motor. So, I just had to trim things down to get the motor to land where I needed it to. |
01-09-2021, 02:40 PM | #6 |
Scooby Guru
Member#: 15822
Join Date: Feb 2002
Location: TOPOHTO
Vehicle:1999 WRB GM6 2.34 LR destroker |
I'd be curious if BRZ EPAS motor would sit right behind GD dash beam and yet be the same length for the steering wheel to sit at it's normal position
I dropped off all bits at machinist today, who is brave enough to try and help me out once he has time, so this won't be updated until after the end of his month in the mean time, I will plan the electrical part of this, turns out the EPAS ECU also seeks for RPM input signal to operate only with the engine running |
01-10-2021, 04:43 PM | #7 |
Scooby Specialist
Member#: 207417
Join Date: Apr 2009
Chapter/Region:
Tri-State
Location: Rensselaer, NY
Vehicle:2009 WRX td06sl2-20gtx 413/423 |
This has me interested now that I have already done this setup on an 89 foxbody mustang. We used a quick ratio manual steering rack to keep things simple. The install wasn't that bad since I already had the whole dash out. What was nice about that kit is that it has its own controller and you can set the desired steering output with a dial.
Would love to get rid of the PS pump and clean up the engine bay. What do you plan on doing with the ports for the old hydraulic lines that were connected to the rack? |
01-10-2021, 05:49 PM | #8 |
Scooby Specialist
Member#: 297799
Join Date: Oct 2011
Chapter/Region:
South East
Location: Knoxville, TN
Vehicle:2003 WRX EJ207 version 8 |
I am still working on my final placement but this is basically where it lands on my setup. I had to trim some plastics off of the HVAC and wiring harnesses. I also broke my brake light switch so watch out for that.
I probably won't have mine up and running until the summer. I only have one more "free" week before the spring semester starts, and I have a pretty busy one coming up so I can graduate. However, if/when I finish I will post my results. And just an FYI, here is the motor controller that I am considering. https://www.agtengineering.com.au/pr...ering-emulator 20wrx09, here is a thread about depowering a steering rack that I found useful. https://forums.nasioc.com/forums/sho....php?t=2632487 Some people recommend plugging the ports (or looping them together) and welding the quill to get rid of the play in the rack. There is a p/n for a shorter belt as well. |
01-13-2021, 11:01 PM | #9 |
Scooby Guru
Member#: 33782
Join Date: Mar 2003
Chapter/Region:
MAIC
Location: Milton Keynes, UK
Vehicle:96 3MI Racing search FIRST, then PM!!! |
Much subscription.
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04-01-2021, 07:50 PM | #10 |
Scooby Specialist
Member#: 297799
Join Date: Oct 2011
Chapter/Region:
South East
Location: Knoxville, TN
Vehicle:2003 WRX EJ207 version 8 |
Any updates?
I have my column physically bolted up so I can drive my car. I am loving the extra legroom. I have the controller, but I need to find a wiring harness from a BRZ/FRS so I can run it at least in failsafe mode. I also have a 15 STi rack on the way. And I still need to figure out a clock spring solution. |
04-01-2021, 07:58 PM | #11 |
Scooby Guru
Member#: 15822
Join Date: Feb 2002
Location: TOPOHTO
Vehicle:1999 WRB GM6 2.34 LR destroker |
the machine shop I dropped it off at hasn't even started
its hard to find good help |
04-02-2021, 09:59 AM | #12 |
Scooby Newbie
Member#: 406963
Join Date: Nov 2014
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so nice
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04-08-2021, 08:55 AM | #13 |
Scooby Guru
Member#: 33782
Join Date: Mar 2003
Chapter/Region:
MAIC
Location: Milton Keynes, UK
Vehicle:96 3MI Racing search FIRST, then PM!!! |
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04-26-2021, 07:32 PM | #14 |
Scooby Specialist
Member#: 297799
Join Date: Oct 2011
Chapter/Region:
South East
Location: Knoxville, TN
Vehicle:2003 WRX EJ207 version 8 |
So, a quick update. I wired up the BRZ p/s motor controller (everything except canbus) and it works. I haven't driven it yet but I've depowered my VA STi rack and now I am waiting on a few odds and ends to install everything.
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04-28-2021, 07:22 AM | #15 | |
Scooby Guru
Member#: 33782
Join Date: Mar 2003
Chapter/Region:
MAIC
Location: Milton Keynes, UK
Vehicle:96 3MI Racing search FIRST, then PM!!! |
Quote:
Also your pics up above are gone now. I'm on my computer and not on my phone btw. |
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04-28-2021, 10:44 AM | #16 | |
Scooby Specialist
Member#: 297799
Join Date: Oct 2011
Chapter/Region:
South East
Location: Knoxville, TN
Vehicle:2003 WRX EJ207 version 8 |
Quote:
I will relink the images. I'm having issues uploading images to the Nasioc host so I link images from my blog instead. I wasn't sure if I had a bandwidth cap. |
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04-28-2021, 04:28 PM | #17 |
Scooby Guru
Member#: 33782
Join Date: Mar 2003
Chapter/Region:
MAIC
Location: Milton Keynes, UK
Vehicle:96 3MI Racing search FIRST, then PM!!! |
Ah, right on!! Thanks for following up so quickly.
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05-07-2021, 02:01 PM | #18 |
Scooby Newbie
Member#: 305358
Join Date: Dec 2011
|
As a quick comment, that part that's glued together may be the portion that collapses during an accident, so you don't take a steering wheel to the chest.
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06-03-2021, 07:23 PM | #19 |
Scooby Specialist
Member#: 297799
Join Date: Oct 2011
Chapter/Region:
South East
Location: Knoxville, TN
Vehicle:2003 WRX EJ207 version 8 |
So here is my final parts list.
I haven't put too many miles on this setup but everything seems to be in working order. On occasion, the p/s assist will cut out in parking lots (ex. very low speed, clutch in; or cold starts). I'm not sure what the issue is there. Might be an alternator voltage thing. I am thinking about doing the diode mod and/or the 3-wire mod as well. I haven't taken the car to the Dragon yet, and my usual testing roads have been busy as hell for some reason. But so far, I like the level of assist that the "failsafe" mode provides. I have a blog where I go into more details, but I am thinking about starting a build thread just to go over the highlights. |
06-03-2021, 07:46 PM | #20 |
Scooby Specialist
Member#: 395793
Join Date: Jul 2014
Chapter/Region:
Tri-State
Location: SLC and Lake Placid
Vehicle:2005 92x Aero Beige |
Very interested. Subscribed
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06-05-2021, 03:35 PM | #21 |
Scooby Guru
Member#: 33782
Join Date: Mar 2003
Chapter/Region:
MAIC
Location: Milton Keynes, UK
Vehicle:96 3MI Racing search FIRST, then PM!!! |
Please do share!!
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07-19-2021, 12:43 AM | #22 |
Scooby Specialist
Member#: 297799
Join Date: Oct 2011
Chapter/Region:
South East
Location: Knoxville, TN
Vehicle:2003 WRX EJ207 version 8 |
A quick update.
A couple of weeks ago I took it through the Dragon for a trip to NC. The steering was a little on the heavy side but nothing unmanageable. I also have 265 summers over 245 all-seasons and a 13:1 rack over a 16.5:1 rack now. It cut out on me a couple of times but I haven't figured out the pattern yet. For most of my 2-3hr drive through the mountains, it was fine. Other than those issues, the system works great. I hear the click of the control module when I turn the key on that reminds me that it is still there. Recently, as in yesterday, I retorqued my suspension rotating points (top hats, ball joints, etc) and the steering is considerably lighter. I guess I did a good ole gutentight method before. My car has long had an issue where the steering did not want to return to center. I have replaced every steering component on this car and I was disappointed to still have the issue. It returns to center easier but I still have to help it. I'm not sure what the issue is there. I started a build thread but I have been having issues uploading images to the Nasioc host. But I am slowing adding more info. https://forums.nasioc.com/forums/sho....php?t=2937433 Oh, and I found this $50 controller for the BRZ EPAS on eBay. However, it is Portugal. https://www.ebay.com/itm/144032280559 I also found these connectors that look like the BRZ connectors so you might be able to make your own power harnesses. https://www.ebay.com/itm/265072946013 https://www.ebay.com/itm/265072955344 I have a few odds and ends to fix but I'm kinda focused on my tall boi shifter now. |
07-19-2021, 03:01 AM | #23 |
Scooby Guru
Member#: 15822
Join Date: Feb 2002
Location: TOPOHTO
Vehicle:1999 WRB GM6 2.34 LR destroker |
from what I have read, with EPAS self-centering relies mostly on the caster
that cutting out is a big issue imho, I would imagine the EPAS has some torque sensors that communicate through CAN with the controller, waiting for some inputs which they are not getting - just a guess |
07-19-2021, 06:47 PM | #24 |
Scooby Specialist
Member#: 297799
Join Date: Oct 2011
Chapter/Region:
South East
Location: Knoxville, TN
Vehicle:2003 WRX EJ207 version 8 |
I have around 5 degrees of caster before the EPAS swap, but now that I think about it, I need to check the tension adjuster torque specs on the rack.
The cutting out doesn't happen often when driving. It does it on cold starts, but as soon as I blip the throttle to back out of the garage it starts working. I'm thinking it is either a voltage issue or a torque sensor issue. I am going to try the diode mod to see if that helps. |
07-20-2021, 12:42 AM | #25 |
Scooby Specialist
Member#: 175624
Join Date: Mar 2008
Chapter/Region:
MWSOC
Location: Wichita, KS
Vehicle:0304 WRX WRX SY WRB |
King Pin Inclination along with caster will help with return to center. There's a great motoiq article that covers it in detail.
https://motoiq.com/the-ultimate-hand...n-and-scrub/3/ |
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