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RX-8 Electric Power Steering Rack Swap into 1988 Chassis , Invisible! by anaverin
Started on: 10-05-2020 02:22 PM
Replies: 19 (457 views)
Last post by: anaverin on 10-10-2020 12:45 AM
anaverin
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Report this Post10-05-2020 02:22 PM Click Here to See the Profile for anaverinSend a Private Message to anaverinEdit/Delete MessageReply w/QuoteDirect Link to This Post
So, We have been using West coast fiero's Saturn vue power steering kit. As anyone who has done this swap knows, it kind of interfers with footroom. Given my Client 's is in his 70s, he has an even harder time getting in and out of the car. So we did some research and found that this 2007 Mazda RX8 EPS rack has the motor contained in the rack, and the rack is approx the same 24 inch length between the inner tie rods in the center.
We then made plastic pieces to mock up how we would make the brackets to hold it, and we came up with this design that we had waterjet just out of 1/4 steel.
I got the steel parts back from water jet and tacted them into place. You can see the old Bracket on the Driver side gets repurposed, and the passenger side one gets eliminated.

Here is what we have so far. I am going to explore controlling it with the Saturn EPS controller. Will update when i know more.

------------------
86 SE FASTBACK T-TOPS
88 FORMULA 4.9
87 GT MEDIUM RED METALLIC stockish


EMAIL : Anaverin@gmail.com

[This message has been edited by anaverin (edited 10-05-2020).]

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Spadesluck
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Report this Post10-05-2020 04:45 PM Click Here to See the Profile for SpadesluckSend a Private Message to SpadesluckEdit/Delete MessageReply w/QuoteDirect Link to This Post
Watching, looks very interesting.
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Rickady88GT
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Report this Post10-05-2020 06:31 PM Click Here to See the Profile for Rickady88GTClick Here to Email Rickady88GTSend a Private Message to Rickady88GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
I love the idea of an electronic assist rack. If I do any more power steeing systems in a Fiero, I will look into an electric rack. I am not sure about the electronic controls of it tho.
I will keep an eye on this thread.
Thanks
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pmbrunelle
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Report this Post10-05-2020 06:36 PM Click Here to See the Profile for pmbrunelleClick Here to Email pmbrunelleSend a Private Message to pmbrunelleEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by anaverin:
I am going to explore controlling it with the Saturn EPS controller. Will update when i know more.


If you have questions about that, I know a thing or two about EPS.

You can always post pics of the connectors and where they go, and we can attempt to figure things out.
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anaverin
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Report this Post10-05-2020 09:34 PM Click Here to See the Profile for anaverinSend a Private Message to anaverinEdit/Delete MessageReply w/QuoteDirect Link to This Post
I am just wondering if i can use the Torque sensors in the Mazda rack, (which i have all the factory service information for) and soder them into the saturn controller. Alternatively I could modify the mazda controller to work, but since we already have the saturn controller working, i would like to try that first. I am going to ohm out the sensors on the saturn rack, to see if they are similar to the 14 ohms of the mazda sensors.

Rest assured though, after spending money on getting waterjet cut parts, I will be figuring out a way to make this work!

thank you for your interest, i will try to upload the service manual stuff for the mazda in case you are curious. I have actually done more research then i was able to convey with the post.

If you have questions about that, I know a thing or two about EPS.

You can always post pics of the connectors and where they go, and we can attempt to figure things out.

[This message has been edited by anaverin (edited 10-05-2020).]

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pmbrunelle
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Report this Post10-05-2020 09:51 PM Click Here to See the Profile for pmbrunelleClick Here to Email pmbrunelleSend a Private Message to pmbrunelleEdit/Delete MessageReply w/QuoteDirect Link to This Post
If the Mazda controller already normally works with the Mazda motor and the Mazda torque sensor, then it seems like it would be easier to work with the Mazda controller, but that's just my first impression.

To make the controller work, it needs to think it's in the Mazda. I think it would be easier to make the Mazda controller believe the lie that it lives in a Mazda. This would be telling it the proper lies via the CAN bus.

The other choice is to make the Saturn controller work with "major organ transplants"... the thing is that the Saturn controller can't reject its new friends!
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anaverin
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Report this Post10-05-2020 10:15 PM Click Here to See the Profile for anaverinSend a Private Message to anaverinEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by pmbrunelle:

If the Mazda controller already normally works with the Mazda motor and the Mazda torque sensor, then it seems like it would be easier to work with the Mazda controller, but that's just my first impression.

To make the controller work, it needs to think it's in the Mazda. I think it would be easier to make the Mazda controller believe the lie that it lives in a Mazda. This would be telling it the proper lies via the CAN bus.

The other choice is to make the Saturn controller work with "major organ transplants"... the thing is that the Saturn controller can't reject its new friends!


I guess i am concerned about the mazda controller wanting to talk to the pcm via can bus. The Saturn controller has already been rigged to work via a dial that is nicely installed into the AUX pod. The owner would like to keep that if possible. As far as usability goes, the setup is amazing other then the motor intruding into the footspace and looking ugly. We will see how this goes. Anything is possible, but we will be working until the solution is satisfactory.

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anaverin
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Report this Post10-06-2020 12:06 AM Click Here to See the Profile for anaverinSend a Private Message to anaverinEdit/Delete MessageReply w/QuoteDirect Link to This Post
First tests are as follows:
Mazda RX8 TQ Sensor at rest =12 ohms
Saturn TQ Sensor at rest = 5 ohms

currently we use the PWR Steering at less then 50 % assist on the Dial. So being that 12/5= 2.2 maybe that means that we would get the same assist (assuming the motors draw equal power, which is a big if) at 110% on the dial. We will be doing some practical experiments this week but farther research indicates that it has proven very complex to replicate the Can signals needed to make the RX8 module work. so for now, we will be trying to make the saturn module (which is a Denso / KOYO product anyway ) work. will let you know how it goes.

[This message has been edited by anaverin (edited 10-06-2020).]

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anaverin
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Report this Post10-06-2020 03:08 AM Click Here to See the Profile for anaverinSend a Private Message to anaverinEdit/Delete MessageReply w/QuoteDirect Link to This Post

anaverin

407 posts
Member since Aug 2002
Welded everything up, and painted it tonight.



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Will
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Report this Post10-06-2020 08:45 AM Click Here to See the Profile for WillClick Here to Email WillSend a Private Message to WillEdit/Delete MessageReply w/QuoteDirect Link to This Post
Are you going to be checking for bump steer?
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pmbrunelle
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Report this Post10-06-2020 12:53 PM Click Here to See the Profile for pmbrunelleClick Here to Email pmbrunelleSend a Private Message to pmbrunelleEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by anaverin:
First tests are as follows:
Mazda RX8 TQ Sensor at rest =12 ohms
Saturn TQ Sensor at rest = 5 ohms


Huh, cool.

If both torque sensors are variable-resistance output, that could be plug-and-play.

 
quote
Originally posted by anaverin:
We will be doing some practical experiments this week but farther research indicates that it has proven very complex to replicate the Can signals needed to make the RX8 module work.


Usually what works to get up and running (at least half the time) is to simply record the CAN bus traffic of an idling vehicle onto a PC (using a CAN to USB interface). If you play back the recording, oftentimes that's enough. If you're lucky, you can sit in someone's idling car and get a recording from the OBD-II port.

Then, to determine which CAN messages are essential, you play back the CAN trace, but with one less message each time. Once you're at the point where taking away any single message causes the EPS to stop functioning, you know you're at the bare minimum.
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Report this Post10-07-2020 08:20 PM Click Here to See the Profile for GetafixClick Here to Email GetafixSend a Private Message to GetafixEdit/Delete MessageReply w/QuoteDirect Link to This Post
Bump steer is not an issue, measurements of '88 and RX-8 racks are nearly identical, no more than 1/8" different, if at all.
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Report this Post10-07-2020 09:14 PM Click Here to See the Profile for GetafixClick Here to Email GetafixSend a Private Message to GetafixEdit/Delete MessageReply w/QuoteDirect Link to This Post
Here are the patterns for the water jet service to make the parts for the RX-8 mounts.
NOTE that the bolt holes in the Part 1 graphic ARE NOT to size, so only a pilot hole, maybe 1/4" dia, should be water jet cut.




[This message has been edited by Getafix (edited 10-07-2020).]

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Report this Post10-07-2020 09:25 PM Click Here to See the Profile for GetafixClick Here to Email GetafixSend a Private Message to GetafixEdit/Delete MessageReply w/QuoteDirect Link to This Post
Jig for aligning the mounts for the RX-8 EPS to the '88 Fiero suspension. Two 1/2 aluminum "L" rails with alignment jigs are taped into place. Those jigs locate the notches in parts 2, 3, and 4. After those parts are tack welded into place, the "L" rails are removed and the two parts 1 are tack welded onto the parts 2 (x2) and parts 3+4. The part 1 that has the 1/4' milled out goes onto parts 3+4 with the "milled" relief facing up to clear the RX-8 EPS.


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Report this Post10-08-2020 06:32 PM Click Here to See the Profile for GetafixClick Here to Email GetafixSend a Private Message to GetafixEdit/Delete MessageReply w/QuoteDirect Link to This Post
Testing RX-8 EPS with temporary connection to Asterix. Yay, It works! Now to create the harness, Alex is up to it!

https://www.facebook.com/br..._processed&ref=notif

[This message has been edited by Getafix (edited 10-08-2020).]

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Rickady88GT
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Report this Post10-09-2020 12:38 AM Click Here to See the Profile for Rickady88GTClick Here to Email Rickady88GTSend a Private Message to Rickady88GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
awesome
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Report this Post10-09-2020 07:50 AM Click Here to See the Profile for RCRClick Here to Email RCRSend a Private Message to RCREdit/Delete MessageReply w/QuoteDirect Link to This Post
Awesome work. I did not realize it was capable of steer by wire, or am I missing something in the video.

Bob

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anaverin
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Report this Post10-09-2020 02:16 PM Click Here to See the Profile for anaverinSend a Private Message to anaverinEdit/Delete MessageReply w/QuoteDirect Link to This Post
All EPS racks provide assistance when they get steering input which would cause them to seem like steer by wire if they were getting their steering input from a wheel not connected to the steering shaft.
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pmbrunelle
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Report this Post10-09-2020 06:08 PM Click Here to See the Profile for pmbrunelleClick Here to Email pmbrunelleSend a Private Message to pmbrunelleEdit/Delete MessageReply w/QuoteDirect Link to This Post
I suppose that both setups (Mazda and Saturn) use a 2-wire DC motor. This is easy to interface compared to a 3-wire motor.

[This message has been edited by pmbrunelle (edited 10-09-2020).]

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anaverin
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Report this Post10-10-2020 12:45 AM Click Here to See the Profile for anaverinSend a Private Message to anaverinEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by pmbrunelle:

I suppose that both setups (Mazda and Saturn) use a 2-wire DC motor. This is easy to interface compared to a 3-wire motor.



CORRECT!
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