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REW-swap with Megasquirt - ABS, EPS, Cluster

Old 10-20-2018, 08:21 PM
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REW-swap with Megasquirt - ABS, EPS, Cluster

Here's my situation: I'm currently the owner of an FD RX-7 mostly-race car (Time Attack / TT / track days). I run a Megasquirt MS3X ECU with a single turbo and I'm really fond of this setup. The bad news - a little less than a month ago I crashed the car hard at a time trial event. It was no fault of my own and I'm not happy about it; but now it's time to move on. My next project will be to build an RX-8 with the REW engine from my crashed FD. I want to keep the Megasquirt because I have the engine dialed in on it and I really like the ECU in general. I've researched REW swaps in RX-8s along with the RX-8 CAN-Bus system and anything relating to those to extensively. There seem to be three main challenges if I go this route - getting the following three systems working properly without the stock ECU: electric power steering, ABS, gauge cluster. I want to lay out my current assumptions to make sure I'm not going into this blind, and also get some advice on what year/model RX-8 to avoid as I search for a car to buy.

1. Electric power steering: I think I can make this work by sending some CAN-Bus signals to the proper addresses. I have a lot of experience with Arduino microcontrollers and I've built a few CAN Arduino sensor input boards that I used on the FD for additional sensor inputs to the Megasquirt. So, I plan to wake up and control the EPS by using an Arduino to send some CAN messages to the proper addresses. Other people have gotten the EPS to work by sending data to the following CAN addresses: 0x200: 00 00 FF FF 00 32 06 81 (some data to show the engine is running?), 0x201: RPM on bytes 0 and 1, speed on bytes 4 and 5, 0x202: 89 89 89 19 34 1F C8 FF (some data to show the engine is running?). I can make the Arduino send all of this data; the RPM and speed data will come from the Megasquirt and the Arduino will read, scale, and send with the proper addresses. Sources for this info: G4+ Mazda RX8 CAN Bus - G4+ - Link Engine Management Mazda CAN Bus ? Madox.NET

2. ABS: This is my biggest unknown right now. Does the non-DSC ABS run without CAN data from the ECU? If I get a car with DSC, can I just swap in a non-DSC ABS and have it work properly? I assume it mainly just needs the wheel speed data. I think the ABS ECU reads these signals directly and then broadcasts them over CAN? To clarify - I don't have any need for DSC, but I want the ABS to work.

3. Gauge cluster: This is the least of my worries. Other people have gotten this to work by using CAN enabled Arduinos, so I think I can make it work too. RPM and speed seems to be in CAN address 0x201, so the same data needed for the EPS should also drive the tach and speed display (hopefully?).

So that's my information dump for now. If anyone is familiar with these systems please check my logic and make sure I'm not going into this blind. My main point of confusion right now is on the ABS - specifically differences between DSC and non-DSC and if I can get them to work independently of the stock ECU.
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Old 11-02-2018, 04:20 PM
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I joined this forum because I read your article and am wrestling with a similar problem for EPS.

I'm not as technical as you, so I can't contribute in that manner (yet!), but my research pointed me to a few articles you might have missed, coming from DIY electric car projects. The best was: RX8 Electric Power Steering EPS CAN Control ? The EV Conversion Guide

I've also attached a write-up of the EPS that I found, which may be of use, but I sense you're a step further down the road than I am!

Attached Files
File Type: pdf
Rx8-Steering.pdf (1.36 MB, 18 views)
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Old 02-18-2019, 03:23 PM
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Some updates on this: I ended up buying a 2004 non-DSC car. It's not running yet, but I have done some learning so far:
  • The ABS is totally standalone, it just needs to see the wheel speed signals. It broadcasts all 4 wheel speeds to the CAN-bus on 0x4B0 which I can confirm by spinning the wheels by hand. Awesome!
  • The non-DSC ABS would not be an easy swap into a DSC car had I gone that route. The hard lines in the engine bay are different, and the wheel speed sensors are different from what I understand. Not impossible though.
  • I have successfully gotten the instrument cluster to work by sending (fake) RPM and speed data to 0x201. The EPS uses the same CAN data, so that's encouraging. I've gotten it to work using an Arduino with an MCP2515 module (the cheap $2 model on ebay), and I've also gotten it to work with a RaceCapture Track MK2 datalogger and a Lua script. I'm going to use the RaceCapture going forward to repackage the CAN data and send it to the correct addresses - the code is simpler and it will already be accessing all of the needed CAN data from the Megasquirt.
That's all for now. I'm getting close to testing the EPS, so I'll update this once I do.
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Old 05-17-2019, 02:26 PM
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Update - I got everything working. Using a RaceCapture Track MK2 datalogger as mentioned above with a Lua script that I wrote to send out CAN data. The EPS works, along with the tach, speedometer, coolant temp gauge, oil pressure gauge, and battery light.

The link below has the script I'm using (post #4 is my current version):
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Old 05-17-2019, 04:13 PM
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Congrats and good job, appreciate all the info
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