Help with Power Steering and MoTec ECU
 

I recently purchased one of SpeedSource's former Koni Challenge Series I RX-8's. The car is setup with a MoTec ECU and Dash. The original owner said that the car never had power steering when he raced it in the Grand Am Koni Challenge with Speedsource. SpeedSource says they did run the cars with the power steering active (eventually?). I know the MoTec ECU needs to send a speed & RPM signal to the CANBUS and the power steering control module. The shop that is working on the car right now says that they are not getting a signal (even a ground signal) to the power steering unit. I assume they are saying they aren't getting a signal from the MoTec. Does the car need to be at speed to send a signal to the power steering?

We've talked to MoTec and SpeedSource, but since the car is almost 14 years old now no one really remembers specifics.

Right now the shop is asking if I want to:

-take the 50/50 chance of replacing the power steering control module and/or rack see if that miraculously solves the problem?

-replace the electronic power steering with a modified traditional manual power steering from some other car?

-gut the gears out of the current power steering that way at least I won't have to muscle against all the internals of an inactive power steering?

-or leave it as is?

It is exhausting without the power steering, I ran the car in 3 sprint races two weeks ago. And with power steering I'd probably shave my lap time down a little. But mainly I'd like to have it incase I find my self in a situation that I need some quick steering response to get out of.

Anyone have any experience with getting the power steering to work with a MoTec (or any other stand alone ECU) and have any advice as far as wiring, signals, power, etc? I'd prefer to get the factory power steering working with the MoTec over anything else. It must be possible because Speedsource says they were running the cars with power steering.

I'd think Motec could tell you if the car needs to be moving to send a speed signal, but from my experience with aftermarket ECUs (which is only 'some', by no means an expert), I haven't seen a case where a signal is dependant on vehicle motion. Stationary, it just reports a speed of zero.

If I was in your shoes, I'd probably insist that the shop trace the wires from the PS module to the Motec. If no one remembers, it may not even be clipped in. I've left signal wires accidentally not clipped into the connectors before, other times signal wires have become damaged or failed due to heat and vibration, etc... If the shop isn't getting ANYTHING on the signal wires between the Motec and the PS, address the wires first. If they are confirmed to be good, hunt through the Motec and related documentation to determine if they are the right outputs, and if those outputs are turned on.

I'd only throw money at the power steering unit once you had signal information from the Motec and it still didn't work.

If you want a fast for sure option, switching to a hydraulic PS removes all the hassle. I did something similar when i swapped to an internally regulated alternator (different car) when i couldn't find why the ECU regulated one was acting up

Going full manual is interesting, I did that on one car, but then the tires were ~40-50mm narrower and the car was 400-600lbs lighter. I would want to keep PS for what you have.

Yeah the first thing I would have done would have been to trace the wiring if I wasn't getting a signal from the MoTec. I was a little confused when I was talking to them why they recommended replacing the PS unit if the signal wasn't even getting to it in the first place. So I'm assuming they checked already, but I will double check that with them. My next thought would be if the wires and connections are solid that the MoTec itself isn't sending the correct signal. And I don't know if that requires us turning something on inside the motel and telling it to send the signal or not. I have no experience in this area, but I told the shop I would do some research before I green lit replacing anything.

Yeah. Again, no experience with a Motec, but the one I've spent a fair amount of time messing with, you can turn on and off inputs and outputs really easily. Start upstream, work down.

Working through a shop to get someone else's mess working is never pleasant. Or cheap.

Anyone have any experience with connecting a Motec to the power steering? So I can relay to the shop exactly what needs to be hooked up and what needs to be turned on to get the right signals to power steering module

Speed and rpm CAN signals are only for controlling the assist and maybe that the engine is running, which the EPS needs to work even at zero speed/engine running. A post here from back in 2005 stated the Speedsource GrandAm car didn't have power steering. Maybe that changed later or was a mistake as in theory it should be able to operate given all the correct power and input signals. It should have a fairly serious main power supply wiring & fuse setup. Without that nothing will work.

I'll go back through all my RX8 info and see what info there is for EPS. Often the troubleshooting data will provide a good amount of info, but not always every detail. There is some info on the web by just googling motec power steering, some relative to the RX8 but the usual working on it and going to do it and then never heard from again ...


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Thanks! I came across the same posts in my search, but like you said they mention the RX-8 and power steering and then don't go into detail except that they have either do it, or it's possible.

TORacing I have merged your previous "Horse" account into this "TORacing" account. i hope you get the eps sorted out

So the shop spoke to Motec, they say everything that is supposed to be turned on or open inside the Motec is. We replaced the PS steering control unit with a loaner and we were able to get a signal on the output side of it. But no still no PS... so we picked up a used rack from a local shop that we know was in working order and put it in. But still no PS.

Sorry for not getting back to you sooner. Regarding the EPS system, I didn't have anything outside of the standard service manual information. You really have to start there and go through as many of the detailed troubleshooting scenarios that you can checking all the signals, connections, values, etc.

If the EPS unit, the EPS Control Unit & Noise Filter, and Torque Sensor are all wired and working properly it seems like it ought to at least have a basic function, but there may be more to it than that. Whether it's all setup & communicating properly through CAN is maybe going to be the hardest part to figure out.

Does it actually need the CAN signaling? I always assumed it would revert back to basic steering assist without adjusting for vehicle speed purely as a safety precaution.

I studied the service manual tonight and have to believe it's related to the CAN driver signal to the control unit. Unfortunately I haven't been able to locate anything from Mazda that defines that signal or that even provides a generic cursory explanation on how the system is intended to work. Logically it seems like there has to be some kind of processing relationship between the Torque Sensor, the Control Unit, and the Driver Signal.

The driver "signal" is the torque reading on the sensor, is it not? At that point the only real thing that seems necessary in order for our steering to function is to know the vehicles speed. It's all a moot point without the proper protocol though. It's not terribly hard to hook up a CAN bus sniffer to the power steering, though you'd need a working setup to begin with.

Those were actually more questions posed to you rather than advice given to the OP. I was curious how the system works. You're right though, I should have known better.

Edit: You know, I was wrong about one small detail. I did not see you refer to it as the "CAN Driver Signal" and thought you were referring to the actual human driver's input. so my mistake for mis-speaking there. Even though it was formed as a question, with an absolute correct hypothesis. Yet when I re-explained exactly how the EPS actually works you proceed to flame me like a child about facebook. Nothing I said beyond the singular reference to the "driver signal" was incorrect, you need to get the fuck over yourself.

Also, I'm on facebook about once a month, so congrats with the bullshit sweeping generalizations. At least when people make them about you, they're pretty much spot on.

So moving on, the online service manual literature is mostly very early copies that are often not accurate and I wasn't sure what you're working from, so I wanted to post up this information from an actual manual; 2005 version. While you don't have the ability to do onboard diagnostics, often good information can be gleamed from the procedures

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Well if your confident that all of the hardware is proper and wired correctly per the service manual diagrams I posted then that only seems to leave a CAN communication/driver signal issue of some sort, but I'd still want to go back through all the service manual info I posted to make sure everything matches up to the various specs and values listed there

Good info

Lock to lock ratio changing from bad information with ECU explained a couple of things.

I really wish you had more information on this! I've got a link ecu in mine and the pas works intermittently, and I've checked the wiring with a meter etc. Also the abs light won't turn off as I don't have the can protocol for that 😒