MPS 6 AWD operation

[kmh001]

In case you missed it elsewhere.....

This is what happens when I take a month off work and get curious about the car. There's been a lot of conjecture and mis-reporting over the years about how the AWD works in the MPS and I decided to take the mystery out of the discussion.

I set up a multi-meter to monitor the '4WD CM' output voltage to the diff coupling solenoid. This voltage roughly correlates to the proportion of torque being transferred to the rear wheels. Unfortunately I don't know what the voltage should be at 50:50 torque distribution, so I can't put this data into proper context, but I can say the highest voltage I saw all day was 6.6v when I nailed it on a loose surface.

We now have objective evidence to demonstrate how and when torque is transferred to the rear wheels. The short answer is, all the time, in varying degrees, except at very low speeds (say below 5 kmh) and when the hand brake is applied.

While monitoring, I drove the car in a range of conditions and never saw zero voltage except as described above. Unfortunately the video is limited to street legal operation so we don't get to see AWD operation across the full performance spectrum.

It's shame I didn't have an analogue multi-meter, it would have given a nicer, more qualitative indication. At least the digital meter gets the message across.

This is how the workshop manual describes the system.......

Electronic 4WD control system outline
• The newly adopted electronic 4WD control system automatically and optimally controls drive torque distribution for the front and rear wheels. Due to this off-road mobility, driving stability and fuel economy are improved.
• Based on the input signals from each sensor, the 4WD control modure (4WD CM) determines vehicle driving and road conditions, and controls output current to the electronic control coupling (4WD solenoid) inside the
rear differential. This control allows for optimal distribution of the drive torque from the engine to the rear
wheels.

And this is how it describes the modules............

4WD CM
• Controls operation of the electronic control coupling (4WD solenoid) based on signals input from the throttle opening angle, speed, differential oil temperature and other sensors.
• Outputs coupling control condition and 4WD warning control information as a CAN signal.
• Controls the on-board diagnostic system and the fail-safe system if there is a malfunction in the 4WD system.

PCM
• Sends the throttle opening angle and engine speed signals, as CAN signals, to the 4WD CM.

DSC HU/CM
• Sends the four-wheel speed and DSC operating condition signals, as CAN signals, to the 4WD CM.
• Sends the coupling torque request signal, as a CAN signal, to the 4WD CM.

And here is how it looks in operation............

YouTube - Mazda MPS 6 AWD operation

[armthehomeless]

Interesting find!

[JestaT]

very interesting and I apreciate the info you have posted great stuff.. it's interesting to see how this system works as it's different to everything else ive seen so far.

Cheers

[Nexus]

Sounds like AWD control could even be implemented on a 3 with a third party ECU - standback, perhaps. Apparently there's a conversion kit - I am wondering how they do it now because it seems a control voltage and maps for that CV are all that's required....

[kmh001]

Sounds like AWD control could even be implemented on a 3 with a third party ECU - standback, perhaps. Apparently there's a conversion kit - I am wondering how they do it now because it seems a control voltage and maps for that CV are all that's required....

The complex variable torque distribution is nice to have, but not entirely necessary. For the application you're suggesting you could just hard wire 12v into the diff solenoid and have permanent 50:50 torque distribution.

The only time it would be undesirable to have 50:50 is when parking when high steering angles make the drive line prone to binding. A low-tech solution to that would be to provide a switch to turn off the rear diff.

[nickows]

very interesting research. thanks for taking the time to let us know what you found and posting the video

[shakespeare]

Thanks KMH001, always good to know how your car works - great vid too. Is the Haldex set-up used on VW's and others similar to the Mazda set-up? You don't have to do as much research (unless you're still on leave)

[kenji]

By any chance, can the mps6 split more than 50% torque to the back. If so, what sort of modifications need to be made? i just thinking if someone can make it to split 70% toque to the back we may have something handle as well as a STI.

[Nexus]

By any chance, can the mps6 split more than 50% torque to the back. If so, what sort of modifications need to be made? i just thinking if someone can make it to split 70% toque to the back we may have something handle as well as a STI.

Not with the current 1:1 clutch pack configuration. I believe I have a replacement design for this solution which amounts to a single-input shaft single-output shaft differential that could be controlled with the same control voltage method that the clutchpack uses. I don't have the resources to do any more than dream it up, but I believe it would work if it can be made as a drop in replacement. A simple 70:30 split wouldn't necessarily apply, but what could be achieved is center differential locking and a means of effecting rear drive bias...basically when the solution reaches it's "lock" configuration, the rears would be trying to travel a certain small % faster than the front...It is based on a run of the mill differential but utilizes a secret solution to control the ratio between the input and output shaft. It would expect the output to be 1:1 most of the time, during which the output shaft is rotating at 9x% of "lock". The "lock" configuration has the output shaft slightly faster than the input; the differential allows the output to be significantly slower than the input (no/minimal torque applied) up to a small % faster (rear bias). I don't expect to be able to prototype it anytime soon, and it would need proof of concept testing to ensure the handling effects are as expected.

[kenji]

That sounds like rocket science to me, haha. Just thought that would make the fun MPS6 to be even more fun to drive. Do you think anyone would/ would had made it happen??