Staggered wheel sizes on MPS6

[99GTT]

We have a hidden switch somewhere to turn off the rear diff/drive to rear wheels? Why have I not found this yet??!!

Thanks for all the info by the way!
:-)

[Victa]

First click on the handbrake turns off the rear diff/coupling/clutch/whatever...

So no power goes to the rear with the handbrake on, designed to allow handbrake initiated drfting...

[EDIT] A popular mod seems to be adding an extra switch to this setuip so that the rear end can be shut off without pulling the handbrake on... Also I have read info that suggests this ALSO turns off DSC [/EDIT]

Chris.

---------- Post added at 11:31 AM ---------- Previous post was at 11:07 AM ----------

Found the article I read a while ago... Mazda 6 MPS

The important bit...
---***---
The handbrake, the engineer explains, communicates with both the all-wheel-drive and the chassis stability systems. It's quite simple, really. A computer controls the clutch pack that connects and disconnects drive to the 6 MPS's rear wheels. Another computer runs the chassis stability system, which selectively brakes individual wheels to restore stability when the front or rear of the car begins to slide. But tug the handbrake, and both systems are instantly neutralised. This feature has been included, Bakaj says, specifically to allow drifting-style fun. And once the car is flicked sideways with a brief dose of handbrake, the intentionally aggressive torque transfer to the rear wheels is designed to deliver the ability to throttle steer. Or, as Mazda's official 6 MPS press material coyly puts it: "The ability to fully balance the car in a turn by deft use of the accelerator pedal."
---***---



Chris.

[shakespeare]

First click on the handbrake turns off the rear diff/coupling/clutch/whatever...

So no power goes to the rear with the handbrake on, designed to allow handbrake initiated drfting...

[EDIT] A popular mod seems to be adding an extra switch to this setuip so that the rear end can be shut off without pulling the handbrake on... Also I have read info that suggests this ALSO turns off DSC [/EDIT]

Chris.

---------- Post added at 11:31 AM ---------- Previous post was at 11:07 AM ----------

Found the article I read a while ago... Mazda 6 MPS

The important bit...
---***---
The handbrake, the engineer explains, communicates with both the all-wheel-drive and the chassis stability systems. It's quite simple, really. A computer controls the clutch pack that connects and disconnects drive to the 6 MPS's rear wheels. Another computer runs the chassis stability system, which selectively brakes individual wheels to restore stability when the front or rear of the car begins to slide. But tug the handbrake, and both systems are instantly neutralised. This feature has been included, Bakaj says, specifically to allow drifting-style fun. And once the car is flicked sideways with a brief dose of handbrake, the intentionally aggressive torque transfer to the rear wheels is designed to deliver the ability to throttle steer. Or, as Mazda's official 6 MPS press material coyly puts it: "The ability to fully balance the car in a turn by deft use of the accelerator pedal."
---***---



Chris.

MPS 3 switch link

MPS6 rear diff switch

[kmh001]

The description you made on your 'centre diff' is actually called a 'transfer case'. It has gears, but no reduction is made. Just changes direction of the power flow.
This description from wiki should help a little better...

http://en.wikipedia.org/wiki/Differe...hanical_device)



(I wrote out a description myself, and then somehow deleted it before posting... FML. )

---------- Post added at 07:40 AM ---------- Previous post was at 06:56 AM ----------

I've also had a look at some other threads on this site about torque distribution, and I'm sorry to say, but most of it is incorrect.

In 2 mins searching I found this...

6 MPS (MAZDASPEED6 In The U.S.)
"Active Torque Split" proactive automatic all wheel drive. Normally front-wheel drive vehicle. Electronically controlled multiplate electromagnetic clutch transfers up to 100% of torque to the rear when needed. Limited-slip differential in the rear.

The MAZDASPEED6 with advanced AWD system analyzes real-time data on steering angle, yaw rate, lateral G-force and engine status to establish up-to-minute road surface conditions, and the vehicle's dynamic status. Normal, Sport, and Snow modes give the perfect amount of torque where it is most needed, and have a performance reaction that leaves conventional gear- or fluid-controlled systems in the dust. Front/rear torque distribution varies from 100/0 to 50/50.

Source: Mazda USA - The Official U.S. Site for Mazda Cars, Crossover Vehicles, SUVs and Trucks

The current Honda Legend, and the now extinct MDX have/had this system. (I will just quickly say now that the CR-V is a completely different setup). Simply put, it's a shaft that goes into a coupling, with wet clutch discs and metal plates. In normal operation, the input slips inside the coupling, producing NO output. When the vehicle needs it, the ECU will send a signal to the 'coupler', magnetizing the clutch plates and discs, locking them together to provide FULL output. It can be varied with lower current to allow output slip. Same output speed, just less torque.
I've just now learnt how the system works (because I haven't bothered to learn), and am trying to pass on some correctness here.
This electro-magnetic clutch system is fantastic. As I said, the Legend has this in the rear diff (instead of seperately) in the SH-AWD badged vehicles, and does the same job.

That 'switch' you have in your car to turn of the rear diff, just stops any power to the electro-magnetic clutch pack, and then enables FULL front wheel drive mode. This switch backs my description.

If you disagree at all, I'm happy to explain this better.
P.S. Just before I go, I do disagree with the extract I pulled and posted before. The electro-magnetic clutch arrangement on the 6's DOESN'T allow for 100/0% torque to the rear, it SHOULD say 100/0% torque to the front wheels, and up to 50/50 torque split, front and rear.
The 6 is primarily a FWD vehicle until rear drive is needed...

I am not confusing the PTO (transfer case) with the centre diff, because the PTO is not a diff. Nor is the diff coupling.

Your own quote says it all: "In a four-wheel drive vehicle, a viscous coupling unit can replace a centre differential entirely". That means it can have a diff coupling instead of a centre diff. That's because a diff coupling is not a centre diff. They are two different things. A differntial, as I have already explained, takes an input and divides it into two. A viscous coupling does not do that.

And if you've interpreted the other quote to mean that the 6 is AWD on demand you are mistaken. The 6 is not "FWD until the rear is needed". Although many joutnalists have misunderstood and misreported in this, so you're not the first to get it wrong. The 6 awd operates constantly unless the handbrake is applied. It even operates in reverse. And no, thanks for the offer, but I don't need you to explain something I already understand.

[Grajy]

I am not confusing the PTO (transfer case) with the centre diff, because the PTO is not a diff. Nor is the diff coupling.

Your own quote says it all: "In a four-wheel drive vehicle, a viscous coupling unit can replace a centre differential entirely". That means it can have a diff coupling instead of a centre diff. That's because a diff coupling is not a centre diff. They are two different things. A differntial, as I have already explained, takes an input and divides it into two. A viscous coupling does not do that.

And if you've interpreted the other quote to mean that the 6 is AWD on demand you are mistaken. The 6 is not "FWD until the rear is needed". Although many joutnalists have misunderstood and misreported in this, so you're not the first to get it wrong. The 6 awd operates constantly unless the handbrake is applied. It even operates in reverse. And no, thanks for the offer, but I don't need you to explain something I already understand.

I have no idea what you're talking about. Normally I'd like to learn about why I'm 'wrong', but in this case, the Mazda 6 doesn't interest me, as I've voiced before (under judgement).
Good luck thread poster, do what you will to your car.
I'll go back to my daily job of 12 years as a mechanic and shut up...
Jon out

[blackbetty]

Thanks Mal for taking the time to post the information up on here. There are alot of 6 drivers who are on this forum too who do care about and want to understand the way the AWD system of the 6 works and Im very thankful that we still have people like you on this forum who care enough to keep posting information like this for us despite us sadly being in a place where the majority of the people think the 6 is quite unworthy of the MPS badge and that the only fun, exciting, fast 6 is a heavily modified one.

I for one appreciate the enthusiasm and knowledge of someone like you

And the original poster of this thread owns an MPS6 too so Im sure they are very grateful for your input

[99GTT]

Thanks Mal for taking the time to post the information up on here. There are alot of 6 drivers who are on this forum too who do care about and want to understand the way the AWD system of the 6 works and Im very thankful that we still have people like you on this forum who care enough to keep posting information like this for us despite us sadly being in a place where the majority of the people think the 6 is quite unworthy of the MPS badge and that the only fun, exciting, fast 6 is a heavily modified one.

I for one appreciate the enthusiasm and knowledge of someone like you

And the original poster of this thread owns an MPS6 too so Im sure they are very grateful for your input

+1
totally agree. Do appreciate your time guys.

Just a little note, when I was on the dyno, assuming there is little to nil resistance right at the start, as soon as you let go of clutch all four wheels start spinning simultaneously atvthe same speed on every run. If one didn't know better, one would assume that it was AWD all the time!

Would love to know exactly how it is set up! All your comments have intrigued me!

[Doug_MPS6]

Some of the confusion arises, I suspect, from the fact that any device mounted between the front and rear drive systems in AWD cars, is intended to cater for the "differential" between the rates of rotation of front and rear axles in certain situations, without which "transmission wind-up" would be experienced between front and rear axles, a situation where stresses are not capable of being relieved except by slippage between the tyres and the road. A clutch pack achieves this by enabling slippage between its component plates (or viscous couplings) to eliminate the wind-up. Any device which is not clutch pack or viscous coupling and which can reasonably be termed a "centre diff" (by virtue of being equipped with gears as opposed to clutch plates or hydraulic engagement between driving and driven members) is essentially there to fullfill the same purpose, although it may include other functions.

The term "differential, was originally employed in reference to the need to "differentiate" between the varying rates of rotation (such as when negotiating corners when the outer axle is rotating faster than the inner axle, this difference requiring accommodation to enable a turn to be executed without tyre scrub and internal stress) in an axle system that not only provided a gear reduction for further fixed mechanical advantage additional to the variable advantage provided by the gearbox, but also turned the longitudinal drive - typically from the front mounted engine - at right angles so as to drive a rear-mounted axle. This term is thus not in the same context as that used for the devices discussed in the preceding paragraph, the only common factor being the variation in rotation speeds of the attendant shafts through which power is being transmitted, regardless of their purpose and direction with respect to the axis of the source of power at the engine crankshaft.

[kmh001]

If one didn't know better, one would assume that it was AWD all the time!

And you'd be right. There's a video floating around somewhere showing where I directly monitored the diff coupling control voltage under a range of different operating situations. It shows that the awd operates all the time, even in reverse. The only time you get 100-0 torque distribution is when the handbrake is applied, and at very low speed with no throttle, such as when parking.

[mattyyyy]

Hi guys, do you know if it is OK to use different brand tyres on the front of a 6MPS than the back although the same size?