Dynos and AWD

[Silver Ecstasy]

Granted, the CX-7 doesn't have AWD all the time, so you wouldn't need an AWD dyno to test the HP.

However, the AWD system states it measures the speed and difference of the front and rear wheels. If you were on a FWD dyno, and the front wheels start to go, but the rears are planted, isn't the computer going to want to spin the rear wheels also?

Or could you just shut T/C off and that solves the problem?

[singlemalt_18]

The urban legend continues...

First of all, the Traction Control has nothing to do with the AWD - it is a "braking system" function. Turning the TC off will only stop the braking system from engaging to limit any detected wheel-slip. If doing doughnuts in the snow, or spinning out on gravel are your goal, then turn the TC off.

Second, the CX-7 AWD can deliver "zero to 50%" of the torque to the rear wheels. This is the range of the "continuously variable" nature of the AWD system. The 50% max limit to the rear only means that the system will never deliver more than EQUAL torque to the front and rear. Simply put, the rear will never deliver more than the front - that is 50-50.

From a standing stop, a step on the accelerator will be sending some torque to both front and rear if you have AWD. The "zero" rear condition will most likely occur under very low resistance driving conditions, such as cruising at a constant speed, on a straight, level interstate highway, especially with a tailwind!:) The phasing out of the rear wheels as overall wheel resistance decreases is done to increase efficiency, thats all. Under normal acceleration & cornering, all the wheels can deliver... that is AWD.

I know there is confusion, & many believe that the rear wheels will only "kick in" after the front start to slip, but that is just not how AWD, or TC works. There's a lot more details starting with post #37 here:

http://www.mazdas247.com/forum/showthread.php?t=123650944&page=3

I may need njcx7 to give me some help here...

In answer to your question - YES! THEY WILL WANT TO SPIN.
My bet is you need a 4 wheel dyno. Good luck!

[Silver Ecstasy]

I see, well thanks so much for your help, you gave me a new found hope that AWD is indeed very much worth it and helpful! I was disappointed in my previous thoughts about the AWD system.

[Mazda3]

The TCS on the CX-7 is not just a braking system function. It is an engine mangement system. It will dump timing to reduce the power if the tires start to spin. Brake based TCS is archaic compared to the new systems.

[singlemalt_18]

The TCS on the CX-7 is not just a braking system function. It is an engine mangement system. It will dump timing to reduce the power if the tires start to spin. Brake based TCS is archaic compared to the new systems.

Very interesting insight into the current state-of-the-art...

It makes sense that more of these various monitoring & control systems are talking to each other. I would guess that the net result here makes for a TCS that operates with much more finesse.

[9Hooker]

having just run through the ice and snow in montana I can attest to

1) the AWD is indeed bueno. AWD "burnouts" on ice can be accomplished
2) the TCS is both a braking and engine system. it doesn't pull timing, it throttles back.
3) in a panic situation on an ice covered highway @ rural idaho, the TCS system is PHENOMENAL. period. i'd be happy to share the story sometime.

[Silver Ecstasy]

How do you know its an awd ice burnout though? I mean, without someone watching outside. I'm not flaming, i'm just asking.

[9Hooker]

my wife was outside :)

[Silver Ecstasy]

Sweet! Thats awesome! So it proves that they all turn lol.

[offset_98]

I'm tempted to throw my FWD up on a dyno here in town after a few thousand more miles...

[Silver Ecstasy]

I'm willing to bet 195 at the wheels.

My 400hp based GTO gets 345 at the wheels.

[9Hooker]

ok, claimed 244, right? The standard auto tranny is somewhere in the neighborhood of 78% efficient... I'll put $5 that it's 190hp to the wheels on a 2wd dyno, 184 on an AWD dyno. +/- 4hp.

I'd love to see the results!!!

[Silver Ecstasy]

I start to wonder how much the trans can handle..