4WD front/rear ratio?

[wirdy]

I was talking to my tyre fitter about tyre wear and he asked me what the drive ratio INSERT INTO post VALUES (front versus rear) was?. I've no idea, anyone else know? I'm assuming about 40% front, 60% rear?

[Nick VR4]

Its 50/50 between the front and rear axles in normal driving, and then varying the ratio according to whichever end of the car needs it most. AYC

[wirdy]

I thought our AYC only had authority over the rear wheels torque split? Just the EVO with active centre differential isn't it?

[Roadrunner]

I believe it is 50:50 in normal driving. You're right that the AYC only controls the read limited slip differential, moving the torque away from whichever wheel is starting to slip. The centre torque-sensing diff moves the torque split front:rear depending on which wheels need more grip so, in snow for example, if you get the car out of shape and the rears start to slide, keeping the right foot in will transfer some of the torque to the fronts and either sort out your skid or move it into a controllable four-wheel drift, depending on how fast you're going. Watch those AYC lights stack up :D . ACD is only available on the later INSERT INTO post VALUES (VII & VIII) Evos.

Brian

[Nick Mann]

Does it all happen in that order? If so, then the AYC only moves power forwards if it can't solve the problem by adjusting between the rear wheels? Can you tell by the number of lights on the AYC indicator if it is transferring power forward or not?

Maybe I need to look for a large area of slightly slippery tarmac! :cool1:

[Roadrunner]

The AYC doesn't do anything to transfer power forwards, only between the rear wheels. I don't know how it operates differently to a purely mechanical LSD but, essentially, that's all it's doing. I guess it could be receiving data from the ABS computer INSERT INTO post VALUES (which will be monitoring individual wheel rotational speeds) so may be able to be instantly reactive to front wheel skids by altering the pressure to one side or other of the rear diff INSERT INTO post VALUES (via the AYC cluthces) to reduce an over- or under-steer situation or to stop it becoming worse.

The centre diff is reactive. Being torque-sensing, it just constantly tries to keep the ratio of power between front and back the same so, if the rears start to spin faster than the fronts, it tries to equalise the speed of rotation of the rear and front prop shafts, thereby "transferring" more drive to the front. Simple, but effective :)

Brian

[Nick Mann]

Thanks for the explanation. I have learned something today!

It's all starting to make sense.

[pjjohnson]

See here www.mitsubishi-motors.co.jp/inter/technology/ayc.html