Rafale, would you be able to provide a picture or link to the pdf where the service manual states that it goes into neutral?
I've always wondered about this "lurch". However, I would describe it as a slight jerk, but I can understand why you would call it lurch, because immediately after the slight jerk, the car will start to roll forward. I can feel it happen in the car every once in a while. I cannot figure out what the conditions are for the transmission to want to engage neutral when stopped. However, I have to disagree with it being the hill start assist because I feel this "lurch" on flat roads.
I've felt how hill start assist works and experienced this several times. When I let go of the brake to get on the accelerator, the hill assist held the car there, even after pressing on the throttle. Hill assist stays engaged until I pressed on the throttle enough to over come the force of rolling back. The response is the same no matter how steep the hill is. I feel that the hill start assist deactivation trigger is when the car senses a slight forward rotation of the wheels from the application of throttle or until the 2 second maximum time limit is reached.
This lurch/jerk Houston CX5 talks about has a different response. It happens to me on flat roads and at the very top of the travel of the brake pedal when releasing it. It's as if the car had gone into neutral while stopped, then senses the driver starting to release the brake pedal, so it engages 1st gear/torque converter, which causes the slight jerk sensation right before the car starts rolling forward and throttle application. If it was hill assist, the jerk should happen immediately after the car starts rolling forward. I feel it's as if mazda included hill start assist in the car to give the transmission time to engage 1st gear/torque converter after going to neutral when stopped on a hill.
From a fuel economy stand point, it would make sense to put the transmission in neutral while idling because there is less drag/fuel wasted compared to having the torque converter engaged when waiting at longer stops. This also compliments the engine start/stop function, i-stop, on some non US models (info on it
here and
here). So for US models, instead of shutting the engine off, it just goes into neutral. Doing this would make it very easy for Mazda to implement this feature without any or many hardware changes, which can be very expensive. A form of cost effectiveness = one design, but many features to customize for different markets.
An example of a car going into neutral when stopped is when I got to drive a relative's civic hybrid and made stops on a hill. When stopped the engine shuts off to save on fuel. The gas engine then turns back on as it senses the driver releasing the brake pedal and transitions towards pressing on the gas pedal. But, when on a hill, as the driver releases the brake pedal, the car will start rolling back before the engine turns back on. Pretty scary feeling at first because the car is an automatic, but act's like it has a manual transmission when on a slope. As a result, you have to be very quick with the brake to throttle transition because there is no drag from the a torque converter to slow down the rolling back. This is where hill assist would greatly help the civic hybrid, so the car would have time to turn the engine on and provide forward motion without rolling back.
