[DFB FGXR6]

Refined Four-Speed Automatic

Wednesday, August 17, 2005

Significant upgrades to the ION 93-4AT four-speed automatic transmission contributes to improvements in fuel economy achieved the BF Falcon and SY Territory RWD model lines.

“Upgrades to the four-speed auto have improved overall refinement, shift quality and fuel economy, while building on the success of existing features such as Sequential Sports Shift, the adaptive shift strategy and intelligent shift program,” Calibration Supervisor Tim Postgate said.

Upgrades to the four-speed automatic include:

Radial dead-end grove clutch plates
A second ‘Ball Check valve’ in the valve body
Addition of Grade Control Logic on Falcon models
Accelerator pedal detent and kickdown switch
Remote transmission oil cooler
Software and calibration improvements

“By incorporating dead-end groove clutch plates with the addition of a second ‘Ball Check valve’ in the valve body, oil flow between the clutch plates has been improved, which in turn has reduced viscous drag within the transmission,” Postgate said.

“The reduction in the variability of clutch response, in conjunction with some software revisions, have enabled more precise calibration of the Park to Reverse shift, or ‘garage shift’, as well as improving shift refinement throughout the range.”

The optimization of clutch response has also improved upshift duration times, so that they are now more:

Refined – smoother shift due to more controlled engagement between friction elements within the clutch
Consistent – upshift is completed within a shorter time period
Predictable – the transmission upshifts when you expect it to

Grade Control Logic

“Grade control logic, which is already a feature of the four-speed automatic on Teritory has now been introduced to Falcon. As per the Grade Control Logic system in Territory, the transmission ‘reads’ when the vehicle is traveling downhill and increasing speed. If t driver applies sufficient brake pedal pressure the transmission automatically downshifts to provide increased engine braking.

This feature helps prevent the need for the driver to ‘ride’ the brakes when driving down steep grades.

As per Territory, Grade Control Logic is disengaged when the driver switches to manual mode for manual sequential gear shifting.

Accelerator pedal detent and kickdown switch

An accelerator pedal detent has been introduced on all automatic Falcon and Territory models, which provides physical feedback when accessing kickdown switch.

When the accelerator pedal is pushed through the pedal detent to the floor, the kickdown switch (which is integrated into the accelerator pedal mechanism) activates the kickdown feature.

Depending on the vehicle speed and the current gear, the kickdown switch will trigger a single or double downshift. However, to prevent potential damage to engine or gearbox, no downshift will occur if the engine speed is already too high to permit a lower gear from being selected.

Revised accelerator pedal map

The accelerator pedal map as been revised for more refined foot rotation versus engine throttle plate calibrations, which has improved drivability and resulted in more linear vehicle performance.

Remote transmission oil cooler

Te new remote transmission oil cooler fitted to all automatic I6 Falcon and Territory models is a heat exchanger mounted to the engine block with a three way coolant thermostat.

It serves a dual function of using engine coolant to provide rapid warm-up of the transmission fluid during start up, as well as improved cooling of the transmission under high load/high temperature operating conditions.

“Te rapid warm-up features delivers a significant reduction in friction losses within the transmission, contributing around 1.5 per cent to the overall improvement in fuel economy within the development program,” Postgate said.

“The remote oil cooler also delivers further refinement to shift quality, as well as reduced fuel consumption, due to better control of the operating temperature of the transmission.”

Software and calibration

Software and calibration improvements to the four speed automatic have delivered a more refined and consistent shift feel, as well as improved shift schedules.

“We’ve taken our most popular transmission and delivered real world customer benefits through improved fuel economy, enhanced durability, more refined gear shifts and the addition of advanced transmission features like Grade Control Logic,” Postgate said.