Abstract:
A multi-speed automatic vehicle transmission has an electronic control unit which permits multiple downshifts if certain conditions are satisfied. Such downshifts are direct and omit engagement and disengagement of one or more intermediate speed ratios. Multiple downshifting may allow the actual speed ratio to better match the ideal speed ratio, for example under heavy braking.
Abstract:
A method and apparatus for modifying the shift map of an automatically controlled vehicle transmission having individually selectable speed ratios. A calibrator determines launch ratio from a plurality of speed ratios and is responsive to ambient pressure and/or ambient temperature. The calibrator may be further responsive to engine speed, engine temperature, transmission temperature, gradient and direction of gradient.