Shift time refers to the time interval between
gear changes in a
transmission. This interval is the time in which
power delivery is transferred to the next selected gear, and
engine speed is reduced or increased to synchronize the speed of the next gear. Shift time is usually in reference to motor vehicles, but can apply to any gearbox. Shift time is measured by the time it takes for the engine rpm to synchronize with the next gear input speed target. This is illustrated by
ZF, describing the 100-300 millisecond shifts of their DCT transmissions.
Reducing shift time is important in
performance
A performance is an act or process of staging or presenting a play, concert, or other form of entertainment. It is also defined as the action or process of carrying out or accomplishing an action, task, or function.
Performance has evolved glo ...
and
racing vehicles because upshifting generally interrupts power delivery to the wheels. Shift time in a
manual gearbox is dependent on the driver, but in
automatic or
automated manual cars, the
electronic or
hydraulic control system must be calibrated and tuned to execute fast gear changes. Historically, a
dual-clutch transmission shifts faster than a standard
hydraulic automatic transmission with a
torque converter or a single-clutch
automated manual transmission. This is possible because the DCT can pre-select the next gear and transfer torque from one clutch to the next clutch with the pre-selected next gear, thus reducing shift times. Standard planetary automatic transmissions have caught up to DCT transmission shift times by also utilizing clutch to clutch shifts. For older transmissions, using a
freewheel
image:Freewheel en.svg, Freewheel mechanism
In mechanical engineering, mechanical or automotive engineering, a freewheel or overrunning clutch is a device in a transmission (mechanics), transmission that disengages the driveshaft from the driv ...
may reduce shift time, as it may not be necessary to use the clutch. A
shift kit is also intended to reduce the shift time of a manual vehicle.
With a
manual transmission
A manual transmission (MT), also known as manual gearbox, standard transmission (in Canadian English, Canada, British English, the United Kingdom and American English, the United States), or stick shift (in the United States), is a multi-speed ...
, upshift time can be reduced by installing a lighter
flywheel. During an upshift, the engine speed must decrease to synchronize with a higher gear; a lighter flywheel will allow the engine speed to drop more quickly, leading to shorter shift times.
Shift times
*A long shift time is considered anything over 625
milliseconds.
*The average manual car driver takes between 500 ms and 1 s to perform vertical gear changes (i.e. 1st-2nd, 3rd-4th, 5th-6th) and 1 - 2 s to perform horizontal gear changes (i.e. 2nd-3rd, 4th-5th). Shift time is also dependent on gear throws (distance between gears), ease of movement,
ergonomics
Ergonomics, also known as human factors or human factors engineering (HFE), is the application of Psychology, psychological and Physiology, physiological principles to the engineering and design of products, processes, and systems. Primary goa ...
of the
gear stick, and gearbox condition.
*For reference, the time it takes for a human to blink can be as quick as 100ms
(.1 seconds)
Example upshift times
Please note that some manufacturers may have different definitions of shift times, this is not a complete list.
See also
*
Powershifting
*
Shift kit
References
{{reflist
Automobile transmissions