Powershifting, also known as full-throttle shifting or flat-shifting, (not to be confused with speed-shifting) is a method of shifting used with manual transmissions to reduce the time where the driving wheels are not powered. Unlike a normal gearchange, in a powershift the driver does not let off the accelerator (unlike speed-shifting, where the throttle is let off very quickly, simultaneously depressing the clutch and shifting into the next gear, rapidly). The clutch is briefly depressed while the shift lever is rapidly shifted into a higher gear, keeping the engine in its power band. In most cases, there is a method of cutting the ignition and/or fuel delivery, in a similar fashion to a rev-limiter, which prevents the engine from over-revving when the load from the transmission is removed. Many aftermarket engine management systems provide this functionality as either a standard feature or as an option, usually combined with launch control.
Another thing that can be done is to partially let off the throttle, rather than hold down the pedal during the shift. Instead of the engine rpm bouncing off the rev limiter, you can allow the rpm to drop only a little or stay where it is. This also keeps the engine in the power band. Additionally, automatic transmissions, while according to the speedometer have uninterrupted engine power, seem to shift like this. I. e., cutting the throttle slightly during full throttle shifting.
- MegaSquirt ECU, DIY engine management systems.
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