Shift-cut

A shift-cut is a motorsport technology that briefly reduces engine power during gear changes, allowing drivers to shift gears faster without lifting their foot off the accelerator pedal.

In normal driving, when you change gears, you typically need to ease off the gas pedal to reduce stress on the transmission. However, in racing, every fraction of a second counts, so drivers want to keep the throttle fully pressed even while shifting gears.

The shift-cut system works by connecting to the car's engine control unit (ECU) through a sensor on the gear lever. When the driver moves the gear lever to change gears, this sensor sends a signal to the ECU, which then temporarily cuts power to the engine for a split second.

The ECU can reduce engine power in several ways: it might stop the spark plugs from firing, cut off fuel to some cylinders, or change the timing of when the spark plugs fire. This brief power reduction takes pressure off the gears, making them easier to disengage and re-engage smoothly.

This technology is especially useful with sequential gearboxes, where drivers simply push or pull a lever to shift gears, and with dog engagement gearboxes commonly found in race cars. These types of transmissions benefit greatly from the momentary power reduction during shifts.

The main advantage of shift-cut systems is that they enable "flat foot shifting" or "no-lift shifting," where drivers can keep their foot planted on the accelerator throughout the entire gear change process. This maintains engine boost pressure and results in faster lap times.

Shift-cut technology also helps protect expensive racing transmissions and clutches from damage that could occur when shifting at high RPMs with full throttle applied, making it both a performance and reliability enhancement.