Shift time

Shift time refers to the time interval between gear changes in a transmission during which power delivery is interrupted. This is usually in reference to motor vehicles but can apply to any gearbox. Reducing shift time is important in performance vehicles or race cars because during shifting the vehicle is rolling without power to the wheels. Shift time in a manual gearbox is dependent on the driver but in automatic or semi-automatic cars the electronic mechanism must be tuned to minimize the time between gears.

One method of drastically reducing shift time is to use a Direct-Shift Gearbox which has two independent clutches that predict the next gear change making the shift time very small. Using a freewheel 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.

In a manual transmission car, shift time for upshifts can be reduced by installing a lighter flywheel. During an upshift the engine revolutions must fall for the same vehicle speed; lighter flywheel will cause the revolutions to drop faster when the engine is unloaded, leading to shorter shift times.

Shift times

• A long shift time (for a VW automatic transmission to trigger an error code) is considered anything over 625 ms
• The average manual car driver: 500 ms - 1 s^{[citation needed]}
• Aston Martin Vanquish: 250 ms
• Ferrari 575M: 220 ms
• BMW M3 E36 with SMG I: 220 ms
• Audi TT Quattro 3.2 (Direct Shift): 200 ms
• Nissan GT-R: 200ms
• Lexus LFA: 200 ms
• Ferrari 360 Challenge Stradale & Ferrari F430: 150 ms
• Enzo Ferrari: 150 ms
• Ferrari FXX: Under 100 ms
• BMW M3 E46 with SMG II: 80 ms
• Ferrari 430 Scuderia & FXX Evoluzione: 60 ms
• Bugatti Veyron (Direct Shift): 8 ms
• Golf GTI (DSG) : 8 ms
• Alfa Romeo Mito & Alfa Romeo Giulietta (2010) Dual Dry Clutch Transmission TCT: 8 ms

See also

• Powershifting
• Shift kit