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 simple terms, a DSG is two separate manual gearboxes (and clutches), contained within one housing, and working as one unit.It was designed by BorgWarner,and was initially licensed to the Volkswagen Group, with support by IAV GmbH. By using two independent clutches, a DSG can achieve faster shift times (8ms), and eliminates the torque converter of a conventional epicyclic automatic transmission.
In a manual transmission car, shift time for upshifts can be reduced by installing a lighter flywheel. During an upshift the engine speed must fall for the same vehicle speed; a lighter flywheel will allow the engine speed to drop more quickly when it is unloaded leading to shorter shift times.
- A long shift time is considered anything over 625 ms
- The average manual car driver: 500 ms - 1 s (vertical gear changes e.g. 1st-2nd, 3rd-4th, 5th-6th): 1s - 2s horizontal gear changes (2nd - 3rd, 4th - 5th, 6th - 7th). As well shift times can change depending on gear throws (distance between gears), its easement of movement, ergonomics of lever and age of gearbox.
Gearbox shift times (Fastest to slowest)
- Marc M (Rocket Arm): 3.1 ms
- Bugatti Veyron (DSG): 8 ms
- AUDI (DSG): 8 ms
- Volkswagen (DSG): 8 ms
- Alfa Romeo Mito & Alfa Romeo Giulietta (2010) Dual Dry Clutch Transmission TCT: 8 ms
- BMW M3 E92 with M-DCT: 80 ms
- Ferrari FXX: Under 100 ms
- Drag car: 100 ms
- Maserati GranTurismo S Cambiocorsa: 100 ms
- Mercedes-Benz SLS AMG: 100 ms
- Automatic/semi-automatic transmission: 100 ms
- Clio RS EDC 200: 150 ms (race mode)
- Porsche PDK: 150 ms
- Enzo Ferrari: 150 ms
- Ferrari 430 Scuderia & FXX Evoluzione: 160 ms
- Lexus LFA: 200 ms
- Nissan GT-R: 200 ms
- Chevrolet Camaro ZL1: 200 ms
- Ferrari 360 Challenge Stradale & Ferrari F430: 250 ms
- Audi TT Quattro 3.2 (Direct Shift): 200 ms
- BMW M5 E60 with SMG III: 250 ms
- BMW M3 E36 with SMG I: 250 ms
- Aston Martin Vanquish: 250 ms
- The fastest (Race gearbox) manual: 250 ms
- Ferrari 575M: 280 ms
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