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 or hydraulic 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)
- Bugatti Veyron (DSG): 8 ms
- AUDI (DSG)(Also S-TRONIC): 8 ms[better source needed]
- Volkswagen (DSG)(Also S-TRONIC): 8 ms[better source needed]
- Alfa Romeo Mito & Alfa Romeo Giulietta (2010) Dual Dry Clutch Transmission TCT: 8 ms
Lamborghini Aventador LP 700-4 [Single clutch ISR gearbox]: 50ms
- Ferrari 430 Scuderia: 60 ms
- BMW M3 E92 with M-DCT: 80 ms
- Ferrari FXX: 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)
- Enzo Ferrari: 150 ms
- 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
Secret formula to average shift point
This formula may be challenging, however, to acknowledge what time your car would shift a gear on average, divide your car's gear ratios and the final drive ratio, and multiply them by 0.5. Below are examples with no shift point claims:
- GM 4L60-E transmission (specifically for the 1994-1996 Chevrolet Impala SS)
- 3.06/1.63/1.00/0.70/3.08*0.5 = 435 to 440 ms
- Ford 4R70W transmission (for the 2003-2004 Mercury Marauder)
- 2.84/1.55/1.00/0.70/3.55*0.5 = 365 to 370 ms
- DaimlerChrysler WA580 transmission
- 3.59/2.19/1.41/1.00/0.83/3.06*0.5 = 225 to 230 ms
- "Tech Tips: Understanding TAP". Automotive Service Association. Retrieved 2006-07-29.
- "Volkswagen makes way for DSG". Paul Tan. Retrieved 2006-08-11.
- "Alfa Romeo UK".
- "Ferrari Factory Site".
- "Ferrari FXX Breaks Cover". Piston Heads. Retrieved 2006-09-23.
- "New Clio R.S. 200 EDC: ‘à la carte’ sports performance". Renaultsport. Retrieved 2014-03-09.
- "2012 Chevrolet Camaro ZL1 - Staged Up Shifts". SupercarHall. Retrieved 2012-02-23.
- "Audi TT Review". Evo Car Reviews. Retrieved 2006-07-29.