We recently received a very detailed technical brief from John Ewald that explain in detail the functions and capabilities of the MINI CVT gearbox. The PDF weighs in at 31 pages and 1.4Mb in file size. You can download it here. The following is an introduction:
An enthusiast community is growing up around the CVT-equipped cars. There is natural curiosity about how each of the onboard components integrate with others in the MINI Cooper CVT, and interest in how each the devices actually function in the cars.
With cooperation from ZF Getriebe N.V. Sint-Truiden (Belgium) we have this
very good mechanical description of the Continuously Variable Transmission
MINIUSA and BMW Group have answered some of the questions it raises. We should now be able to pull together a much better understanding of this very capable gearbox, the heart of our Cooper CVT.
The ZF ecoTronic VT1F Gearbox is used in the MINI Cooper CVT and MINI One
CVT. It is simple, reliable engineering married to powerful computing and
controller software to produce a very capable car with the flexibility to
meet more driving situations than any single gearbox. There are three
forward selections: Drive (D), SportDrive (SD), and the virtual-manual
Steptronic (1,2,3,4,5,6), as well as Reverse (R), and Park (P). The CVT
replaces all the complexity of gears and layshafts used in traditional
transmissions with two hydraulically-controlled variable-diameter pulleys
(variators) and a metal Van Doorne pushbelt to produce turbine-smooth
acceleration, and better economy and performance than a standard automatic.
The manual mode is strong and precise enough to permit throttle-steering in
track day driving, and still flexible to drive in commute traffic without
Owners are enthusiastic about their CVT-equipped MINIs!
A dedicated Forum was established on MINI2.com to explore the character of
these cars and to share experiences and ideas. This group found all manner
of details on the gearbox and develops driving technique suggestions to
wring the most from this CVT package.
A big thanks to John for all the hard work he's put into the document and all the people that have helped him along the way.
+ PDF Link / MotoringFile