Accumulator Chambers

2013 Mini Cooper Countryman, Standard TransSECTION Accumulator Chambers
WARNING: This page does not describe the selected car, but rather 43 other vehicles, including the 2006 BMW M3, 2006 BMW 330Ci, 2006 BMW 325Ci, 2005 BMW M3, and 2005 BMW 330xi. However, it is still accessible from the selected car via links, so may be relevant.

The accumulator chambers are similar in function to "fluid dampers". The accumulators are used to improve shift quality by absorbing apply pressures on the multiplate clutches providing a cushioned clutch engagement. See Fig 1 .

Clutch applied fluid pressure directed to an accumulator piston and helped by a spring force opposes an accumulator fluid line pressure creating an action similar to a shock absorber. The apply pressure pushes the clutch piston against the steel/friction plates causing initial engagement. Once the clearance between the clutch plates is taken up by the piston travel and the plates begin complete engagement the fluid pressure builds very rapidly. The accumulator is connected to the clutch apply circuit which at this point starts to absorb the rapidly building pressure. The accumulator piston moves upward accommodating the high pressure fluid causing a delayed complete engagement. See Fig 2 and Fig 3 .

Fig 1: Identifying Accumulator Chambers
G00317113Courtesy of BMW OF NORTH AMERICA, INC.
RENDER: 1.0x

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