The PCM controls the duty cycle to CPC A and B to gain the proper clutch overlap and apply/release rates. As the blue trace steps up, the transmission upshifts into the next gear. The graph demonstrates the transmission shifting from first through seventh gears. The light blue waveform shows the secondary shaft clutch pressure sensor the red is the mainshaft clutch pressure sensor dark blue shows the shift command. The mainshaft and secondary shaft clutch pressures alternate as the transmission upshifts (figure 2). The CPC solenoid A is in charge of the secondary clutch pressure, and the CPC solenoid B is in charge of the mainshaft clutch pressure. There are six, pulse width modulated, linear solenoids that control the mainshaft and secondary shaft clutch pressures (CPC A and B), servo piston pressures (CPC C and D), torque converter clutch pressure (CPC E), and line pressure.Īll of the linear solenoids, except the line pressure solenoid, are normally closed, so when the solenoid is electrically off, it’s also hydraulically off, or not passing fluid pressure. Check out the October 2017 issue of GEARS for an overview of how the Acura DCT-8 is constructed, including mechanical powerflow. The shift solenoids control the torque converter lockup valves (solenoids A and B) and they shuttle shift valves (solenoids C, D, and E), which direct pressure to the appropriate hydraulic servos. The five shift solenoids are normally closed, on/off design. There are eleven solenoids in the valve body (figure 1). Unfortunately, the electronic and hydraulic control for the Acura 8-speed DCT is back to being fairly complex. This simplified the hydraulic operation, making the hydraulic schematic easier to read. Line pressure was directed to the clutches when in a gear, and CPC pressure was directed to a clutch when the transmission was between gears.Īfter a decade or so, Honda engineers figured out that the CPC solenoids could always control pressure to the clutches, so their next generation of transmissions primarily used CPC solenoids for total clutch control. The shift solenoids states changed frequently because there were in-gear states and in-between gear states. When looking back to the five-speed transmissions from the early 2000s, you’ll find a fairly complicated electronic and hydraulic system that uses shift solenoids to position shift valves, where either line pressure or clutch pressure control (CPC) pressure is directed to the clutches. Honda/Acura transmissions have evolved quite a bit over the past couple decades.
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