Please enable JavaScript to view this site.

MaxxECU online help

The BMW DCT CAN protocol is not yet released, still under testings and development.

BMW DCT related links

BMW DCT Wiring information.

BMW E90/E92 (DCT) EXTRA CAN PROTOCOL.

BMW INPA diagnostic tool.

BMW DCT error codes.

BMW DCT TCU firmware flashing.

DCT clutch relearn.

MTune - DCT Settings.

MTune - DCT Control.

DCT Realtime Data description.

DCT hardware upgrade.

 

Will be updated when released!

 

 

 

DCT settings

 

Gearbox type

Specifies the gearbox type and the TCU (Transmission Control Unit) used. The actual TCU version is the most important thing here.

BMW GS7D36SG (with BMW 335 TCU)

BMW GS7D36SG (with BMW M3 TCU)

Note: BMW M4 DCT support will probably be available later in 2020 (if there is demand for it, let us know).

 

Shifter type

Specifies which gear shifter is used.

OEM BMW shifter - with this option, stock shifter, SPORT button (BMW 335) or drivelogic button (BMW M3) must be present and communicate directly with the TCU.

Note: later on, there might be support to run this solution without the stock shifter...(if there is demand for it, let us know).

 

Shift hardness

Specifies the shift hardness source.

Drivelogic/sport button - use the M3 drivelogic button, or the 335 SPORT button for shifting hardness.

 

TCU speed source

The vehicle speed source we report to the TCU.

Vehicle speed (using TCU OEM rear end diff ratio) - Can ONLY be used when your rear end diff ratio is 3.15 for the M3 TCU and 2.65 for the 335 TCU.

Undriven wheel speed (using rear end diff ratio setting) - Uses the correct vehicle speed (undriven) and your rear end diff ratio to calculate a correct TCU speed value.

Driven wheel speed (using rear end diff ratio setting) - Uses the correct vehicle speed (driven) and your rear end diff ratio to calculate a correct TCU speed value.

Undriven & Driven wheel speeds (using rear end diff ratio setting) - Uses the correct vehicle speed (undriven and driven) and your rear end diff ratio to calculate a correct TCU speed value.

Dyno Mode (using rpm & current gear), does not work below gear 2 - Dyno mode, mainly for customers mounted a front wheel speed sensor, but heading to a RWD dyno where front wheel is not moving. <-- Experimental.

Note: The 4 speed values we send to the TCU has a direct relation to shifting points, performance and clutch slippage during shift operations. Therefore the vehicle speed inside MaxxECU must be very precise and accurate, otherwise this will not work.

 

Shiftcut source

Specifies which function to trigger the MaxxECU Shiftcut input.

torque request from tcu - Uses the torque request input to trigger the internal shiftcut input (preferable use this method).

shift signal from tcu - Uses the shift input (which happends a few milliseconds before the above actual torque request signal) as shiftcut input trigger.

Note: The reason why we have this option, is because we have seen issues with the above Torque request from TCU signal from the TCU in some application (for an unknown reason).

 

 

clip1093

The above image is an example of how the different signals MaxxECU is receiving during an up shift event from a M3 TCU, and also how it should look like!

1. The shift signal is received (Green).

2. Gear indication (Blue) will increment during the up shift event.

3. The Torque reduction signal sends a signal to the MaxxECU indicating to lower engine torque (shiftcut) during the shift operation.

 

 

How to determine the Shiftcut source

 

Multiple torque reduction signals in one single shift operation

clip1094

If you get the above, several torque reduction signals during one single up shift event, you cannot use torque request from tcu as the shiftcut source. You have to use shift signal from tcu as shiftcut source.

Note: Currently we dont know what is causing this, but abviously the TCU is unhappy with some torque value does not match a calculated value inside the TCU, read more on how we control the TCU.

 

 

Lack of torque reduction signal randomly

clip1095

In the above example, we get a very short, or not even an Torque reduction Request signal at all, in the above case, you must use shift signal from tcu as shiftcut source.

 

 

Examples

 

Shiftcut delay time when using the shiftcut signal from TCU as shiftcut source.

clip1096

Note: If using the Shift signal from TCU as shiftcut source, an shift cut delay of around ~0.040sek (40msec) is necessary to make torque reduction at the correct time.

 

 

clutch kick time

Specifies the clutch kick time.

switch input (while input active) - Activates the clutch kick feature (releases the pressure on the clutch in gearbox) while the digital input DCT clutchkick/burnout mode is triggered.

 

 

DCT protection

 

clutch slip engine cut

Specifies whether to protect the gearbox clutches against clutch slippage, it is HIGHLY recommended to have this enabled. It uses the below settings for activation of engine cut.

 

max clutch slip on load

Specifies the maximum allowed clutch slippage when under "load" (VSS > 30km/h, TPS > 15%, RPM > 2000).

Note: we dont pay attention to the slippage during launch and 1000ms after launch is deactivated.

 

max clutch slip during shifting

During DCT shiftings, we cant calculate the slip rate, therefore during shifting we allow a higher slippage to prevent unnecessary engine cuts during shiftings.

 

 

DCT Warnings

 

max allowed upshift time (low load)

Specifies the maximum allowed shifting time (ms) during low load. Below 30% TPS.

 

max allowed upshift time (normal load)

Specifies the maximum allowed shifting time (ms) during normal load. 30 - 80% TPS.

 

max allowed upshift time (high load)

Specifies the maximum allowed shifting time (ms) during high load.  Over 80% TPS

 

max allowed downshift time

Specifies the maximum allowed shifting time (ms) during a downshift.