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SDC3
User Manual
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MoTeC SDC3 User Manual

SDC3
Subaru Diff Controller
User Manual
© Copyright – MoTeC Pty Ltd – 2001-2008
The information in this document is subject to change without notice.
20 June, 2008
Contents
Introduction.........................................................................1
SDC3 Functionality.............................................................2
Mode selection ................................................................................................... 2
Lock Calculation ................................................................................................. 3
Slip Control......................................................................................................... 4
Slip control example................................................................................ 4
Diff Control Methods........................................................................................... 4
Current Control........................................................................................ 4
Duty Cycle Control .................................................................................. 4
Speed Measurement .......................................................................................... 5
Speed Calculations ................................................................................. 5
Brake Status....................................................................................................... 5
Throttle Calibration ............................................................................................. 6
Communications................................................................................................. 6
PC CAN Connection................................................................................ 6
Vehicle Communications......................................................................... 6
MoTeC ADL/M800 Communications ....................................................... 6
Miscellaneous functions ..................................................................................... 6
Diff Temperature Override....................................................................... 6
Fault indication ........................................................................................ 7
ABS Active Detection .............................................................................. 7
SDC Manager ......................................................................8
Computer requirements...................................................................................... 8
Connecting to a SDC3........................................................................................ 8
Installing SDC Manager...................................................................................... 8
Managing Configurations.................................................................................... 8
Changing Configurations .................................................................................... 8
User Mode Tables................................................................................... 8
File | Setup | Input Setup......................................................................... 9
File | Setup | Input Tables...................................................................... 10
File | Setup | Output .............................................................................. 10
File | Setup | User Modes...................................................................... 11
Monitoring SDC3 Data...................................................................................... 12
Sending Firmware ............................................................................................ 12
SDC3 Installation..............................................................13
Appendices .......................................................................14
Appendix A – Fault Codes................................................................................ 14
Appendix B – SDC3 Pinout and Links .............................................................. 15
SDC3 Connector Pinout ........................................................................ 15
Links...................................................................................................... 16
Appendix C – CAN Wiring Practices................................................................. 17
Appendix D – Removing ABS systems............................................................. 18
Appendix E – ECU Communications ................................................................ 19
Receiving SDC3 Data ........................................................................... 19
Receiving ECU Data ............................................................................. 20
Appendix F – CAN Messages........................................................................... 21
50Hz Messages .................................................................................... 21
25Hz Messages .................................................................................... 22
MoTeC SDC3 1 Introduction
Introduction
The Subaru Diff Controller 3 (SDC3) is a direct replacement for the Driver Controlled Centre Diff (DCCD) controller in the 2008 WRX STi and similar vehicles.
This manual covers the installation, configuration and functionality of the SDC3.
MoTeC SDC3 2 Functionality
SDC3 Functionality
Mode selection
There are six user selectable control modes, four of which are user configurable. The control modes are selected
using the C.DIFF +/- toggle switches in the centre console, and indicated on the dash board as follows:
Switch Direction Dash Display SDC3 Mode
+
-
LOCK
ODO
100% lock
ODO
User Mode 4
ODO
User Mode 3
ODO
User Mode 2
ODO
User Mode 1
ODO
0% lock
MoTeC SDC3 3 Functionality
Lock Calculation
Lock percentage applied to the centre diff is determined primarily by the vehicle speed, throttle position or manifold pressure, and front to rear wheel slip.
Each the four user modes are configured with an acceleration table, a braking table, a desired slip table and slip control parameters. Slip control and ABS override may be disabled if not required.
The lock percentage for a user mode is determined according to the following strategy:
Vehicle Speed
Throttle Position or Manifold Pressure
Front & Rear Speed
Accel
table
(% lock)
Brake
table
(% lock)
Desired
Slip table
(kph)
Slip
control
params
Brake
OFF
ON
Slip
Calculation
(% lock)
+
100%
Lock
MIN
5%
Lock
OFF
ON
ABS
Lock
0%
Handbrake
OFF
ON
The lock percentage for the full lock mode is determined according to the following strategy:
100%
Lock
5%
Lock
ABS
OFF
ON
0%
Lock
Handbrake
OFF
ON
% lock
The lock percentage for the zero lock mode is determined according to the following strategy:
% lock
0%
Lock
5%
Lock
ABS
OFF
ON
% lock
For information on configuring the user modes see the SDC Manager section.
MoTeC SDC3 4 Functionality
Slip Control
The slip control strategy detects slip (i.e.: rear speed ≠ front speed) and increases diff lock to maintain slip close to the value specified in the Desired Slip table. The Desired Slip table specifies the value above which additional diff lock will be applied, according to the slip control setup parameters.
The calculation of lock percentage for slip control is determined by the Slip Control Range and Max Slip Control Lock parameters which apply to all user modes.
The following algorithm determines the %lock for slip control. The desired slip is the output from the Desired Slip table.
IF Rear Speed > Front Speed THEN Measured Slip = Rear Speed – Front Speed ELSE Measured Slip = Front Speed – Rear Speed Slip Control Factor = (Measured Slip – Desired Slip) / Slip Control Range Constrain Slip Control Factor to the range 0 to 1 Slip Diff Lock = Slip Control Factor * Max Slip Control Lock
NOTE: Slip is specified as speed difference between front and rear wheels, not as a ratio of the speeds.
The addition of the calculated slip diff lock percentage is shown in the lock percentage strategy above.
Slip control example
Max slip control = 10% lock
Slip control range = 20 km/h
Desired slip (from Desired Slip table) = 10km/h
For a measured slip of 15km/h, slip diff lock = ((15 – 10) / 20) * 10 = 2.5%
For a measured slip of 30km/h or above, slip diff lock = 10%
For information on configuring the slip control parameters, see Setup | User Modes in the SDC Manager section.
Diff Control Methods
The SDC3 implements two methods of driving the centre differential, selectable in the configuration.
Current Control
Current output control regulates the solenoid current waveform by setting a minimum current and ripple factor for a particular lock percentage. The parameters for this control mode are pre-configured for the factory centre diff
solenoid and should not be changed. This is the recommended mode of operation.
Duty Cycle Control
Duty cycle output control provides a PWM solenoid drive from 0 to 100% duty cycle for 0 to 100% calculated lock.
The frequency of the drive pulses changes linearly between specified frequencies for 0% 100% lock. This mode is not recommended as the effective diff lock will change with diff temperature.
An absolute limit for solenoid current can be configured for either control method, and is pre-configured for the factory centre diff solenoid.
For information on configuring the diff control method, see Setup | Output in the SDC Manager section.
MoTeC SDC3 5 Functionality
Speed Measurement
The SDC3 can be configured to use one of two different methods to measure wheel speeds:
ABS CAN (Default method)
Four wheel speeds are detected by the ABS unit and transmitted over the CAN bus to the SDC3. This is the method used by the factory DCCD controller and requires no modification of the wiring. Individual wheel speeds can be enabled or disabled and the speed calibration can be adjusted for different wheel sizes and
sensor teeth.
Wheel Speed Sensors
Up to four wheel speed sensors may be wired directly to the SDC3 connector by modifying the vehicle wiring. The wheel speed inputs can be configured as hall effect or magnetic sensors with adjustable thresholds, and individual sensors can be enabled or disabled. The speed calibration can be adjusted for different wheel sizes and sensor teeth. Magnetic sensor input thresholds are individually configurable for front and rear sensor pairs according to the current front and rear speeds.
Front, rear and vehicle speeds are calculated from the wheel speeds, and all speeds are transmitted in CAN messages for logging by the ADL (Advanced Dash Logger).
Front speed, rear speed and vehicle speed are also transmitted over CAN in a format that can be received by the MoTeC M800 ECU. The MoTeC WRX V910 OEM ECU (if fitted) can be configured to log these wheel speeds or use them in engine control strategies.
For information on configuring speed inputs, see Setup | Input Setup in the SDC Manager section.
Speed Calculations
The method of calculating front, rear and vehicle speeds is dependent on the status of the brake input.
When the foot brake is applied, speeds are calculated as follows:
• Front Speed is the faster of the two front wheel speeds.
• Rear speed is the faster of the two rear wheel speeds.
• Vehicle speed is the faster of the calculated front speed and rear speed.
When the foot brake is not applied, speeds are calculated as follows:
• The front speed is the average of the two front wheel speeds, weighted 80% towards the slowest front wheel speed. If one front wheel speed is less than half of the other front wheel speed, then front speed is simply the faster of the two front wheel speeds.
• The rear speed is the average of the two rear wheel speeds, weighted 80% towards the slowest rear wheel speed. If one rear wheel speed is less than half of the other rear wheel speed, then rear speed is simply the faster of the two rear wheel speeds.
• The vehicle speed is the average of the front and rear speeds, weighted 80% towards the slowest speed. If either the front or rear speed is less than half of the other speed, then vehicle speed is simply the faster out of the front speed and rear speed.
If any wheel speed exceeds 300km/h, the sensor reading is ignored until its speed returns to below 300km/h for 2 seconds. This is to prevent erratic behaviour from noisy wiring or faulty sensors.
Brake Status
The SDC3 can be configured to use one of two different methods to measure brake pedal and hand brake status:
CAN Status (Default method)
The brake pedal switch is wired directly to the ABS unit and the hand brake switch is wired directly to the body integrated unit (body computer). This is the method used by the factory DCCD controller and requires no modification of the wiring.
Direct Wired Switches
The brake pedal and hand brake switches may be wired directly to the SDC3 connector by modifying the vehicle wiring.
MoTeC SDC3 6 Functionality
Throttle Calibration
The throttle position sensor input can be calibrated using a table to convert voltage to throttle position. This allows non-linear calibration of throttle position to more closely model the change in torque vs. throttle butterfly angle.
The SDC Manager configuration program allows throttle input voltages to be read directly from the SDC3 in order to perform 0% and 100% calibrations.
For information on calibrating the throttle input, see Setup | Input in the SDC Manager section.
Communications
The SDC3 communicates on the factory CAN bus at 500kBit/sec.
PC CAN Connection
A CAN interface to the SDC3 is provided using a MoTeC OEM Communications cable that plugs into the SDC3 board. This cable also provides the power required if the MoTeC CAN cable is used to interface with a PC.
The MoTeC UTC (USB To CAN) adaptor or the MoTeC CAN cable can be used to connect the PC to the CAN bus.
Vehicle Communications
The SDC3 communicates with the ABS module, Body Integrated unit, ECU, Yaw/G sensor and Steering Angle Sensor over the CAN bus using the factory wiring loom.
The SDC3 receives wheel speeds, brake status, yaw, lateral G, longitudinal G, steering angle, ABS status, throttle position and manifold pressure on the CAN bus.
MoTeC ADL/M800 Communications
The SDC3 transmits CAN messages at 50Hz containing information about all input and output functions, such as speed readings, diff currents, duty cycles etc.
The SDC3 transmits CAN messages at 25Hz containing diagnostic information such as fault flags, firmware versions etc.
The ADL can be configured to receive all these channels and an M800 ECU can be configured to receive a subset of the channels.
To configure an ADL to receive SDC3 messages, use the ‘SDC3’ and ‘SDC3 Diagnostics’ communications templates included with Dash Manager.
See Appendix E – ECU Communications for information on configuring an M800 ECU to receive SDC3 messages.
The transmission of CAN messages can be disabled. This feature may be used to prevent reverse engineering of user control modes.
Miscellaneous functions
Diff Temperature Override
The diff temperature override functionality allows a specified control mode to be used if the rear diff overheats.
If this functionality is enabled, the current user control mode (1-4) is overridden with the configured override mode (0%, 100% or one of the 4 user modes) while the rear diff temperature input is active. The diff temperature override does not occur if the thumbwheel is in the full lock or open lock positions.
To prevent rapid transitions between control modes when the diff heats or cools, the diff temperature input must be stable in a new state (high or low) for 2 seconds before the input is considered to have changed.
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