Nissan ATTESA Control
This function is designed to control the ATTESA pump assembly directly from your Nexus series ECU. It allows the removal of the OEM ATTESA control electronics and gives the tuner complete control over the pressure applied to the transfer case and thus the torque delivered to the front axle.
ATTESA is the Nissan AWD system as used in R32, R33, R34 and R35 GTR.
It comprises of a wet hydraulically actuated clutch system that can split torque up to a 50:50 front/rear split. In the OEM application, it utilizes a combination of parameters from various sensors to decide whether or not to apply drive to the front wheels to assist with traction. In normal every day driving, the vehicle operates almost entirely in RWD.
Basic ATTESA Schematic
ATTESA system component overview
Some R33 and R34 systems added an additional longitudinal G sensor, a hydraulic failsafe solenoid, and in 'ATTESA Pro' equipped models (Vspec and VSpec 2) a hydraulic locking mechanism in the differential called Active LSD (ALSD) was added along with a controller which now updated 100 times faster.
ATTESA Control Function Requirements
- Accumulator Pressure Switch - Required (for pump output to activate. always working except if AWD switch is enabled and switch is off).
A simple on/off hobbs type switch which is closed-circuit when pressure is low. Recommended to be wired to an ecu AVI/SPI with Pull-Up enabled. Switch On: 1v, Switch Off: 4v.
- ATTESA Fluid Tank Level - Optional
Input to enable or disable pump output when fluid is low.
- Transfer Case Pressure - Optional but recommended for Closed-Loop control. Enabled from the 'Sensors' node of the ECU setup.
A 0-500psi pressure sensor would be recommended as the working range of pressure for the ATTESA unit is approximately 0 - 300psi. This is a new sensor that needs to be added to the hydraulic piston assembly in the rear of the transfer case.
- AWD On/Off Switch - Optional
Input to enable or disable system.
- Handbrake input - Optional
Input to change AWD target to 0psi when input is active. For motorkhana use.
- G-Force sensor inputs - Optional
Input to allow AWD pressure target to be corrected with Lateral or Longitudinal G's. The Nexus IMU or external G sensors can be used.
- Steering Angle - Optional
Input to allow AWD pressure target to be corrected with Steering Angle input.
- Wheel Speed Sensors - Optional
Input to allow AWD pressure target to be corrected based on detected wheel slip.
- ATTESA Pump Motor - Required
On/Off 25A Output direct to motor + or DPO to motor relay.
- ATTESA Solenoid - Required
PWM HCO or HBO direct to solenoid. Operating frequency is 200hz.
- Failsafe Solenoid Output - Optional for R33/R34 pump assembly.
On/Off direct to solenoid. DPO or HCO or HBO. Draws 0.7A. Output on when AWD enabled.
- Control Mode
Closed Loop (requires ATTESA Transfer Case pressure sensor)
Open Loop duty cycle
- Pressure Target Correction (all toggle on/off)
- Wheel Slip correction - 8x8 table for addition of AWD pressure based on calculated wheel slip.
- G-Force Correction - 8x8 table for addition of AWD pressure based on G-Force.
- Steering Angle Correction - 8x4 table for addition of AWD pressure based on steering angle.
- Bleed Mode.
When pressed in software, ECU checks for 0 engine RPM, then pulses AWD solenoid 1s on, 2s off for 15 seconds. Pump pressure switch and pump output should work as normal. After 15 seconds, bleed mode disables and button must be clicked again to repeat the process.
Special care should be taken when configuring and tuning this function as high pressure hydraulic fluid is involved. While the Nissan system is fairly robust and resistant to damage from incorrect tuning, there is still the possibility of component failure from improper tuning of the ATTESA system.
Fitting a pressure sensor to the transfer case is highly recommended to allow for closed-loop control. The function defaults are configured for this control Mode and pressure targets mapped for aggressive AWD response.
If you wish to operate the function in Open Loop without the addition of a Transfer Case Pressure Sensor, then the Main Table values will need to be remapped to duty cycle values. These duty cycle values can be derived from the Closed Loop Base Duty table, choosing the appropriate duty cycle for the desired front drive.
R32 Pump Assembly Diagram