The factory manifold air pressure (MAP) sensor was upgraded from the factory 1 bar absolute sensor to a 3 bar sensor for visibility of boost pressure on the Ecutek logs. Whilst splicing this sensor into the Mazda wiring harness, the MAP signal was also wire into the supercharger control system.
The pressure control logic now operates as per below:
• The dial on the HMI selects the maximum boost pressure setpoint (anywhere up to 8 psig)
• The actual in-use pressure setpoint for the PID control block is calculated by multiplying the engine throttle percentage (foot pedal) by the maximum boost pressure setpoint, that is if the dial is set to 8 psig then:
– 0% throttle equates to a boost setpoint of 0 psig
– 50% throttle equates to a boost setpoint of 4 psig
– 100% throttle equates to a boost setpoint of 8 psig
– The relationship is linear and constantly variable with throttle position
• When throttle position is less than 50% the process variable is the pressure sensor immediately downstream of intercooler (upstream of engine throttle body)
• When throttle position is greater than 50% the process variable is the MAP sensor (downstream of the engine throttle body)
This setup gives excellent control of boost pressure and engine torque by modulating throttle pedal. Further refinement of PID tuning constants has also been completed. These changes have had a improved power delivery and driveability.
