2.8 KiB
Electronic Throttle Body (ETB)
WARNING: An electronic throttle, if misconfigured or damaged, has the ability to open the throttle without your foot on the pedal, potentially leading to engine damage or a crash. Proceed with caution!
rusEfi supports controlling an electronic throttle body. Also called "drive by wire", this means there's no physical cable between your foot and the throttle. Your foot presses on a pedal without a cable, just a sensor. The ECU interprets this information, and converts it to a desired position for the throttle, and then works to drive the throttle plate to the desired position.
This offers a number of benefits:
- Rev limiter by simply closing the throttle (not yet implemented)
- Superior idle control
- No need to route a cable to the throttle
- Programmable throttle target curve/nonlinearity to improve drivability with a large throttle on a small engine
Theory of Operation
Electronic throttles typically consist of:
- A brushed DC motor. Positive torque pushes the throttle open, and negative torque pushes the throttle closed.
- A position sensor. This tells the ECU the true position of the throttle, so that the ECU can use the motor to hold it where we want it. This is a potentiometer or hall effect angle sensor, depending on the throttle, though they both function the same.
- A "limp home" return spring. This spring pushes the throttle plate back towards a position that's nearly closed, approximatly the correct amount of air for idle (generally 3-10% open).
rusEfi hardware and software have components to deal with all three of these parts of the throttle.
- DC motor driver H-bridge(s) to control the motor. An H-bridge can apply a variable voltage (via PWM) in either direction to the motor.
- Analog inputs and corresponding software to detect the position of the throttle and accelerator pedal.
- A control algorithm that uses a table to linearize the return spring, and PID to move the throttle to the targeted position.
Configuration & Tuning
Hardware Configuration
If you have a pre-assembled board, ignore this section! The default settings are correct.
Different H-bridge chips are controlled differently. So far we have experiences three different ways:
VNH2SP30
PWM on Control pin, two on/off direction pins are specifying direction.
TLE9201
PWM on Control pin, open/close using one on/off direction pin, second direction pin unused.
TLE7209 mode
PWM on both direction pins, one for forward another one for reverse.
TLE7209 is an example of two wire mode.
Pinouts
See https://raw.githubusercontent.com/wiki/rusefi/rusefi_documentation/oem_docs/VAG/Bosch_0280750009_pinout.jpg for personal choice of colors for VAG ETB.
