AFR (lambda probe)
The AFR connector has two 5V analog inputs. One of the inputs is designed for the connection of a common lambda probe or a wideband lambda controller. The other input is for general use and allows the input of any signal from 0 to 5 volts, for example a MAP pressure sensor.
AFR Input Pinout
| Number | Function | Range | No. Signal in Software |
|---|---|---|---|
| 1 | VDC | +5V | |
| 2 | GND | 0V | |
| 3 | AUX1 (AFR) | 0..5V | 4 |
| 4 | AUX2 | 0..5V | 1 |
Lambda Sensor Input
Electric Connection
The lambda probe does not require electrical power from Accudyno, so you only need to connect the sensor signal to the AUX1 input (pin 3) and GND common ground (pin 2).
A wideband probe with its corresponding controller can be used through the Wideband´s analog output. A common 4-wire universal probe can be connected directly as they do not require a controller.
In the Knowledge Base you will find a list of the most common lambda probes and the manufacturer´s recommended wiring of each one. This list is not exclusive and other probes not listed here may be connected to Accudyno.
Calibration
Calibration is done through the calibrarion wizard in the software or can also be done manually if your sensor is not listed. We just need the calibration values to convert from voltage to AFR or lambda. The calibration must be entered to signal #4 in the software.
TIP
If your wideband controller is not listed, select any another controller from the list and then change the calibration values on signal #4 using the information provided by the manufacturer.
Please note that the calibration always must be expressed in lambda values, not AFR. Then in configuration - Units you can select whether you want to display in AFR or lambda.
Applications of Lambda Measurement
The lambda value is independent of the type of fuel. The stoichiometric lambda will always be 1.0. But the AFR value, that is, the relationship between grams of air and grams of fuel will depend of the type of fuel. For example, the AFR that corresponds to a lambda 1.0 will be 14.7 for gasoline.
That means that for the combustion to be stoichiometric, it is necessary to burn 1 gram of gasoline for every 14.7 grams of air. Or what is the same, to convert from lambda to AFR you have to multiply the lambda value by 14.7 for gasoline or by 6.47 for methanol.
For your convenience, these values are preloaded into the Accudyno system.
| Fuel | Stoichiometric value |
|---|---|
| Gasoline | 14.7 |
| Diesel | 14.5 |
| Methanol | 6.47 |
| Ethanol | 9.0 |
What is the optimal value of lambda?
The optimal value will depend on what the goal is. In standard gasoline cars, it will be above 14.7 in regime, with a lean mixture of about 15.4 because it is the value with the least consumption and lower emissions. Although the value may vary depending on the driving condition, for example during acceleration the mixture will be enriched to give more power momentarily.
However, in racing sports you will want maximum power, even despite having high consumption and emissions. In that case the typical lambda value is around 0.85 to 0.88, which corresponds to 12.5 to 13.0 AFR for gasoline. The value can be higher or lower and with the help of the dyno you will be able to discover what the optimal value is for your engines.
Auxiliary Input
Electric Connection
The auxiliary input signal must be in the range of 0 to 5 volts. The input is entered through AUX2 (pin 4) and common ground GND (pin 2).
This input can be used to input any analog signal such as a second lambda probe, a MAP pressure sensor, a Blow-By sensor, etc.
5V
If your sensor runs on 5V power, you can take it from VCC (pin 1) on the AFR connector. The consumption of the sensor should not exceed 100mA.
Calibration
The calibration of this auxiliary signal must be done in input #1 in signal calibration in the Accudyno system.