Analogue Inputs USER1 & USER2

The BROWN and RED wires of the I/O Cable are two 0-5 Volts single ended analogue inputs (USER1 & USER2). They can be used for sampling voltages such as TPS (Throttle Position Sensor) and MAP (Manifold Absolute Pressure), but remember that the measured voltage should not exceed 5 Volts. They are not suitable for measuring pulse inputs unless the pulses have been processed by an external circuit.

The USER voltages are sampled at a resolution of 10 bits at a rate determined by logging configuration parameters (default 10 sample/sec). The 2 channels have at least a 10k ohm input impedance. The 10 bit resolution means variation as small as 5 milliVolts can be detected, but in practice the noise limit sets the resolution to as low as 15 to 20 milliVolts.

Note that unterminated inputs will float and may show a voltage level when not being used. Either ignore this effect or physically connect all unterminated inputs to the BLACK Ground wire.

WBlin GREEN & BLUE on I/O Cable , Wideband Output
[Linear AFR Output - 2J1 units]

A synthesized linear WBlin voltage is produced by the onboard microcontroller using a 10 bit A/D PWM converter (with single pole filter). We describe this as having an accuracy of 9.5 bits (rather than 10) to distinguish it from outputs on our other units that use more accurate hardware DACs. Other Tech Edge controllers use a more accurate 12 bit DAC for better performance, and this one of the major differences between 2J and other Tech Edge controllers.

* Note-1: WBlin- (green) must be tied to a voltage close to GND. Failure to do this will cause WBlin+ to be undefined.

2J1's WBlin can output a maximum of 5.00 Volts and can be re-programmed. A special feature of WBlin is what we call a differential output. The WBlin+ output wire (BLUE) is the signal, and the WBlin- output wire (GREEN) is the ground reference (actually an input). This arrangement is designed to reduce the amount of noise and possible voltage offset errors seen by a device connected to WBlin. The WBlin differential output is described more fully here. WBlin can be re-programmed using the Config utility to cover any part of the AFR range from Lambda = 0.6 to free-air over the 0 to 5 Volt range.

For the default mapping shown, to convert WBlin to an AFR, simply multiply the measured voltage by 2 and add 9. The advantage of a linear output is that it's easy to write a conversion function from the wideband voltage to AFR.

* Note-2: Remember that WBo2 is a Lambda meter and is "calibrated" to display AFR for fuels with a stoich AFR of 14.7 (ie. "unleaded"). For other fuels that don't have a stoich value of 14.7, the x-axis (AFR) of the graph shown here should be modified.

* Note-3: while the WBlin output is accurate, the Lambda data in the RS232 data frame is inherently more accurate and does not suffer from some possible sources of signal degradation that beset all analogue data.

NBsim VIOLET on I/O Cable , Simulated Narrowband Output
[Simulated NB Curve]

A synthesized narrowband (NBsim) voltage is produced by the onboard microcontroller using an 8 bit A/D PWM converter (with single pole filter), and a 65 word lookup table. Linear interpolation improves lookup accuracy. We describe this as having an accuracy of 7.5 bits to distinguish it from outputs on our other units that use hardware DACs. The full 0 to 5 Volt output is available, but restricting the output to 0 to 1 volt reduces the number of possible steps to around 200 (~5 mV per step).

The NB output is designed to be compatible with the raw output of a Bosch LSM-11 sensor. Refer to this eXcel spreadsheet for the graph of the default NBsim vs AFR.

As NBsim can re-programmed it is possible to do a number of interesting things such as fooling the engine's ECU (if equipped with a NB sensor) into running richer or leaner than it would do otherwise.

Pulse Inputs - RPMLO and PULSEVSS

2J1 has two PULSE channels that are captured for logging. These are separated into two inputs (RPM & VSS), with RPM being primarily intended for use with an ignition coil or tach style signal (0-12v COIL). Refer below for details of the Secondary VSS input. Diagram at right shows routing of RPM input via the Low-Pass filter that can be used to assist with installations that generate a large amount of high frequency noise on the RPM pickup. :

* RPM input for direct connection to a COIL (or a Tach signal as generated by some vehicles). The WHITE input normally connects to the wire going between the points and the COIL. On vehicles that have electronic ignition and a distributor you would connect to the point between the transistor switch (or ignition amplifier) and the coil. The COIL input should never be connected to any voltage greater than 12 Volts or damage to the WBo2 unit may result.

* VSS input for a lower voltage "logic level" signal as is generated by some sensors or produced as a low voltage output by an ECU (possibly the input to a transistor ignition amplifier). the 5 volt pulse will be at some small multiple of the engine's revs. Unfortunately, the loading (low input impedance) of the RPM input sometimes makes it infeasible to connect to sensitive circuits such as an inductive crank angle sensor. External circuitry may be required to connect to a Variable Reluctance pickup, or VSS style sensor.

The RPM and VSS inputs can be used at the same time, and are represented by two separate fields in the RS232 data frame.