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SMT6 Developers Manual - Engine Signals

SMT6 DEVELOPERS MANUAL

Perfect Power Online Manuals.

 

Support for your SMT6 Unit.

ENGINE SIGNALS

The SMT6 is an advancement of the UNI5 (SMT5) unit, with many features added.

This section gives an overview of the various applications. The applications are separated by the way the SMT6 is wired into the car :

 

Piggy-back : The unit modifies the input or output signals of the existing ECU. The signals are routed THROUGH the SMT6, which necessitates the cutting of some wires.

 

Stand Alone : The unit "tees" in to some engine signals for the purpose of measuring them, and produces its own outputs for the assistance of the engine and its driver. Typical applications are adding extra injectors, or producing mapped ignition for a carburetor engine.

 

 

ENGINE SIGNAL COMPATIBILITY

 

Normally no one pays attention to the signals. Connect them, and it works. However, since you want to use them on the SMT6 you must understand them, it is vital to know what they are.

 

 

IGNITION PICKUPS

 

These are the sensor(s) mounted on the crank, or the CAM, or inside the distributor. They give information as to the crank position, and cylinder identification. The input trigger level can be set. The pickup input(s) can take any signal, which passes a  threshold of :

 

High Level : 2.5 Volt
Low Level : 0.1 Volt

 

The input impedance is 10K Ohm, which is great for "tapping in", but had to be lowered for standalone magnetic pickups. The following pickups are available :


MAGNETIC (RELUCTANCE) SENSOR
A 2 wire + screen device, outputs a bipolar signal. The signal must be greater than  4.0 Volts. The signal amplitude depends on the distance and the speed of tuning. Check that the amplitude is greater than positive 4.0 Volts during starting. Use a 470 to 1K Ohm "LOADING" resistor to reduce possible interference from the ignition.

 

OPTICAL SENSOR
A 3-wire device : ground, signal, supply. The signal output is normally a "dry" switch. This means it connects to ground at specific times, but no signal comes out of it, unless a "pull-up" is used. The pull-up can be provided by the ECU. If not, then an external pull-up must be used. The pull-up can be to the battery, or +5 Volts, whatever is available.

 

HALL EFFECT SENSOR
A 3-wire device, same as above.


The following sensors can pickup different "teeth" patterns, which differ between each manufacturer :


UNIFORM TEETH PICKUP
The teeth (or holes) are distributed evenly around the track. Each point has the same width. This signal can be used for recognition of the RPM, and for advancing and retarding. A second sensor is required when used in a wasted spark application.

 

MISSING TEETH PICKUP
This is a single wheel with 36 to 60 teeth, and one (or two) teeth missing to identify a particular cylinder. The SMT6 can recognize this signal for piggy-back application, and this signal can be modified. This signal is not useful for standalone ignition application. A derivative of this pickup is the "double ended" signal (both wires have a signal), which can be simulated in a piggy-back application.

 

2 UNIFORM TEETH PICKUPS
One pickup has the firing information (IG1IN), and the other has the cylinder information (IG2IN). Both signals can be advanced or retarded.

 

ODD TEETH PICKUP
This is a signal, with a non-uniform pattern around the track. This signal can be used for picking up the RPM, but this signal can only be retarded. The length of each pickup pulse is not important.

 

 

ANALOG SIGNALS

 

This is a voltage in the range from 0-5 Volts (or 0-10 Volts), which contains information such as temperature, airflow, throttle position and manifold pressure (AMP). The  SMT6 can use these signals, and it can map them.

 

 

DIGITAL FREQUENCY SIGNALS

 

This is a signal, which swings from 0-5 Volts. The frequency contains the information. Such signals are transmitted from airflow sensors. The SMT6 can work with such a frequency signal.

 

 

IGNITION OUTPUT SIGNALS

 

This is a signal from the ECU to the external ignition "trigger" amplifier. The signal may go from 0 to approx. 3 Volts. When high (2.5 Volts) current flows through the coil. The SMT6 can recognize this signal. However, if this signal is a "feedback" signal on a different wire to signal to the ECU the current flow through the coil, then this signal can't be modified in the piggy-back mode.

 

 

DIGITAL PWM SIGNAL

 

This signal swings from 0-5 or from 0-12 Volts. The WIDTH contains information. Such signal is used for opening idle motors, cam switching and turbo waste gate control. Depending on the application, such signal can be modified.