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SMT6 Developers Manual - Piggy-Back Applications

SMT6 DEVELOPERS MANUAL

Perfect Power Online Manuals.

 

Support for your SMT6 Unit.

PIGGY-BACK APPLICATIONS

A piggy-back system relies on the standard ECU. The signals to and from it are modified within the operating parameters of the standard ECU. Thus the achievements are modest, but nevertheless worthwhile if any engine modification was performed, or  when the stock engine must be tuned to its absolute peak. The piggy-back mode is particularly important for "environmental" tuning to reduce emissions and fuel consumption.

 

The following section catalogs the various engine signals, since the SMT6 has to understand (and modify) them.

 

 

IGNITION MODIFICATION WITH UNIFORM TEETH PICKUP

 

The IG1IN input takes this signal. You can choose the trigger edge. You need not connect a second pickup signal. The modified input signal is available on IG1OUT, and a special bipolar output is produced on IG1SP. Operating modes are : 10, 11, 12, 13.

 

 

IGNITION WITH MISSING TOOTH PICKUP

 

The IG1IN input connects to it in mode 1. The modified input is available on IG1OUT and on IG1SP outputs, and an INVERTED signal on IG2OUT. The outputs are square waves. The inverted signal is used to simulate a "balanced" input to the ECU.

 

 

IGNITION WITH ODD TEETH PICKUP

 

This signal can consist of various length and varying patterns. It must repeat within 2 turns of the crank. The teeth per turn entry is the amount of teeth (or holes) per TWO crank turns. This signal can only be retarded, which is sufficient for superchargers and turbo's. If advancing is required, then the pickup must be advanced, and the SMT6 retarded with an equal amount.

 

 

ANALOG AIRFLOW METER MODIFICATION

 

The airflow meter output is routed through the SMT6, and the output is offset compensated and mapped. The signal range is from 0 to 10 Volts. The manual refers to this as analog fuel tuning, and any other analog signal can be mapped.

 

 

FREQUENCY (DIGITAL) AIRFLOW METER MODIFICATION

 

This signal is square wave : the frequency contains the airflow information. This signal can be modified, but not in the missing tooth method. The input is on IG2IN, and output at IG2OUT. This operation requires mode=10.

 

 

AMP (MANIFOLD PRESSURE) MODIFICATION

 

This is an analog signal on the range 0-10 Volts. Same as airflow meter mods.

 

 

CLOSED LOOP LAMBDA TUNING

 

Most engines run in closed loop lambda, at least up to 2500 RPM. The output of the lambda (oxygen) sensor is routed through the SMT6, and the signal can be mapped. Due to the highly nonlinear characteristic of the sensor, caution must prevail. The analog limits should be used to restrict the signal swing in to areas where the ECU detects a fault.

 

 

ENGINE TEMPERATURE TUNING

 

Yes, this is possible. A cold engine runs richer, and if this is the desired effect, then this signal can be mapped. Some modern engines apply some logic and prevent successful tuning. Technically this is an analog signal tuning.

 

 

ROAD SPEED GOVERNOR

 

The road speed is signal originating from the drive train. Some manufacturers restrict the max speed. Such a speed restriction can be raised or lowered in mode=11. Consider the safety aspects when raising the speed restriction.