Haltech Platinum Interceptor - Manual (Page 5)

Interceptor Manual
5
How does the Haltech Interceptor Work?
All factory ECUs will have a sensor used to calculate engine load, and a sensor used to track
engine position.
The engine load sensor (in order of highest to lowest preference) is usually an airflow meter
(AFM), a manifold absolute pressure (MAP) sensor, or a throttle position sensor (TPS). Some
engines may have all of these sensors, but the lower preference sensors are used for diagnostics
or transient fuel calculations, and have no effect on the calculated engine load. These sensors
usually output 0 – 5V analogue voltage or a frequency voltage signal that the factory ECU uses
to calculate engine load. This engine load is then used to calculate how much fuel to inject into
the engine.
Fuel Control
When installing the Haltech Interceptor, the signal wire from the engine load sensor to the ECU
is cut and rewired so that the sensor signal output goes into the Haltech Interceptor. The Haltech
Interceptor then produces a new signal that is connected to the ECU input for the sensor. The
interceptor can now make changes to the load signal of the engine so that the factory ECU
thinks that the engine load is different to what it actually is.
The factory ECU has tables inside its memory that are used to calculate the required injection
time to achieve the desired fuel mixture at various engine load and RPM sites. By altering the
engine load signal, the interceptor can alter the position in the tables that the factory ECU is
using to calculate the injection time. Generally it is possible to enrich the fuel mixtures by
increasing the engine load signal, and to lean the fuel mixtures by reducing the engine load
signal.
Inside the Haltech Interceptor is a memory that retains its data even when the interceptor is
turned off. Within this memory is a table of percentages that are mapped against engine RPM
and engine load. The interceptor calculates the engine RPM and load, and then extrapolates a
percentage out of the table that it can apply to the input load signal to produce an output signal
altered by this percentage. The tuner of the Haltech Interceptor can tune the percentage tables to
output an altered signal that results in the factory ECU thinking the engine load is different to
the actual engine load and changing its injection time to achieve the desire fuel mixture ratio
across various engine load and RPM.
Ignition Control
The engine position sensor is usually a Hall effect or Reluctor type sensor that is fitted to detect
teeth, slots, or magnets on the crankshaft or camshaft of the engine. The factory ECU uses the
signal produced by this sensor to calculate engine speed and position, and using this
information, it can generate pulses that result in a spark at the desired ignition advance angle.
When installing the Haltech Interceptor, the signal wire from the engine position sensor to the
ECU is cut and rewired so that the sensor signal output goes into the Haltech Interceptor. The
Haltech Interceptor than produces a new signal that is connected to the ECU input for the
sensor. The Haltech Interceptor can then alter the phasing of this signal to advance or delay the
signal on its output relative to the true engine position. The result of this is that the factory ECU
thinks the engine is in a slightly altered position to the actual position, and therefore it will
produce its ignition spark advance output at a similarly altered position.