Innovate Motorsports ST-12 - Manual (Page 3)

3
1 Overview
The SuperTune-12 is a complete data acquisition system for advanced engine tuning. The system is
capable of logging up to 12 Air/Fuel channels and also includes flexible sensors for RPM, MAP,
Temperature, Duty Cycle, and analog inputs.
The ST-12 can power, manage, and consolidate data from up to 12 specialized LC-1STs (Lambda
Cable) wideband oxygen sensor controller cables. The specialized cables are functionally identical to the
standard LC-1ST cables, except they are 18 ft. long, terminated with a single ST-12 (DB-15) connector,
and sleeved in a rugged thermal insulator.
The ST-12’s LC-1ST is a Wideband Controller used to measure the Air/Fuel Ratio (AFR) or Lambda for
an engine. For gasoline-driven engines, the theoretically optimal air fuel ratio is 14.7 pounds of air for
every pound of fuel. At this ratio, theoretically, all available oxygen in the air combines with all available
fuel. This ratio is called the stoichiometric ratio. Stoichiometric for different fuels are as follows:
Gasoline 14.7
LPG (Propane)
15.5
Methanol 6.4
Ethanol 9.0
CNG 17.2
Diesel 14.6
The measurement Lambda is the actual air fuel ratio over the stoichiometric ratio. A Lambda
measurement of “1” equates to the air fuel ratio of 14.7 (for gasoline engines). When Lambda is less
than 1 the engine runs “rich”, i.e., unburned fuel exists in the exhaust stream. If lambda is greater than 1
the engine runs lean, i.e., free oxygen (0
2 ) is present in the exhaust. Depending on the engine, maximum
power is typically delivered when the engine runs slightly rich (for example at lambda values of 0.8 to 0.9
for most engines). This instrument provides a means to measure the actual air fuel ratio or lambda in the
engine in operation directly from the exhaust. For this a special wide-band oxygen sensor is used to
measure the lambda value derived from the oxygen content (or lack thereof) of the exhaust gases.