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EXHAUST GAS ANALYSIS
WITH LAMBDA/OXYGEN SENSOR. Measuring exhaust gases to determine the air-fuel ratio has been a problem for every serious engine builder/tuner. The only reliable and accurate way was to use an infrared exhaust gas analyzer. However because of its slow response - up to 8 seconds before a stable reading - the use of this kind of equipment could cause engine damage when lean mixtures were experienced. Further transient response was difficult to analyze. With new technologies there are now a series of high speed high performance air-fuel ratio monitors (such as HALTECH ™ UEGO air fuel ratio meter) but these still tend to be expensive. The need for a high performance, high speed air-fuel ratio monitor is now fulfilled by the HALTECH ™ HALTUNER via an oxygen sensor transmitting its signal to a 30 segment LED type display. OPERATING PRINCIPLES O2 sensors work by measuring free oxygen and create a signal when fitted in an exhaust system when the exhaust gas temperature is between 360oC (680oF) and 900oC (1650oF). With the HALTECH ™ HALTUNER the signal is the shown via a 30 segment LED type display: 10 red lights for lean mixtures, 10 green lights for around stoichiometric (Lambda 1) and 10 orange lights for rich mixtures, The later is of special interest for high performance and racing engines. Racing engines give best power when running slightly rich, whilst for emission conscious vehicles a mixture closer to stoichiometric (Lambda 1) is desirable. The HALTUNER works with most fuels and is auto calibrating, therefore it is not feasible to assign exact air-fuel ratio numbers to specific LED’s on the HALTUNER’s scale. The middle of the display (green LED’s) is the stoichiometric air-fuel ratio of 14.7:1 on normal pump gasoline. The last rich light on the scale is approximately 11.5:1 for gasoline. The last lean light is approximately 16.5:1 for gasoline. TUNING FOR POWER OR ECONOMY Tuning for optimum power requires a richer ratio that tuning for optimum economy. With a typical engine the best power occurs near a 12.5:1 air-fuel ratio (gasoline). In the same engine, the best fuel economy occurs near a 15.5:1 airfuel ratio (gasoline). Whether tuning for power or economy, a properly set-up fuel system will give a richer reading during acceleration and a leaner reading during deceleration than the optimum numbers above. Use your HALTUNER as an instrument to evaluate the effect of tuning changes or as an indication of maintenance problems such as a dirty air filter, more importantly it can be used as a safety device to notify the driver of a lean mixture that may cause engine damage, CAUTION The use of leaded fuel will seriously reduce the life of the oxygen sensor. If leaded fuel is used (pump fuel or race fuel), remove the sensor and install the plug after tuning. Certain other fuel additives may damage the sensor over extended periods. A damaged sensor will indicate a leaner reading that is correct for the same operation. |
