Show! It isn't as accurate as the AEM wideband gauge ......but does have some merit for limited applications.
Read......
How the Factory (narrow band) O2 sensor, ECU and AutoMeter A/F ratio gauge work together. The A/F Ratio Meter is a voltmeter with a range of 0 to 1 Volt. The meter displays the output voltage of the vehicles oxygen sensor through 20 LED's. The first LED will come on at a voltage of .050V, the second at .100V, the third at .150V, etc. LEAN RANGE: Four red LED's (.050 to .249V)
STOICHIOMETRIC RANGE: Ten yellow LED's (.250 to .749V)
RICH RANGE: Six green LED's (.750 to 1.000V) The stoichiometric (STOICH) air/fuel ratio is the chemically correct ratio, theoretically all of the oxygen and all of the fuel are consumed. The mixture is neither rich nor lean. However, due to the fact that combustion is never perfect in the real world, there will always be a small amount of oxygen left in the exhaust. This small amount that is left is what the oxygen sensor measures. The smaller the amount of oxygen that is left in the exhaust, the richer the A/F ratio is, and the higher the oxygen sensor voltage is. The ECU monitors the voltage from the oxygen sensor. If the ECU sees an oxygen sensor voltage greater than .450V, it immediately starts to reduce the amount of fuel that is metered into the engine by reducing the fuel injector duty cycle. When this happens, the A/F ratio starts to go in the lean direction, and the oxygen sensor voltage starts to go down. When the voltage drops below .450V, the ECU immediately starts to increase the fuel metered to the engine by increasing the fuel injector duty cycle to produce a richer A/F ratio. This occurs until the oxygen sensor voltage goes above .450V. This repeating cycle happens very fast (many times per second). The ECU is said to be in closed loop. It is constantly monitoring the oxygen sensor voltage and adjusting the on time of the fuel injectors to maintain a stoichiometric A/F ratio. This A/F ratio produces the lowest harmful exhaust emissions, and allows the catalytic converter to operate at peak efficiency, therefore reducing the exhaust emissions further. Since the oxygen sensor output is non-liner and very sensitive at the stoichiometric A/F ratio it will cause the A/F meter LED's to bounce back and forth rapidly. A very small change in A/F ratio causes a large change in oxygen sensor voltage as can be seen on the graph. This causes the A/F ratio meter LED's to rapidly cycle back and forth, and is normal operation when the ECU is in closed loop and trying to maintain a stoichiometric A/F ratio. The oxygen sensor is very accurate at indicating a stoichiometric A/F ratio. It is also very accurate at indicating an A/F ratio that is richer or leaner than stoichiometric. However it can not indicate what exactly the A/F ratio is in the rich and lean areas due to the fact that the oxygen sensor output changes with the oxygen sensor temperature and wear. As the sensor temperature increases, the voltage output will decrease for a given A/F ratio in the rich area, and increase in the lean area as shown on the graph. During wide open throttle (throttle opening greater than 80% as indicated by the throttle position sensor) the A/F ratio will be forced rich by the ECU for maximum power. During this time the oxygen sensor outputs a voltage that corresponds to a rich A/F ratio. But the ECU ignores the oxygen sensor signal because it is not accurate for indicating exactly what the A/F ratio is in this range. The ECU is now in open loop, and relies on factory programmed maps to calculate what the duty cycle for the fuel injectors should be to provide a rich A/F ratio for maximum power. The A/F ratio meter should indicate rich during this time. During hard deceleration the ECU will command an extremely lean mixture for lowest exhaust emissions. This may cause the A/F ratio meter not to indicate anything. The A/F ratio is so lean that it is outside the range that the meter will indicate.
TT Conversion BACK ON!!!!
(real expensive too!) |
