|
Is like a little Oxygen Analyzer
Well in a little way. Even though a wideband o2 sensor should be used for accurate readings, it is not always needed. Other types of related equipment can provide further information, like using an better oxygen analyzer or exhaust gas analyzer to check combustion emissions and then you might think of the catalytic converter.
Reduce emissions
As mentioned elsewhere, when the air fuel ratio is about ideal, just slightly under the stoichometric ratio, therefore just a little lean, it will allow the catalytic converter to operate at maximum efficiency thus reducing CO2 emissions.
Better fuel economy - fuel efficient car
An oxygen sensor that has become defective or even damaged may lead to an increased fuel consumption, increased emissions and also decreased power.
When the air fuel ratio is slightly under the stoichometric ratio, it will also result in near optimum gas mileage, with less per mile cost and the car becomes more fuel efficient.
No lean air fuel ratio at supercharging or turbocharging
The intake manifold pressure levels are affected or changed as in supercharging/turbocharging, where boost gauges are used to monitor these pressures, and then the air fuel ratio is also affected, as mentioned earlier. With too less fuel at boost, the mixture gets too lean, as it shouldn't be. Therefore, an air fuel ratio meter provides additional control and insurance.
Simple and useful
Air fuel meter gauges for narrow band oxygen sensors, are indeed useful. They can be always connected since the oxygen sensors they monitor are always there.
All air fuel meter gauges below are to be used with narrow band oxygen sensors.
These sensors are already existing in all cars since around 1980, in the exhaust manifold, or they can be installed in an exhaust header.
So, the 10 led units that are most common are probably calibrated in 100 mV steps ie 100mV, 200 mV, 300 mV and so on.
Some points;
- The value scales of the gauges below are not realistic, since the exhaust gas temperature affects the output voltage areas of a narrow band sensor, in the lean and rich areas. Only the mid stoichiometric point (lambda = 1) output level from a sensor is quite temperature independent.
- The output from an o2 sensor isn't linear, the output voltage switches fast across the middle. In spite of this, none of the meters are designed with that aspect in mind. If the lean and the rich area would have been monitored more in detail, relatively, the number of leds would have to be more in the low lean area and the the upper rich area. Hence, 1 led would be sufficient for the middle 'lambda = 1' area (ca 250 - 650mV), since the output switches quite fast between the lean and rich thresholds. However, the average level (lambda 1) can be viewed in somewhat good way (although an internal averaging capacitor in an air fuel meter could have made it easier).
Therefore, a lower threshold of such a lambda=1-led could be set to 250 mV and the upper threshold at 650 mV. Hence, the average level would be [250 + 650]/2 => 900/2 = 450 mV which is the average level that the ecu measures as lambda 1. But since the o2 sensor switches so fast, anything between these voltages is lambda 1.
The led color arrangement that seems to be the most common is: lean:red, lambda 1:
yellow, rich:green
used by Efi, Lambda Link, Halmeter, (Split Second, with more colors), Lumenition, J&S and K&N. The Alpha meters also use that but also have red leds above the rich area.
The Edelbrock and Equus use: lean:
red, lambda 1:
green, rich:yellow
The RSR has an opposite order since the lean area is green. The manufacturer displays it in use for motorcycles.
|
