Air/fuel Gauge... How Does It Work?

[BSK]

hey all!!

could someone please enlighten me on how an air/fuel gauge works?

ie: where does it take its readings from?

why does it sit on 14 under acceleration and at idle but when backing off moves upto 18 and hangs there for several seconds or until i accelerate again and it moves back to 14.....

cheers guys..

[PHATR32]

well it gets its reading from the oxygen sensors, which are located after the turbos.

ummmm, thats all i know!

if you search the web, for oxygen sensors, it show you.

steve

[BSK]

howstuffworks.com gave me a basic insite into O2 sensors. but id still like to know what its actually reading..

im guessing when the needle moves up over its optimal point its registring excess oxygen in the exhaust but when it moves below is it registering an excess of unburnt fuel (lower oxygen ratio)...

any tuners out there ??

[vannic]

i took this from this link Cheaply Monitoring Air/Fuel Ratios. i'm building the jaycar air/fuel mixture kit at the moemtn and the instructions that come with it have a fantastic explaination of the air/fuel mixture gauge.

All unleaded petrol cars use an exhaust gas oxygen sensor. As the name suggests, this sensor is mounted in the exhaust flow - usually in the exhaust manifold - and sniffs the composition of the exhaust gas. Specifically, it measures the ratio of oxygen in the exhaust gas with that in the atmosphere. It does this is to determine whether the air/fuel ratio is rich, stoichiometric, or lean. The ECU uses this information as part of its self-learning technique, . . . The most commonly used sensor generates its own voltage output, which varies between 0-1 volt. In round terms, if the sensor output is about 0.2 volts or less the mixture is lean, and if the output voltage is over 0.8 volts it is rich. However, the precise value of the output voltage is less important than its relative value - whether it is "richer" or "leaner" than the mid-point voltage.

The ECU constantly adjusts the mixture depending on the driving conditions. ie. if you are accelerating, you require more fuel in the mixture so the ECU tells the injectors to inject more fuel and resulting in a richer mix. if you're backing off, its just the opposite.

hope this helps

Edited May 20, 2006 by vannic