Can some one tell me what the air/fuel guage is supposed to tell you. I ordered one for my car but i don't know what it really does.

 

it measure the residual Oxygen in the exhaust. there are two kinds of O2 sensors. wideband and all others. wideband has 5 wires typically, and is more sensitive and can give a true measurement of your a/f ratio from about 10 - 20 with good accuracy. it is quite expensive compared to a normal 1 or 3 wire O2 sensor.

a 3 wire has the signal wire and a positive and negative for a built in heater to bring it to temperature quicker. a one wire only has signal. temperature plays a key part in one and 3 wire measurement. it is not as crutial in the wideband (from others feedback).

all O2 sensors signals are measured in volts. the computer or gauge interprets the volt signal. its pretty much an electrode. a one or 3 wire O2 sensor can really only measure accurately near stoichiometric (14-15.4) otherwise it is just a ballpark signal to let the computer know to add or remove fuel. a stock ecu just fluctuates back and forth from lean to rich in splits of a second to maintain near the optimum ratio. more advanced efi systems like F.A.S.T use wideband sensors and can maintain a required ratio rather than fluctuating above and below a desired ratio.

hope that helps.

mike

 

Return it and spend the 30$ on gas. Atleast the gas will serve a purpose, unless all you are wanting is a light show. Narrow band o2 sensors are damn useless for tuning.

 

i would agree a wideband is optimal for tuning, but in some cases a cheap narrow band and the 30 dollar gauge can help get it semi-close. i hope to run a wideband set up this winter, but i am using a narrow band and gauge just to let me know if my tune is grossly off. if i change up the discharge nozzle and it bogs, the a/f gauge display does match up. it will pop lean exactly in time with the bog so it can be used as an indicator and less for a tuner. also, 99% of all efi cars out there use em and some are 12 seconds from the factory. just playing devils advocate. :-)

 

I guess i'll get the fuel guage. Thanks guys.

 

I would not trust my engine to a device that is "semi-close". Maybe its just the fact I used to own a rx7 and a few little pings = game over motor so I wouldnt waste my time even looking at an AF gauge.