air/fuel ratio, what is it?

[alex99gst]

Alright, ive read some about what air/fuel ratio is but I didnt understand it. I was wondering if anybody knew what it was and could explain it to me. Also, what air/fuel ratios are good and what are bad for a 2g eclipse gst. Thanks

 

[KRAZYKOREAN]

Its self explanatory, Its the ratio of the mixture of air and fuel.

 

[CvicKila02]

Originally posted by KRAZYKOREAN
Its self explanatory, Its the ratio of the mixture of air and fuel.

I believe that he was asking what the numbers ment like 11:1 12:1, not the definition of Air:fuel ratio

 

[Enigma_Man]

Air fuel ratio is the ratio of mass of air to mass of fuel. If your car is operating at 14:1, then for every 14 Kg of air that enter the engine, 1 Kg of fuel enters the engine.

(The following data is for cars using Gasoline, it changes for different fuels. But it generally applies to _all_ cars, including your 2G )
It just so happens that 14:1 is the optimum ratio for pollution prevention. The gasoline burns fairly completely.

Most cars strive to achieve 14:1 air/fuel ratio when just cruising around, to obviously limit the amount of pollution they create.

The optimum air/fuel ratio for power is approximately 12:1. When you are at this ratio, you are getting the maximum efficiency out of the gasoline.

A "Lower" number like 10:1 or 9:1 means the car is running "rich" which means there is more fuel (or less air) than before. A high number like 16:1 etc is "lean" (less fuel more air).

When an engine runs lean, a lot of heat is produced, and not much power. This is very bad for an engine, and can break it very easily.

When an engine runs rich, the exhaust temperature is cooler, and generally "safer" although it will also make less power than optimum 12:1. Somewhat counterintuitively, too much gasoline actually cools down the explosion a little, and helps to carry out more of the heat when not all of it burns.

Our cars, when you stomp on the loud pedal go to something approximately like 10:1 air/fuel ratio, just to be on the safe side (people abuse these cars, the engineers prefer safe sides of things).

The way our cars try to seek out the optimum fuel-efficient 14:1 is by using the O2 sensor. The O2 sensor reports whether the car is richer or leaner than 14:1 (it can be used for tuning, but it is not very accurate and cannot directly measure air/fuel ratios other than 14:1 very well). The ECU keeps getting richer and richer until the O2 sensor voltage goes high, then the ECU keeps going leaner and leaner until the O2 sensor voltage goes low. The whole system is in constant fluctuation.

When you go to Wide-Open-Throttle, and the car runs Rich to be "safe" it ignores the O2 sensor. The ECU calculates based off of measurements from the Mass airflow sensor how much fuel it should put into the engine. The car is only able to semi-accurately calculate the correct air/fuel ratio if everything on the car is stock, changing things like hacking the MAS and whatnot will change the readings the ECU sees, and may change the air/fuel ratio. People use Air-Fuel Computers to change these measurements, and "trick" the ECU into changing the air/fuel ratio in the engine.

Hope that helps some, sorry 'bout the huge-long post

-Jesse

 

[KRAZYKOREAN]

YEAH I apologize for my post I read the question incorrectly. Stupid KRAZYKOREAN. well anyways. Listen to Engima he knows his shizznit

 

[alex99gst]

hey thanks to all of you for your posts, especially you enigma man. It was really helpful.