Air-fuel ratio
From Celica GT-Four / Alltrac - ST165 ST185 and ST205
Available Unit IDs: C01, C02, C03, C04, C05, C06, C07, S01, S02, V01, V02, V03.
Example: <google uid="C01"></google>, <google uid="C01" position="left" ></google>
AFR - Air-Fuel Ratio
Air-fuel ratio (AFR) is the mass ratio of air to fuel present during combustion. When all the fuel is combined with all the free oxygen, typically within a vehicle's a combustion chamber, the mixture is chemically balanced and this AFR is called the stoichiometric mixture (often abbreviated to stoich). AFR is an important measure for anti-pollution and performance tuning reasons. Lambda (λ) is an alternative way to represent AFR.
A stoichiometric mixture is the working point that modern engine management systems employing fuel injection attempt to achieve in light load cruise situations. For gasoline fuel, the stoichiometric air/fuel mixture is approximately 14.7 times the mass of air to fuel. Any mixture less than 14.7 to 1 is considered to be a rich mixture, any more than 14.7 to 1 is a lean mixture.
The standard ECU uses an oxygen sensor to monitor the AFR to try to maintain the ideal under certain conditions. Under normal operating conditions the standard 185 ECU keeps the WOT AFRs to fairly safe, rich, levels - between 10 and 11:1. If too much air is passed through the air flow meter it will make the mixture super-rich to protect the engine - AFRs of 7-8:1 are not uncommon in this situation. This is so rich it is bordering on misfire, and seriously reduces output power.