A/F is controlled to 14.64 (near lambda=1) during closed-loop control of most SI gasoline engines to allow 3-way exhaust catalytic reactions. A/F ratio is constantly varied during diesel combustion since it is primarily diffusion-controlled combustion.

Maximum fueling for CI (diesel) is usually limited by end-of-burn or smoke limits to about lambdai

Hi,

It is the Air/Fuel ratio that you can find by completing the equation of combustion. Basically, it says that your using X kg of air to burn a kilogram of fuel.

But, I think that this type of question can easily be answer by google or wikipedia.

http://en.wikipedia.org/wiki/Air%E2%80%93fuel_ratio

The ideal or stoichiometric Air/Fuel ratio for many gasoline type hydrocarbon fuels is very close to 15:1, for diesel engines its vary to 18 to 70.

The average Air/Fuel ratio for gasoline engines is the stoichiometric one and it is equal 15 while Diesel engines usually work at lean mixtures (greater than 18)

A/F is controlled to 14.64 (near lambda=1) during closed-loop control of most SI gasoline engines to allow 3-way exhaust catalytic reactions. A/F ratio is constantly varied during diesel combustion since it is primarily diffusion-controlled combustion.

Maximum fueling for CI (diesel) is usually limited by end-of-burn or smoke limits to about lambdai

Yes, agree with all. In engine control, the parameters read is either lambda or phi by measuring O2 content in exhaust gas. the amount of fuel is controlled by injection pressure and duration and varies based on engine load and speed. A/F ratio may vary from one manufacturer or grade or additive to the other.

For SI engine, depends on it is lean burn or stoich. engine. For lean burn depends on the operation conditions, phi is between 0.6-0.7. For a stoich engine, it normally run a little bit rich for emission purposes. There is always a bias logic to run a bit rich and lean to make the 3-way cat to work.

For a CI engine, normally there is no throttle. Hence, AFR is not really controlled. It is running lean all the time.

For diesel engines 13:1 to 16:1

For petrol engine 7:1 to 10:1