Exhaust
A major benefit of fuel injection systems is better control 
of toxic exhaust emissions.   Unburnt gasoline 
(hydrocarbons) and nitrogen-oxide emissions are toxic for 
the environment, anyone who has ever been near the 
exhaust of a running car can attest to the unpleasant 
odor—not fun to breath.  A fuel injection computer 
measures the level of oxygen in the exhaust and calculates 
the air fuel ratio.  The ideal ratio, as you may remember, is 
14.7 to 1 air to fuel.  If the ratio is higher i.e., more air or 
less fuel, it is referred to as “lean”.  
A lean condition can result in high nitrogen-oxide 
emissions, low power, engine knocking, even engine 
damage.  If the ratio is lower than 14.7 to 1 (less air or 
more fuel), the condition is called “rich”.  A rich condition 
can result in unburnt hydrocarbon pollution, carbon 
deposits on engine parts, clogged passages, and poor fuel 
economy.  It falls to the computer to keep the air fuel ratio 
as close to 14.7 to 1 as possible UNDER ALL 
CONDITIONS- something that is impossible with a 
carburetor.  An additional benefit of this on the fly 
controllability is fuel economy.  The computers fine tuning 
provides the precise amount of fuel needed, and not a 
drop more.  Thus waste is minimized, unlike a carburetor 
where it’s optimized for one scenario and operates 
inefficiently otherwise.  
      
      
Oxygen sensor diagram