Fuel Injection - Evolution Journey

This is a fully automotive powertrain article.
Disclaimer: I am a novice in this area. If experts read this kindly correct...

Q: Why & How did FI ( Fuel Injection) systems evolve?
For a long time carburetor based engines dominated the automotive world. The were good and could make your car run smoothly. However, increasing emission norms & better systems being used by the air planes eventually led to their extinction  in the four-wheeler world ( Though my XCD-135 bike still uses a carburetor for managing the air-fuel mixture). The major things that led to the death of carburetor engines are :

• Too many compensations where needed making the design look like spaghetti code. The were compensations for idling, for cold start among other things.
• Carburetor icing had plagued high altitude flying machines, this led to development of what we today know as EFI systems ( Electronic Fuel Injection). They started off as SPFI  (Single Point Fuel Injection) & then evolved into MPFI ( Multi Point Fuel Injection)

With the new FI systems it was necessary to have electronics to control the fuel injection. This was done by having solenoid controlled fuel injectors. These injectors could be actuated by providing what is generally called the "Fuel Pulse" and the timing & the duration (pulse width) of the pulse could control the amount of fuel sprayed into the manifold. The Advantages of  the new Fuel Injection system ( Now of course its quite old) were :

• Better efficiency due to the fact that the fuel-air mixture could be made LEAN or RICH ( not fat for god sake !!).
  
• No carburetor icing wherever it was applicable. Just in case you are wondering what is Carburetor icing, it is the basically formation of ice in the carb's venturi due to condensation of humid cold air (due to further drop in the venturi). This is often accompanied re-conversion of the fuel from its atomized format to more liquid format.
• EFI systems will also help in reduction of NOx emissions due to which it is better complaince with emission norms is possible.  

The story is more compilicated than what has happened so far because soon a need was felt to control the ignition, Cams, valves and what not. There was also emergence of the EGR concept ( which was present even the carb engine days). The compensations & corrections that were needed to the various parameters based on vehicle parameters like Engine RPM, AC ( air conditioning), vehicle speed  ABS etc has transformed the electronic control systems into a work of art.
In the next post on this topic, I will be going into the various systems that influence a engine & how the EMS ( Engine management system) handles them.
more on....
carb icing
EFI


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