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I want to completely understand how EFI works. Moreover, how and in what form it receives the message from the accelerator pedal. I specifically want to learn how it is implemented in Honda sedans like Civic and City AT versions.

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    Welcome to Motor Vehicle Maintenance & Repair! What is your end goal? EFI is a pretty broad subject. Maybe if you told us what you know right now and what you expect to learn, we'd be able to provide you enough education at a high level, you could then ask questions which will get you into the weeds where you want to be. As you've asked the question, it's a very broad subject. Feb 5, 2018 at 15:30
  • Start with the simpler Bosch K-Jetronic and work up from there...
    – Solar Mike
    Feb 5, 2018 at 16:34
  • This isn't a practical problem - you'd get a better general knowledge of HOW it works by reading Wikipedia this site is more for real problems you're facing.
    – Criggie
    Feb 6, 2018 at 5:51
  • Thank you for your reply. Well, exactly, I am interested in controlling the throttle with a computer of an automatic transmission sedan. Feb 6, 2018 at 6:21
  • You realize most cars produced today have what is called drive by wire (DBW) versus drive by cable (DBC), where the "wire" is a computer controlled throttle body and the "cable" is directly connected to the throttle pedal? Major manufacturers have been using this method for about the last 10-12 years. Feb 6, 2018 at 13:51

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EFI works by measuring the air flow. The accelerator pedal is directly connected to the throttle valve on old cars and indirectly (via an electrical connection) on new cars. There is a separate air mass flow meter (typically hot wire) that measures the mass of incoming air. When the mass flow is known, the EFI can using open loop control adjust the amount of fuel injected to match the amount of airflow.

There is also a second control system, the closed loop lambda control. The lambda sensor measures the oxygen levels in the exhaust, and the closed loop control maintains the oxygen level at near zero to result in complete burn with no residual oxygen. The reason for this closed loop control is that the catalytic converter works the best with stoichiometric air/fuel ratio.

All of this is done digitally using computers. The injectors are either closed or open, never partially open, and the amount of open duration is digitally controlled.

I'm pretty sure you could have found all of that on Wikipedia article about fuel injection already.

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  • Exactly that, and the throttle position sensor lets the ecu know how far the throttle blade is open. It's is a simple potentiometer that sends a signal back in the form of a voltage reading. It's all simple yet clever stuff.
    – DamoC
    Feb 6, 2018 at 0:01
  • Thank you for your reply. Well, exactly, I am interested in controlling the throttle with a computer of an automatic transmission sedan. Feb 6, 2018 at 6:22

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