Open and Closed-Loop Electronic Control

Hello aburani

You would need to advise the Make/Model of each unit before a proper answer could be given to you.

If these units are on a power alternator unit, or car/truck/etc, also advise Make/Model/Year of the power alternator unit, or car/truck/etc.

Reply here, with

Kind Regards....

In open loop control, the engine is provided an amount of fuel that should be correct for the conditions sensed by the system's inputs, such as mass air flow, coolant temperature, throttle position, rpm, etc. In a spark ignition engine, the resulting mixture will be quite close to stoichiometric, but might be off by a percent or two. This is plenty close enough for good overall engine performance, but not close enough for controlling emissions adequately (to today's standards).

In a closed loop system, the actual output of the combustion process is measured as it comes out of the engine. By measuring, in particular, O2 (oxygen) levels in the exhaust gas, the system can then "know" whether to inject slightly more or less fuel to achieve the optimum O2 level. (This level is is closely regulated to enable the catalyst to both oxidise any unburned hydrocarbons, but also reduce any NOx emissions: too rich and one reaction does not work, too lean and the other does not work)

"Closing the loop" means that the output of the system (in this case represented by O2 levels) is fed back into the input to correct the process.

GA.

Without O2 sensors in the tailpipe of HD diesels in tractor trailer sized engines, how do they monitor exhaust to close the loop? Or do they not have closed loop emission system?