[Diy_efi] Re: EMS inputs/output?

[alex averbuch]

Cheers Huw,
What do you mean when you say that the "EMS constantly sends the mixture 
rich/lean"?
Does the EMS actually tell the injectors to apply a rich mixture and then a 
lean mixture, twice every second?!  That sounds primitive to say the 
least... wouldn't this method restrict the engine's performance to a 
considerably?

Would you be able to explain, in more detail, why the EMS does this?

Alex

>
>for lambda to work - (at least a narrow band sensor, a wideband is >totally
>different), the ecu constantly - at the rate of around once or twice a
>second - sends the mixture rich/lean. The lambda sees this as a 
>square->wave
>with varying mark-space ratio, the electronics then does some maths and
>signals rich or lean and compensates accordingly. This compensation is >an
>adjustment of the "mapped" or pre-calculated fuelling - the open loop
>fuelling. The reason for this is that a std lambda is a narrow band
>instrument that only really works around stoichiometric, a wideband >lambda
>can work over a wider range and thus would not need the alternating 
> >mixture.
>    Ping sensors can be very simple accoustic sensors, but to filter >out
>unwanted noise a complicated dsp chip is usually used, this is normally
>"gated" with the ignition signal to ascertain which cylinder is >pinging, a
>project on it's own I'd say!
>    Dwell is the time the coil is charged by the battery, it is >normally
>longer at cranking or low battery voltages and is controlled 
> >electronically
>to prevent overheating the coil at low engine speeds.
>    Huw
>

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