Fast 30400-KIT-EZ-EF Instructions Manual - page 61
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wideband oxygen sensor provides very accurate feedback to the ECU so it knows if more or less fuel is
needed to achieve the desired air/fuel ratio. Adjusting the fueling based on feedback from an oxygen
sensor is commonly referred to as “closed-loop” fuel control.
Closed-loop fuel control is a very powerful feature. It constantly makes fueling adjustments to
compensate for different engine conditions. It is at its best when operating with well-tuned base fuel
tables. Developing good base fuel tables requires significant time and experience. Closed-loop fuel
control can help compensate for less than perfect base fuel tables. However, there are limits to what it
can do. It is not a substitute for proper tuning. The more work closed loop has to do, the less efficiently
it can keep the actual air/fuel ratio close to the target ratio.
The Adaptive Learning feature of the EZ-EFI
®
system goes beyond normal closed-loop fuel control.
Besides using the oxygen sensor feedback to adjust instantaneous fueling, it also uses it to adjust the
underlying base fuel table so that over time, it tunes itself. Closed-loop fuel control is happily left with
only fine adjustments to make.
The theory of the Adaptive Learning feature is pretty straight forward. Actually implementing it is
rather complicated. But all of that work is built into the ECU already. All that is left to do is drive.
Operational Notes:
The EZ-EFI
®
system has a “pre-squirt” feature that helps starting by injecting a measured
amount of fuel into the manifold at key-on. A clicking sound can be heard from the throttle
body as the injectors pulse. Once this feature has been activated (key-on, fuel injectors
cycled), it will be disabled until the engine has run. This prevents flooding the engine if the
ignition is cycled on and off multiple times for whatever reason. Also bear in mind that less
“pre-squirt” is used at higher engine temperatures. If the engine is hot enough at key-on,
there may be little to no “pre-squirt” clicking heard. For both of these reasons, not hearing
the injectors clicking at every key-on is not a sign of a problem.
A “flood clear” mode is available if the engine does somehow become flooded and does not
want to start. If the throttle is held open past 80% while cranking, no fuel will be injected.
Continue to hold the throttle open while cranking. Once the extra fuel is purged and the
engine starts to fire, release the throttle and allow the engine to settle on its own.
In normal conditions, it is good practice (but not strictly required) to key-on and listen for the
“pre-squirt” feature (injectors clicking in the throttle body) to finish before cranking the
engine. This takes about 2 seconds to complete.
The wideband oxygen sensor has an internal heater to keep it at the correct operating
temperature. The warm-up process begins at key-on. If the engine has cooled completely in
particularly cold weather, giving the sensor some time to heat up (allowing 10-15 seconds
between key-on and cranking) may contribute to smoother starting. The “O2 On” LED
displayed on the hand-held’s Live Dashes will indicate when the oxygen sensor has warmed
up and begun functioning properly. Until then, there will be no closed loop fuel control.
Moving the throttle pedal during the first several seconds after key-on (as the fuel pump is
being primed) will also cause additional fuel to be injected. This has the effect of adding
additional “pre-squirt” fuel. This is typically not required. Care should be taken to avoid
accidentally moving the pedal during this time.