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Discussion Starter · #1 ·
Just curious about this design.

According to my knowledge, the O2 sensor is used to
sense the O2 level after the gas was burnt, so the engine
relies on it to adjust the Air/Fuel ratio in real time.
One HO2S was installed for the front bank, and another
for the rear bank. This design is actually a redundancy
in engineering design in case one fails. In fact, it's almost
impossible for the two O2 sensor to give exactly the same
reading anytime.

In this situation, will the ECU average the two readings, or
just rely on one of them?

It is known that the mass-air-flow (MAF) sensor also plays
an important role in the car's gas economy. So when will
the MAF be used in car's operation? what situatons can be
called open-looped?

Another confusion in my mind is generally most engines are
designed to have a fuel cut-off mechanism, or the fuel supply
is stopped when the gas pedal was lifted and the throttle was
closed unless the RPM of engine drops to a certain level.
For vulcan specificly, what's the RPM for fuel cut-off?
In practice, I tried to drive my sable in a pulsed fashion,
which means I usually accelerated the car to ~45mph,
then eased off the gas pedal and let it costed for a while.
As most of us know, this car has an ability to maintain
its speed fairly well. When the speed dropped to ~40mph,
I pressed down the gas pedal and boosted the car to
50mph, then lifted up the gas pedal and let it coasted again.
Actually, I didn't see any gas mileage improvement by this
fashion. Therefore, I doubt if Taurus/Sable were designed
to have a fuel cut-off mechanism or not.
 

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first of the 2 sensors are there for sequential injection and enables the computor to more precisly control fuel one sensor for each bank anabling the computor to control fuel to each bank seperatly.
Secondly the maf sensor is read all the time enabling the computor to determend engine load in conjunction with the throttle sensor and things like rpm.it also helps with ignition timing and fuel mixture.
As for driving style you will us more fuel this way as every time you press the acclerator pedal you are adding a rich mixture of fuel and this runs the motor in open loop mode you are better of holding it steady to keep the motor in closed loop mode.

Just like an old carby motor has an accelarator pump in the carby moving the pedal in an efi tells the computor to had more fuel thus running richer than realy needed.

Ian
 

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Yup, the computer ignores the O2 sensors on heavy throttle. It relies on just the MAF for those conditions.

The fuel only cuts off during deceleration. Hold a steady speed for best gas mileage. Thats what that marvelous cruise control system is for.
 
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