lean stock fueling

[Paul466]

Hi All! The ST comes set up lean do to epa in my understanding from past posts. Since I live at altitude (Denver) would the lower air density create good fueling in stock condition? also if I get my ecu flashed would the tuner take altitude into consideration?

 

[HoebSTer]

since there is an O2 sensor or two, it should adjust automatically for this in the mtns. It wouldn't hurt to adjust co settings and idle screw.

 

[Karson]

O2 sensors only sniff the exhaust gases for AFR readings - nothing barometric.

Without looking, I believe we have an intake air pressure sensor that will take into account air density. Then that reading goes to the ECU to account for varying altitudes.

What I'm not sure of, though, is if it just reads it at startup (likely), or continually.

 

[Koinz]

::015::

O2 sensors only sniff the exhaust gases for AFR readings - nothing barometric.

Without looking, I believe we have an intake air pressure sensor that will take into account air density. Then that reading goes to the ECU to account for varying altitudes.

What I'm not sure of, though, is if it just reads it at startup (likely), or continually.

All the sensors work as a system providing the ecu with updated information continually. It would be useless if it just provided the signal at startup. Page 1-3 in Features.

 

[Karson]

All the sensors work as a system providing the ecu with updated information continually. It would be useless if it just provided the signal at startup.

I get that there a multiple input sensors, each providing its unique data to the ECU to provide dynamic fueling. I made the mistake of haste of not really thoroughly describing what I meant before I bounced out of work.

There was a bulletin posted on '07 FJR's describing that their (1) MAP sensor only read shortly after start up. Whether or not this carries ANY similarities to the S10, I don't know. I believe the S10 only has one MAP sensor on it, so I thought it might be relevant to his question about altitude.

Do you know for sure if the intake air pressure sensor provides constant barometric pressure feedback to the ECU?

 

[Karson]

Nice read, Koinz. I'm assuming it does based off that page you referenced. Thanks for that tip!

The injection duration and the injection timing are controlled by the ECU. Signals that are input from the
throttle position sensor, accelerator position sensor, coolant temperature sensor, lean angle sensor,
crankshaft position sensor, intake air pressure sensor, intake air temperature sensor, rear wheel sensor
and O2 sensors enable the ECU to determine the injection duration. The injection timing is determined
through the signals from the crankshaft position sensor. As a result, the volume of fuel that is required
by the engine can be supplied at all times in accordance with the driving conditions.

 

[jaeger22]

The ECU I used in my DR-650 DIY EFI conversion uses the MAP sensor when it if first turned on to calculate the static air pressure and then reads it continually while the motor is reading to determine the Manifold Air Pressure. Some EFI systems use a separate air pressure sensor and can sample it continuously. MAP is the main indicator of engine load and is used with RPM in the S10 to address one of the fuel maps tables(Speed Density). The other table is addressed by Throttle and RPM (Alpha-N) and the two results are blended together to determine the injector pulse time.

 

[HoebSTer]

O2 sensors only sniff the exhaust gases for AFR readings - nothing barometric.

Without looking, I believe we have an intake air pressure sensor that will take into account air density. Then that reading goes to the ECU to account for varying altitudes.

What I'm not sure of, though, is if it just reads it at startup (likely), or continually.

Aren't you saying the same thing? Doesn't the level of oxygen in the mixture for the burn effect the temp reading at the o2 sensor? As it gets hotter from a low level of oxygen being burnt, then it increases fuel to compensate? Don't the O2 sensors act like a pyrometer probe based on heat?

 

[Koinz]

Aren't you saying the same thing? Doesn't the level of oxygen in the mixture for the burn effect the temp reading at the o2 sensor? As it gets hotter from a low level of oxygen being burnt, then it increases fuel to compensate? Don't the O2 sensors act like a pyrometer probe based on heat?

Not sure it's based on heat Jeff. It's oxygen content. Rich mixture generates a small voltage to the ecu around .9 volts. Lean mixture voltage is around .1 volts. The ecu strives to maintain 14.7 to 1 mixture which is ideal combustion depending on fuel of course.

This voltage is generated by comparing the difference between ambient oxygen level and the oxygen level in the combustion gases. (source plagiarized from Wikipedia) ;D

 

[Karson]

Good discussion here, fellas.

My understanding is the only purpose of the O2 sensor is to sniff the exhaust gas. Too much O2, the 0-5V the O2 sensor produces is low(er) voltages indicating to the ECU that it needs to send more fuel. Not enough O2, indicated by a higher voltage and thus indicates to the ECU that it needs to hold back on sending fuel. That's it. I don't know if going from sea level to 13'ers high up in the mountains would result in enough precise info from the O2 sensors to the ECU to adjust fuel properly.

The MAP sensor's sole job is to read air density and provide feedback to the ECU for fueling. Just as the air box temp sensor does with temperature in its own regard to the appropriate amount of fueling based on ambient air temps near the intake.

Finally, the miniature monkey with an abacus inside the ECU calculates using those inputs, and more highlighted in that paragraph below, to how much fuel the injector(s) deliver.

It makes sense if you don't think about it, and I'm far, far, FAR from a FI expert, and these are my own interpretations as a layman. ::008::

Now, someone like autoteach, please put this into a more understandable form.

 

[talonboy]

To answer the original question, a carbureted bike would run richer at high altitude, but an electronic fuel injected bike will compensate for this my using the o2 sensors and MAP sensor. The bike should run fine at most any temp/altitude.

Keep in mind the o2 sensors are only used in closed loop. The other sensors are most likely used all the time.