ECU thread

[resago]

The ECU uses lookup tables to determined the amount of fuel to inject based on MAP/MAF,IAT,RPM readings. It can even have a different table for each gear. This also applies to timing.

It then looks at the O2 sensor to see if the values in its tables achieved the AF ratio it wanted. This does not apply to timing.

So you can't just modify the input (MAF/MAP/IAT) reading because the computer will eventually adjust fuel inj based on the O2 sensor. This amount is called the Long Term Fuel Trim(LTFT) adjustment.

you can't feed a constant signal to the o2 sensor because under acceleration, it expects to see a rich condition, and at cruise, a lean condition.

this explains why when you do a map/maf mod, you see short term gains, but then nothing.

this would also predict that an o2 sensor mod would take some time to take effect.

doing both SHOULD give you immediate and long term results. If you do an O2 sensor mod only, you are not getting the benefit of altered timing.

More later.

[hg2]

The ECU uses lookup tables to determined the amount of fuel to inject based on MAP/MAF,IAT,RPM readings. It can even have a different table for each gear. This also applies to timing.

It then looks at the O2 sensor to see if the values in its tables achieved the AF ratio it wanted. This does not apply to timing.

So you can't just modify the input (MAF/MAP/IAT) reading because the computer will eventually adjust fuel inj based on the O2 sensor. This amount is called the Long Term Fuel Trim(LTFT) adjustment.

you can't feed a constant signal to the o2 sensor because under acceleration, it expects to see a rich condition, and at cruise, a lean condition.

this explains why when you do a map/maf mod, you see short term gains, but then nothing.

this would also predict that an o2 sensor mod would take some time to take effect.

doing both SHOULD give you immediate and long term results. If you do an O2 sensor mod only, you are not getting the benefit of altered timing.

More later.

The signal voltage coming from the efie is just added to what's already going to the ecm,it doesn't make it remain a constant. What ever voltage is already coming out of the o2 sesnsor remains the same plus what ever voltage the efie is adding and will fluxuate with acceleration and back down to idle just like it always has,but also carrying the added voltage.

[jacobnbr1]

The ECU uses lookup tables to determined the amount of fuel to inject based on MAP/MAF,IAT,RPM readings. It can even have a different table for each gear. This also applies to timing.

It then looks at the O2 sensor to see if the values in its tables achieved the AF ratio it wanted. This does not apply to timing.

So you can't just modify the input (MAF/MAP/IAT) reading because the computer will eventually adjust fuel inj based on the O2 sensor. This amount is called the Long Term Fuel Trim(LTFT) adjustment.

you can't feed a constant signal to the o2 sensor because under acceleration, it expects to see a rich condition, and at cruise, a lean condition.

this explains why when you do a map/maf mod, you see short term gains, but then nothing.

this would also predict that an o2 sensor mod would take some time to take effect.

doing both SHOULD give you immediate and long term results. If you do an O2 sensor mod only, you are not getting the benefit of altered timing.

More later.

The computer is too smart for tricking.

The computer is trained to find inconsistancies in the data and counter react for that data and/or spit a DTC for the driveability issue.

Im not saying it can't be done and adjusted from season to season.

If you have the know how you can accomplish this but what I and most others desire is a painless automatic system that already does it for us and the pcm is the answer.

Has anyone ever used the computer in "open loop" mode and tricked it to stay there?

Open loop mode is the part of the PCM that reads only factory settings and those can be adjusted by reflashing the PROM(programmed read only memory) CHIP of the PCM.

From the open loop status the PCM ignores all sensor data and runs on default.

Eventually you will get a DTC for the PCM not being able to go into closed loop though.

I still think the best way for this is to restrict airflow completly as if it never existed thus de-tuning the engine in the 1st place and adding the HOD to gain it back later on down the line after th MAF..

[resago]

>The computer is too smart for tricking.

like they say its only as smart as the person who programmed. What I am suggesting is to give it a set of data it has a corresponding value for. If the input looks valid, it will go about its business without throwing codes.


>The computer is trained to find inconsistancies in the data and counter react for that data and/or spit a DTC for the driveability issue.

these inconsistencies specifically would be an input with no corresponding output. If you don't give it input outside of its range, it shouldn't throw codes. I see people throwing codes when they modify an lookup input but not a followup input (MAF/MAP and o2). If you do both and don't put the input or result outside of the computers preprogrammed expected response, it should work.

I am looking for how much IAT ties into timing and fuel as well.

[jacobnbr1]

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1995 Ford Truck F 150 2WD Pickup V8-351 5.8L
Vehicle Level Powertrain Management Computers and Control Systems Intake Air Temperature Sensor Description and Operation


Description and Operation
Notes

Intake Air Temperature Sensor






PURPOSE
The Intake Air Temperature (IAT ) sensor measures the temperature of the incoming air flow. The Powertrain Control Module (PCM ) uses this information to adjust the fuel injection base pulse width, EGR flow, and ignition timing.

CONSTRUCTION
The IAT is a two lead thermistor type sensor with a negative temperature coefficient and is located in the intake air flow path.

Descriptive Schematic






OPERATION
The PCM applies a 5.0 volt reference voltage to the IAT signal lead while the signal return lead is connected to a common sensor ground. As the temperature of the incoming air increases the resistance of the IAT decreases and the voltage drop across the IAT decreases.

A decrease in air temperature will increase the resistance of the IAT and raise the voltage drop across the sensor.

The normal operating range of the IAT is 3.50 volts (50°F) to 1.02 volts (158°F).

Note : Due to its negative temperature coefficient minor increases in resistance across the IAT circuit harness and ground connections can result in temperature values that are much lower than actual.

RELATED DIAGNOSTIC TROUBLE CODES

DTC 112 - The IAT sensor output is less than the self-test minimum, 0.2 volts.

DTC 113 - The IAT sensor output is greater than the self-test maximum, 4.6 volts.

DTC 114 - The IAT sensor output is out of self-test range, 0.3-3.7 volts.



Some of this stuff don't have outputs...






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[resago]

awesome, thanks!

[jacobnbr1]

awesome, thanks!

Let me know if you need that for a specific car?

[resago]

comparing the tables, which has the most bearing on timing and fuel?

[hg2]

comparing the tables, which has the most bearing on timing and fuel?

Are you asking which sensor has a bearing on timing?

[resago]

yeah. which has a bigger influence, MAF vs IAT