Who is the BOSS?

[BoyntonStu]

We want to hack the ECU on our car to lean (raise) the 14.7:1 Air Fuel ratio.

There are many sensors to mod.

There are possibly many to deal with: Intake Air Temp, MAF/MAP, #1 O2, #2 O2, #3 O2, #4 O2, Throttle Position Indicator, and ???

The question is is, Who is the BOSS with the final last word of leaning the mixture?

BoyntonStu

[godoveryou]

If it's a GM or Bosche Motronic unit let me know. If it's a GM unit I have probably written code for it at some point and can let you know. If it's a Motronic ECU, I can give you the operational theory for it.

Be specific about Year, Make, Model, Engine, and ECU part number please.

To give you a general answer though -
Closed Loop: O2 sensor cross referenced to Alpha N (TPS), MAF/MAP, Coolant/Air Temp.
Open Loop: MAF/MAP cross referenced to Coolant/Air Temp, Alpha N

GOY

[BoyntonStu]

If it's a GM or Bosche Motronic unit let me know. If it's a GM unit I have probably written code for it at some point and can let you know. If it's a Motronic ECU, I can give you the operational theory for it.

Be specific about Year, Make, Model, Engine, and ECU part number please.

To give you a general answer though -
Closed Loop: O2 sensor cross referenced to Alpha N (TPS), MAF/MAP, Coolant/Air Temp.
Open Loop: MAF/MAP cross referenced to Coolant/Air Temp, Alpha N

GOY

I have a Moronic ECU LOL!!!

"Closed Loop: O2 sensor cross referenced to Alpha N (TPS), MAF/MAP, Coolant/Air Temp"

What do you mean by referenced? Is it the BOSS or can the O2 reading be overridden by the Alpha N (TPS), MAF/MAP, Coolant/Air Temp?

etc.


Thanks,

BoyntonStu

[godoveryou]

96+ Motronic systems are likely one of the most advanced series of ECM's to date. It's ability to adjust and self diagnose are amazing and it's data refresh rate is beyond that which I have every seen other ECM's duplicate. While Moronic is funny, it's noplace close to accurate.

It very hard to answer specific questions without knowing what platform we are talking about. I can only answer on basic theory.

In closed loop the ECM has set lookup tables for fuel and ignition based on O2 input. The O2 voltage is then compared to the MAF/MAP, air/coolant signals to for diagnostic reasons. There are preset limits for adjustment. In OBD2 they are more restrictive. When your O2 indicates that the ECM should be opening the injectors for less time than what the MAF/MAP would indicate for the given air flow, engine, and air tempature it adjusts down. However, it can only adjust so far before your ECM thinks that your O2 is misfunctioning, and goes into open loop or limp home mode and refers to the MAP/MAF for primary fuel metering. OBD1 systems let you get away with a lot more as far as limits.

If you wanted to get the most out of closed loop, I would set my Air/Coolant temps to be hot, adjust the MAF/MAP to show little airflow (don't get crazy here, do it with respect), and then manipulate the O2 to show a rich condition. When you do all this, your ecm will likely advance timing up to it's threshold, so be aware of preignition. The most I would adjust the MAP/MAF is .5 volts in a 5 volt system. .5 is very extreme, and you could go very lean doing this, be careful.

Build a system that you can kill everything with one switch in the event of an emergency. It's easy to put a hole in a piston if you are careless.

GOY

[jimbo40]

So then what happens when you add o2 extenders to pull the sensors out of the stream of exhaust?

[BoyntonStu]

96+ Motronic systems are likely one of the most advanced series of ECM's to date. It's ability to adjust and self diagnose are amazing and it's data refresh rate is beyond that which I have every seen other ECM's duplicate. While Moronic is funny, it's noplace close to accurate.

It very hard to answer specific questions without knowing what platform we are talking about. I can only answer on basic theory.

In closed loop the ECM has set lookup tables for fuel and ignition based on O2 input. The O2 voltage is then compared to the MAF/MAP, air/coolant signals to for diagnostic reasons. There are preset limits for adjustment. In OBD2 they are more restrictive. When your O2 indicates that the ECM should be opening the injectors for less time than what the MAF/MAP would indicate for the given air flow, engine, and air tempature it adjusts down. However, it can only adjust so far before your ECM thinks that your O2 is misfunctioning, and goes into open loop or limp home mode and refers to the MAP/MAF for primary fuel metering. OBD1 systems let you get away with a lot more as far as limits.

If you wanted to get the most out of closed loop, I would set my Air/Coolant temps to be hot, adjust the MAF/MAP to show little airflow (don't get crazy here, do it with respect), and then manipulate the O2 to show a rich condition. When you do all this, your ecm will likely advance timing up to it's threshold, so be aware of preignition. The most I would adjust the MAP/MAF is .5 volts in a 5 volt system. .5 is very extreme, and you could go very lean doing this, be careful.

Build a system that you can kill everything with one switch in the event of an emergency. It's easy to put a hole in a piston if you are careless.

GOY

thanks

With respect to IAT. When cold, air is dense and the engine needs more fuel. When cold the resistance is high.

As IAT increases, the resistance goes down and the air becomes less dense. Therefore, less fuel is needed.

Am I correct?

I believe that I had it backwards because the 'hack' was to use a 20K resistor in place of the IAT sensor, and that meant cold to me.

Therefore to properly hack for leaning, one must place a resistor in parallel to the IAT and open the connection to cut back to stock.

BoyntonStu

[JojoJaro]

96+ Motronic systems are likely one of the most advanced series of ECM's to date. It's ability to adjust and self diagnose are amazing and it's data refresh rate is beyond that which I have every seen other ECM's duplicate. While Moronic is funny, it's noplace close to accurate.

It very hard to answer specific questions without knowing what platform we are talking about. I can only answer on basic theory.

In closed loop the ECM has set lookup tables for fuel and ignition based on O2 input. The O2 voltage is then compared to the MAF/MAP, air/coolant signals to for diagnostic reasons. There are preset limits for adjustment. In OBD2 they are more restrictive. When your O2 indicates that the ECM should be opening the injectors for less time than what the MAF/MAP would indicate for the given air flow, engine, and air tempature it adjusts down. However, it can only adjust so far before your ECM thinks that your O2 is misfunctioning, and goes into open loop or limp home mode and refers to the MAP/MAF for primary fuel metering. OBD1 systems let you get away with a lot more as far as limits.

If you wanted to get the most out of closed loop, I would set my Air/Coolant temps to be hot, adjust the MAF/MAP to show little airflow (don't get crazy here, do it with respect), and then manipulate the O2 to show a rich condition. When you do all this, your ecm will likely advance timing up to it's threshold, so be aware of preignition. The most I would adjust the MAP/MAF is .5 volts in a 5 volt system. .5 is very extreme, and you could go very lean doing this, be careful.

Build a system that you can kill everything with one switch in the event of an emergency. It's easy to put a hole in a piston if you are careless.

GOY


Its days like this that I'm glad I drive a diesel. Its so much simpler with diesels. Your throttle position is mapped to a 'Torque' reading and the torque value controls the amount of fuel you inject. Its always the same, for each throttle position value. (It has a delta for IAT, Coolant temps, Baro and MAF.)

On Diesels, the BOSS is the ECM. The ECM looks up the values it commands from the calibration tables. Adjust the calibration tables, and the ECM will obey your values. No adaptive mechanisms for lean or rich air, like 'Short-term and long-term fuel trim' on gassers.

[godoveryou]

The ECU is still the boss of gasoline engines, there's just more factors. The great number of readings and inputs, the greater the precision and accuracy.

I like diesel but the ECU is not the problem with petrol engines.

[Cadillac]

thanks

With respect to IAT. When cold, air is dense and the engine needs more fuel. When cold the resistance is high.

As IAT increases, the resistance goes down and the air becomes less dense. Therefore, less fuel is needed.

Am I correct?

I believe that I had it backwards because the 'hack' was to use a 20K resistor in place of the IAT sensor, and that meant cold to me.

Therefore to properly hack for leaning, one must place a resistor in parallel to the IAT and open the connection to cut back to stock.

BoyntonStu


Just move the sensor to a warmer location.

[BoyntonStu]

Just move the sensor to a warmer location.

I live in south Florida.

Is "Just move the sensor to a warmer location." a polite way of saying:

"Go to Hell" ;>)


BoyntonStu

[godoveryou]

Well, while moving to hell :D just be careful with the throttle. No matter if it's open or closed loop, the throttle is the biggest factor in fuel usage. :)

No.... I don't really want you to go to hell.... :)

[Jaxom]

So then what happens when you add o2 extenders to pull the sensors out of the stream of exhaust?

You desensitize the sensor. The O2 signal to the ECM will respond to changes in the fueling more slowly, which will in turn cause the ECM to compensate for these changes more slowly. The fuel mixture normally swings back and forth between slightly rich and slightly lean as the ECM compensates for changes....desensitizing the sensor will make these swings more pronounced and the overall effect will be less accurate fuel delivery to the engine. It will sometimes be too rich, and sometimes too lean.

I don't see this as a viable solution for the skewed O2 readings that are caused by HHO usage. I know some people report good results from it, but that's just chance. Random changes in fueling will help some and hurt others.