air fuel ratio on 4age 16v engine without catalytic convert

[apsogosGTi]

hello mates!
Today i did a general check my mechanic, the engine is senond gen tvis 16v 4age european specs.No catalytic converter so the co idle mixture should be adjust from the variable resistor.
I check my co at idle at about 800 rpms and was 0.24% better than a catalytic
So we adjust it at about 1.50 % with all electrical equipment off (be carefull when the cooler fan opens the idle increaces so must wait the cooler fan to stop to adjust)
The lamba at this point was about 0.980 .The co mixture percent interferes lambda so when you change the variable resistor value the lamba value alters.
The thing i am trying to understand is my lamda value for a close to perfect air ful ratio should be eg at 1.00 ?Can someone of our specialist explain to us some things.?
After adjusting i believe that the engine was more smooth than before.

[yoshimitsuspeed]

It sounds to me like you are running a non US ECU so I think it would help a lot if you could tell us exactly what your setup is. If you have an O2 sensor then it should be fully responsible for maintaining stoich at idle and cruise.

[apsogosGTi]

good morning,
i have no o2 sensor and no catalytic converter.My car is a 1988 2nd generation 4age 16v tvis engine european specs.Ae92 hatchback corolla.So for adjusting the co idle mixture i have to connect it with co analystist and set it to 1.5% co + - 0,5 % from my variable resistor.

[totta crolla]

Set the co% to factory specs. and ignore the lambda reading.

[apsogosGTi]

Set the co% to factory specs. and ignore the lambda reading.

why is this mate? and after some time factory specs will alter again?

[totta crolla]

Set the co% to factory specs. and ignore the lambda reading.

why is this mate? and after some time factory specs will alter again?

Emission test will include co%
I guess you could set the co% to factory spec. and then check the Lambda value for that setting so that you can return it to that Lambda setting if it changes ?
Why would you not want to use factory co% setting anyway ?

[apsogosGTi]

I am trying to understand if the factory specs is equal to a specific lamda value and all together to an optimum afr.

[s24a]

I am trying to understand if the factory specs is equal to a specific lambda value and all together to an optimum afr.

If you are looking for theoretical "best specifications" for A/F ratio on an engine , it is defined as "Minimum Best Torque" for the engine, which is the leanest fuel/air ration and timing which produces the maximum torque for any given speed and load point.
This obviously is different for every engine type (L-head, 2-valve reverse flow head, crossflow, multivalve crossflow), is generally for part throttle and idle areas anywhere around 15 to 15.5 A/F ratio with the appropriate spark advance that gives best torque for that A/F ratio.

As you state in your original post that you found the spec for your engine to be 0.980 lambda , and if we use a gasoline stoichometric ratio of 14.7 parts air to one part fuel mass, this gives you a calculated A/F ration for your idle CO of (14.7 * 0.980).
This equals 15.0:1 A/F ratio. So Toyota is setting their idle very close to the theoretical MBT point for fueling.
I say close, because cycle to cycle variation and cylinder to cylinder variation is to be expected, so my guess is Toyota has enrichened the mixture slightly and also trimmed the timing a little (-2º off MBT timing) in order to be on the plateau of the curve.
This will stabilize idle better. Going a little richer probably makes the idle even more stable, but that is throwing fuel away if the engineers felt their settings were best for idle fuel consumption, as in Europe you have a liters/km number that OEMs have to report, and that sways buyers that look for this.

[apsogosGTi]

I am trying to understand if the factory specs is equal to a specific lambda value and all together to an optimum afr.

If you are looking for theoretical "best specifications" for A/F ratio on an engine , it is defined as "Minimum Best Torque" for the engine, which is the leanest fuel/air ration and timing which produces the maximum torque for any given speed and load point.
This obviously is different for every engine type (L-head, 2-valve reverse flow head, crossflow, multivalve crossflow), is generally for part throttle and idle areas anywhere around 15 to 15.5 A/F ratio with the appropriate spark advance that gives best torque for that A/F ratio.

As you state in your original post that you found the spec for your engine to be 0.980 lambda , and if we use a gasoline stoichometric ratio of 14.7 parts air to one part fuel mass, this gives you a calculated A/F ratio for your idle CO of (14.7 * 0.980).
This equals 15.0:1 A/F ratio. So Toyota is setting their idle very close to the theoretical MBT point for fueling.
I say close, because cycle to cycle variation and cylinder to cylinder variation is to be expected, so my guess is Toyota has enrichened the mixture slightly and also trimmed the timing a little (-2º off MBT timing) in order to be on the plateau of the curve.
This will stabilize idle better. Going a little richer probably makes the idle even more stable, but that is throwing fuel away if the engineers felt their settings were best for idle fuel consumption, as in Europe you have a liters/km number that OEMs have to report, and that sways buyers that look for this.

firstly i want to thank you for your analytic post. Secondly i didnt understand all the thing that you wrote cause i have 100% knowldegde at mechanical and physics
how exactly should i know my gazoline stoichometric ? i am using here in Greece 100 octane unleaded fuel , i have recently rebuild my engine and my c.r is about 10.6.
Generally i want to adjust my engine mixture at best settings for its setup!now we simple words this co idle mixture adjustment is only for idling or can effect all the band of hp?and why is this setting altering after few kilometers ?by the way i have set my advance to about 10 degrees, with ecu diagnosis connected and at about 800 rpms with hot engine.

[s24a]

firstly i want to thank you for your analytic post. Secondly i didnt understand all the thing that you wrote cause i have 100% knowldegde at mechanical and physics
how exactly should i know my gazoline stoichometric ? i am using here in Greece 100 octane unleaded fuel , i have recently rebuild my engine and my c.r is about 10.6.
Generally i want to adjust my engine mixture at best settings for its setup!now we simple words this co idle mixture adjustment is only for idling or can effect all the band of hp?and why is this setting altering after few kilometers ?by the way i have set my advance to about 10 degrees, with ecu diagnosis connected and at about 800 rpms with hot engine.

Gasoline stoichometric value is as varied as the blends of fuel worldwide. It can also vary depending on the season, as cold season gasoline has more volatile components to ease the staring when cold.
So no good answer, and only a fuel lab analysis can tell you what your present 100 octane fuel is, and then next week it could be different!
That said, I typically have found the value to be between 14.67 and 14.74. This is unadulterated petrol. Alcohol changes it, reducing the stoicometric value as percentage alcohol goes up.

I think you are pretty close right now based upon the information you have provided. Since you claim to have 100 octane fuel, then possibly a couple degrees more idle timing might be beneficial.
You want to stay away from any timing settings that result in heavy load spark knock. That is not good.

As for idle CO setting affecting the rest of the ECU fueling tables, this is really not the case. As load increases the ECU (MAP-based) will use a different table, and in the transient from idle to part throttle the ECM provides an acceleration enrichment function. So not to worry. If it were an Airflow Meter system, then again this is taken care of in the flowmeter.

I would concentrate on the CO setting that with adjusted timing results in a smooth idle at the lowest (800rpm) setting that the engine will allow.
That is the best condition to shoot for.

[apsogosGTi]

thank you s24a!
i have not a flowmeter, i have map sensor based system (the oem one).So whatever i set at the co value as the load increases the ecu will use some different map and in case is wrong ,it will try to "correct" it.
Now i am thinking tommorow to change the advance from 10 to 12 degrees that will also affect the co mixture setting yes?Generally i use for spark plugs denso iridium iq20.But now i have the denso oem ones inside.

[totta crolla]

Toyota did a pretty good job for you with the engine and the stock settings.
What are you trying to achieve by changing things ?

[apsogosGTi]

since i ve made some small changes to my engine eg
a small comporession bump from oem 10.1 to eg 10.6 cr , a 20v header with custom free flaw exhaust system, a more free flow intake the Bmc Cda, a higher octane gazoline 100 octane ,a 100% synthetic 10w40 oil ,one of the best the amsoil amo and 20v clutch flywheel.I tryied to take the most advantage from my engine.

[yoshimitsuspeed]

since i ve made some small changes to my engine eg
a small comporession bump from oem 10.1 to eg 10.6 cr , a 20v header with custom free flaw exhaust system, a more free flow intake the Bmc Cda, a higher octane gazoline 100 octane ,a 100% synthetic 10w40 oil ,one of the best the amsoil amo and 20v clutch flywheel.I tryied to take the most advantage from my engine.

The stock AFRs are still going to be about as ideal as you are going to get without getting it on a dyno. If you really want to make power then that's where you are going to have to fiddle with things. Of course if you really want to maximize power then you will want aftermarket engine management.