Lambda vs AFR short explanation video

[BULL]

 

[1971demon]

In my defense..I was a bit sleepy...

 

[jonx96]

I utilize excel as much as possible!

 

[1971demon]

In my defense..I was a bit sleepy...

So thats the way yer gonna be eh...

 

[1971demon]

So thats the way yer gonna be eh...

 

[fumanchu182]

I came up with my own number games. Stoich or a Lambda of 1.0 for a Hellcat is 13.85 (FAR value of 0.0722, divide 1 by 13.85). So lets say I want to target 11.50 as my AFR, what would that be in Lambda, well it's a ratio value, less than 1 means rich, more than 1 means lean. To get my modifier value to add to FAR I came up with the following

((1/11.5) - 0.0722) = ~0.0147. The correct place to stuff this value would be in either table 34230 FA Power enrich based on aircharge or 34243 FA Power enrich based on pratio.

I feel like Lambda in a dodge PCM is nothing more than a gimmick unless my maths are wrong. So lets say I want to target 11.5 from 13.85. That's a percentage in Lambda so solve for x...

13.85 * x = 11.50
x = 11.5/13.85
x = ~ 0.830

Well that's great and all but how can I convert that to FAR... to know what to add to my modifier tables...

 

[white1]

I came up with my own number games. Stoich or a Lambda of 1.0 for a Hellcat is 13.85 (FAR value of 0.0722, divide 1 by 13.85). So lets say I want to target 11.50 as my AFR, what would that be in Lambda, well it's a ratio value, less than 1 means rich, more than 1 means lean. To get my modifier value to add to FAR I came up with the following

((1/11.5) - 0.0722) = ~0.0147. The correct place to stuff this value would be in either table 34230 FA Power enrich based on aircharge or 34243 FA Power enrich based on pratio.

I feel like Lambda in a dodge PCM is nothing more than a gimmick unless my maths are wrong. So lets say I want to target 11.5 from 13.85. That's a percentage in Lambda so solve for x...

13.85 * x = 11.50
x = 11.5/13.85
x = ~ 0.830

Well that's great and all but how can I convert that to FAR... to know what to add to my modifier tables...

From a tuning standpoint, your mind is in the right place, but not exactly correct. Stoich is for a certain fuel, NOT a vehicle. Why the hellcat has an error built in I'm unsure. A few example of stoich displayed in AFR is 0% ethanol gasoline = 14.7 10% ethanol gasoline is roughly 14.5 E85 is 9.76 methanol 6.46 and diesel is 14.50.

Lambda is stoich at 1.00 the way it was explained to me is Stoich means a complete burn. It takes 14.5 parts of air for every 1 part of e10 gasoline to have a complete burn. Rather than remembering stoich values for many different fuels, its easier for tuning purposes to just use lambda imo

1.0 is stoich no matter the fuel, so if you're looking for a certain enrichment rate, you can just calculate (or cross reference a chart) to see what your target lambda should be regardless of fuel.

For example, on most NA hemi builds I target a lambda of .85 which calculates out to 12.5afr for gasoline. For e10 that would be about 12.3afr and for e85 would be 8.20 afr

Rather that trying to remember all the stoich values in my head. I just set the log to read in lambda and go from there. Other ways would be to reference one fuel (gasoline for example) if my wideband is reading 12.5 afr while configured to display gasoline afr, I would be correct no matter the fuel.

Remember, and oxygen sensor is just that. Nothing more. It is measuring unburnt oxygen in the exhaust system and calculating a reading. If you're using a stand alone wideband and tuned properly you should display 14.7 on 0% ethanol gasoline, 14.5 on 10% gasoline, 9.76 for e85 and so on. The reading will not change based on fuel even though the stoich value does.

I'm beginning to realize I'm rambling. Hopefully I didn't confuse anyone any worse than they possibly were

 

[Hickster]

Not any more than when I look in the mirror. Or is that scared. Scary and confused. There we go.

 

[Speedy!]

I came up with my own number games. Stoich or a Lambda of 1.0 for a Hellcat is 13.85 (FAR value of 0.0722, divide 1 by 13.85). So lets say I want to target 11.50 as my AFR, what would that be in Lambda, well it's a ratio value, less than 1 means rich, more than 1 means lean. To get my modifier value to add to FAR I came up with the following

((1/11.5) - 0.0722) = ~0.0147. The correct place to stuff this value would be in either table 34230 FA Power enrich based on aircharge or 34243 FA Power enrich based on pratio.

I feel like Lambda in a dodge PCM is nothing more than a gimmick unless my maths are wrong. So lets say I want to target 11.5 from 13.85. That's a percentage in Lambda so solve for x...

13.85 * x = 11.50
x = 11.5/13.85
x = ~ 0.830

Well that's great and all but how can I convert that to FAR... to know what to add to my modifier tables...

You got the math right, that's the important thing and @white1 filled in the other part.

When I was figuring all this out I built a spreadsheet that I could punch in a desired AFR and it would give me the lambda and PE value I needed to reach it. .0722 + .0147 = .0869. 1 / .0869 = 11.50. .83 x 13.85 = 11.4955

Going with Flex I had to think in lambda.

 

[fumanchu182]

From a tuning standpoint, your mind is in the right place, but not exactly correct. Stoich is for a certain fuel, NOT a vehicle. Why the hellcat has an error built in I'm unsure. A few example of stoich displayed in AFR is 0% ethanol gasoline = 14.7 10% ethanol gasoline is roughly 14.5 E85 is 9.76 methanol 6.46 and diesel is 14.50.

Lambda is stoich at 1.00 the way it was explained to me is Stoich means a complete burn. It takes 14.5 parts of air for every 1 part of e10 gasoline to have a complete burn. Rather than remembering stoich values for many different fuels, its easier for tuning purposes to just use lambda imo

1.0 is stoich no matter the fuel, so if you're looking for a certain enrichment rate, you can just calculate (or cross reference a chart) to see what your target lambda should be regardless of fuel.

For example, on most NA hemi builds I target a lambda of .85 which calculates out to 12.5afr for gasoline. For e10 that would be about 12.3afr and for e85 would be 8.20 afr

Rather that trying to remember all the stoich values in my head. I just set the log to read in lambda and go from there. Other ways would be to reference one fuel (gasoline for example) if my wideband is reading 12.5 afr while configured to display gasoline afr, I would be correct no matter the fuel.

Remember, and oxygen sensor is just that. Nothing more. It is measuring unburnt oxygen in the exhaust system and calculating a reading. If you're using a stand alone wideband and tuned properly you should display 14.7 on 0% ethanol gasoline, 14.5 on 10% gasoline, 9.76 for e85 and so on. The reading will not change based on fuel even though the stoich value does.

I'm beginning to realize I'm rambling. Hopefully I didn't confuse anyone any worse than they possibly were

Completely understood and tracking, I guess when I go E85 that will a help for sure. It just messes with the mental map that Dodge set stoich to be 13.85 in Hellcats on the display, but you are correct it is by fuel type, for 93 octane a stoich of 14.7 is 1 in Lambda. I switched my VCM scanner from Lambda to 14.7 AFR and sure enough it is display 14.7 for stoich or close to it and then when enriched it gets to ~12.5. I switched it back to Lambda because I didn't want to do a brain freeze on how I was thinking in fuels.

@Speedy! what kind of fun am I in for with a straight E85 race tune?

 

[jonx96]

Completely understood and tracking, I guess when I go E85 that will a help for sure. It just messes with the mental map that Dodge set stoich to be 13.85 in Hellcats on the display, but you are correct it is by fuel type, for 93 octane a stoich of 14.7 is 1 in Lambda. I switched my VCM scanner from Lambda to 14.7 AFR and sure enough it is display 14.7 for stoich or close to it and then when enriched it gets to ~12.5. I switched it back to Lambda because I didn't want to do a brain freeze on how I was thinking in fuels.

@Speedy! what kind of fun am I in for with a straight E85 race tune?

It does mess with the afr gauge. But If done right it will be 100 percent correct for e85.
You will idle at 9.8 and a stoich of 1 if you update everything correctly. It takes a lot more than just adjusting the 3 stoich tables.

 

[white1]

It does mess with the afr gauge. But If done right it will be 100 percent correct for e85.
You will idle at 9.8 and a stoich of 1 if you update everything correctly. It takes a lot more than just adjusting the 3 stoich tables.

Completely understood and tracking, I guess when I go E85 that will a help for sure. It just messes with the mental map that Dodge set stoich to be 13.85 in Hellcats on the display, but you are correct it is by fuel type, for 93 octane a stoich of 14.7 is 1 in Lambda. I switched my VCM scanner from Lambda to 14.7 AFR and sure enough it is display 14.7 for stoich or close to it and then when enriched it gets to ~12.5. I switched it back to Lambda because I didn't want to do a brain freeze on how I was thinking in fuels.

@Speedy! what kind of fun am I in for with a straight E85 race tune?

Its "different" thinking in Lambda. Until you do. Once you get that in your brain, it makes everything so much easier. You only have to worry about one number so to speak. Stoich = lambda even though stoich can change between fuels, lambda never does.

Having past experience as an analyzer technician in a pertochem industry probably helps me look at things differently as well

 

[jonx96]

Its "different" thinking in Lambda. Until you do. Once you get that in your brain, it makes everything so much easier. You only have to worry about one number so to speak. Stoich = lambda even though stoich can change between fuels, lambda never does.

Having past experience as an analyzer technician in a pertochem industry probably helps me look at things differently as well

I never think in AFR. There is no point to do so. I do utilize the AFR Gauge in the car. Just to see where I am at somethings.
One could just bump up injector data and leave everything else alone. Technically lambda Doesn’t change doing this. But I prefer to update everything as it should.

 

[Speedy!]

My onboard afr gauge is set to change with fuel used. I figured this is how the factory would do it and I know things are doing what they're supposed to.

 

[fumanchu182]

https://docs.google.com/spreadsheets/d/1uYSQeDEMhGIolAYCdreuVwLCztnnKOr9b0QcKh9t-k0/edit?usp=sharing

The above is my spreadsheet I cooked up while doing my tuning for e85. Please enjoy and make copies and use! The first sheet is just a good general table of values for references to have in mind. As an example I look at my current tune that targets .85 lambda and I say in the new revision I want to target .80, I know where to approximately look. The second sheet allows you to copy in your current PE data - [ECM] 34230 - FA Power Enrich Aircharge Based: Fuel/Air ratio adder for WOT power enrichment based on cylinder aircharge and modify it. Since we have to tune in FAR, Lambda still doesn't work right and imo is still a gimmick, just my .02 so we still have the ugly conversion from AFR to FAR but hey automated. Sheet 3 is just some constant data that I wouldn't recommend messing with.

 

[jonx96]

I think you are over thinking the AFR and Lambda. Here is my spread sheet super simple and basic.
You shouldn't have to start with afr to go to lambda. No those are not the values I use in my tune I must have hit save on the last datalog I looked at for someone

But your sheet looks good for a direct copy and paste of the power enrichment table.

 

[jonx96]

One thing to keep in mind if trying to tune in afr and why it gets confusing
Depending on the stoich used afr is changed. So dodge not using .068 really throws the whole AFR calculation off and why lambda of 1 makes more sense or lambda of .85
So in this example .068 with the same values in the power enrichment table as .0722 afr is thrown way off and it takes a different value to command lambda at power enrichment.

 

[white1]

https://docs.google.com/spreadsheets/d/1uYSQeDEMhGIolAYCdreuVwLCztnnKOr9b0QcKh9t-k0/edit?usp=sharing

The above is my spreadsheet I cooked up while doing my tuning for e85. Please enjoy and make copies and use! The first sheet is just a good general table of values for references to have in mind. As an example I look at my current tune that targets .85 lambda and I say in the new revision I want to target .80, I know where to approximately look. The second sheet allows you to copy in your current PE data - [ECM] 34230 - FA Power Enrich Aircharge Based: Fuel/Air ratio adder for WOT power enrichment based on cylinder aircharge and modify it. Since we have to tune in FAR, Lambda still doesn't work right and imo is still a gimmick, just my .02 so we still have the ugly conversion from AFR to FAR but hey automated. Sheet 3 is just some constant data that I wouldn't recommend messing with.

View attachment 69253

Lambda is Lambda. AFR is converted from Lambda based on fuel. IMO its way easier to understand because fuel doesnt matter. Lambda=Stoich no matter the fuel.

 

[fumanchu182]

I get what your saying, I just hate the ugly Lambda -> AFR -> FAR conversion. Hence spreadsheets to the rescue to automate.

I think you are over thinking the AFR and Lambda. Here is my spread sheet super simple and basic.
You shouldn't have to start with afr to go to lambda. No those are not the values I use in my tune I must have hit save on the last datalog I looked at for someone

But your sheet looks good for a direct copy and paste of the power enrichment table.

View attachment 69277

Lambda is Lambda. AFR is converted from Lambda based on fuel. IMO its way easier to understand because fuel doesnt matter. Lambda=Stoich no matter the fuel.

 

[Speedy!]

Funny, my cheat sheet look just like @jonx96 I just built a function to calculate it all out until I had it sorted in my head.