Lambda of 1 means 14.68 for pure gasoline.
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This thread hurt my head,
I am commanding 14.4 as stoich (split the difference for "May contain up to 10% Ethanol").
When setting up my NGK through the scanner how should I proceed if I want to use lambda for tracking fueling errors considering I am not commanding lambda 1.00 ?
perfect
thanks
If you read the thread, you could answer both questions (the first would require some work on your end in the math though). Since I'm bored right now...
1) 0.62 lamda for 14.4 stoich is 8.928 AFR. This ends up being your adder. The divisor is just 5/(14.4*0.48). The 0.48 comes from the range of the AFX (.62-1.1). This makes the divisor 0.72338. So it becomes V/0.72338+8.928.
2) Really? I posted the equation in this post: http://www.hptuners.com/forum/showpo...7&postcount=37
Thanks for the reply, I had figured it out prior to reading your response.
My issue was clearly my understanding of lambda. Once you set what lambda 1.00 is anything outside of that is just the ratio of stoich. I had my ahhh hhha monent when I was doing the math.
So to make it easier to understand for anyone else who may read this:
The range of the NGK/AFX in Lambda is .62-1.1 (.48)
Multiply the lowest value of the range ( .62) by Stoich (14.4 commanded in my case)
.62*14.4= 8.928 (lowest output)
Next take max output voltage (5v) and divide it by [(commanded) stoich * range (.48)]
5(v) / 14.4 (stoich) * .48 (range) = 0.72338
You end up with
V
_____ + 8.928
0.72338
Again thanks for the help!
Winner winner, chicken dinner!
The biggest hurdle people have is understanding the concept of lambda and what the gauge is actually reporting.
If you guys want to simplify it further you could just use the lambda function and then create a PID for afr that multiplies the lambda by the current stoich ratio of your calibration. This exact reason is why I try to tune everything in lambda!
Here is a spreadsheet I made to help aid in getting the logging correct
If there are any flaw's that I overlooked please let me know and I'll correct them.
I've found that using the lambda range instead of the AFR range from the NGK works better when making a transfer function. The output voltage of 1 lambda ends up being right where you'd predict it to be using the lambda range to generate the equation instead of the AFR range.
The thing is my spreadsheet comes up with the same lambda range that the instruction pamphlet says as well. Mine says it has a range of 0.62-1.10 Lambda and my spreadsheet has the same range using the afr range as well.
9afr/14.57stoich=0.6177
16afr/14.57stoich=1.0981
when rounded to 2 decimal places that is .62-1.1
The reason I use the afr scale to figure out the slopes and adders in the spreadsheet is because it has more resolution than just using the 2 decimal point lambda scale included with "some" widebands. Furthermore the transfer function for afr is given in the pamphlet as well as being 1.4*Volts + 9 and that also gives me the same data as calculated above.
I'm setting up my new NGK, and I can't come up with the same numbers as you posted above.
5/14.4*.48 gives me 0.166667. But if I use 5/14.4/.48 then I get your .723379...are we supposed to divide by the voltage range instead of multiply?
To confirm, my stoich is 14.628...
.62-1.1=0.48
.62*14.628=9.0694 (lowest input)
5/14.628/.48=0.7121
So the formula is V/.7121+9.0694 for me, correct?
How do I access the scanner config to use more than 4 total digits? I'm using the beta.
Im using
Volts/.7095 + 9.102
I thought this was the correct ratio?
Yep thats what my PCM says 14.68, thanks
i was just going thru this thread, as i did use the canned ngk setting in hptuners for the afx unit.
correct me if im wrong, but every time you change your stoich value you have to setup the wideband offset for this?
No actually you will want to use Volts/.709 + 9.068
Reason:
Stoich for HPTuners is 14.68 but you don't setup the afx to read 14.68 on its display as stoich. The afx will always display 14.57 when its at stoich so you want the VCM scanner to read the analog output as 14.68 when the actual display on the wideband itself reads 14.57.
This is why I made the spreadsheet above to simplify everything. I've set it up with multiple different stoich ratios with different fuel types and it works perfectly! This is also why I tune everything in lambda so I don't have to worry about afr's with different fuel types.
A similar explanation would be E85. You would set your tune up with a stoich of ~9.7 however the afx will still read 14.57 on its display when your at stoich but you can setup the scanner to read 9.7afr from the analog of the afx when the afx display reads 14.57. Use the spreadsheet and never look back!