Equivalence Ratio of Wideband

[ferocity02]

Can someone double check my logic here? I would like to calculate equivalence ratio from my wideband. It's an AEM wideband with AFR and lamdba vs. volts shown here on page 9, Table 3: http://www.schnitzracing.com/manuals/AEMWBK.pdf

According to this table, a lambda of 1 corresponds to an AFR of 14.63975469.

But, my tune uses a B3601 value of ~14.2 (for gas with some ethanol).

So in order to calculate equivalence ratio from the wideband that corresponds to my tune, would it look like WB_EQR = 14.2/WB_AFR? Or would I just do WB_EQR = 1/WB_Lambda?

If the first equation is correct, can I use the lookup function to call in B3601 so I don't have to change the calc pids file if B3601 changes?

If it matters, this is a '01 turbo Silverado running 2bar MAFless COS5. I'm just getting started with COS5 and would like to use EQR to calculate the BEN's. I believe tuning will be done in OLSD and I will likely end with SOLSD, maybe CLSD.

Thanks!

[mr.prick]

Both equations are correct.

Stoich / AFR = EQ
1 / Lambda = EQ

AFR / Stoich = Lambda
1 / EQ = Lambda

Lookup function would need to be defined in the calc_pids.txt anyways.

The easiest multiplier (BEN) would be
Commanded EQ * WBO2 Lambda

[ferocity02]

Both equations are correct.

Stoich / AFR = EQ
1 / Lambda = EQ

AFR / Stoich = Lambda
1 / EQ = Lambda

Lookup function would need to be defined in the calc_pids.txt anyways.

The easiest multiplier (BEN) would be
Commanded EQ * WBO2 Lambda

But both equations give different results. Lets say my wideband is putting out 1.5V and B3601 is 14.2. According to Table 3 in the link above, 1.5V corresponds to AFR=13.0 and Lambda=0.888.

WB_EQR = 14.2/13.0 = 1.09
WB_EQR = 1/0.888 = 1.13

The issue I think is that according to the wideband Lamdba=1, is an AFR of 14.64 not 14.2. So should I not be using Lambda from the wideband?

[mr.prick]

Use the Lambda voltage output.
You can create any combination of AFR based off Lambda.

There is a spreadsheet for this here.
How to match wideband output to {B3601} (http://forum.efilive.com/showthread.php?13229-How-to-match-wideband-output-to-B3601&p=117265#post117265)

[ferocity02]

Still confused here...

EQR = stoich / AFR

So in this equation, should "stoich" be the same as what's in B3601?

I think the lamdba vs. voltage that the AEM outputs (shown in Table 3) is the lambda for gas, not lambda for something like E10 which is what I'll be working with.

Here is that spreadsheet with my AEM data. Do I need to change cell B13 to 14.2 and then use the "Lambda Expression" to calculate Lambda from the wideband voltage?

[Wheelz]

EQR = AFR / stoich


Fixed it

[ferocity02]

Fixed it

I think I have it right.

[Wheelz]

I think I have it right.

My bad. Forgot its 1 / lambda

[joecar]

EQR is defined as 1/Lambda.

[joecar]

Also note calulating (or reverse calculating) AFR = stoich *lambda = stoich/EQR, note that stoich is as assumed by the device...

i.e. in case of wideband you use the wideband's assumption of stoich.

[darcy]

If you have a Lambda output from your wideband, using that rather than AFR avoids all the back and forth calculation.

A WB is not really AFR guage, but a lambda guage, and the AFR displayed is simply the WB's interpretation of AFR based on the stoich value programmed into it.
When this isn't the same as in your tune it get's confusing. Hence why most folks around here prefer to use EQRatio.
The PCM also works in EQR and uses B3601 just to calculate fuel mass.

That way, regardless of what B3601 is, you need only compare Commanded EQR vs WB EQR.

[ferocity02]

Still confusing to me, but are you guys saying it doesn't matter what my wideband assumed stoich AFR is, WB_EQR=1/WB_Lambda no matter what?

And then my BEN from WB would just be WB_BEN= GM.EQIVRATIO*WB_Lambda?

[darcy]

Correct on both. :)

[ferocity02]

Hmm okay, so youre saying lambda outputted from my AEM wideband (as lambda vs. volts) is independent of fuel type? If that's the case then the equation WB_EQR = 1/WB_Lambda makes sense.

[ferocity02]

Having an issue here... For my BEN correct I'm using WB_BEN= GM.EQIVRATIO*WB_Lambda to correct my VE table in vacuum and boost. B3601=14.17, and I'm commanding EQR=0.99 in cruise, but my cruising AFR =14.92 and the BEN is basically 1.0.

I'm calculating WB_Lambda from the Lambda vs. voltage data shown in Table 3 in this link: http://www.schnitzracing.com/manuals/AEMWBK.pdf

Is this the correct way to calculate Lambda from the wideband?

What's going on here?

[ferocity02]

After lots of hair pulling I think I'm using the wrong expression for WB_AFR.

For the AEM wideband's assumed stoich of 14.63:
CALC.AFR = EXT.AD * 2 + 10

For a stoich of 14.17 in B3601:
CALC.AFR = EXT.AD * 1.9371 + 9.678

Yes? No?

[darcy]

I just looked a small section of your log; frames 4600-5200 - here you're commanding 0.99, and average external volts is 2.47volts = 1.02 lambda.
Average AFR in this section would be 14.85, but on gauge calibrated for gasoline (stoich = 14.68) would be 14.97

This would put your BEN at very close to 1. (.99*1.02 = 1.01)

Is this how you're seeing your results?

[ferocity02]

Yes that's what I'm seeing.

So I think you and I made the same conclusion, my calc PID for AFR is wrong. I'm using the AFR vs. voltage curve shown in AEM's table, which assumes a higher (14.64) stoich AFR than my B3601 (14.17).

If I do the rough math I think the new expression in my above post makes the AFR spot on with what I'm commanding +/- BEN.

[ferocity02]

I changed my AFR pid to be WB_AFR = WB_lambda * stoich AFR

Now it matches the data as it should. I was getting caught up thinking the wideband measures AFR, when it actually measures lambda. And lambda=1 is stoich no matter what's burning.

[mr.prick]

The voltage to AFR expression should be:
({EXT.AD}*1.9356)+9.678

14.17 will be 14.17xxxx in {B3601}

[joecar]

I changed my AFR pid to be WB_AFR = WB_lambda * stoich AFR

Now it matches the data as it should. I was getting caught up thinking the wideband measures AFR, when it actually measures lambda. And lambda=1 is stoich no matter what's burning.+1

also note:
NA PE: 0.86 lambda
Boost PE : 0.80 lambda

regardless of what it's burning (and ignoring B3601).

[ferocity02]

Only weird thing now is that the wideband gauge is displaying the incorrect AFR since my stoich AFR is not its stoich AFR. I'll have to switch it to display lambda instead.