using 14.047 for desired AFR and not 14.63?

[98 tigershark]

Hey all,
I have switched to lambda so I could learn more about tuning in general.
I seems a little backwards. So I have a problem that is a little different.
Mt car does not like to idle at stoich (14.047 for my stoich now), never did. My motor likes to Idle 13.97 AFR. It is not the fuel this time either as the motor is much happier now over all adjusting the needed AFR tables. But how do I convert the open loop to Lambda with this AFR up to operating temp and then to idle. It is not stoich but the motor likes it, This is not uncommon I am told for a built motor. So how do you convert AFR to LAMBDA accurately here. PE is now fine. I do not have my PC in front of me so I am sorry if I have said something wrong but I think you get the idea. Any ideas?
98 tigershark

[gmh308]

Hey all,
I have switched to lambda so I could learn more about tuning in general.
I seems a little backwards. So I have a problem that is a little different.
Mt car does not like to idle at stoich (14.047 for my stoich now), never did. My motor likes to Idle 13.97 AFR. It is not the fuel this time either as the motor is much happier now over all adjusting the needed AFR tables. But how do I convert the open loop to Lambda with this AFR up to operating temp and then to idle. It is not stoich but the motor likes it, This is not uncommon I am told for a built motor. So how do you convert AFR to LAMBDA accurately here. PE is now fine. I do not have my PC in front of me so I am sorry if I have said something wrong but I think you get the idea. Any ideas?
98 tigershark

If your stoich afr is 14.05, then idling at 13.97 would be 13.97/14.05 = 0.994 lambda. Which is within 1% so very close.

[SSpdDmon]

Hey all,
I have switched to lambda so I could learn more about tuning in general.
I seems a little backwards. So I have a problem that is a little different.
Mt car does not like to idle at stoich (14.047 for my stoich now), never did. My motor likes to Idle 13.97 AFR. It is not the fuel this time either as the motor is much happier now over all adjusting the needed AFR tables. But how do I convert the open loop to Lambda with this AFR up to operating temp and then to idle. It is not stoich but the motor likes it, This is not uncommon I am told for a built motor. So how do you convert AFR to LAMBDA accurately here. PE is now fine. I do not have my PC in front of me so I am sorry if I have said something wrong but I think you get the idea. Any ideas?
98 tigershark

The whole idea of going with lambda or EQ is to get away from AFR. The only time you need to know AFR is when you are deciding what to put in your tank. If it's E10, then you set B3601 accordingly. Once you do that and program your WB per my suggestions on the previous pages, you work with EQ or lambda from that point forward. You're done with AFR. Everything else in the tune and your logs should be EQ or Lambda from that point forward. If you need to....make a custom commanded EQ or Lambda pid. Then, you take the value that you have set in B3601 and either say WBO2/B3601=lambda or B3601/WBO2=EQ. That way you can work with EQ or lambda in the logs.

[98 tigershark]

Yes that does answer the question very well and it is appreciated very much.
Thanks again, I owe you guys.
98 tigershark

[SOMhaveit]

I've read this in its entirety and I have a headache.

So, I now know we have E10 in my area.

That means when my analogue wideband says 14.6 AFR, it really isn't 14.6, but is actually 14.1, which is what I want. So, if I'm running SDOL, and I'm commanding 14.6 and getting 14.6, which is what I need. And if I am commanding 12.8 AFR @ WOT, and my wideband indicates I am at 12.8 AFR, am I actually getting 12.36 AFR?

If that's how it's working, it's easier for me to keep doing what I've been doing?

[mr.prick]

No, it means that you need to change {B3601} to match the fuel you are using.
If you fill up w/E10 you need to change the value of EQ1 to 14.13AFR.
Changing {B3601} will change all fuel/AFR based tables.
Whatever your WBO2 is showing is (should be) what AFR actually is,
you need to richen the AFR in the tune.

[SOMhaveit]

OK, help me out please.

Even though I set all of my tables with B3601 at 14.63 and tuned the VE table while the car was running on E10, now I should set B3601 to 14.13?

My logged AFR and the AFR on the dyno mirrored each oher pretty well. Does the gas analyzer on the dyno misinterpret AFR with E10?

Isn't everyone saying that the wideband sees lambda and reports that as 14.63 whether you are running unmixed fuel or E10, or am I misinterpreting the posts in this thread and some other things I've read?

I thought G Banish said if you are running E10, when the wideband says the AFR is 14.62 i's actually 14.1x.

I guess I'm confused, not that that would be so unusual.

[mr.prick]

If your WBO2 is working/configured properly then
whatever it shows, that is what AFR actually is regardless of fuel type.
Filling up with E10 does not mean the WBO2 will be off.

If you are tuning with 14.63AFR you are a little lean for E10.
You set EQ1 {B3601} to the fuel type
(there is a spreadsheet in this thread somewhere)
and tune from there.

[Mr. P.]

Lemme take a stab at it - Greg Banish is right:

An O2 sensor only reports the amount of oxygen present in the exhaust stream - NOT the amount of 'unburnt fuel' or 'observed AFR' or anything else like that. in other words, the ONLY thing the O2 sensor can tell you is percentages, or "you're 2% lean" or "you're 5% rich" or "you're perfectly stoich". YOU have to take that percentage reported by the WBO2 sensor and do the math yourself based on the fuel you have put in the tank, like so:

Pretend example - If the WBO2 voltage is reporting that it's 3.5% LEAN, then the ACTUAL AFR is either:

a) 1.035 * 14.63 = 15.14 (in the case of pure pump gasoline fuel);
b) 1.035 * 17.2 = 17.80 (in the case of LNG natural fuel);
c) 1.035 * 15.5 = 16.04 (in the case of LPG propane fuel);
d) 1.035 * 9.0 = 9.315 (in the case of E100 ethanol fuel);
e) 1.035 * 14.6 = 15.11 (in the case of diesel fuel);
f) 1.035 * 14.1 = 14.50 (in the case of E10 pump gas fuel);
g) 1.035 * 10.0 = 10.35 (in the case of E85 fuel);
h) 1.035 * 13.8 = 14.28 (in the case of Sunoco GT-Plus 112-unleaded fuel);
i) 1.035 * 15.0 = 15.53 (in the case of VP 110 race fuel);
...
and the list goes on depending on the fuel you are burning. In each of these cases a cheap dash gauge will report "15.1" because the gauge assumes you are running pump gas with a stochiometric ratio of 14.63:1 because the gauge was hard programmed with that value. Likewise the PCM is seeing the same voltage from the O2 sensors but rather than assuming it goes and does a lookup of {B3601} and uses that value in all it's math; the issue is, if {B3601} doesn't match the correct value for the fuel actually being burned then the PCM is unknowingly fueling the motor incorrectly. In the usual case where {B3601} is 14.63:1 but you are burning E10 (14.1) then the PCM will unknowingly be fueling the engine about 5% lean; this will cause terrible economy but not hurt anything... UNTIL you go WOT, or worse yet WOT + boost!

Becuase of all the variance in fuels nowadays it is important to (1) set {B3601} correctly, and (2) stop thinking in terms of "AFR" in your VE tuning but instead use percentages (lambda or EQ ratio) - it's mentally similar to changing to the metric system, but in the end after you get your mind around the different units it's SOOO much easier.

Mr. P.

[joecar]

An O2 sensor only reports the amount of oxygen present in the exhaust stream - NOT the amount of 'unburnt fuel' or 'observed AFR'

What Mr. P. said... this is the key.

Pretend example - If the WBO2 voltage is reporting that it's 3.5% rich, then the ACTUAL AFR is either:

a) 1.035 * 14.63 = 15.14 (in the case of pure pump gasoline fuel);
b) 1.035 * 17.2 = 17.80 (in the case of LNG natural fuel);
c) 1.035 * 15.5 = 16.04 (in the case of LPG propane fuel);
d) 1.035 * 9.0 = 9.315 (in the case of E100 ethanol fuel);
e) 1.035 * 14.6 = 15.11 (in the case of diesel fuel);
f) 1.035 * 14.1 = 14.50 (in the case of E10 pump gas fuel);
g) 1.035 * 10.0 = 10.35 (in the case of E85 fuel);
h) 1.035 * 13.8 = 14.28 (in the case of Sunoco GT-Plus 112-unleaded fuel);
i) 1.035 * 15.0 = 15.53 (in the case of VP 110 race fuel);
...

Did you mean to divide by 1.035 rather than to multiply by 1.035...?
i.e. row a) would be 14.63 / 1.035 = 14.13...

1.035 is Equivalence Ratio... i.e. EQR or simply EQ... (which equals 1/Lambda)... as various people have observed, it seems that EQ is what the PCM uses internally (i.e. for determining commanded EQ from all the lookup/modifier tables...) and applies B3601 to the "calculation" only at the very last moment prior to calculating injector on time... GM even provided the pid GM.EQIVRATIO (commanded EQ).

I have learned to think in terms of EQ, and after doing it for a while it really does come naturally... there's no going back.