VandykeT/A

Ok I'm new to hptuners and I have the greg banish DVD. He tunes in lambda. What is the difference in lambda vs afr? He does this to eliminate confusion when using fuels with ethanol. We'll fuels around here have 10 percent. Does the ECM change the stoich on it's own based on what fuel is used? If not how do you know what to change stoich to. All the older cars I've looked at have stoich at 14.68 does that mean all older stock vehicles are actually running leaner because the ECM doesn't know that fuel has the ethanol in it. I'm just confused. Thanks

1970camaroRS

iTrader: (8)

When tuning in lambda, if your chosen stoich in HP Tuners matches your scanner and your lambda PIDs, that's all that matters. After that, AFR no longer matters and you're working directly with sensor voltage on a lambda scale.

The WB AFR sensor reads a given voltage (2.5v) at stoich regardless of fuel. 2.5v = 1 lambda for e85, e0, e10, etc. These will all be different AFRs. But, that doesn't matter anymore. However, the difference between e0 and e10 isn't a ton, but it could be the difference between exactly right and slightly wrong.

In a production vehicle, many have ethanol sensors now to let them switch between different tunes to compensate for e85. Usually cars running e10 just run a tad bit lean since the factory tune was done for e0. And as we've seen from factory tunes, they tend to be slightly rich anyway.

joecar

AFR = Lambda x stoichAFR

where stoichAFR depends on fuel being run (e.g. E00 is 14.7, E10 is 14.2).

As said, Lambda is independent of fuel being run (CL is 1.00, PE is 0.86, boost is 0.77).

Non Flex-Fuel PCM's assume a fixed stoich AFR (e.g Y-car 14.68, F-car 14.63).

Flex-Fuel PCM's figure out the stoich AFR either from an alcohol content sensor (if fitted) or from performing some trim-based calculation/lookup (if not fitted with sensor).

Trims are able to make up for difference between E10 and E00.

If you tune VE table with the wrong stoich AFR, then the difference will be accounted for in the corrected VE table. If you set the stoich AFR to match the fuel, then the VE table will be more "correct". But, it works either way.

VandykeT/A

So I still need to manually change stoich for the fuel being used? And if lambda x stoich is the afr then if the ECM has stoich entered as 14.68 and the wideband shows 1.00 then I am at 14.68 afr. And say at wot I've commanded a 13.0 afr then my wideband should read .89 correct? And let's say my stoich is at 14.68 and the wideband reads a steady 1.0 and I go and change the stoich to say something like 14.2 should I still be seeing a 1.00 on the wideband I'm still a little confused.

joecar

If you change the stoich in the tune from 14.68 to say 14.2, during OL, your wideband will report a richer value of lambda (0.97), and then when CL is entered, the wideband will report stoich lambda (1.00).

1970camaroRS

iTrader: (8)

Don't even worry about AFR. Just tune to the lambda on the WB.

joecar

+1 forget about AFR.

The correction factor is simply: commanded EQR x wideband lambda

( if you need % then modify )

VandykeT/A

Ok I understand now. I appreciate it. Now, do all widebands have the ability to show in lambda. I've got a ngk/ntk.

Atomic

iTrader: (37)

Not all do, and you have to know what the wideband assumes is stoich. The NGK has a lambda analog output in lambda, but it uses 14.58 as stoich for some reason.

For what its worth, ive found the E10 gas around me to have an afr of roughly 14.42

VandykeT/A

Ok I'm confused again. If the wideband assumes a stoich value and the ecm has a stoich value its going to shoot for in closed loop I don't understand how tuning in lambda makes the afr irrelevant. If my wideband has lambda set at 14.58 and the ecm has lambda at 14.68 and I'm tuning something like say E85 wouldn't that cause everything to be considerably lean even tho everything is tuned to 1.00.

01ssreda4

iTrader: (96)

I never caught on to the lambda sillyness. Some swear by it, obviously. I did manually adjust my stoich ratio in the tune to e10, figuring no stations around here carry e00 anymore. I setup my NGK based on AFR and what I found on the HPTuners forum.

joecar

Yes, until CL is reached.

The PCM uses stoich to calculate (in OL; and in CL before applying trims) the fuelmass that is needed to go with the calculated airmass; if its stoich does not match the fuel, then the difference can be made up by trimming, this is what happens with E10; E85 may cause the trims to peg (or not leave enough room for trimming).

VandykeT/A

I had my cam only camaro tuned professionally and the stoich value was actually set to 14.42. All the stock cars I've seen have been 14.68. I still for the life of me can't understand how lambda makes the afr irrelevant. I know the goal is to make the wideband match what the ECM is commanding I just don't see how that if the wideband and the ECM aren't set to read the same stoich how can you ever know if your rich lean etc.

1970camaroRS

iTrader: (8)

E10 is 14.22, E0 is 14.68...some people split the difference and tune to 14.42 and let the fuel trims pick up the minor error in CL.

Or...you just ignore AFR and tune to lambda 1, because lambda is lambda regardless of fuel. PE .85-.87 lambda or whatever makes the most power. The actual AFR is irrelevant if you skip the extra step of converting everything over to an artificial number. You're just making things more complicated and adding extra chance of error. Why not just tune using the native outputs?

My wideband is set to report 2.5v =1 lambda, with a range of .7 to 1.3 lambda...can't remember those voltages off the top of my head. If this ends up being 14.2 or 14.65 or eleventy-billion, I don't care. If it's 1 lambda, that's 2.5v which is stoich, which is correct.

RonSSNova

iTrader: (3)

Your ngk wb display only reads afr. You can't change that.

To get it to read lambda in the hpt scanner you will have to write a custom pid for it under the user defined section for the enhanced IO menu. Search the hpt forum, its given in there somewhere.


In CL operation, your engine will operate st Lambda = 1 no matter E10 or E0 fuel being used.
As was mentioned, E10 simply causes the trims to go a bit rich.

In OL, there will be a slight error. Unless you change the stoich in the tune to match your fuel.
I dont bother with my corvette.
My nova runs on E85, stoich 9.77. No choice but to change that!

Atomic

iTrader: (37)

The lambda equation for the NGK is given in the manual, if I remember correctly.

1970camaroRS

iTrader: (8)

My commanded Lambda in my scanner is: [PID.6001]/14.2222 which is commanded AFR/stoich. This is where it's important to have your stoich match between the scanner and HP tuners.

My Lambda error is setup as: 100*(([AUX.20121]-[USER.9006])/[USER.9006]). AUX.20121 is my Wideband in lambda. USER.9006 is commanded lambda. It is very important for this to have units in %.

Then you just setup a histogram to log Lambda Error % plotted against VE vs. RPM vs. MAP (again, units in % is key).

RonSSNova

iTrader: (3)

My commanded lambda in the scanner is 1/EQ Ratio

Ron

RonSSNova

iTrader: (3)

Yes, you are correct.
Ron

1970camaroRS

iTrader: (8)

Yep, and that's [SENS.118] or [PID.6010] or similar like PID.68 which on E67 PCMs is actually lambda already...but these don't always work for everyone. I found AFR commanded Hi Res divided by stoich to work every time.