Does the PE effect Lambda when in open loop?

[Bill00Form]

I was just wondering when tuning if Lambda is always based on stoich or is it stoich times PE. So should you should see .86 lambda or 1.00 while in PE? Also, should the VE table at wot be based on stoich (which would then be changed by the PE table)?

Thanks,

Bill

[joecar]

Stoich corresponds to lambda 1.000.

PE should be commanding lambda 0.86 or so for a NA engine.

Lambda is irrespective of stoich (i.e. lambda 1.000 is the stoich for any/all fuels).

Commanded lambda can be sourced from trimming (1.000), from the open loop table, or from the PE table (0.86).

VE is airmass and so is independent of lambda (wherever lambda is sourced from); VE is certainly independent of stoich.

VE determined cylinder airmass (grams of air).

Commanded lambda (regardless of source) determines the commanded fuel wrt to the stoich AFR (i.e. divide the stoich AFR by lambda to get the AFR)...

i.e. fuelmass = airmass / stoich AFR / lambda.

[joecar]

You also have to distinguish between PCM commanded lambda and wideband measured lambda.

[joecar]

CL: when PE enables, the PE table is the only active commanded fuel table.

OL: when PE enables, the PE table and the OLFA tables are both active, the richer one (at the current operating point) is selected.

[joecar]

If you ever see a PE commanded lambda of 1.000 then you're in trouble.

[Bill00Form]

Thanks, Joe.

So I logged 2 runs at the track with the same tune. One shows a lot of WB02 lambda values in the .88 and .89 range but the next run shows a lot in the .91 range.

This is in open loop.

Is that normal to vary so much? What could be causing this? Thanks

[joecar]

Hey Bill,

For some reason your PE is getting leaner, may be with temperature...

if you post your tun and log files, someone may find the cause...

[ the COS's have a table to correct any IAT deviation ]

[Bill00Form]

Sure, here are the two files.

Thanks,

Bill

[Bill00Form]

Here is the tune file.

[joecar]

VE table does not look right (I don't see how it can flatline while RPM is ranging above 4700 rpm).

[joecar]

log 6c: measured WO2LAM 0.88, commanded EQIVRATIO 1.155 (BEN would calculate to 1.016, acceptable)
log 6d: measured WO2LAM 0.91, commanded EQIVRATIO 1.152 (BEN 1.048, diverges)

in both cases DAT was 96°F and RPM was 5700...

I don't see directly why the divergence, but it seems to me the air model is not correct.