Re: Tuning in Open Loop for Newby

["Bruce Plecan" <nacelp@bright.net>]

Quick someone cover me

Open loop
   For intial cold engine operation.
   On a hot restart, til timer runs out for O2 sensor ignore (generally)
Closed loop
   ECM runs self test, everything is fine, and using O2 sensor for final AFR
trim.
Limp Home Mode
   Something crashed the system ( ie EPROM Failure), and the ecm using the
netres for
   fueling, with no timing corrections

The Gray Zone
   The ecm doesn't like something, and is using a default for it.  If a hard
failure then the SES lite
   is on.   How ever, some things can go out of bounds, but not hit the
enable for that flag to set ie
   like a TPS that doesn't read high enough to get to PE, so PE is still
using a lean commanded
   AFR.  For example, the PE enable needs 80% TPS.  TPS only reads to 75%
commanded AFR
   would be say 13.5:1 instead of the 11.5 that you might expect.

Now

> > I would guess that the short amount of time that the engine runs in open
loop
> > makes tuning in that area a non-issue except for drastic engine mods
where
> > tuning is required to get it to run period?

True

> Screech!  Terminology time, methinks.
> Closed loop = learning mode = feedback from O2.  This is not like "limp
> home mode" which is a completely different calibration.

True

 The only problem
> with tuning in closed loop is that the system will "learn" itself
> away from the settings you've programmed by changing the BLMs and
> make you chase your tail as you try to fix it.

This can happen, but can be avoided with, blocking the C/L operation, or
limiting the BL bondaries

If you limit the BL boundaries,
then looking at the Integ numbers will tell ya which direction you need to
go where to satify the ecm.

But, if tuning without an O2 sensor, you must stay with the C/L type
calibrating.
If you suspect a bad O2 sensor, just set the C/L enable high and see how the
car does.
Bruce

> Someone shoot me if this is all wrong, but it appears to be something
> worth clarification.
> -greg

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