AFR calc from Diacom data... was RE: Adding another O2 sensor

[Marteney, Steven J.]

Well, the fuel economy recently slightly decreased with the headers, but the
calc'd AFR at 12.5:1 is traceable to day 1.  Last night, on the 30 minute
ride home, coolant temps were up over 180.  It was a little warmer here
yesterday.  The computer reads the sensor in the front of the intake
manifold, right? (TPI V-8)

So, the enrichment mode setting at 175deg, is that the whole story behind
the aftermarket chips and their 160 deg stat requirement?  Just to fool the
computer into richening the mixture?

Need to get the high speed link going.  As anyone encountered wiring
problems causing differing O2 readings?  I'm considering running a dedicated
ground from the O2 case to the ECM.  Bad idea?

Thanks a bunch!  I'll keep working on it.
Steve (starting wideband research effort)

-----Original Message-----
From: Ludis Langens [mailto:ludis at cruzers.com]
Sent: Tuesday, November 07, 2000 9:35 PM
To: gmecm at diy-efi.org
Subject: Re: AFR calc from Diacom data... was RE: Adding another O2
sensor


"Marteney, Steven J." wrote:
> 
> The 12.5:1 AFR goes back to pre-header days.  Coolant temps were running
> 190-195 back then.  Now, they have dropped to 175 with the headers and
> cooler, dryer air (something unusual for East Coast of FL).  I have never
> seen it drop out of CL mode, but am not sure.

If your CTS is really showing just 175, then you might very well be
stuck in warming-up enrichment mode.  FYI, the Fiero 2.8 stays in this
mode until CTS reaches 80C/176F.

Also note, the "closed loop" flag doesn't mean that the ECM, at that
moment, is using the O2 feedback for closed loop fuel control.  It
simply means that a certain subset of conditions has been met for CL. 
For example, ALDL will show CL even during PE (aka WOT) operation.

> My question, does the 8192 link show the commanded AFR?

I think so.  The mask $32 code (circa 1986) appears to send a two byte
value that's the commanded AFR.

-- 
Ludis Langens                               ludis (at) cruzers (dot) com
Mac, Fiero, & engine controller goodies:  http://www.cruzers.com/~ludis/

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