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

[Romans, Mark]

Add on...

Or you are running too cold to be in closed loop.  Something
else is going on.

Mark
----- Original Message -----
From: "Romans, Mark" <romans at starstream.net>
To: <gmecm at diy-efi.org>
Sent: Monday, November 06, 2000 8:30 PM
Subject: Re: AFR calc from Diacom data... was RE: Adding another O2 sensor


> Steve, if Diacom shows you are commanding a 12.5 to one afr then
> you are in PE, not regular closed loop.
> The 15.5 (If it's 89 Code) is Hwy Fuel, a commanded leaner afr
> for fuel economy.  I had mine set at 16.0 to one and got a lean
> misfire. So I went back to 15.5 at speeds above 52 mph, light load
> ect.
> Mark
> ----- Original Message -----
> From: "Marteney, Steven J." <smarteney at xlvision.com>
> To: <gmecm at diy-efi.org>
> Sent: Monday, November 06, 2000 7:14 AM
> Subject: AFR calc from Diacom data... was RE: Adding another O2 sensor
>
>
> > Burp! Oh, excuse me.  I think I've had too much food for thought lately.
> :-)
> > Hee Hee, bad joke.  I have not checked anything you mention, and have
> > thought about them but the thing I am getting hung up on is predicted
gas
> > mileage.  I use the rpm figures to calculate the time period of one
> > revolution.  From this I can get the injector duty cycle, reported PW
div
> by
> > revolution period.  I then take the lb/hr injector rating times 8
> injectors
> > times the duty cycle and divide by 6 lbs for a gallon of gas.  (Is that
> > right 6.0lb = 1 gal go juice?)  This gives me gallons per hour.  I then
> take
> > the mile per hour report and get mpg from that.  I've been suprisingly
> > accurate at predicting the car's gas mileage as calculated from the
> odometer
> > and gas pump data.  That gave me confidence in my fuel equations.  The
MAF
> > is reading is a mystery to me.
> >
> > Now to complicate matters, I tried this method out on a friends car.  It
> is
> > actually my old 87 IROC 305, bone stock.  We did the same test, 70-ish
mph
> > on the highway.  I rated his injectors at 19lb/hr and stock fuel
pressure,
> > but didn't verify them.  Ran the same equations on the data and got a
> > predicted mileage of 24-ish mpg.  That's right where the car ran when I
> took
> > it to Ohio last year.  Yet again, I think my fuel calcs are right.
> >
> > Now the plot sickens...  The AFR ratio calcs from the MAF reading and my
> > fuel calcs for 3 data sets yielded 14.5:1, 14.8:1, and 15.5:1.  The
15.5:1
> > may be invalid.  I think there is some coast down data from an I-95 off
> > ramp, I'll check.  So, I'm confused.  Here's a car that is getting 24mpg
> and
> > says it's running at 14.7:1.  My car says 17mpg, but also says 12.5:1.
> So,
> > I'm trying to determine is the MAF just reading wrong and the BLMs are
> > compensating and I'm really running at stoich?  Or, is the O2 sensor
> reading
> > false lean and I'm really running at 12.5:1 AFR all the time?
> >
> > Thinking out loud again, thanks!!!
> > Steve (considering heated O2)
> >
> >
> > -----Original Message-----
> > From: rr [mailto:RRauscher at nni.com]
> > Sent: Friday, November 03, 2000 6:21 PM
> > To: gmecm at diy-efi.org
> > Subject: Re: Adding another O2 sensor
> >
> >
> > Steve,
> >
> > There may be some additional items to check in your quest for AFR from
> > BPW. Have you checked the 'raw' bpw values to see how accurate the
> > diacom software is? The other is the actual bpw itself. A bpw of 2 msec
> > won't give 2 msec worth of fuel. There is the opening time to contend
> with.
> >
> > Food for thought,
> >
> > BobR.
> >
> > Marteney, Steven J. wrote:
> >
> > > I kinda started drawing the conclusion that they were indeed pretty
good
> > > when switching.  It's a rather clever solution to get a non-ideal
> product
> > to
> > > work, and work well.  I've been banging on the list about AFR and O2
> > > inaccuracies thinking that my car is lying to me.  Still
investigating.
> > > Went through all my Diacom data since day 1 and the calculated AFR is
> > > consistently 12.5:1 +/- 0.3.  The interesting thing is the calculated
> AFR
> > is
> > > gradually rising as the gas mileage also rises.  I'm going to attempt
> this
> > > weekend to do the same highway test on my friend's bone-stock IROC
(with
> a
> > > new MAF sensor.)
> > >
> > > Still playing!
> > > Steve
> > >
> > > -----Original Message-----
> > > From: Bruce Plecan [mailto:nacelp at bright.net]
> > > Sent: Friday, November 03, 2000 2:33 PM
> > > To: gmecm at diy-efi.org
> > > Subject: Re: Adding another O2 sensor
> > >
> > > They are at least as fast if not more so then the oem ones.
> > > Remember the ecm is shooting for a 14.7:1  AVERAGE, do it hammers
things
> > > real rich and lean.
> > > The oem one's ******errors****** is when folks try to read them as a
WB.
> > > They develope cross counts at the same rate as the oems, from what I
can
> > > see.
> > > At the Powwow we had a scope on the WB and you could see the
individual
> > > cylinder firings, and how they swung rich lean.
> > > Bruce
> > >
> > > > Any comparisons to a wideband to show how GOOD they are at measuring
> > > 14.7:1
> > > > in switch-mode?  Are they extremely good at it, or still full of
> error?
> > > > Steve
> > > >
> > > > -----Original Message-----
> > > > From: Bruce Plecan [mailto:nacelp at bright.net]
> > > > Sent: Thursday, November 02, 2000 12:40 AM
> > > > To: gmecm at diy-efi.org
> > > > Subject: Re: Adding another O2 sensor
> > > >
> > > >
> > > > IF, all your doing is reading side to side for 14.7:1 comparisons,
> Sure
> > > why
> > > > not.  The oem  sensors are of a switching type.  They are not meant
to
> > be
> > > > WBs.
> > > > Bruce
>
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