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

Tue Nov 7 14:51:26 GMT 2000

Diacom doesn't SHOW a commanded 12.5:1, it's just what I am calculating.
Unfortunately, I have never been able to get the high-speed link to work to
show all the good stuff like timing and LV8.  If it is the case, what would
cause my car to be PE mode?  TPS voltage is steady, and unchanging at
cruise.  Also, is there an ECU file that points to the commanded AFR stuff?
Tunercat only does WOT AFR.  The 15.5 I saw was only for about 20 Diacom
frames on the 87.

For reference, I'm still running a 165 MAF w/ stock, but slightly modified,
89 APYU3516 code.

Steve

-----Original Message-----
From: romans at starstream.net [mailto:romans at starstream.net]
Sent: Monday, November 06, 2000 11:30 PM
To: gmecm at diy-efi.org
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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