Fuel Econ and Hiway Mode

[Dave & Irina Eicher]

My understanding about EGR is: EG is fed back into the intake charge
reducing the O2 in the cylinder. If the fuel is cut back appropriately to
maintain the correct AFR, the effect is like reducing the displacement of
the engine. Properly done, I'm told EGR does improve economy for this
reason. Does anyone have a different understanding? thanks, dave

Dave Eicher
319-295-8348 work deeicher at collins.rockwell.com
319-922-2626 home sailors at mwci.net
319-431-9001 cell

----- Original Message -----
From: <timsiford at hushmail.com>
To: <gmecm at diy-efi.org>
Sent: Monday, October 09, 2000 8:41 AM
Subject: Re: Fuel Econ and Hiway Mode


> Great information Bob!
>
> Tim
>
> At Sun, 08 Oct 2000 23:23:05 -0400, Bob Valentine <bob at tecmark.com> wrote:
>
> >
> >With the seemingly renewed interest in fuel economy lately around here,
> >I've spent some time messing with Hiway Mode in the '730 / 8D / AUJP
> >calibration.   Seen mention of it in the archives, but no details of
> >the
> >settings.   With 93 Octane pushing $1.90 around here, want to get as
> >much
> >as I can for what I pay.
> >
> >Here is what I found in the ANHT_HAC and what I've done.  None of it
> >would
> >have been possible without the ANHT_HAC,  thanks (for the 10^6 time)
> >to
> >whomever wrote it.
> >
> >$81A7  Min coolant for Hiway Mode moved FFh to 76h  (70deg. C)
> >$81A8  Max kpa for Hiway Mode moved 2Bh to 32h (50kpa)
> >$81A9  Min RPM for Hiway Mode moved FEh to 40h (1200 rpm)
> >
> >$8482 Lockout time for Hiway Mode moved 0Ah to 01h (1 second)
> >$8484 Min speed for Hiway Mode moved FFh to 01h (1 mph)
> >
> >Table at $8485 for A/F vs. Kpa
> >Table at $81AB for S/A vs Kpa
> >
> >The results are pretty cool.    As soon as all conditions are met, 02
> >sensor voltage drops to around 75-85 mv, and stays there until
> >acceleration.   Integrator locks at 128, and no error codes set.
> > Having
> >a WB02 would be nice here, since I already know my 02 doesn't read 14.7
> >A/F
> >correctly.    Plugs do not show any detonation or burn signs.
Transitions
> >to power are just fine, butt-o-meter indicates a slight improvement.
> >
> >Keep in mind I run no cats; I'm not sure what extended lean A/F ratios
> >would do to a cat but I doubt it would be good.    I haven't done enough
> >highway driving to make any definitive statement as to improved mileage,
> >but mixed driving is up a good amount, 150 miles and still 1/4 tank
> >left,
> >usually refill time by now.
> >
> >Initially I was planning on trying to add EGR back in, but I thought
> >about
> >it and couldn't see how diluting the A/F mixture would help economy.
> >Also, turning on Hiway didn't require adding any wires and hoses - just
> >changing bits.
> >
> >-> Bob Valentine
> >-> bob at tecmark.com
> >--------------------------------------------------------------------
> >--------
> >To unsubscribe from gmecm, send "unsubscribe gmecm" (without the quotes)
> >in the body of a message (not the subject) to majordomo at lists.diy-efi.org
> >

----------------------------------------------------------------------------
To unsubscribe from gmecm, send "unsubscribe gmecm" (without the quotes)
in the body of a message (not the subject) to majordomo at lists.diy-efi.org