Fuel Econ and Hiway Mode

[Len Sabatine]

     Exhaust Gas Recirculation is proportionately induced into the Intake 
charge
     to Reduce Detonation and Oxides of Nitrogen Emission levels. The key is
     Supression of Detonation . Detonation is a great way to trim 15% power
     output , damage cylinder walls , pistons , rings and rod bearings, to name
     a few of the problems that are associated. EGR is kin to artificial Octane
     in a pollution controlled combustion engine.
     Len

>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
> > >--------------------------------------------------------------------
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>
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