Fuel Econ and Hiway Mode

[timsiford at hushmail.com]

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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