Compression Ignition Addict

Join Date: Dec 2013

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**Help my feeble brain figure out how to fool my truck's computer.**

So I'm sitting here, visiting my mother in the hospital, who is sleeping. I got to thinking about my truck's MPG and how the built in computer is so far off. For instance when my dash says I'm getting 21 MPG I'm really getting around 18 MGP. One of the things I like about the Mini Maxx is that I can reprogram my speedo based on the real tire size. When I installed the Mini Maxx I entered the measured tire diameter as 34.25 and it made my speedo more accurate. Not perfect but better.

According to my GPS and a LEO friend's radar, my speedo is about 2 mph off at 60. So when my truck thinks I'm going 60, I'm really going 58. This got me to thinking that not only is my speed off, so is my odometer and therefor so is the calculated MPG. If I drive for an hour at 60 mph, my truck thinks it's gone 60 miles when I've really only gone 58, so the amount of fuel I've used is really to get me 58 miles down the road - not 60. To make this equation easier for my pea brain, let's say my computer says I got 60 MPG. That means that since the truck thinks I went 60 mile, but really only went 58 - my MPG is misstated by 2 MPGs.

See where I'm going with this? Here's my question. Could I, via the Mini Maxx, fool the computer by adjusting my tire size? For instance, what if I plugged in that I'm running 37 inch tires (or whatever) to get my speedo accurate - could I get the MPGs shown on the dash to be accurate as well? If so, how would I calculate what should be input? Any math majors out there? Help me, it bugs me that the computer is so far off.

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Last edited by mhutch2; 03-08-2014 at 12:51 PM.
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