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Old 07-14-2012, 04:39 PM   #7 (permalink)
JRMichler
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Join Date: Feb 2011
Location: Phillips, WI
Posts: 974

Nameless - '06 GMC Canyon
90 day: 33.45 mpg (US)
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You might be better off looking at MAP than TPS. MAP is Manifold Absolute Pressure. On my truck, idle is about 4 PSI MAP and WOT about 14 PSI MAP. In between, torque is roughly proportional to MAP.

At low RPM, MAP increases a lot with only a little throttle opening. You can be near maximum torque with the throttle open only a little bit.

Back when I was getting 27 MPG, I was usually passing in 3rd gear. Now, most of my passes are in 5th gear. Although, I did do a 4th gear pass about 3 or 4 weeks ago.

My goal is to pass at no more than about 5 MPH over the speed limit. This requires advance planning.

Calculating the best way to accelerate and cruise from a BSFC map is a good intellectual exercise. Most people are better off to focus on improving trip mileage. I developed my acceleration technique by looking at trip mileage at a fixed point about a half mile from where I start. In my truck, the best technique is to use 1st gear to get rolling, then immediately shift into 2nd. I'll shift to 2nd when I hit 1500 RPM in 1st, and into 3rd when I hit 2500 RPM in 2nd. My accelerations are at 13 to 14 PSI MAP. Accelerating like a granny did not work as well.

You have to find what works best in your vehicle. The BSFC chart gives useful information, but does not tell the whole story.
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The vacuum gauge plus wheel covers helped increase summer 2015 mileage to 38.5 MPG, while summer 2016 mileage was 38.6 MPG without the wheel covers. Drove 33,021 miles 2016-2018 at 35.00 MPG.
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