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Old 07-14-2012, 04:39 PM   #7 (permalink)
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JRMichler's Avatar
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.
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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