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Old 10-22-2010, 09:47 PM   #9 (permalink)
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4ringcircus's Avatar
Join Date: Oct 2010
Location: Minneapolis
Posts: 31

Ford Ranger - '97 Ford Ranger XLT 4x4
90 day: 21.28 mpg (US)
Thanks: 2
Thanked 18 Times in 1 Post
We'll I am 3/4 of the way into the tank and here is what I discovered: With moderate throttle and higher RMP's the vacuum goes up to 1.5 and higher. However, this really sucked down the gas, and I went through the first quarter tank way too fast.

Doing some more research I found threads on BSFC ~ break specific fuel consumption. If accelerating, it is better to put it in the tallest gear possible and give it no more than 80% throttle (avoid fuel enrichment) and quickly get up to speed. This of course causes the vacuum gauge to plummet to nearly 0 vacuum. Despite the low vacuum, the engine is extremly efficient at converting fuel into speed. And as accelerating is not an efficient manuever to begin with, the best way to maximize FE is to work within the engines highest efficiency. Search BSFC threads in the hypermilling section for more info.

Once up to speed, I begin using the vacuum gauge. I try to keep it between 1.5 and 2.0. Best practice while cruising is to ease off the throttle to let the vacuum nudge up but not so much as to start loosing speed. The gauge makes it very easy to do this, and has really helped me drive more efficiently. My truck is good for around 45 to 55 mph when driving with this amount of vacuum.

Using these techniques, I have earned back all the fuel economy I wasted on the first quarter tank and I might be heading for yet another new mpg record! I'll post my results in my garage.

Thanks everyone.
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