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Old 10-27-2010, 04:51 PM   #17 (permalink)
Frank Lee
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Join Date: Jan 2008
Location: up north
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Blue - '93 Ford Tempo
Last 3: 27.29 mpg (US)

F150 - '94 Ford F150 XLT 4x4
90 day: 18.5 mpg (US)

Sport Coupe - '92 Ford Tempo GL
Last 3: 69.62 mpg (US)

ShWing! - '82 honda gold wing Interstate
90 day: 33.65 mpg (US)

Moon Unit - '98 Mercury Sable LX Wagon
90 day: 21.24 mpg (US)
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Quote:
Originally Posted by t vago View Post
Fine and dandy, but where would I find a decent diff gear that will fit my truck without me having to do a lot of machining work to make fit, and without having to spend a total of much more than $1000? I've got the tallest available 3.55 gear already.
Perhaps a slightly taller tire would help?

Quote:
Um... Your post above highlights the widespread fallacy of using MPG as opposed to L/100km. I actually happened to do this mind game, and I got substantially different results.

235.2 / 19 MPG = 12.4 L/100km

Now, assuming an 8% improvement, that means I used 8% less gas to go the same distance. In other words, I went the same distance using 92% of the fuel I would have normally used. So, 12.4 L/100km * 0.92 = 11.4 L/100km. And, 235.2 / 11.4 = 20.7 MPG.

Doing this with an wildly optimistic 20% improvement: 12.4 * 0.8 = 9.9 L/100km. And 235.2 / 9.9 = 23.75 MPG.

Therefore, I could save anywhere from 1.7 MPG to 4.75 MPG with this mod. And that's assuming 19 MPG as a starting point. With 21 MPG, which is what I'm shooting for now with my aerocap, the gains are a little more.
I wouldn't call 20.52 vs 20.7 substantially different. Besides, if the 8-20% figures assumed benefit are given based on the mpg system, then that is where they're "accurate" yes?

I didn't use the wildly optimistic 20% because it's... wildly optimistic.

Quote:
Finally, keep in mind that my goal is to improve the fuel economy of my existing truck, while retaining its existing power output capability.I don't want an econobeater, and spending thousands of dollars transplanting a different engine and transmission is similarly not an option. An econobeater can't haul a ton of gravel, nor can it haul 4 or 5 cans of recyclables and mulch at a time.
If you are seriously hauling that much, the vast majority of the time, then OK. Color me amazed though!
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