Quote:
Originally Posted by cons
"One thing you should know is that I'm at high altitude (~7000 ft average).
That definitely plays a role as it effectively turns my 3.5L engine into a
2.8L (there's about 21% less air up here...less air means less fuel) and it means less wind resistance." From 5speed5 today
If true, me being at 6,500 feet turns my 2.3 into a 1.85L engine, helping to explain to me why these numbers seem a little too high.
I've heard you can't even throw a curve-ball at high altitude because the threads don't get grip on the air. I've asked others out here who say they get way better mileage up here too.
SO, these numbers seem way high. I don't want fellow ecomodders thinking I'm full of BS. I would be a skeptic hearing about a truck doing 60 mpg.
But remember, I think altitude plays a big role, and these 60 mpg are under pretty ideal conditions on only HWY (roundtrips uphill and downhill, upwind and downwind).
It might not be that out there for a small truck with a small engine.
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cons,sorry just getting back to town.
I'm in agreement that short test runs can be problematic as to accuracy.
I'm also in agreement that EFI is probably 'smart' enough now to lean mixtures at altitude whereas in the days of carburetors you might have to re-jet to avoid rich conditions.
Somewhere,I did a thread on elevation vs air density which may help on that issue.
If you have an established baseline mpg at say,a constant 55-mph ( forget EPA numbers ) you can do your comparisons against that realizing that weather and road conditions will affect it.
If you're going to do your testing at 55-MPH,then there is a relationship already established which you can use to reverse-engineer your new Cd.
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A 10 % drag reduction will net you a 5 % mpg improvement at a constant 55-MPH ( no stops! no messin' around! ).
If say the Ranger originally had a Cd 0.44 like my T-100,the if you were to streamline it down to Cd 0.12 ( like GM's Solaraycer ) that would get you down to only 27 % of the original drag,a 73 % reduction.
At a 73 % drag reduction,this should improve MPG at 55-MPH by half the percentage,or 36.5 %.
I'm not sure what the Rangers original baseline would be at a constant 55-MPH,but say it was for example, 27 MPG,then the Cd 0.12 would get you 36.85 mpg.