Quote:
Originally Posted by MetroMPG
Nice find, that reference to the old Mustang economy run!
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The old US econo run stuff is great...all my learning is from the great Australian Total Economy Run in the late 70's, early 80's, and a lot of very good stuff from David Vizards Car Craft stuff. Having had a mate with a 351 C, a 350 Chev, and my own SOHC Pinto engined Cortinas like his 1972 2 door 1600 Cortina GT, his 2000 cc Pinto, and his Mini Clubman, I've been around the block with all his theory and real world calc's.
The Total Economy run data was very advanced. It gave 62 to 68 mph economy figures, and explained that even the best automatic transmissions gave a 15% loss of fuel economy. They used the Grand Prix Efficiency Index to calculate very accurate 62 mph Imperial MPG figures.
In 1977 and 1980, Wheels Magazine in Australia did two high speed Sydney to Perth runs
In 1977, a big 3750 pound Falcon GS 4.9 with 4 speed SR manual, a high compression 9.4:1 4-bbl 302 Cleveland used to get 10.6 US mpg at 80 mph average on a 2640 mile Sydney to Perth cruise from a 207 hp powerplant.
In 1981, a 2450 pound Alfa Romeo Alfetta 2.0 liter twin DCOE carbed 5 speed. It got 13.6 mpg at 83.5 mph over the same distance. But those roads weren't US fine cement, and there were tired drivers trying to foresee wombat, wallaby, kangaroo and bull hits.
Despite the road load changes, it shows you just how a 28% fuel saving at 3.5 mph more required a 253% capacity drop, a 65.3% weight drop, and a 23.8% drop in cdA.