Quote:
Originally Posted by t vago
Trouble is, I'm not sure if doing either of these things would actually gain any FE on my truck. Either option would push my engine speed well below 2000 RPM at cruise (1800 with the 3.23 diff, and 1560 with the Laycock unit), and any gain from running at lower engine speeds may likely be offset by the fact that the engine would be running well into the bad part of the torque curve. Nobody's been really able to produce a dyno chart for my engine (apart from the OEM propaganda), showing torque at speeds below 2000 RPM, so I can't really tell for certain.
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My F150 is actually geared too high (engine too slow). For one thing the a/t downshifts at the touch of a feather. For another it turns less than 1000 ft/mn piston speed at 55 mph. There seems to be something to this 1000-1200 ft/mn piston speed as being the zone for best fe. I think when one is lacking dyno and bsfc data, the piston speed thing will get one in the ballpark.