Power/fuel economy correlation

A customer of ours had a Bully dog 6NZ cat engine, it started out at 475 hp... with the bully dog program in the ecm it went up to 600hp at the wheels.
I saw the numbers and it showed an almost 1 mpg increase with the 600hp, and he could let his wife drive thru the hills due to less shifting which she had some troubles with...win, win!! unfortunately the truck was stolen!!! black 379 Pete.... he had also removed the mufflers at the time of the bully dog letting the engine breath!!

 

The math in this example has 1 big flaw. 2 engines running 1600 RPM will pull that grade at the exact same speed. Engine RPM must drop to go slower (assuming both trucks are in the same gear). Drop RPM and the rate of fuel consumption changes. There is not enough information given in theat example to calculate (or even estimate) fuel used.

Stricting talking power. It takes more power to pull a grade in 20 seconds than it does to do it in 30 seconds. You cannot get something for nothing, you either need to use more fuel or make the engine/driveline more efficient to go faster.

Efficiency is the key to getting more HP and using less fuel. When you tune an engine to get more HP and you also see better MPG, the main thing changed was timing advance to gain efficiency. It does NOT mean more power means better MPG. It means BSFC went down due to a more efficient tune. There is no direct correlation between power and fuel econonmy. Power and work does have a direct correlation, but you need to add efficiencies to get fuel economy in the mix.

The bottom line, you need more power to go faster. But that does not say anything about efficency. If both tunes were at peak efficiency, more power would mean more fuel too. So getting to the top of the hill 10 seconds fater would use more fuel.

 

my 365 h.p. 11.1 untouched ser 60 gets 6.5-7.0 m.p.g. ave cruise speed 64 m.p.h. a friend has a 2011 cat with a haney tune 650 h.p. at the rear wheels. 1.4 m.p.g. than before tune. no smoke. no dropping gears steady 70. the cost paid back in m.p.g. difference in 7 months.