Quote:
Originally Posted by night9
I know this is way off topic but I was curious about seeing your trucks speed vs mpg chart. It would be interesting to reference. Considering your style of driving, I would assume, has more to do with the amout of time the engine is off and the truck is coasting rather than true ability of the motor to sip gas.
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I'm not sure how much a speed vs. mpg chart is really going to tell. Most all my driving is engine-off pulse and glide, so my speed is rarely constant.
I think the issue you're referring to is that fuel economy in terms of miles/gal has to do with two issues:
A) How much work/power is required
B) How efficiently that work/power is produced
Part A has to do with both drving style & non-engine vehicle mods. For example, driving slower (or aero mods) decreases the work required because there's less aero drag. Using less brakes also means the engine needs to produce less work per mile.
Part B is addressed by engine mods and, to a lesser extent, driving style. For example, I've switch to low weight synthetic oil, advanced the injection timing, added a ram cold air intake, etc. All these things mean I get more power from the same amount of fuel. The pulse and glide technique helps to, because it keeps the engine at higher loads where the engine is more efficient.
Recently, I've been using my loggers to try to get a handle on these two things (using vehicle speed, engine speed, ECM estimated torque, and ECM estimated fueling). According to that, I'm typically averaging about 0.22 hp-hr/mile and a BSFC of about 0.50 lb/hp-hr (~28% brake thermal efficiency). I'm not sure how accurate the ECM-estimated torque is, but those are the numbers I'm getting.