Interesting fuel consumption...

In my manual turbocharged motor I get better milage if I remain between

2500 and 3500 rpm than if i sit at 2200rpm in a higher gear. I'm guessing its to do with engine load more than revs. I was getting 15l/100km driving like miss daisy getting to 5th as soon as the engine sounds happy to do so on dual carriageways (70mph)with lights and through city, and now i get around 11.8l/100km if i dont let her get to 5th unless im drifting along in a particularly long section. Watching the manifold pressure I can see that ive a lot lower load at 2800rpm in 4th than at 2200ish in 5th - i'd be about ambient in 5th, and about 7psi below ambient pressure at 2800 rpm.

Looking at the fuel maps for my car it shouldnt make a difference at those loads as anything below 2800rpm has the same base fuel mapping and so should only alter with RPM. Odd i know.

J

that's interesting that the higher revs seem to give better mileage. they translate into 42.9 MPG and 29.4 MPG (US). i normally get about 39/41 MPG in my echo. (1500 cc)5 speed. i do find that running the revs and using a 'free running' engine speed, i get better mileage. i suspect it has to do with the spark being retarded during low vacuum/low flow conditions. i don't know the revs as my echo has no tach. i suspect the two engines are of the same basic unit . the echo is produced in 1300 cc versions for other countries. normal speeds in my travel are up to 75 MPH (120 k.) as well as in-town travel. of course, i use the cheapest fuel that burns and lies in the tank. (regular) . another feature that's interesting, is the fuel cutoff at revs over 1400 and closed throttle. the injectors are disabled at these conditions, no idle fuel is burned til the revs are below about 1400 rpm. we have a fair bunch of hills here in western pennsylvania and west virginia. sammmm