what uses less fuel.
cruising at,

35mph - 1900 rpm - 10hg vacuum
or
35mph - 2500 rpm - 18hg vacuum


difference being 3rd and 4th gear.

just curious if the amount of fuel is dependent on rpm or load.
was told i save more fuel leaving it in gear and just full decel as apposed to putting in neutral and coasting.

 

Also curious what the economy would be like in 5th@35MPH...

Generally if you're coasting in gear you will be using zero fuel, though when it gets down to 1500RPMs it begins injecting regardless.

 

tough question! i bet if you had some super long flat road, and set the cruise control for each case (3rd and then 4th) the difference between the two would be really small.

4th is better because the transmission is straight thru. 3rd might be better because the engine is in a better spot in its BSFC curve. each difference is small though.

i think 5th would be worse, as the rpm is too low AND you have the non direct trans ratios.

if you looked at injector duty that should actually tell you

 

i see. i know its miniscule but over a 230mi range per tank im sure there would be a small gain. im trying to get 20mpg with my ported turboii. lol its got an fd pump in now and runs extremely rich lol. i managed 16mpg. only a 2mpg loss with such a large streetport. lol.

 

the turbo's seem to do best when you keep the RPM's up, but stay out of boost and stay out of the secondary injectors, so like under 3500rpm. the stock ECU will stay in closed loop, so mileage is good.

 

i dont know but my stock ecu is terrible, i get 200-210 miles to the tank full! i got up to 235 miles once but that was going into ECO mode lol