The air per revolution is lower but the total cubic feet per minute going past the throttle is higher.
But not much. The limiting factor is the closed throttle plate. The idle air control system will meter the air.
dave G
I agree. I have been fussing over getting a new high mileage car (50mpg) I have two OLD cars a 98 merc v-8 mountaineer and my wife has a 2000Lincoln LS v-8. After doing the math it will not pay for me at this point to do anything as the LS gets 28mpg on the freeway and the merc. we do not use for long trips gets only 20 21 on the freeway. Both cars are worth almost nothing in a trade but no payments helps ease the pain of the gas cost until one of them has a major expense illness.
Hypermiling with an automatic is an oxymoron of sorts. About 15% of the engine’s power is “lost” in the transmission (which is why it needs to be water cooled). Do not turn off the engine in any circumstance because it may turn off the hydraulic pumps in the transmission.
No, not true. the automatic transmission has SOME slippage, but not so much that the engine won't turn -- I mean, otherwise, the engine wouldn't be able to turn the wheels either! In a stickshift, the fuel will not be turned off when coasting, it'd cause problems when you push in the clutch, and also it'd probably be bumpy when the fuel is shut on and off. In an auto (GM's cars for about the last 20 years, Toyotas*, I'm sure all makes got it over time), the torque converter eliminates any bump from shutting fuel off, but it doesn't cause the engine to not turn. And it doesn't matter if the engine is *making* power, strictly that it's rotating fast enough to run the accessory pully (which, after all, works properly at idle.) The computer will turn the fuel back on at ~1000 RPM, since at that point you *would* start having problems from torque converter slip not letting the engine spin fast enough, and stalling when your car finally comes to a dead stop. In some (most?) cases, the fuel also won't be cut when air conditioning is running, the A/C compressor draws enough power it'd affect driveability.
Edit: scepticus has a post about some stick cars that DO also shut off fuel. So never mind about that 
*Some Toyotas. I’ve seen two totally seperate fuel injection systems on them… the Geo Prizm I had (rebadged Corolla) had a really simple fuel system, it just measured vacuum and put in how much fuel it thought was right; no idle control, no EGR, no fan control, no tranny control, etc. The other FI system I’ve seen on them, the transmission’s computer controlled (even on a 1986 Camry!), electronic idle control, etc. This one does fuel shutoff.
I know for a fact a 1994 Corsica won't run the engine -- I had one and driving down from the Eisenhower pass, the fuel was off for so long that the temp gauge went to full cold and it got a bit chilly in the car 8-). Yeah, that's not bad, my parents 2000 DeVille gets about that, it's nice to have a V8 with reasonable mileage. What hurts is the V8s that get like 10-15MPG. In Europe they measure fuel consumption as "liters per 100km". We don't user liters or km here, but it's useful to think of mileage as "gallons per 100 miles". A 12MPG SUV is doing 8.3 gallons per 100. A 28MPG car is doing just over 3.5. Going from 28 to 50 gets you to 2 gallons per 100 miles... So a high MPG car is better, but you're already most of the way there compared to having a vehicle with mileage in the teens. It depends. The tranny in my Buick has a lockup torque converter; when locked, it's locked just like on a manual. There's not MUCH I can do about it, but sometimes just driving 1 or 2 MPH faster, or varying the throttle, will get it to lockup. It'll lock as low as about 30MPH.Yep, depends, my brother gets 44 mpg in his auto Civic, 40 mpg in his stick, because he likes to drive the stick car harder (“more fun”). Modern automatics are surprisingly efficient.
Leave it in neutral all the time and attach a horse or team of motivated individuals. Your mileage will skyrocket!
i thought all fuel injected vehicles have fuel cut off on the overrun?(as we say in england)
Well, the guy CNN interviewed as a “typical” hypermiler was doing all those things on camera, including screeching around the off-ramp curve at 50 or 60 just so he didn’t have to touch the brakes. He also drove much slower than the rest of the traffic and enjoyed returning single-finger waves. I predict that he’s either gonna slide sideways into something or trigger someone’s road rage, and that will be the end of him.
I agree that planning your acceleration and braking in advance as much as possible (to minimize both) can be a great fuel saver. By the way, coasting in neutral is illegal in some (most? all?) states.
some posters deny the existence of DFCO as if it were the Flying Spaghetti Monster.
Hey, I know the FSM exists! I saw it on Fox!
“Hypermiling” sounds like yet another politically correct euphemism. Makes it sound so magnificent and powerful, like cutting in the hyperdrive. Translation: Hypermiling=Driving slowly and annoyingly in the hopes of saving perhaps <$5.00 a week at best. While this may be a semi-significant amount of money, if you’re going to be an a@@hole to other drivers in the hopes of saving a little cash, you may as well just stop tipping then. You’ll save more money and inspire less road-rage, whilst still accomplishing pi@@ing off people.
My apologies to those that practice this on empty stretches of road, and/or where safe, but gawd, I swear I was behind someone that was attempting to “Hypermile” their already sub-compact car on a freeway onramp today.
What exactly did he do to you? Make you obey the speed limit for the whole length of the on ramp?
I think that there are few things ruder than driving like your on your way to a fire, saving <5 minutes a week at best. If your time is that important, why don’t you cut in line at the lunch counter, slam doors in people’s faces instead of holding them open for them, and run through the hallways, pushing and shoveing people out of your way as you head to your car. You’ll actually save more time and piss fewer people off.
So YOU were the person in front of me doing 30 the whole way down the on ramp! For some of us it’s not about saving a minute or two every day by driving fast. It’s about staving off the drowning in peanut butter feeling when you’re stuck behind a slow driver and wondering if they’re actually more than semi-conscious. And I try to drive courteously. I let the person get in front of me when they needed to get in, only to be stuck behind them as they created a hazard for themselves and me as I tried to merge into fast-moving traffic. At no point did I even tailgate them, as I felt my will to live slipping away… Driving excessively slowly when there are people behind you is every bit as discourteous as driving like a bat out of hell. I’ll bet you’re the person who laboriously takes 5 minutes filling out a check in the supermarket checkout line too. Peace.
Very unlikely to be me. If I plan to only go 30~50 mph, I stay off the freeway, I let faster cars pass, and I usually accelerate quite briskly, using about 75% of full throttle.(the throttle opening where most engines deliver their lowest specific fuel consumption) This results in me actually out accelerating much of the traffic. Believe it or not, accelerating too slowly actually worsens your gas mileage. The key is avoiding pointless acceleration, not accelerating like a turtle.
Pointless acceleration, even at a snail’s pace, is still pointless acceleration.
You are destroying your brakes by going into neutral.