Hypermiling and freewheeling

[Scott]

There seems to be a "new" trend to significantly increase mileage by using driving techniques like coasting to stops, etc. From what I gather, it's a bit different than freewheeling, but maybe someone knows better about that. Is the only difference that in free-wheeling you're in neutral, but doing the hypermiling way keeps you in gear?

When I first read about this I immediately thought about Studebaker and freewheeling. I guess Saab had freewheeling systems in the 1960s.

Anyway, it's interesting to see that some people have increased their mileage by tens of miles per gallon just by the way they drive (mostly in-town)

[PackardV8]

People lie a lot, too. Guarantee no one is increasing fuel economy by "tens of miles per gallon" by coasting. I used to drive 30-50kmi a year, keeping careful records for tax purposes, and it only made a slight difference in fuel consumption.

Modern EFI systems cut fuel completely when the throttle is closed and the transmission is in gear, so engine braking uses NO fuel on most vehicles. Kicking it into neutral will decrease engine braking and give a longer coast-down, but the engine immediately returns to idle and uses fuel. Depending on the programming of the transmission, fuel economy coasting is pretty much a wash with an automatic and only a slight increase with manual shift.

FWIW, back in the '80s, GM built freewheeling into their automatics to increase economy. They were disconcerting to drive - come over the top of a hill, let up on the throttle and the car accelerated down the hill. Unfortunately, they didn't increase the size of the brakes to compensate for decreased engine braking and the bigger Buick-Olds-Cads ate up the little rotors and pads in a few thousand miles, negating any fuel savings.

Engineers know about "ton-miles" - it takes a given amount of energy to move mass x distance. There are only five variables these days:
1. Rate of acceleration. Slower takes less fuel.
2. Cruising speed. Slower takes less fuel.
3. Using AC reduces fuel economy 1-3 mpg
4. Going into neutral at long traffic lights. Economy is slightly better when the converter isn't loaded.
5. Minimize the number of times a vehicle is started from cold. Combine all the daily errands into one trip. Cold starts increase fuel consumption dramatically and increase wear on components.

It is possible to get really nutty by shutting off the engine if the wait is longer than 30 seconds and by shutting off the engine and coasting into a parking spot. These show a slight but definite increase in fuel economy, but are a bit dangerous.

Bottom line - most "Hypermiling" stories are like the Fish 100MPG carburetor back in the day - just another urban legend. It is possible to decrease fuel consumption, but the easiest way is to start with the most economical car possible and then leave it parked as much as possible.

thnx, jack vines

PackardV8

BTW - Saab used freewheeling on their three-cylinders-oil-in-the-gas-two-stroke because with the throttle closed at high RPMs, the bottom end wasn't getting lubricated.

The early Stude Borg-Warner freewheeling was discontinued for the same reasons the later GM - drivers didn't like the feel and it was very hard on brakes in hilly country. It is still present in overdrives kicking out below the engagement point, but not really a factor in fuel mileage.

[Chris Pile]

Ever little bit helps, Jack - we don't have to fine tune our systems to save all the unburned fuel, but we can save some of it.

In my experience, I found I could get another 50 miles to the tank by using hypermiling techniques - I had to when I lost my job and gas shot up over $2.50.

Instead of using my engine braking habit, I kicked the 5 speed out of gear to coast, pumped up my tires to the max recommended, went easy on the "go pedal" instead of hot rodding around like a boy racer, short shifted, and in general used all the tricks I learned on this forum to extend the fuel in my tank.

Chris Pile
Midway Chapter SDC
The Studebaker Special

[N8N]

quote:Originally posted by PackardV8


The early Stude Borg-Warner freewheeling was discontinued for the same reasons the later GM - drivers didn't like the feel and it was very hard on brakes in hilly country. It is still present in overdrives kicking out below the engagement point, but not really a factor in fuel mileage.

That and freewheeling is no longer legal.

I'm still trying to figure out how my '05 Impala was able to be sold to the public, because between the gear ratios and the ultra-loose TC, there is essentially no compression braking although FMVSS 102 (I think?) requires it.

nate

--
55 Commander Starlight

http://members.cox.net/njnagel

[PackardV8]

Hi, Chris,

Agree completely, driving carefuly can decrease fuel consumption slightly; especially if one changes driving styles from

quote:hot rodding around like a boy racer,

to the focused effort of maximizing mileage, the difference might be fifty miles on a tankful. Say your daily driver goes 500 miles on a 20 gallon tank = 25 MPG. Upping this to 550 miles, that would be 27.5 MPG, a 10% decrease in fuel consumption. The national average is 12,000 miles driven per year. The savings, using these round numbers, would be $153 a year or 43 cents a day. However, the general public poops around anyway, so the shift in their driving habits would be much less drastic than that that you described.

I still say "hypermiling" is an urban legend and no one is getting "tens of more miles per gallon" by so doing.

thnx, jack vines



PackardV8

[tutone63]

One thing that I have noticed here that no one has touched on is the speed that you drive. Although this is usually only effective in a highway situation. They say that every ten miles over sixty (on average) will greatly decrease your economy. I heard on a radio show that you can safely add two dollars per gallon for every ten miles over sixty that you drive, when it is all averaged out...at least that is how I remember it...

Either way, when I drive my 1992 mercury 50+ miles round trip every day I have just given up and started driving 45. People hate me, but I don't care, I have really noticed a difference in the past two months.


She may have bugs and she may have dings, but that just proves I drive this thing!!

[61hawk]

Okay that said, how long before we start seeing interstate highway speed dropped from 70 mph to 60 mph? It happened before, nothing stopping it from happening again. Has anyone tried driving 55 mph on a lone stretch of highway lately? It feels like you could get out and walk faster.

Lee

[Scott]

Is freewheeling really illegal in the US? Is it a federal law? What statute is it? I doubt very much it is federal, but state law. Can anyone cite any law in the US against it? How is it enforced? Does the trooper pull you over and say, "Aha! You're in NEUTRAL! Get out of the car and spread 'em!"?

Would this mean it is illegal to drive your 1920s Studebaker with freewheeling if you wanted to? I doubt it. We can drive our cars without seat belts (at least where I live) if the car was made before they were required by law.

I have read that freewheeling is illegal in the UK, but again, how can such a law be enforced? How can it be proven that you've been freewheeling it?

[N8N]

yes, I believe the act of coasting in neutral is illegal in many states, but also the freewheeling mechanism itself is illegal to sell as part of a new vehicle and has been for a couple decades. Now if your car was so equipped from the factory or it was an available option when the car was built, there's not a whole lot they can do about it.

Personally, I don't like it anyway so it's of no concern to me. I grew up learning to drive on cars with stickshifts and high numerical ratio final drives, so having the car not slow down at all when I lift off the gas is a little disconcerting. I'd put up with it in a Stude though because it's the only factory way to get a wide gear spread, but I'd probably pull the cable out around town so it didn't drive me nuts.

nate

--
55 Commander Starlight

http://members.cox.net/njnagel

[5859]

I remember being taught it was illegal to freewheel in drivers training. How is it enforced? Who knows?

[N8N]

I can't remember if it was one of the LEO's that hang out here or in a Usenet group that I occasionally read that claimed to be able to tell whether a car was coasting or not down a hill by the way the suspension was loaded. I don't know exactly what one would look for...

nate

--
55 Commander Starlight

http://members.cox.net/njnagel

[Chris Pile]

quote:claimed to be able to tell whether a car was coasting or not down a hill by the way the suspension was loaded.

Well, Nate - if the engine is under load it will affect how the suspension reacts, but I can't think of any visible clues an observer might notice.

I've noticed my daily driver will handle corners better during engine braking instead of coasting out of gear. Feels like it squats a little durng engine braking.

Has anyone ever observed this effect?

Chris Pile
Midway Chapter SDC
The Studebaker Special

[StudeRich]

Well that would depend, if it's one of those transportation devices with front wheel drive, or it's a real CAR with rear wheel drive! [:0]

quote:Originally posted by Chris Pile

I've noticed my daily driver will handle corners better during engine braking instead of coasting out of gear. Feels like it squats a little durng engine braking.

StudeRich
Studebakers Northwest
Ferndale, WA

[bob40]

Dang.I have always liked the looks of early Eldorados and Toronados from 1967-70.Now I find out they are only transportation devices,not a real CAR.

[S2DSteve]

I remember reading some years ago that Russian drivers would accelerate to cruising speed, then cut the engine and coast to almost 0, then repeat over and over again, in the belief it would improve mileage. They would also run without lights at night to reduce alternator drag.


Steve Hudson
The Dalles, Oregon
1937 Dictator Flatback sedan (for sale)
1949 "GMOBaker" 1-T Dually (workhorse)
1953 Commander Convertible (show & go)
1953 Champion Starliner (custom/rod project)
1954 Champion Coupe (daily driver)
1960 Hawk (future project?)