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Author Topic: 100 mpg?  (Read 17406 times)
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Dean Los Angeles
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« on: July 08, 2008, 12:40:17 AM »

Ok, 100 mpg. We all want it.
The government has a "250" mpg (or 100, 200, or 500) carburetor salted away somewhere.

So you guys are extra smart, let's do some math.
To be useful, lets say 60 mph @ 3,000 rpm.
Since that is a mile a minute, 100 miles = 100 minutes.
100 minutes times 3,000 rpm = 300,000 revolutions.

one gallon = 128 ounces divided by 300,000 revolutions = .000427 ounces per revolution.
No matter how many cylinders we have, we can't use more than 4 ten thousandths of an ounce per revolution.

one gallon of regular unleaded gasoline = 114,100 btu
114,100 btu divided by 300,000 revolutions = .38 btu per revolution.
That ain't much heat.

1 horsepower = 2,544 btu/h
114,100 btu times 0.6 gallons/hour = 68,460 btu = 21.91 horsepower.

It better be a REALLY dinky car.

If I made some basic math error let me know. Don't quibble over SAE VS brake hp. The point is, no matter how you cut it, you are never going to see 100 mpg in a car you would buy. And be happy with it. Or carry a stick of lumber. Or 4 people.

The Honda Ruckus might be your best bet. 5 hp, 43 mph, 107 mpg


Or you can stick with that 30 gallon gas tank times $7 bucks a gallon = $210

Side note: So the gas prices are putting a severe crimp in your budget? Do you run out and get a Toyota Prius? No!

According to Edmunds.com the answer is a Chevy Aveo! The Aveo doesn't get the mileage, but the $10,200 price advantage ($23,770 VS $13,595) makes up for it. Yes, the Aveo is a pile of crap, but the only criteria was best bang for the buck. ($10,200 divided by $4.50 a gallon = 2,267 gallons of gas.)

Interesting Edmunds note #2:
So that SUV is killing you with $100 fill ups? Trade it in on a Toyota Prius? No!

For a lot of owners, you either can't find a dealer that will take it as a trade in, or they will give you less than you owe. You end up paying on the old car AND the new car. The answer is, if saving money is the object, to keep the SUV!
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« Reply #1 on: July 08, 2008, 04:49:37 AM »

I owned 2 cars that have no counterpart today:

~1980 Toyota Starlet - 4 pass, Manual trans, RWD econobox, 50mpg actual.

~1990 Chevy Sprint - 4 pass, Manual trans, FWD econobox, 45mpg actual.

Both of these were low-cost, low-tech (carburator, no computer), and suitable acceleration and hill climbing ability.  These were freeway safe commuters.  Today we have the Smart Car with 41mpg, seats 2, and is not freeway safe.

If a modern car company took one of those old econoboxes, put in current digital engine controls, it would perhaps improve mileage another 20% at the same HP level.  Common Rail diesel technology would go 20% more than that.

While the V8 engines went from 15 mpg hwy to 26 mpg, and jumping from 200HP to 505HP (Corvette), economy cars didn't show similiar gains in mileage, and in fact, lost mileage in general.

The best economy I ever got out of a freeway commuting motorcycle was 70mpg on a XT500 Yamaha thumper.  Maintenance costs outweighed the fuel savings though.  And it sucked at carrying groceries in the rain.

While I don't think 100 mpg is possible, I don't understand why must lose ground either.



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Ratliff
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« Reply #2 on: July 08, 2008, 09:14:50 AM »

For cost stamped steel construction is hard to beat. However, if the car companies ever got serious about sandwich composite cars I believe we could see 1,800 lb to 2,000 lb four passenger road cars at least as safe as today's much heavier stamped steel cars. The ripple effects would be better handling and smaller engines.

http://www.scaled.com/projects/gmcar.html

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sanger351
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« Reply #3 on: July 08, 2008, 09:42:35 AM »

When in Italy we drove around in my brother in laws Opel Astra diesel.  With 5 adults, luggage and me driving it like I stole it (any one who's driven in Rome knows) We averaged 40 mpg.  With one or two people and in the country we averaged almost 60 mpg.  Sure it topped out at about 90 mph, but I would buy one in a heart beat if that car was offered here in America.  I see GM plans to offer a version of it here, but it does not get the mileage of the euro car because of our EPA requirements.  BTW why do we have to go backwards like MRC said, compare the mileage of a new diesel truck to a late 90's diesel truck. 
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bearingburner
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« Reply #4 on: July 08, 2008, 10:01:58 AM »

My problem here in the Northeast is not $4/gal gas but $5/gal heating oil. I used approximately 1200 gal last winter and it was not particullly  cold just snowy.Sure puts a hole in tne lakster budget.
With the gas pricing I can just stay home.
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jimmy six
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« Reply #5 on: July 08, 2008, 10:20:17 AM »

I too look to MPG. I drive a Honda Civic HX a very rare model no one bought, mine is a 2003. I think they were made from 1996 to 2005 or 6. 38 city 44 hyway. I have a 5 speed and the automatics were a constantly shift style which aparently no one liked. The 1.7 liter engine had the highest compression but was tuned for milage. I have no idea why Honda quit making them. They were the lightest available including aluminum wheels, no antenna, wind-up windows, no AC, etc.

Kelly retail is now $500 over what I paid for it. 40K miles and added factory air. I hope by the time we needa new car the little diesels will be here. Europe laughs at the Prius.
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« Reply #6 on: July 08, 2008, 01:04:02 PM »

I owned 2 cars that have no counterpart today:

~1980 Toyota Starlet - 4 pass, Manual trans, RWD econobox, 50mpg actual.

~1990 Chevy Sprint - 4 pass, Manual trans, FWD econobox, 45mpg actual.

Both of these were low-cost, low-tech (carburator, no computer), and suitable acceleration and hill climbing ability.  These were freeway safe commuters.  Today we have the Smart Car with 41mpg, seats 2, and is not freeway safe.

If a modern car company took one of those old econoboxes, put in current digital engine controls, it would perhaps improve mileage another 20% at the same HP level.  Common Rail diesel technology would go 20% more than that.

While the V8 engines went from 15 mpg hwy to 26 mpg, and jumping from 200HP to 505HP (Corvette), economy cars didn't show similiar gains in mileage, and in fact, lost mileage in general.

The best economy I ever got out of a freeway commuting motorcycle was 70mpg on a XT500 Yamaha thumper.  Maintenance costs outweighed the fuel savings though.  And it sucked at carrying groceries in the rain.

While I don't think 100 mpg is possible, I don't understand why must lose ground either.

I'd like to add my 78 Ford Fiesta to this list.  Not only did I get 42 MPG with it, it handled as well as my MGB, and I could carry all my band gear in it.  All from a 1600 with an overhead valve engine, 4 speed tranny and seating comfortable enough for my 6'5" frame.

Imagine what it would do with EFI! 

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« Reply #7 on: July 08, 2008, 02:37:19 PM »

The biggest problem with newer cars is weight.  All those 14 air bags, power (seats, door locks, windows, mirrors, sunvisors, etc) add weight.  The crash requirements add weight.  Emissions equipment adds weight.  Accelerating and maintaining that weight takes some fixed amount of energy.

One of the simplest and most effective mpg increase was the overdrive trans.  Fuel injection also helps part throttle mpg.  More aerodynamic shapes help mpg.

Engine technologies like common rail diesel and direct gas injection have more advantages.  Hybrids are only recapturing some of the energy already expended, thus extending the mpg.  There is no voodoo or black magic.  You can not defeat the laws of physics.

But unless we all drive in too small of vehicles without all the luxury and safety requirements I think 100 mpg will never be realized.  You can add my $.02 to the pot.
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« Reply #8 on: July 08, 2008, 03:10:26 PM »

I seriously considered building an entry for the automotive X-prize, but didn't like the way they did the rules.  Basically they were stuck on getting 100mpg, regardless of how slow the speed was, as opposed to getting the highest mpg at normal highway speeds.

100mpg was done over 30 years ago by some pretty normal vehicles, low drag, small engine, and at a whopping 45mph or so.  One of these I'm thinking about ran at Bonneville.

Anyway,  I would think some of the big fuel savings out there would be a simple fiberglass tail cone added to a trailer.  How much diesel would that save on your trip out?  Heck, it might do double duty as shade with some extra poles once on the salt.  It's not a new idea by any means, but why aren't we of all people doing it? 
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fredvance
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« Reply #9 on: July 08, 2008, 03:22:50 PM »

What is a tail cone Ive seen the nose cones?
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« Reply #10 on: July 08, 2008, 03:27:48 PM »

What is a tail cone Ive seen the nose cones?

Pretty much only seen in research, but same idea as a nose cone, except covers the entire trailer rear end.  Imagine you would have to make one, as I don't know of any production ones.

On second thought, a vortex generator might make more sense for less effort, assuming your trailer fits in a wind tunnel  grin
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Glen
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« Reply #11 on: July 08, 2008, 03:37:53 PM »

Vortex generators for trailers have been around for years. I believe that Nishmotorsports.com has info on their use.
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« Reply #12 on: July 08, 2008, 04:09:11 PM »

In the 1980s before Congress scrapped the planned CAFE standards GM , Ford and Mopar were planning to go with direct injected 2 cycle engines . They say they run cleaner and get better milage per hp plus being lighter and cheaper to make . If the fuel prices stay high maybe they will renew the rights to the design with the Australian patent holder .

John
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Tom Bryant
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« Reply #13 on: July 08, 2008, 04:12:55 PM »

I would like to bring something up that I don’t hear too many people addressing. INFLATION…has anyone checked what part of our income was being spent for gasoline in the 50s, 60s, etc. (Today it take $4 to buy what $1 did in 1970 and fuel mileage was in the toilet) I don’t like pay $4/gal for gasoline, but the truth is that we have been spoiled by the “good life”. Our cars today require almost as much to operate the accessories as was required to propel the car 50 years ago. I drive a 2002 Firebird TansAm. I love the car, it gets 26 mpg on the highway, it has A/C, P/S, P/B power seats, rides like a wagon and handles like a dream. Do I want to give it up for basic transportation with none of the amenities? No yet!

I just finished reading a three-book set by Smokey Yunick. Among the very interesting things he had to say (unfortunately laced with blue language and numerous sexual exploits) he was heavily involved in alternative energy research in the mid-80s. With the exception of his “Hot-air Engine, which he never did get the corporate world to buy into, his basic conclusion was that there wasn’t an alternative fuel that was viable. He was looking at the BTU cost and the BTU delivered. 

Technology is advancing and we may see something in the near future that will satisfy our needs/wants. GM has a car in the works that sounds interesting. Check http://www.teslamotors.com/ for another interesting car…only 99,000 euros (155,000 US) but they promise a family affordable car in 2010.

Tom
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Ratliff
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« Reply #14 on: July 08, 2008, 04:27:13 PM »

I would like to bring something up that I don’t hear too many people addressing. INFLATION…has anyone checked what part of our income was being spent for gasoline in the 50s, 60s, etc. (Today it take $4 to buy what $1 did in 1970 and fuel mileage was in the toilet) I don’t like pay $4/gal for gasoline, but the truth is that we have been spoiled by the “good life”. Our cars today require almost as much to operate the accessories as was required to propel the car 50 years ago. I drive a 2002 Firebird TansAm. I love the car, it gets 26 mpg on the highway, it has A/C, P/S, P/B power seats, rides like a wagon and handles like a dream. Do I want to give it up for basic transportation with none of the amenities? No yet!

I just finished reading a three-book set by Smokey Yunick. Among the very interesting things he had to say (unfortunately laced with blue language and numerous sexual exploits) he was heavily involved in alternative energy research in the mid-80s. With the exception of his “Hot-air Engine, which he never did get the corporate world to buy into, his basic conclusion was that there wasn’t an alternative fuel that was viable. He was looking at the BTU cost and the BTU delivered. 

Technology is advancing and we may see something in the near future that will satisfy our needs/wants. GM has a car in the works that sounds interesting. Check http://www.teslamotors.com/ for another interesting car…only 99,000 euros (155,000 US) but they promise a family affordable car in 2010.

Tom


The energy density of hydrocarbon fuels is what makes the airline industry feasible.
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