Engine technology and MPG

[red-beard]

Originally Posted by sc_rufctr

I can't remember the teacher that said it but apparently there is that much energy in a tank of gas.

If you think about it we have cars that can travel above 200 mph on an engine that may be 20% efficient at best.
How fast could that car go if the engine was 99% efficient?

--------------------

As a side question. How efficient are modern rocket and jet engines?

Not 18,000 mph.

What you need to understand is that heat engines work via thermodynamic principles. The maximum theoretical efficiency of any system comes from the Carnot cycle and is limited to the difference between the hottest temp in the cycle and the lowest temp, divided by the hottest temp, all in absolute numbers. Most of the cycles require input of energy (compression) and have losses which cannot be recovered (friction, heat of vaporization of water in combustion, etc).

Add to this that a car engine has to operate over a wide range of operating conditions.

Something the hybrid car is supposed to do it allow a smaller, more efficient, specially tuned engine to operate and store energy (in the batteries) so that the car car be still operated over a wide range of operating conditions. The problem is, it is still an internal combustion engine. It isn't THAT much more efficient.

If you look at the hybrids, you will find that they are more areodynamic, lighter, have higher pressure tires, etc. I don't know the details, but I expect better than 50% of the gains are created there. And let's also bring up regenerative braking.

If you took a Hybrid, removed the batteries and all of the other associated junk, and replaced it with a 60-70 hp 1.0l VTEC, with a 6 speed manual transmission, I expect you could get similar mileage. And it would be 1/2 the cost...

Most of the people in this country buy an SUV because they have a lifestyle which includes the need for one, at times. It would be more fuel efficient to have a tiny commuter care during the week, and the SUV for other times. But that means doubling the number of cars.

Or you could rent the SUV when you need it. But that is not convinient.

The best way to asses two different cars is not on just fuel efficency, but on the overall cost of ownership for a set period of time. Money is a pretty good indication of how much energy was required to build it, run it, maintain it, etc.

[JeremyD]

Poo Poo 1.201 Imperial to US - so only 75 mpg - you are right - get me my Ford F-150

[oldE]

Originally Posted by onewhippedpuppy

This. Frankly it's baffling to me that we don't have more diesels. Excellent MPG without compromising performance. I always hear the line "Americans won't buy diesels", but then I also hear that it's difficult to find a VW TDi or some of the MB diesels because they're popular. There's really no need for all of the hybrid high-tech complexity, just get a car with the 100 year old engine technology for as good/better MPG.

I'm looking for a used compact truck 4x4 that will get decent MPG, in my mind the only truck worth considering is a Toyota Tacoma. With a 4-cylinder and a 5-speed it's a 24-ish MPG truck, and gutless as hell. Elsewhere you can pick up a diesel HiLux (Tacoma) 4x4, crew cab, diesel that will get 30+ MPG all day long and tow similar to a 1/2 ton. How can anyone claim that 30+ MPG trucks wouldn't sell here? Or 30 MPG full size SUVs?

While I agree with almost everything you've said here, it isn't quite "100 year old technology"
The real difference in the past 5 years has been very high fuel pressures and computer controlled injectors to allow multiple injections of fuel during a power stroke. All the urea injection is doing is cutting down on oxides of nitrogen in the tailpipe. The power has been made by that time.
My 2006 TDi is light years ahead of the previous TD I had and the current generation is almost as far ahead of my car. Mileage isn't that much better, but it's hard to argue with the torque the engines produce.
As an automotive journalist wrote some decades ago: people talk horsepower, but they drive torque. I almost never see the high side of 3000 RPM.
5 liters /100 Km is usual trip consumption. Poor mileage is 5.5 liters / 100 Km.

Like you, I would happily park a truck like my 2wd F150 (not the Ferrari) with a small modern turbo diesel in my driveway. I don't need 4wd, I don't need a crew cab, just an 8'bed and some torque to pull a 2 horse trailer with little fuss. (And I wouldn't mind getting better than 20 mpg with the thing, either.)

Cheers
Les

[sc_rufctr]

Originally Posted by red-beard

...

The best way to asses two different cars is not on just fuel efficency, but on the overall cost of ownership for a set period of time. Money is a pretty good indication of how much energy was required to build it, run it, maintain it, etc.

That's an excellent point. I always think of TCO when considering a car to buy.

[kaisen]

Originally Posted by JeremyD

Poo Poo 1.201 Imperial to US - so only 75 mpg - you are right - get me my Ford F-150

Are you sure?

1 US Gallon = 3.785 liters
1 Imperial Gallon = 4.546 liters

Therefore 1 US Gallon = .83 Imperial Gallons

60 Imp mpg x .83 = 49.8 US mpg

50 Imp mpg x .83 = 41.5 US mpg

Still very impressive
Too bad they won't meet our more stringent emissions requirements

[scottbombedout]

Originally Posted by kaisen

Are you sure?

1 US Gallon = 3.785 liters
1 Imperial Gallon = 4.546 liters

Therefore 1 US Gallon = .83 Imperial Gallons

60 Imp mpg x .83 = 49.8 US mpg

50 Imp mpg x .83 = 41.5 US mpg

Still very impressive
Too bad they won't meet our more stringent emissions requirements

So 90 on a run x .83 = 74.7 US mpg
50 in town x .83 = 41.5 US mpg

I can live with that. So how come it wont meet your emissions requirements?
I only pay £20 road tax because the emissions are supposed to be so low.

[1990C4S]

Originally Posted by john70t

I try not to intake unknown and unwanted substances. Period.
But if I was to willingly inhale a known substance into my lungs, it would be within the framework of the constitutional fathers or common sense.


The CAFE standards the OP mentioned, and of which I spoke of before,..ummm...speaks for themselves.

25mpg.
Same as the Model T.

I won't question your 'intake'. But I will question the Model T reference. It is simply a myth.

Try about half that. 10-12 mpg. I am reasonably familiar with these cars and their engines, they simply aren't efficient enough to get that mileage.

Confirmed by a co-worker (who owns four) and here:

Ford Model T Frequently Asked Questions (FAQ) - The Frontenac Motor Company Brass-Era Automobile Collection

Add to that, the gas available 'in the day' was crap, mileage back then would have been worse, not better.

[kaisen]

I'll go on record stating that I LOVE diesels, and I've owned a BUNCH of them over the years.

BUT......

According to the EIA , diesel is $0.45 per gallon more than gasoline here in the US ($3.91 vs $3.56).

So, if you have a 2011 Volkswagen Jetta SE 2.5 automatic getting 33 mpg (official EPA freeway rating) using $3.56 gasoline it costs you $1723 to drive 15,000 miles. If you had 2011 Volkswagen Jetta TDI diesel auto getting 42 mpg (official EPA freeway rating) using $3.91 diesel it costs you $1396 to drive the same 15,000 miles. So you save $327 per 15,000 miles.

But you also paid a $2,300 premium for the diesel over a similarly equipped gas engined Jetta (GL w/ Convenience Pkg = $20,660 is the same car as $22,995 base TDI, except motor). That $2300 premium would take 105,000 miles to break even.

Let's make it more interesting and look at a 2011 Hyundai Elantra automatic getting 40 mpg (official EPA freeway rating) using $3.56 gasoline it costs you $1335 to drive 15,000 miles The Elantra and the Jetta are very similar in size, and they have the same horsepower (but the diesel makes more torque). They share similar 0-60 times. But it's cheaper to buy a similar Elantra, even with leather and moonroof and other additional features of a Limited, it is still $2300 less than a base TDI.

Maybe Americans CAN do math

[scottbombedout]

Interesting figures.
However my diesel was only £600 more than the equivalent petrol model. Resale value on the diesel after one year is £1,600 more.

Service intervals on the diesel are longer than the petrol. The services are cheaper (I checked with the service manager beforehand).

Road tax is £20 on the diesel per year, £120 on the petrol per year.

The insurance was £150 per year cheaper for the diesel.

Diesel is dearer than petrol by about 4% per gallon over here. Your difference seems higher. According to Audis own figures the diesel is 41% more fuel efficient than the equivalent petrol on the combined cycle.

I think over here at least the figures work out pretty favourable for the diesel.

[kaisen]

Originally Posted by scottbombedout

I think over here at least the figures work out pretty favourable for the diesel.

That seems to be the case in most of Europe. If our diesel were cheaper, it would help.

[Scuba Steve]

Originally Posted by scottbombedout

So 90 on a run x .83 = 74.7 US mpg
50 in town x .83 = 41.5 US mpg

I can live with that. So how come it wont meet your emissions requirements?
I only pay £20 road tax because the emissions are supposed to be so low.

From what I understand, one government (either here, or over there... not sure which) focuses more on particulate emissions while the other wants lower levels of particular gasses emitted.

Diesel Cars in Europe vs. America - Why Diesel Vehicles Are Expensive in US - Popular Mechanics

And then there's another challenge for diesels--stricter U.S. emission regulations. The 50-state light-duty vehicle limit for emissions of nitrogen oxides is 0.07 grams per mile. In Western Europe, the limit is 0.29.

Unfortunately that's the most specific requirement comparison I could get right away.

[oldE]

"Volkswagen of America, Inc. today unveiled its cleanest diesel ever for the U.S., the Jetta TDI. Additionally, the company announced that this new clean diesel will be available to the U.S. market in the spring of 2008. This Jetta TDI will meet emissions standards applicable in all 50 states, including the most stringent "TIER 2/BIN 5" or "LEV II/LEV" requirement limiting nitrogen oxide (NOx) emissions to 0.05 g/mile."

Having that information, I suspect the relative price or diesel in the US (price is usually around that of Regular in the GWN) is the biggest factor for many.

About 1/3 of the VWs sold around here are diesels (according to a friend who works in a service dept).

I think for many, an automobile is an emotional purchase. I looked at a Sonata before I purchased the Jetta TDi and felt I could live with it and crunched the numbers, but appreciated the way the Jetta felt.
On this board we see dozens of threads with a similar theme: "Should I buy "x". If the numbers were all anyone went by, it wouldn't matter if the car was uglier than a bulldog's back end (or front end, for that matter). We would shoehorn ourselves into a tiny POS and congratulate ourselves for the 'good deal'.
But we don't. We like looking at cars, we like how they feel. Few of us ever wring every last gram of performance (speed, handling, mileage or carrying capacity) out of our cars, but we talk ourselves into things like all wheel drive, extra seating capacity, convertibles and sports cars for God's sake.

Ain't life grand?
Les

[JeremyD]

Originally Posted by kaisen

Are you sure?

1 US Gallon = 3.785 liters
1 Imperial Gallon = 4.546 liters

Therefore 1 US Gallon = .83 Imperial Gallons

60 Imp mpg x .83 = 49.8 US mpg

50 Imp mpg x .83 = 41.5 US mpg

Still very impressive
Too bad they won't meet our more stringent emissions requirements

Originally Posted by scottbombedout

Audi A3 - Saving you fuel - Audi.co.uk

Ours is the 1.6tdi shown here. Doesnt set the world on fire but I got 90mpg on a 50 mile trip coming home yesterday (wife and 3 kids).
I have never seen less than 50mpg around town.

so 90mpg X .83 = 74.7 mpg I rounded up...

And while I understand the TCO and the increased price of diesel (auto, retail) I think many of you are missing the bigger picture...

Auto diesel (in the US) is more expensive because it's in low demand. It's almost a boutique blend vs gasoline.

Really - diesel has higher energy per gallon - Diesel engines produce more low end torque. the US market likes it's big trucks and vehicles - which are more easily moved with torque vs HP.

An automotive gasoline engine will produce about 15 HP hours on a gallon of gas. An automotive diesel will produce about 20 HP Hrs

[john70t]

How about a diesel hybrid?
1). Using a % blend of biodiesel made from scrap cellulous(wood from deconstruction, farming waste, industrial hemp or other fast growers, etc).

2). Rear petrol engine. Front regenerative hub motors for braking and hard accelleration.

3). Tall thin tires of hard compound with high clearance allows for getting through snow, and the hybrid function can become all time 4wd when needed.
An added benefit is a butt-high seat easy to get into.

4). Strong frame and ball hitch for towing match-fit areodynamic trailers of different sizes. No need for a huge vehicle while getting groceries, but could haul sheetrock on the weekends or luggage for a vacation.

5). Conical/shaped rear helps areodynamics which account for a large percentage of power used. There is a stock Civic project that added a cone to the rear and was getting 70-95mpg.

[krystar]

Originally Posted by john70t

Tall thin tires

less tread u have, the longer the braking distance is. hard to market a car that gets 100mpg but 60-0 distance is couple of feet higher than a competitors

insight uses 175/65/15's. stops 2700 pounds of car 60-0 in 128ft.
prius uses 195/65/15's. stops 3042 pounds of car 60-0 in 118ft.

of course not a fair apples to apples comparison. but as a layman buyer, prius is a safer car based on that information

2010 Honda Insight vs. 2010 Toyota Prius Comparison Test on Inside Line

[Jared at Pelican Parts]

My 2007 Focus daily driver gets 38MPG on average. Over 40MPG on roadtrips.

My grandpa boght the last year Mercury Grand Marquis with the 4.6L and he gets close to 25MPG

It's all in how you drive it.

[red-beard]

???

[RWebb]

Most of the people in this country buy an SUV because they have a psychological aversion to being SEEN in a MiniVan, hence the "need" for one...

[kaisen]

Originally Posted by RWebb

Most of the people in this country buy an SUV because they have a psychological aversion to being SEEN in a MiniVan, hence the "need" for one...

That's why you wanted a Grand Cherokee, right?

[RWebb]

nope - besides I ALREADY have a "mini" van...

Slow Going