What's better, Big engine or small engine?

To ignore engine efficiency is to make the question useless.. Engine efficiency IS the question.

If the engines both have the same internal friction and turn the same number of revolutions for the entire trip then I'd say the smaller engine would be the choice for efficiency sake because it has less pumping loss than the larger engine, all other things being equal. (A very general statement because there are so many other variables.)

This experiment is performed everyday. There are lots of cars available with either a smaller 4 cylinder engine or a larger 6 cylinder engine. The larger engine consumes more fuel. It does it because it generates more power. More power = more fuel. Which is why you buy a small engine.

Wrong sir.

You will need exactly the same power in both cases. Read the thread again carefully, and read answer #1 made by guest. Research what intake means, (pumping in guest's reply) You may want to think a little about it, and than reply again.

Wangito.

Your question doesn't specify what you mean by "a trip", so let's pick one - the standard US EPA schedule for fuel economy testing:

http://www.fueleconomy.gov/feg/fe_test_schedules.shtml

Under these carefully controlled and identical conditions, the large engine will use more fuel. You can certainly design a trip under circumstances which will give you the result you're looking for, but since you failed to specify your test conditions, I stand by my answer.

Let's look at another situation. Let the cars sit still and idle. Which engine will use the most fuel? Obviously the larger, since it requires more power to idle a large engine than a small one.

Let's choose another situation. Let's look at the "sweet spot" - the torque / speed combination under which each engine gives the best mileage. Under these conditions, the smaller engine will still out perform the larger. (However, at it's best torque / speed, the larger engine may well outperform the smaller at it's worst.)

Was there a point to this post?

Sorry, but he's right. The large engine consumes more power because it has more internal friction. Fact of life. Yes, one COULD make the smaller engine require the same amount of power to operate, but then why?

There are certain economies of scale to be gained from a larger engine - i.e. faster (not necessarily cheaper) acceleration, and better fuel economy at high speeds - but as previous posters mentioned there are many variables.

Why buy a smaller engine, given the choice? They cost a bit less and they will get better fuel economy for most drivers. I have personally bit the bullet and gone to the smaller 8, but of course I am much older now.

While we're here, the 1966 Honda S-600, a two-seater sports car with a teeny tiny, highly engineered 4-cylinders got me more than 75 mpg on the highway (big Canadian gallons). But then it had a roller-bearing crank and cam, tuned exhaust like a GT-40 and four separately tunable (that was fun!) carbs. Red lined at 13,500. I'm sorry I had a tantrum and sold it.

S-600!! What a great little car! You should be drawn and quartered for selling it, but we have all done such things. Even the twin-cylinder coupe (Z 600? or 600Z?) was fun, although nowhere near as sophisticated.

The 2.0 L will burn more fuel because it weighs the same as the much heavier 4 L. The 4L will not have to work as hard as the 2L to move the same weight.

Respectfully stated, the smaller engine will be more efficient, as stated in other replies. By stating that the larger engine is working less hard, what really takes place is that the larger engine is throttled more, which leads to greater pumping loss. Imagine a compressor with the discharge fed to a partially closed valve, the other connection of which is vented to atmosphere. The compressor may pump to 100 PSI, and consumes power to do so. But by venting the compressor output by throttling through a valve, the energy in the formerly compressed air becomes unrecoverable. Energy cannot be destroyed. It is manifested in some other way, but once down to atmospheric pressure, it cannot be used for any purpose requiring motive action. That is the principle of entropy, energy which becomes unrecoverable. Conversely, if an air turbine is used for pressure letdown to atmosphere instead of a throttling valve, shaft work can be recovered from the turbine.

For that reason, a gasoline engine operated with a minimum of throttling or no throttling will always be most efficient, all other factors being equal. At half the displacement, the two liter engine wins hands down for a given power requirement within its capability.

The four liter engine can be made to produce just about the same mileage as the smaller one at highway speeds by using very high gearing, so the engine turns perhaps 1200 to 1500 RPM at 60 MPH. The driver might not like the feel, because it will not be responsive without downshifting. What really is meaningful is displacement per mile. The four liter engine can operate at a lower speed in that regard due to greater torque output. That principle cannot apply in city driving due to lower speeds, idling, and the need for throttling of either engine, where again the smaller engine wins out, and the larger engine burns more fuel due essentially to scale-up considerations.

Smaller engines with turbocharging and intercooling (removes heat of compression from the turbocharger) often provides the best of both worlds regarding good power with reasonable fuel consumption.

One additional consideration regarding efficiency is compression ratio. A high compression engine is really a "high expansion" engine, in which the burned gases expand more before the exhaust valve opens, recovering more energy due to additional "push" on the piston crowns. Expansion ratio benefits have been known for over 150 years, in the form of early cylinder valve cutoff in steam engines. The objective was to run a steam engine with no throttling, but instead varying the steam cutoff timing to match needed power output.

Bernie Katz

Hi berniek, A lot depends on the terain, how old these engines are, engine tuning, gearbox ratios, whether it is dry, wet or snow conditions and who is driving! The last one is crucial in any equation. I have driven cars with highly tuned 3 liter engines, and cars with poorly tuned 1.6 liter engines over the same long distance and hilly journey in Norway and the highly tuned 3 liter engine used a 3rd less fuel than the poorly tuned 1.6 liter engine. Two years later I made the same journey with a highly tuned 1.6 liter engine and and a poorly tuned 3 liter engine, and the 1.6 liter engine was twice as efficient as the 3 liter engine. In all these cases the journeys where driven in summer and winter. I did notice however, that in the winter months the 3 liter engine was better for driving uphill in the snow and icy weather, the reason for this was that I could drive uphill in a higher gear in the 3 liter than the 1.6 liter! The variables are so many that it would be wrong to say one way or the other.

A yellow corvette averages 30+ MPH in real life while an Electric Hybrid with an EPA overrating upwards of 50 MPG will be lucky to get 25 mph in real life.

The public has been duped again. Congratulations for point out the facts about MPG. Keep up the good work.

You may wish to also explain the "green advantage" of the larger more efficient engine as compared to the electric hybrid engine that in truth is using good clean electricity transmitted over a public grid generated by a dirty ole power plant IMBY on average burning 50% coal at 25% efficiency (75% waste) (in the US) and producing 30 tons pollution per customer each year based on 50MBBTU per family. Now they want to add autos to the dirty ole power plant energy equation and generate 60 tons pollution per person per year. Give us all a clean breath of truth.

I have absolutely no idea what you are talking about!

What about a blue Corvette?

As any good Quebecer knows, blue cars do not go as fast as yellow ones, red ones are the fastest. Also, sharp cars go faster than dowdy ones.

There is no production hybrid that uses power from the grid. Where on earth did you come up with that? You're not seriously thinking that a Honda Civic hybrid or a Prius, or Lexus RX 400 or a Ford Escape Hybrid actually uses power from the grid are you? Only cars that have been modified and future plug-in hybrids will use power from the grid.

Also, many studies by various car mags and consumers groups find the the Prius hybrid gets 45-46 mph all around average. Not as high as the EPA tests, but Toyota has always said the the tests don't apply well to hybrids. The Prius without the hybrid system would be as efficient as any other car of similar weight, engine size and type, and aerodynamics, meaning it would get about 32 mpg. My only very slightly larger 4 cylinder Honda Accord rarely gets over 28 mpg in average driving.

Current power plants average over 30% efficiency, with 36% projected by 2020. But even at 30 percent, you're right, a car with an ICE can do about as well.

Anyone who takes the time to read the car and consumer mags, comparing their results with EPA numbers can see that the EPA numbers are very reasonable, given the stated conditions. Car and Driver gets generally lower figures because they are enthusiasts, and Consumer Reports gets fairly close to the EPA numbers. But there is very high consistency -- in other words, Car and Driver is always somewhat lower, by the same percentage. So EPA is a good gage, but optimistic. Edmunds average is consistently 1 mpg lower in their test cycle than the EPA city rating. For the Corvette the EPA number is 18, so Edmunds would get 17. 30 will never happen, yellow or not, unless you spend your day driving at exactly 40 mph on a flat road in sixth gear.

I've had lots of vehicles at the 16MPG (imperial) range, and with little reason why; 1965 Chevy Biscayne 230CID 2SP Auto, 1968 Rambler 343CID 4bbl 3SP Auto, 1974 Olds Cutlass 350CID 4bbl 3SP Auto, 1974 Plymouth Roadrunner 360CID 4bbl 3SPD Auto(a very hot little number), 1984 Chevy 5/4T truck 4SP manual, etc.

Several 25MPG as well. My 1976 Honda Civic 1277cc ran 26MPG and was none too heavy, maybe 900 Lbs, yet my 1992 3600Lb 4.9L Cadillac SeVille gets 25MPG.

My 1991 Olds Eighty-Eight 3.8L averaged 35 MPG, and I got 48MPG with my 1983 Daytona 5Sp Manual 2.2L Turbo which I dare say likely put out as much horsepower as my Cadillac, and was certainly a fair bit heavier than my Civic.

A friend of mine had a mid-70's Olds Ninety-Eight 455CID Auto that gave 25MPG while towing a trailer to the East coast.

I might not be helping to answer your question here, but sometimes displacement is not the only factor. If the vehicle is too heavy for the smaller engine, fuel economy, and performance may suffer. Older carb tech pales in comparison to fuel injection, and Multi-port fuel injection is better yet. Turbocharge Multi-port, and now you're talking.

Many times, if a 2.0L is fuel efficient and sufficiently powerful for a vehicle, I believe that it would be more efficient than a 4.0L engine on the same platform driven in the same manner, yet should you be in hilly territory the 2L might be too small to perform & might even yield poorer fuel economy.

Sorry about all of that trivia, and more directly in response to you're question......

First; you can not ignore the engine's efficiency, and still have an answer to your question. All things being equal, including the engines efficiency, it will take more energy to operate the larger engine and by default it will consume the larger amount of fuel. It is possible to have a larger engine with greater efficiency resulting in greater fuel economy, so, "Bob's your uncle"

No scientific means were used, or harmed, in testing to formulate this response (and yes, the Cadillac is heavier than 3600LB.), just a guess

Hi...I appreciate all these responses but it occurs to me that there is a lot of faulty logic being applied. Here's what I mean. The very premise of the question is wrong from the get go. The questioner is trying to reduce variables to a single unknown by the "all-else-equal" technique so that he may obtain some real fuel consumption numbers.

IMHO that is impossible in this case because changing any single component--in this case displacement--invariably leads to other changes. All-else-NOT-equal.

The several forgoing analyses might be pretty close to valid if we were to build a hypothetical test bed. Perhaps two identical four cylinder engines mechanically linked in tandem turning a generator with a resistive load. First we run some power output test curves with both engines driving the load. Then we turn off the fuel to one engine and run the same testing scenario. Same accelerations, same frictions, same RPMs checked at regular intervals, same load variations, etc. This might come pretty close to all-else-equal and yield some reliable data.

This however has nothing whatsoever to do with reality or helping the questioner decide between a big engine or a little engine.

I think an empirical approach is more appropriate in this case. The last respondent cited numerous real world examples but did not draw specific conclusions.

Without spending a great deal of space giving details, I will tell you that in the real world in which I live, the larger displacement engine has always given me equal or better mileage AS LONG AS WE ARE COMPARING SIMILAR TECHNOLOGY. The question is a lot like asking "how long is a piece of string?" The only real answer is, "Just long enough to get the job done."

Lonnie

Assuming the weights are the same, acceleration rates are the same, and the cars are driven in precisely the same manner, then a rule of thumb is that the smaller engine will propel the car more efficiently, because it will be throttled less, leading to lower pumping losses. HOWEVER...

Things are not necessarily that simple. In practical examples, the gearing in the smaller engine may be numerically higher (in other words, the smaller engine will run at a higher speed, for a given road speed.) At some speeds, it could be that the smaller engine might be running at a speed above its best efficiency point. The only way to know is to look at the BSFC (brake specific fuel consumption) curves for the engines in question.

At wide open throttle on a dynomometer, the engine torque curve (the one you see in car mag tests) will look like the BSFC curve turned upside down -- in other words BSFC is at its minimum at the torque peak (where the engine runs most efficiently, IF the throttle is wide open). Some have jumped to the conclusion that engines should always be run at the rpm corresponding to the torque peak -- which is also an oversimplification. In fact, there is not a single BSFC curve for an engine, but either a BSFC map or a set of BFSC curves, that show not just the BSFC vs rpm at full load (full throttle), but the BFSC at various RPM's and loads. In general, a given gas engine will range from about .45 lb/hp/hr at its most efficient to .65 lb/hp/hr (or more) at its least efficient. (These figures are for the engine running at RPMs and loads in its normal driving range. If the engine is idling, then it produces no useful (brake)hp so BSFC gets extremely high, and you get infinitely poor MGH)

So... there are pumping losses, which favor large throttle openings (therefore small engines) for best efficiency. Then there are the inertial, fluid dynamics, thermal, and acoustic effects that change in various ways with rpm and throttle setting that favor certain rpms over others, and certain loads over others.

Long answer -- and even then, a gross oversimplification. But sure, the 2.0 liter engine wins, as shown in the market place in hundreds of tests of cars that are available with both 4cyl and 6cyl engines.

Thermodynamically smaller engine should consume less fuel.

Interesting question. But you left out one important criterion: the terrain over which both vehicles will travel...and, accordingly, the application of gearing. Here's something I learned long ago--a similar question pertaining to trucking--that would have bearing on your question it seems.

That question went something like this:

As between a tractor with high-capacity engine and another with small, which would be the better choice (more fuel efficient) for operation in either of flat terrain or mountainous terrain.

The answer was that the smaller engine should be selected for mountainous terrain: since gearing, not power, is best for climbing, use of power in lieu of leverage to climb to the top is wasteful both going up and coming down.

Over flat terrain, greater power (greater engine capacity) has the advantage since it is not so much gravity opposing forward progress as headwind. To maintain the same speed the smaller engine must turn faster and labor harder to make progress.

Therefore, it would appear that the nature of the trip must be speficied for there to be a (figuratively speaking) conclusive answer to your question. But a reasonable generalization would be that the larger engined...can cruise more efficiently over flat terrain, where its power is not wasted against a continuous bucking wind; while the smaller engined...will be more efficient in mountainous terrain since less power will be wasted.

the 4L will be less efficient as it will have higher friction losses(both from extra weight of the engine and from internal engine friction....unless you lighten the 4L car to make the total weight equal.

All a large engine can add is greater acceleration = more gas.

On an infinite steady state trip the 2L will use less gas.

. Assuming an identical trip in terms of mileage and acceleraetion

As I understand it, there's more to it than just the mass of the engine. On flat terrain, a larger heavier vehicle (housing the engine) would seem also the have the advantage of greater momentum when confronting a constant headwind. Buffeting by wind would seem to have a much greater deleterious effect on the progress of a lighter-weight vehicle; and force it to labor harder and faster--consuming more fuel relative to work done--to make the same forward progress. And then there's the rotational momentum of the engine itself. While it might be true that more fuel is consumed to bring the larger engine up to cruising speed on an open highway, once that speed is attained the greater turning mass (its momentum) ought to assist in keeping the engine turning, thereby lessening fuel demand; in contrast, the smaller engine, having less rotational momentum, would expend more energy--and more fuel--at cruise speed just to keep the engine from slowing when encountering headwind resistance. So, taking from guests suggestion above, perhaps best way (rather than idling the competing engines) to compare would be to operate the vehicles under no-headwind condtions, but under load using a dynamometer. Under zero load the engines could be compared for open terrain simulations. Setting programmed resistance in the dynamometer could be used to compare the vehicles under simulated mountain conditions. What do you think?

Hi Guest. I brought up this question of terrain in my first blog. As a mechanical and marine engineer for 45 years, I have worked on engines from 5bhp to 40,000bhp. Steam reciprocating engines, steam turbines, diesel and gas engines, stirling engines and many more, and I was quick to notice that engine efficency depends on many variables! We often hear for example, that diesel engines have a higher efficiancy than gas engines, but in the lower capacity diesel engines, this is not true. I will give you an example; a diesel engine of 1,000cc in a motor car is about 18 to20% efficient, the same as an efficient gas engine. A ships diesel engine of say 40,000cc is about 38 to 44% efficient. Then there is the question of terrain, in a heavy sea, a ships engine operates just like a car engine going uphill, 2 to 4 days, for example. This question about fuel efficiency is a fools game, at the end of the day, nobody wins other than the fuel companies, unless you log every journey, stating fuel consumption against milage. So why bother?

Scapolie,

Thanks for a very informative and interesting perspective.... As one who actually does log vehicle miles (using my trip odometer) the bother has proved very useful, to me at least. Whereas my vehicle is rated to get 15+/- city- and 20+/-open-road MPG, I have found my vehicle consistently gets 18+ and 25, respectively. When it falls below these (for two loggings in succession), I know the engine is in need of tuneup or air filter replacement.

While the lifting of a ship by waves is not exactly analogous to a motor vehicle ascending and descending hills--after all, except when near a coast, waves do not have current (in the sense of a stream) but, rather, are merely translations of vertical motions in a horizontal direction--the comparison (in the sense of a boat's prop or impeller encountering repetitively varying resistance) is adequate to make your point about the futility of attempting "folkways" comparisons between engines; which (if I may) leads to the inference that the only realistic and valid way to make such comparisons is under well defined and controlled laboratory (like) conditions...one in which variables, especially driver personality variables, can be controlled, limited &or eliminated.

Another analogy, perhaps equally or more apropos, might be as pertains to railroading...if any railroading (both European type and American) officianadoes would care to weigh in....

Scapolie:

Smaller diesels are more efficient than their petrol counterparts. Compare fuel mileage from actual testing (not imagination) of the VW Jetta Diesel vs the VW petrol Jetta. The diesel is far more efficient.

Produce the BSFC graphs for a the 1000 cc diesel engine in question for which you are claiming laughably low efficiency. Also produce the BSFC graphs for a comparable 1000 cc petrol eninge. Compare them. Post them here.

Questions about fuel efficiency a fools game?? Why bother?? Because a Prius, at 45 mpg, uses less fuel than a Hummer at 10 mpg. The fools are those who cannot perceive the difference, who do not care, and who think the science and research behind those numbers is trivial.

One Hp = 550 #'/" 200 Hp =110,000 #'/". For an 80,000 # rig, that would indicate a capability to rise (Climb) 1.35 '/". Let's take a 3 % slope. 1.35 '/" / 0.03' rise/' run = 45 '/", or 30 mph. 400 Hp would still be running 90 '/", or 60+ miles per. Guess what happens at a 6 % slope?

Shifting out of granny on the uphill slope is always a trick, and the extra 200 Hp might make the difference between making or not the shift to 2 before you roll back to a stop.

Then going down on the return, the same rule of thumb that the 200 would only be able to limit speed at about 15 mph with a Jake brake helping, whereas the 400 would be just as safe at 30.

imagine driving your car behind these trucks, and whch do you want to be following? how many 4 wheelers smash up trying to get around the snail?

RichH

I think it is better and easier to understand ,if you operate both of engines at idle speed (with out load) ,for the same period and measure exactly the fuel consumption for both of engines ,I think the larger engine consumes more fuel than smaller one because it should over come more internal resistance than smaller one ,and it is increasing directly with ,the load applied during the trip

Your argument points up how subjective Wangito's topic is. But I can't quite see how idling the two engines--where neither does work--is an apt comparison. And if a smaller engine turns at x times the larger (it cycles more over the same time delta), it is questionable whether or not it encounters less internal resistance friction. But your suggestion--it goes very much to carburetion or injection it seems to me--reminds one of a persistent point of discussion back during the muscle car days. One point of controversy back then seemed to be whether to fit the big V8 with a two-barrel or four-barrel carburetor. What one most often heard was that the two-barrel would give best mileage per gallon. But what was left out was the way in which the car was driven: whether for maximum acceleration--where the four-barrel got the nod; or without regard for acceleration from stop--where the two barrel was supposed to be more efficient. However, I could never find reason to judge either to give better cruising fuel efficiency...so long as one did not have a lead foot...so long as one drove not for acceleration but for miminum fuel consumption--with a feather foot. After all, two identical engines will only use fuel at a rate up to their theoretical limits.

I had a 1979 ford pickup with a 400 cid engine. I blew the engine (the crank

broke). I put in a 460 cid engine. vastly superior. better power. substantially

better mileage. Same tranny, gear ratio, etc. go figure.

I had a 1978 Ford LTD station wagon with the 400 cid engine and the opposing rear seats for a couple of the kids. What a pig. 15 -17 mpg (imperial units). I ended up replacing the engine, the tranny and the rear end at various times. I loved the car when it was working, great ride and very comfortable for a family with 5 kids and a live-in mother-in-law. Maybe I should have replaced the 400 engine with the 460. I always heard good things about the 460.

In spite of it all we had some great memories with that car and our Starcraft tent trailer. In some ways I wish we could turn back the clock, the kids asleep, the sound of rain falling on the tent trailer, the faint hiss of the propane lantern, and me curled up with a good book, but then I wouldn't be a grandfather.

Please forgive me for waxing nostalgic.

460 is alot of cubic inches, but you would need to give it some compression. Back around 78' they were still choking these motors. Add a nice cam with some lift and an aftermarket valvetrain on some ported heads. A new intake manifold and Demon carb. would be getting over 20mpg.

I got way better gas mileage when I swapped out the 386 and put in a 350 engine into my GTO. Everybody said that is was because "the bigger engine isn't working as hard. Thats just my experience. Really don't know why...my driving habits didn't change. But the newer engine was like, 8 years further advanced in technology than the old 386. (I know...Goats and LeMans ran 387's in the US...it was a 386 in Canada..okay!)

However, my neighbour's kid had a little four cylinder that he destroyed in two years because it was too small to do the job. We put in a 6 cylinder, and he has been running it just fine for 5 years now. Should you consider the replacement cycle of the engine as part of the efficiency "rating"? If so, then why are we not all driving Detroit Diesels. But I digress.....grin.

How Cruel!! Goats ran 389's... Pontiac's most famous and beloved engine. Google "389 with trips". Check the lyrics to the Beech Boys song "Little GTO".

Tearfully,

Ken

Bahh to your GTO. I took one on with an Edsel and clobbered it in a two-mile straight line.

The thing I find interesting, though, is that ever since MPG got heavy government involvement it has been pitiful. Big 8's in the 60's got way better mileage than the little 5 litres do today. (Based on personal experience not a fancy survey, but if a government somewhere is willing to pay me, I'll do the survey.) Of course Esso Regular was 106 octane when I was pumping gas.

(Tears welling up in my eyes)

HOW DARE YOU blaspheme my beloved GTO!

Actually, at the time (mid 60's), I thought most such American cars were silly (sort of). I was an effete-intellectual-eastern-commie-pinko-liberal ferin car driver. I was more impressed by 50 cc Kreidler motorcycles that produced 427 hp per liter (61 cubic inches) than by American V8s which could only produce 60 bhp per liter (as in the 425hp 427 Ford). But nevertheless, just as I would rather really see Marilyn Monroe in a movie than go to see a Shakespeare production, I did have this lust for cars like the GTO, the Galaxy 500 Fastback w/427, the SS369 Chevelle (later), the 289ci/271hp Mustang, etc. Even though I preferred European cars, I'd memorized the bore and stroke dimension for every American V8 produced between 1950 and 1964.

Now... I think "What the heck were you thinking, Ken? When you were putting around in your '57 MGA, (which cost $75 in OK condition, but the seller thought it needed a new clutch -- really only needed a $0.35 seal) you could have been picking up babes in a '57 Chevy??!! Instead of going out with the skinny booky National Honor Society girl, you could have been going out with the girl with real bazoongas!"

But sheesh, an Edsel?? What were YOU thinking? (Actually, I remember Edsels as having really interesting steering wheel/instrument clusters -- very space age/Jetsons looking, if I recall.)

Tearfully is right. My first new car after several old Fords and a well worn 59 Chevy 348 was a 65 GTO tri-power four speed convertible. I still dream about it. Either Car & Driver or Road & Track stated during testing that it would do 92 MPH at the point where the end carburetors would be on the verge of opening, and would do it at 15 MPG (carb linkage was mechanical from the factory). I did 140 MPH in that car after a Crane camshaft installation, Mallory ignition, and carburetor tuning, 6000 RPM in top gear with a 3.55 rear.

We had a 389 in the family Catalina -- the car I learned to drive in, along with a 1959 Mercedes 180. (At the time, Mercedes's were rare in the US, and my dad, who was so frugal that we mixed our milk 50/50 real/reconstituted dry, bought the cheapest available one because he intended to keep it 30 years, making it extremely low cost. He came close -- had it for about 20 years.) I was too young (born in 1950) to buy a GTO when they were new, but really lusted for them, probably more than any other American car. Even then, I was something of an eco not, so I was not too thrilled with the inefficiency of trying making a 4000 lb car go fast (in days when a 250cc Honda GP bike could blow any of the the muscle cars into the weeds). But even so... I lusted for the GTO.

Remember how many songs were about cars? Hard to imagine anyone singing about them today. What would the lyrics be? "Little Prius, with your 90 cubic inch ICE with its 16 bit multitasking combustion control module, 1.5 kilowatt nickel metal hydride batteries, continuously variable transaxle with planetary gearset for proportional electro/combustion engine torque splitting, full regenerative braking, Little buddy gonna shut you down, when I turn it on , wind it up, little Pre eee uss.

OH geeezz. Just thought of this. The car I lusted for even more than a GTO was the original AC Cobra (not the damn cheap steel-bodied truck-frame Mustang pretend toy -- but the real, aluminum-bodied tube-frame deal.)

So, imagine this: There was a girl in town who my older brother dated. She was way beyond good looking, and had this exotic edge as well. Very smart, hard driving, perfect body, and really enjoyed sex, so the rumor went (and my talks with my brother convinced me the rumors were not unfounded.) But, at the same time, she was essentially unattainable -- she had to really like you, and she didn't really like just anyone. In my mind, she was a dream girl, right there.

But here's the thing -- her older brother had a Cobra, which she was able to drive pretty frequently. Would you want to date this girl? I was 14-15 at the time. Would you think she might be the stuff of fantasies??

"What would the lyrics be?"

Here is one you might remember. The names have been changed to protect the innocent.

While riding in my SUV,
What to my surprise.
A little Toyota Pirus was following me -
About one third my size.
The guy must've wanted to pass me up
As he kept on tooting his horn. Beep! Beep!
I'll show him that a SUV
Is not a car to scorn.
Beep beep. Beep! Beep! Beep beep. Beep! Beep!
His horn went beep beep beep. Beep! Beep!
[Slow]
I pushed my foot down to the floor
To give the guy the shake.
But the little Toyota Pirus stayed right behind;
He still had on his brake.
He must have thought his car had more guts
As he kept on tooting his horn. Beep! Beep!
I'll show him that a SUV
Is not a car to scorn.
Beep beep. Beep! Beep! Beep beep. Beep! Beep!
His horn went beep beep beep. Beep! Beep!
[Normal]
My car went into passing gear
And we took off with gust.
Soon we were doing ninety -
Must've left him in the dust.
When I peeked in the mirror of my car,
I couldn't believe my eyes:
The little Toyota Pirus was right behind -
I think that guy could fly.
Beep beep. Beep! Beep! Beep beep. Beep! Beep!
His horn went beep beep beep.
[Faster]
Now we're doing a hundred and ten -
This certainly was a race.
For a Pirus to pass a SUV
Would be a big disgrace.
The guy must've wanted to pass me up
As he kept on tooting his horn.
I'll show him that a SUV
Is not a car to scorn.
Beep beep. Beep! Beep! Beep beep. Beep! Beep!
His horn went beep beep beep.
[Fastest]
Now we're doing a hundred and twenty -
As fast as I could go.
The Pirus pulled along side of me
As if we were going slow.
The fellow rolled down his window
And yelled for me to hear,
"Hey, Buddy, how can I get this car
Out of second gear?!"
Beep! Beep! Beep! Beep! Beep! Beep!

That's great! Yeah I remember that well. There were tons of songs like that. She's so fine, my 409... She's not a big motorcycle, just a groovy little motorbike... Little deuce coupe...

Is this starting to sound like an ad for Kay-Tel(sp?) records? Call now, and get those songs you loved...

Chuck Berry's Maybelline.....great song. Another great one was Hot Rod Lincoln. Son, your gonna drive me to drinkin' if you don't stop driving that Hot... Rod.... Lincoln.

You will get a lead foot while driving to those two.

Well, as I'm sure a lot of people know, engines are more efficient when they are working moderately hard (not lugging or under working). I noticed something strange with my first car, and I did this over the course of 10-15 tanks of gas (it was the difference between 29 mpg and 23 mpg!!!). I got better gas mileage going 75-80 than I did 65 mph. One thing about this car it was incredibly aerodynamic. It's drag coefficient was 0.29. I just assumed that this particular engine (3.0 Liter V6) was just so much more efficient at 2400 rmp's than 2000 that the extra drag from the extra speed wasn't a problem, so it thus got better mileage. I think one reason why it was able to do that was because it was really aerodynamic. For reference, a 2005 Corvette drag coefficient is 0.29 also. Drag coefficient is drag per unit area, so it can be compared across different vehicles. My old car sadly was a 1991 Mercury Sable. My new car (2003 VW Jetta, 1.8L Turbo Diesel) doesn't get better mileage the faster you go... which makes sense. I can get 50 mpg at 65 mph, but because I'm always in a hurry, I get 43 mpg at 75 mph. The mileage isn't really amazing in any respect because I have 90 F#@$ing horsepower. The Jetta's Drac Coef. is 0.31, and from what I've read, the difference of 0.01 can mean the difference of 2 MPH, at Nascar speeds so 0.31 means it's a huge difference in drag (also considering trucks have a drag coeff of 0.35-0.4, and remember it's drag per unit area not total drag!).

A compression ignition (Diesel) engine is more efficient than a spark ignition engine for two reasons: It is not throttled (except in rare instances for smoke control in the past), and it has a compression ratio of about twice that of a spark ignition engine. As stated before, we speak about high compression engines being more efficient than low compression engines, but it is really the correspondingly high expansion ratio after combusion which adds to efficiency. Have you ever listed to the exhaust of a Model A Ford? Even at idle, you can hear a "pft-pft" sound which is the remnants of combusion gas escaping as the exhaust valve opens. Those engines had compression (expansion) ratios of only 4:1 to 6:1 (later), so combustion gases wound up in the exhaust manifold while more energy could have been recovered with higher expansion ratios. Today, compression ratios are returning to 10:1 or higher in some instances where supported by combusion chamber design, and very accurate spark timing set by knock sensors and the ECU.

Bernie Katz

Here is a third reason. There is more energy in the same volume of diesel compared to petrol.

Matching the best effeciency point is the key to any engine application. Normally, small engines win that battle. For the need of instant torque and power, there is no substitute for displacement, but, you give away effeicency at the normal operating point. You can force a big engine to have instant power, but not a small one.

Think back to physics I... The two cars will take the same amount of energy to complete the trip, thus they will burn the same amount of fuel.

Why buy a smaller engine you ask? They tend to be more efficient. There are good arguments for either of them being more efficient in this thread, but overall...

...Or maybe its a conspiracy, "The Man" just wants us to drive slower.

In Physics I or in thermodynamics, consider what happens to the potential energy in compressed gas when it expands into a vacuum. The same principle applies to throttling of an engine. The smaller engine will be operated with less throttling than the larger for power output within its capability.

Bernie Katz

Right, for the same output the larger engine will be less efficient due to throttling (good point, it hadn't occurred to me!). This makes the original assumption of equal efficiency a bad assumption. I'm still a student (junior), so thanks for the reply, it got me thinking about thermo again.

Aircooled guy: I hated thermo in undergraduate school, but working in chemical engineering for 20 years, its needs and principles really struck home. Last 20 years have been as an electronic design consultant, and understanding of all disciplines in engineering is necessary to speak a client's language.

Bernie Katz

This thread is getting a little lost. For comparison the supercharged (single stage centrifugal compressor with intercooler) 24 litre (1650 CI) RR Merlin of World War two vintage has a design horsepower of 1000 kw. The marine racing supercharged quad turbocharged with intercooling) 6 litre (360ish CI) Jaguar (Leyland) engine is also designed to produce 1000 KW.

Which one would you put in your car? Why?

There is no comparison. The Merlin (and Griffin, for that matter), were designed for reliability, and relatively low speed operation. The 6 liter Jag falls into the "frequent rebuild" category, and will not go 2000 hours between overhauls.

Bernie Katz

I remember my father during the gas crisis in the 70's. He had a Ford Maverick with a 302 V-8 and got 19mpg. He switched to another Maverick with a 250 six and got the same 19 mpg. He then swithched to 4 cyl front wheel drive stick shift cars and that is what he continues to drive to this day. He also checks his mileage on every tank full.

Since most cars are specifically made to traverse our roadways and our speeds are regulated by law, why not design most cars to have the drag, tranny, engine specs, et cetera that will allow the most energy efficient car a the most reasonable price ?

They could use some standardized "moderate terrain" and 45-75 mph speed range as a guide to optimization. Of course, to do anything right efficiently would require some true engineering thought, NOT the thought that the most possible $$$ have to be extracted from such an exercise !

Does that just make too much sense ? Maybe this thought is too idealized ?

From my own personal experience in the marine world. Two boats identical except for the engine displacement performing identical workloads, the one with the larger displacement will generally have have "significantly" better efficiency.

In the situations where extreme differences in efficiency are found, the smaller engine is usually too small for the job and is being overworked. (Like a Mercruiser 5.0L in a 28ft) A more suitable 7.4L would run lazily along at a low RPM to push the boat at cruising speed whereas the 5.0 would be screaming at the top of its powerband to achieve the same speed.

There is a lot more total friction and heat loss occurring within the overworked engine, thus making it more inefficient. This will also lead to a short engine lifespan.

Also, if you place the same 2 engines in a much smaller boat you'll probably find the difference in efficiency to be much closer together as neither engine will be overworked.

So maybe your solution is to buy cars with big engines and place bricks under the gas pedal? I scratch my head sometimes wondering about how it seems like cars are getting more inefficient with time. Full size pickups used to get 20-25 MPG. Why do they only get 13-15MPG now?

You would also need to change the gearing so that the larger engine sweeps a similar volume/second to the small one.

Is the problem with the pickup trucks the way that the NOx and similar pollutant issues have been addressed?

Here's a new pebble for the pool. A number of airlines have invested in more powerful engines for their aircraft. The justification is that the larger (and presumably heavier) engine means the plane will climb faster to a higher altitude, and arrive at its destination having consumed less fuel...

But that's because 90% of the flying effort is done at a high altitude - thinner air = less resistance. The fuel saving from the high flying more than makes up for the greater cost of getting up there in the first place. And regardless of comparable engine efficiency, the faster you go up the more energy it takes (unless you're a dirigible).

Absolutely. The pebble is there to point out that size is not important; it's what one does with it that counts.

http://www.simetric.co.uk/si_cc2hp.htm

The gearing is what should be focused on here. I have a 558hp/520lb./ft motor in my car that gets +30mpg on the highway, because I'm turning less then 2000 rpm @ 75mph in 6th gear. The car weighs only 3050lbs.

The size of the gallon should be clarified. Gallons are bigger in the UK than other countries...

30mpg U.S. = 36.03 U.K. Gallons

Thanks

This looked wrong to me at first, because American kids used to be taught:
"A pint's a pound the world around",

I'd kind-of assumed that this might at least be true in the US - but no, when I checked I found that a US fluid ounce of water weighs 1.04 ounces.

That's quite an 'education' for a metricated type.

If you want to be truly upset, metrically, note that an imperial fluid ounce of water weighs an ounce. A gallon (imperial, again) weighs 10 pounds. Worse yet, a cubic foot of water weighs 62.5 pounds or 1,000 ounces.

The ultimate slap-in-the-human-face, though was replacing Fahrenheit, based, cleverly, on people with 0 about as cold as the majority could take and 100 about as hot. Now we compare ourselves to pure water which is becoming more and more scarce.

Then we can go on at length at length where the metre was supposed to be 1/40,000,000 the distance over the earth's average circumference from the Equator to the north pole through Paris. And it's not.

While I'm bitching, it might be fine to have these little teeny 'miles' called kilometres in dinky countries like France, but in North America I don't like the idea of moving things that are just 200 miles away to 300.

And in music:

"I love you, 36,369 cc's and 9,092 cc's
36,369 cc's and 9,092 cc's
And a hug around the (knees?)."

Or scripture:

"Thy 5 and a bit metres and thy staff, they comfort me."

Written like an Englishman.

But... SFIK, a cubic foot of water is a bit lighter than 1000 ounces, (actually, nearly 0.4% less), so perhaps you are overstating your case? But I suspect you are still upset over the loss of £sd - much easier to divide around the apostles.

Are you also a fan of Ray Charles (take these chains...)?

I say, old chap, no Englishman here. Only Canadians, eh?

And yes, I must apologize for the inaccuracy, I was getting carried away with my argument there. A cubic foot of water weighs 62.4 lbs if memory serves. I used the calculator and got too exited by the closeness.

Sadly the reality of it all is that when you go to buy something it's always smaller for the same price regardless of the measurement system. As for p-s-p (I don't have a funny L on my machine) I never really understood it, especially guineas, crowns and sovereigns.

BUT... we shouldn't be basing things on ten anyway. We SHOULD be using hex (even though it's inaccurately named) for everything and not wasting so many bits of memory and cycles converting. Long division is so much easier, too.

Not really related to cars, though so I shall cease.

Ah - Anglais ou Francais faux , n'est ce pas. Vraiment, un Anglais ne parle jamais francais; et aussi, un Francais veritable n'admettrait jamais qu'il parle l'anglais.

Semi-seriously, though, hex may be great for computers, but didn't the Babylonians have a better counting system for human affairs? Good for packing boxes, and even handled five and six cylinders comfortably (but perhaps someone knows of a seven-cylinder car engine - that would defeat it).

The whole series of Wright-Patterson radial engines, from about 700 to 4360 cubic inchs haaqve one to four banks of seven cylinders.

RichH

I did say car engines. Weren't those aircraft engines? (so a bit specialised for general arithmetic)

I prefer "more bounce to the ounce" to "more wham to the gram"

30 miles per gallon US. is equal to 12.74 Km/L, or 36.03 U.K. Gallons.

This looked wrong to me at first, because American kids used to be taught:
"A pint's a pound the world around"

Not this kid. We were taught and used SI in school when I was a kid, I'm 45 now. The reason why is because we knew that we would need to to stay competetive around the world. I've designed boiler plants for hospitals over in Scotland and only SI was used throughout the drawings. You get use to using it and it makes sense too. U.S. is very different, but I'm fine with using that. I have a habit of answering in U.S. if the thread starter is unclear on units, or doesn't list his location. I get eager to post sometimes and may not be as sensitive to units. lol! I'll pay closer attention.

I learn something everyday. I wasn't aware you guys took SI about the same time we did. Was it in the curriculum across the USA, do you know? I find most Americans I talk with seem to know very little about metric.

I, for one feel very fortunate to have learned imperial measure, both Canadian, & American measure, and then to have learned SI. Many, our age or older, whine about metric being a pain in the keester.

For those here, who were since schooled in SI only, I feel there truly is something missing for them.

However, the poor question of " What's better, Big engine or small engine? " is being slaughtered here, and I'm inadvertently helping.........

So, I'll try to be brief. I'm guessing many of you would have also found this thread interesting, even though the same thing happened there;

http://cr4.globalspec.com/thread/4621

It seems to me that a discussion on units and measurement systems would go far...... Imperial measure varies from UK version to Canadian version to American version and most likely there are more variations. Metric is not so straight forward either.

I guess I said I'd be brief, so, I'll go bye now

"I learn something everyday. I wasn't aware you guys took SI about the same time we did. Was it in the curriculum across the USA, do you know? I find most Americans I talk with seem to know very little about metric."

Our curriculum began on the individual town school district level as far as I know, not the state level. Although SI could have been implemented as a madatory at the state level, like Iowa testing was, but I'm not aware of SI being implemented on a national level across the U.S.. My kids are also using it, and I live in the same town I went to school in. It begins as part of the math curriculum and branches into science, chemistry and our physics courses.

My experience was about like TLGEngr's re SI units. As a kid in high school in New York (1964) we learned the metric system, and routinely used it in science classes. I moved to Pennsylvania in 1966, and it was the same there. That it has not caught on here more in general usage, is amazing, given the intervening 40 years.

I think it was a sign of the times. We started to see metric heavily around the early 70's in the schools. We were getting prepared as alot of U.S. engineers were working over in a booming Saudi Arabia in the mid to late 70's.

To suggest that 30 mpg = 36.03 U.K. Gallons might be keeping things just a little too simple. There are those of us who think of MPG as a rate, and gallons as a unit of volume.

I still feel that the use of the Firkin, Furlong, Fortnight system is preferable. It would avoid all these problems

Just the fact that they all begin with "F" already makes it a better system. Ya got yer friggen Firkens, yer friggen Furlongs... Makes it easier to converse.

"To suggest that 30 mpg = 36.03 U.K. Gallons might be keeping things just a little too simple. There are those of us who think of MPG as a rate, and gallons as a unit of volume. "

30MPG = 36.03 UK Gallons http://www.teaching-english-in-japan.net/conversion/miles_per_gallon

I fear you are missing the point. The chart you reference has columns. The columns in question are headed "Miles Per Gallon (US)" and "MPG (UK Gallons)". They are assuming that you interpret the latter to mean "Miles per gallon, in UK gallons". So, 30 MPG (US) is equivalent to 36.03 MPG (UK), just as the chart says. Nowhere does the chart say that any number of MPG is equal to any number of gallons. MPG is a rate. Gallons is a unit of volume. A rate cannot equal a unit of volume. To say so is a bit like asking "How many feet per second are there in a football field?"

Thus, you can see, I think, that I would find your original statement (that 30 MPG = 36.03 UK Gallons) to be a little funny. Granted, it loses most of its tiny bit of humor if it needs to be explained.

Sorry Ken, I was out of line and added 12.74 Km/L above to clarify the conversion to SI. We all make mistakes in haste so I appologise. Thanks for speaking up and responding regarding my error.

THE GALLON

It is not as simple as volumetric differences of the unit volume be it gallon US or Imperial. Note that the density of fuel changes with temperature ... currently several law suits are active in the USA due to lack of temperature correction at time of purchase.

As it turns out this maybe be a trivial point since there appears to be NO minimum energy density (Btu content per unit mass or volume) specified for any liquid fuels sold in the USA. Energy density is often a function of pedigree of the specific fuel's source stock and refining processes. This is true for diesel, bio diesel, ethanol, and (I suspect) gasoline. These variations appear to be as much as +/- 5%. Then we throw in additives, E5 to E85, etc ... it gets really messy quickly.

Further, there are variations in energy release characteristic during combustion of fuels within the same type.

And what are the (always optimistic) EPA highway ratings for your car. And the results in the Car and Driver test? When was your fuel flow indicator and totalizer last calibrated?

all in good time, scope for employment of generations of engineers, as yet unborn, looms...

Back in the fifties there was the famous Mobilgas Economy Run. All the entrants were driven by non professional drivers. In 1955 several drivers were selected from the Solitairs hot rod club of which my older brother was member. He was taught how to drive economically with no coasting or driving below the speed limits allowed. Several drivers drove each car during run with a representative from Mobilgas observing. The winning cars were not the Cadillacs, Packards, Lincolns and such. Yet many cars in that class got 24-28 in actual mpg. In outright fuel economy cars such as the Studebaker Champion with overdrive completed the 180 mile course with 39 mpg. All this from an inline flathead six of ninety horsepower in a 3,200 lb car. I know this doesn't answer your question but it serves to alert you about just how much driving habits can affect gas mileage. I realize there is far less energy in today's gasolines. Perhaps that too would explain the difference in today's, poorer by comparison, results.

Hmmm, Can anyone remind me what was my original question?

Wangito.

The answers to paragraph 1 were established very early: as the question was posed there would be no difference - until we include the losses of the transmission, in which case the system could be modified so that the larger engine used less fuel.

The answers to the second question (SFIK not yet given) would be because a) the question was unrealistic, and b) it takes less energy to manufacture the smaller engine.

No need to complain if people thereafter pursue their own related interests, I think. (In my view, the issue is not so much "large" or "small", but "where does the optimum really lie?")

Fyz

Wangito:

Let me think..... it had to do with cars, right?

Your question illustrates something I've noticed many times, here, there, and everywhere. The question is very clear, and has clear answers:

A. Ignoring efficiency differences, then the two engines use exactly the same amount of fuel, (reasonably assuming that you meant that all other conditions are held the same).

B. The small engine is more efficient, and costs less, (and would usually weigh less, although in your scenario, it does not).

But then, those two answers to the second question need to be defended. Defending the second part of answer B is fairly easy, also assuming reasonable interpretation -- in other words, small engines are generally less costly than larger ones.

But defending the first part of answer B is not so easy, because a great many people base their opinion on very very small sample size: e.g.: "My uncle's Hummer once got 82 mph... therefore big engines are more efficient." So then, you can only get out the BSFC charts for each engine in question. If you do that, you will find that, at the 15 hp required to move an average car across a level road at 55 mph, most small engines are more efficient that most large engines. Only a very large hill will get even a small engine up to its optimum BSFC, so under ordinary conditions the smaller engine wins. You can point to EPA tests which are highly repeatable, and which accurately reflect some synthetic standard, and come to the same conclusion. But all the italicized words above reflect assumptions -- and everyone makes his own.

Getting back to what I've noticed, here, there, and everywhere: people read into the question more than is there. (It reminds me of the dreaded "airplane on a conveyor discussion", in which the question did not say that the conveyor was "trying to stop the airplane" or that it was "holding it at zero air or ground speed" but many were convinced they'd read that. Many were also convinced that the motion of free rolling wheels could transmit a very large force to the airframe, despite evidence everywhere to the contrary [has no one pulled a wagon or ridden a bike?])

I'm gonna go sing "Little GTO" for awhile.

Ken

Thanks Ken,

Seldom seen: An answer so clear, it made me understand my own question.

you were damn right about participants, so eager to demonstrate their knowledge (?)that they can't care less about the questions.

Wangito.

I am taking the liberty to go to my next question. This one Will be concerning motor oils.(Ken, Bernie K, are you ready?)

Wangito.

Your question:
1) "Which one of them will consume more fuel, and if so, why?"
2) "Th[e]n why buy a small engine?"

The problem: Vehicle same weight, same trip path, 1 enigine 2X the displacement of the other

Simplifying assumption: drive line/transmission the same and cylinder size/displacement is same for both engines, resulting in 4 versus 8 cylinder

If the smaller engine suceeds in making most of the trip in the highest gear ... then the large engine will require the same number of revolutions to make the same trip.

This implies that the larger engine will be firing 4 cylinders that will be fueled (hopefully at lower rates but not guaranteed) that are not required at to accomplish the task. However, if the task is to tow a load (say a boat) the smaller engine may not be up to the job.

Answer to questions
1) Lower fuel consumption = the smaller engine
2) why buy a small engine = Your Personal choice; mine is the smaller engine for the higher mpg and lower fuel consumption (and emissions)

A good source for comparative data http://www.vcacarfueldata.org.uk/search/

Currently I am driving a 1995 CIVIC that gets 38 mpg combined average. I hope to install a 50-55 mpg engine/drive train this spring while I wait for the clean diesel with series hydraulic hybrids (HHV) that should in the above 65 mpg combined average range. Using this technology EPA has demonstrated 80+ mpg combined average in a 1.9 ton vehicle that could do 0-60 mph in about 8 seconds.

Goodish answer - but not to the question that was asked. The question specifically said "ignoring engine efficiencies" - and you're reasoning is all about why the engines might give different efficiencies. On the other hand, you've assumed identical transmission ratios, which wasn't part of the specification. The most likely gear ratios for the efficiencies to be identical is with the smaller engine turning at higher revs. In that case, the losses in the transmission system will almost certainly be lower for the larger engine. Therefore, the answer to the first part of the question as posed is that it is likely (not certain) the car with the large engine will use less fuel. The second part is probably clearer - the small engine should be cheaper, both in money and energy-to-make. However, equal efficiency is not a very likely result* with present engine designs as most two-litre engines are four cylinder, and most 4-litre engines have eight cylinders.
*Unless the vehicle is very large and heavy.

I think a more significant (but difficult) question would really be "what is the optimum size", taking everything into account. In principle, I suspect (but don't know) that a 4-litre, 4-cylinder engine could be at least as efficient as a two-litre engine for both compact and standard size US cars - but they require different gearing than is currently available, and would be revving a great deal slower than the smaller engine. In practice, drivers might not choose to use the higher gears that would take advantage of fuel efficient driving techniques because of vibration and lack of power**.
The potential for high efficiency from this relative size of engine was demonstrated in the "Mobil Economy Runs" in the UK, where 'sub-compact' (US definition) vehicles with 3-litre 4-cylinder engines routinely used less fuel than equivalent vehicles with smaller engines; of course, these were manual transmission vehicles with 'overdrive' gear settings***, so it was practical to reduce the revs. (The US experience reported by taejonkwando in post 54 was not all that different - but four cylinders would doubtless have performed even better)

Fyz

**And of course, it's contrary to the way large engines are marketed...
***I haven't seen an overdrive gear in years...

re:

***I haven't seen an overdrive gear in years...

Actually, in almost all five and six speed manual transmissions, at least the top ratio, and often the top two, are overdrive ratios. This has been true since five speeds came into wide usage (seventies) and this eliminated the need for auxilliary "overdrive" gearboxes. In automatics, most four (and greater) speed automatics have a real overdrive (in addition to the lockup torque converter that was occasionally incorrectly called an overdrive.)

Hi Ken

Thanks for this - I'm glad to be wrong here. It's probably distorted my perception that the last time I drove a car where the fifth gear was an overdrive was back in the 1980s - that was about a factor of 1.2. (Curiously, my recollection is that the update of that model didn't have an overdrive, but was more economical nonetheless)
Perhaps I'd better start looking for a car with a (relatively) large four-cylinder engine and significant overdrive.

Fyz

I agree. I think that with my gearing at 120 Km/hr. (+/-75mph) taching less than 2000 rpm in 6th gear and only 1386Kgs. (3050lbs.) The 3.42 final ratio gives me the best of hard driving, or highway economy. The motor size is only a 5.7L (346ci.) You can run 558/520 and still get over 12.74L/km (30mpg) naturally aspirated if you have the gears. I'll email you a some pics. if you want to get a look.
Transmission 1st Gear 2.97, 2nd Gear 2.07, 3rd Gear 1.43, 4th Gear 1.00, 5th Gear 0.84, 6th Gear 0.56, Reverse 3.28, Final drive 3.42

Yes, a pushrod V8.