While your point is valid about anecdoti Jeff, it remains that efficiency is a function of load and capability. An engine with more torque is going to work less under the same circumstances than one with less.
I recently drove two identical model cars, but one was a 4 cylinder and one was a 6 cylinder. Real world mileage experiences of people who own the 4 cylinder versions are no better than those who own the 6's. I could easily see why when I had a chance to really compare performance. On a stretch of interstate the 4 cylinder had to rev about 500 RMP higher than the 6, to go at the same speed. That 4 was other wise quite impressive in terms of its acceleration, etc. Geared differently to accommodate a poorer torque curve than the 6, and less horsepower, made it at the very best, no better than the 6.
What people here have been saying is that there is real world experience out there on the street that defies the notion that all things being equal a 4 will always be more efficient than a 6. It's simply not true. There's not even reason to believe that it should be true.
Just a point about engines in general. The number or cylinders is only one measure of its characteristics. An Offenhauser 4 cylinder can out perform any GM V-8 ever made and it gets terrible fuel mileage. Engine performance is a function of displacement and efficiency and what the engine was designed to do. High rpm for speed, low rpm for torque, etc.
I know of some 4 cylinder economy cars that can out accelerate vehicles with
8 cylinder engines with superchargers.
Blanket statements that one engine is going to be more economical based on the number of cylinders is just plain wrong.
Actually, they will work the same, because they are putting the same amount of power.
Depends on how it is geared and driven.
But we're not quite on the same page. If you have a car that is not underpowered, it is going to take the same amount of energy to move it from point A to B. However, if if has significantly more power than it needs, more than 150 HP for small car like a Honda Civic, then the mileage will suffer.
Of course, it's not always true. There is no such thing as always.
It takes more energy to turn a bigger engine that a small engine.
Which takes more energy? To turn over big block Ford or the one-cylinder engine on Dad's old lawn tractor? The big block Ford, of course. There's more bearing surfaces to have friction, more air/fuel mixture to compress, a large volume to suck air into.
While it is obvious for a huge engine compared to a small engine, the same principle holds form a 2.0 Litre 4 cyl engine vs. a 2.5 litre six cylinder using the same technology.
However, that doesn't mean that the difference is always going to be huge. The Honda Accord 4 cyl (2.4 litre) only gets about about 2 mpg more mileage than the 6 cyl (3.5 litre). So while the smaller engine is more efficient, it is not hugely more efficient.
There are things you can do to make a engine have higher power output, more all of which get more air or air/fuel mixture into the engine, like more valves per cylinder, which allows more mixture or air to enter the cylinder, add a turbocharger or super charger, which also pushes more air into the cylinder or run the engine at a higher speed, which does the same thing.
And there are things which increase the efficiency, like storing some of the mechanical output of the engine as chemical energy (or electrical energy) which can quickly be converted to mechanical energy via a motor (hybrid), use Atkinson-cycle engine (like the Toyota Prius), use a transmission which is geared well (my car has plenty of power to maintain 70 mph at 2000 RPM, yet the car is geared to run at 3000 RPM, so the engine seems more responsive), particularly one with an infinite number of steps between the highest and lowest ratio (continuously variable transmission, also like the Toyota Prius) and using variable valve timing.
And, of course, how much mileage one gets is determined by how one drives.
I imagine he would have been just fine in a V6. The point was, moving to a smaller engine, with less HP/torque, caused him to need to rev the engine way higher than he would have needed to in the V6 or in an 8.
(For those in southern california, I'm talking about the I-15 Cajon pass.)
I know it freaks me out when I drive my wife's V6 Vue and see the tach go up to four or six thousand rpm. On my truck, the tach rarely goes over 2000 rpm.
I don't know where you get THAT idea. Curb weights on comparable class (ie midsize or fulsize) vehicles have stayed similar or actually gone UP due to all the mandated safety equipment. My wife's 1993 v6 powered car (Eagle Vision) actually weighs a couple hundred pounds more than my 1973 v8 powered car (Plymouth Satellite). But it does get about 10 mpg better, thanks to a locking torque convertor, an extra gear in the transmission, and electronic engine and transmission management.
Bingo. Wow- Lloyd and I agree! Mark this date! :-)
Seriously, putting more gears in the gearbox, cleaning up aerodynamics, AND the advent of the locking torque convertor are worth far more than EFI and weight reduction (which hasn't really happened anyway) combined.
The 2008 Civic only gets 35MPG. The difference is that the '87 car weighs 1000 lbs less due to all the extra safety gear in the '08 car. The honda tech guy was quoted as saying, "rook! Godzirra!" Oh, wait - I meant, he was quoted as saying, "I wouldn't want to get in an
A couple of things there though- the Civic has gotten a class or two larger in size as well. An 87 Civic is more comparable to a Fit today. FAR more comparable. Today's Civic is comparable to an 80s Accord.
And another thing- no way in hell did an 85 Civic actually get 45 mpg anywhere but on an EPA dyno! That POS was lucky to get 30 once it had more than 30k miles on it. And today's Civic, even though larger, would out-accelerate an 87 by a HUGE margin.
MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.