True, if hugely embarrassing, story: When I was in first grade, I wanted to find out a little bit about the Vietnam War, since my former-Marine father had been a participant but wasn’t exactly verbose on the topic when questioned. I went to the library, checked out a grownup book, and read a sentence about the “gas-operated M16 and its jamming problems.” I interpreted to mean that the rifle had a tiny model-aircraft-style engine in it that gave it fully-automatic firing capacity. I retained this delusion all the way to my first day as a cadet in the Civil Air Patrol a few years later, at which point I was lampooned, and rightly so, for expressing it.
Go ahead and laugh at me as well—but how many of you have read something about the famous Coventry Climax engine being a “fire pump”? Were you utterly, if temporarily, confused? Did you know what that meant? Did you think it was an engine for a fire engine? It’s not, of course. It’s just what it says it is. It’s a fire pump. Have you ever actually seen a fire pump? They’re fascinating devices, and the Coventry Climax ones are particularly so because, hey, it’s a racing engine being used to pump water.
The Coventry Climax FW weighed 180 pounds bare, because it needed to be capable of transport by (a few pairs of) hands. Compare that to the 640-plus pounds for a Chevy “rat motor” and you can see that only one of the two could possibly be used for fire pump duty. Nor would you want to put a 454 in a mid-engine Lotus formula car; the handling balance would be best described as “challenging.”
Once we get into the world of everyday vehicles, however, the issue isn’t quite so cut and dried. Or it shouldn’t be, anyway. Most of us are thoroughly familiar with the generally-accepted history of how Detroit’s big-cubic-inch “dinosaurs” were humiliated by the “advanced” high-revving, small-bore engines of the German and Japanese competition. The overhead-camshaft wonders from overseas got moped-like fuel mileage, revved to motorcycle speeds, developed thrilling power, and never, ever, experienced any reliability issues… right?
The truth was a lot more complicated than that, of course. The former Axis powers (and the Coventry Climax-using Brits) relied on high-strung inline-fours and the like as an unintended consequence of fairly stringent postwar taxation on vehicle size, engine capacity, and fuel usage. It’s not that anyone wanted to power their 5-Series sedan with a 1.6-liter four-banger—it’s that such an arrangement was often the only way prospective buyers could manage to afford both the car and its associated tax burden. The most absurd example of this philosophy which comes easily to mind is the two-liter Ferrari 208. Can you imagine being able to afford a new Ferrari and at the same time being legitimately afraid of the tax bill that accompanied a three-liter engine?
This state of affairs didn’t last forever. Everyone from Honda to Jaguar provided progressively larger and lazier engines as time went on, both for our market and for the folks back home. At the same time, Detroit was building the “Quad Four” and the twin-cam Chrysler engines, even as Ford used its partnership with Mazda to create a mid-’90s Escort GT that could match the 16-valve GTI and Corolla GT-S rev for rev. There was a brief period of time—let’s call it Peak Engine—when you could get a relatively large 32-valve V-8 in everything from FWD domestic sedans to M3-class ‘bahn-burners to Lincoln Navigators to the Lexus LS which instigated the arms race to begin with.
Today, much of that glorious hardware is gone, replaced by prosaic four-bangers and commodity-grade V-6s with long strokes, low redlines, and computer-controlled turbochargers to make the whole mess palatable. I have a particular hatred for the generic two-liter turbo four which seems to power every single car under $100,000 nowadays. Sometimes I think their flat torque curves and asthmatic high-rpm behavior represent a deliberate attempt to get us used to the oft-predicted anodyne future of mandatory electrification, the same way an automaker will often facelift an existing car to slightly resemble its impending replacement.
Before we go gently into that good night, however, I want to poll the Hagerty readership and get your thoughts. What’s the superior approach to engine construction: large swept area and low revs, or short-stroke tachometer-pegging exuberance? Everything’s relative, of course; we could be talking Corvette vs. S2000, or we could be pitting my cherished Kawasaki ZX-14R against the BMW S1000RR. Given the choice, would you rather twist or rev?
I took a brief and very amateurish look into the physics of combustion chambers and whatnot. What I discovered was this: The longer you take in a combustion cycle—in other words, the slower you turn the crank—the more power you lose to the cylinder head and engine block in the form of waste heat. A larger combustion chamber exaggerates this effect. So if all else were equal, a 10-liter engine spinning at 1000 rpm would be less efficient than a one-liter engine spinning at 10,000 rpm. This is irrespective of throttle opening and airflow, by the way.
Ah, but in the real world, you can’t ignore the fact that lower throttle openings are inherently less efficient. So the little 125cc Honda Grom with its throttle twisted wide open at 65 mph gets three times the mileage of my 1441-cc Kawasaki using just a tiny amount of opening to travel at the same speed. True, the Grom is absolutely tapped out at 65 while the ZX-14R will smack its 186 mph limiter hard enough to bop your faceplate against the windshield—but in a world where we had no expectation of traveling at triple digits, even for a moment, you’d be foolish to pick the larger, heavier option.
So far, it looks like the little engines have everything their own way and that our European cousins were, in fact, on the right track—but wait, there’s more. You can’t discount the effects of friction, which increase nontrivially as piston and crank speeds increase. And while you’re using less raw material to make a small engine, it often needs to be considerably more expensive stuff. There are no titanium connecting rods in an old Cadillac 500 V-8, because you don’t need to rev it to the point where the inertia of a connecting rod becomes a major issue.
The faster an engine spins, the more difficult it is to get the combustion chambers properly filled in the allotted time, which leads to expensive and complex arrangements for intake and exhaust. Using that Cadillac 500 as an example again: it doesn’t need four valves per cylinder and it doesn’t need coffee-can exhausts, because there’s plenty of time to get the air in and out. As a consequence, your powerplant is cheaper and easier to assemble and service. This made a big difference 50 years ago, but in 2019, the engine is no longer the primary determinant of vehicle cost.
It is, however, still a major factor in vehicle packaging. You couldn’t have miracles of space efficiency like the Smart, the non-electric variants of the Mitsubishi “i,” or the Toyota iQ if you had to use a small-block Ford to power the things. Big engines are heavy, of course, but they also require more steel, rubber, and airspace around them. Look at a Viper and a Porsche 911 if you want an illustration of this.
I’m inclined to give the win to small, high-revving engines based on their efficiency and packaging advantages. There’s just one little problem, and it’s this: Bigger, lazier engines simply work better in the real world. They’re easier to drive in traffic, particularly if you’re the kind of driver who likes having a clutch pedal. Their emphasis on low-end torque makes them a pleasure to operate in hilly terrain. Last but certainly not least, they are easier on the ears, the mind, and the soul. This is doubly true when long distances are involved.
Let’s say that the small-bore solution is technically correct, but the big engine addresses our human needs in a way that is difficult to describe with charts and figures. Which is not to say that it’s not thrilling to wind a Yamaha R6 or an AP1-generation Honda S2000 all the way to the redline, because it is—but it’s equally thrilling to listen to a Corvette or Viper growl its way down Mid-Ohio’s back straight.
If the above statement is really correct, then why do so many of us hate the modern low-rev turbo engines? They offer an ersatz sort of big-bore behavior while also providing a tiny bit of 6000-rpm theatrics. What’s not to like? After some further contemplation, I think it goes back to human factors. These two-liter turds never really sound like they enjoy their job. They groan at the low end and they moan at the high. Their computer-controlled torque lacks the arrogant muscle of a big-block V-8 while their long-stroke emphysema fails to satisfy the way a proper naturally-aspirated high-rev engine can.
In short, the big engines might be inefficient while the small ones might cause weariness, but the modern turbos are good at precisely nothing which truly matters. I could quote Scripture here; I think Revelation 3:16 applies. Or I could confuse future generations of Civil Air Patrol cadets by saying this: it’s gratifying to have a big engine, and it can be thrilling to have a fast-revving one, but the modern four-cylinder turbo is the worst of both worlds and is probably the least lovable gas-operated option—except, of course, for the M-16.