Every hot-rodder and speed demon knows that “there’s no replacement for displacement,” as the saying goes. It means: if you want power, then you need a big area for combustion—regardless of whether or not air is managed with turbocharging or supercharging. However, that idea has been turned on its head by a couple of generations of automotive engineering. Yesterday’s cars might boast 400 cubic inches of displacement (and eight cylinders), but fall behind a three-liter V6 (or smaller) in terms of power to the wheels. Small is the new big.
Here’s the bottom line: gone are the days when engine power was determined solely by its size. More efficient fuel delivery, higher compression ratios, variable valve timing, and on-board computers have enabled engineers to create engines that are as fuel efficient as they are powerful.
The 213 cubic-inch V-6 engine (below) in the new Acura NSX supercar (above) develops 500 horsepower—22 percent more power than the 427 cubic-inch engine in a 1966 big block Chevrolet Corvette.
For example, the 213 cubic-inch V-6 engine in the new Acura NSX supercar develops 500 horsepower and 406 pound-feet of torque—22 percent more power than the 427 cubic-inch engine in a 1966 big block Chevrolet Corvette. The Acura is by no means an isolated example. The same displacement V-6 (see image at the top of this page) in Nissan’s GT-R is rated at 600 horsepower with 481 pound-feet of torque.
“Customers in many segments—especially luxury brand buyers—look for powerful engines to deliver enjoyable driving performance or to haul their families and their stuff,” said Paul Williamsen, national manager of strategic communications for Lexus International. “But powerful engines can have costs including some that don’t appear on the window-sticker: conventional ways of making powerful engines may result in more fuel being consumed, they add weight, which compromises handling, braking, and fuel consumption, and generally produce more emissions.”
Cubes versus Liters
Let’s get our terminology clear so we can compare apples to apples. Since today’s engines are measured in liters as opposed to cubic inches, here’s a basic conversion formula:
One cubic inch is equivalent to 0.01639 liters, or
One liter contains approximately 61 cubic inches
There are plenty of online calculators to make the conversion easy. Do the math, and you’ll discover that the two-liter engines common in modern passenger cars are about one-third the size of the small block V-8s found in similar cars produced 50 years ago.
Why are today’s engines so much more powerful than they were in the 1960s and 70s? Although modern internal combustion blocks operate on the same principles as their predecessors, engineers have reduced inefficiencies due to poor fuel delivery and internal friction.
In the 1960s, a typical fuel pump delivered 8 to 10 psi to the carburetor. Pressures in today’s direct injection fuel systems average about 2,000 psi. (That’s not a typo.) While carburetors relied on engine vacuum to draw air and fuel into the cylinders via the intake valves, direct injection delivers the fuel directly into the combustion chamber, eliminating puddling that reduced fuel economy and increased carbon monoxide emissions out the exhaust.
Today’s Pipsqueak Engines Versus Yesterday’s Muscle Cars
Superchargers and turbochargers in today’s small block engines enhance airflow versus natural aspiration: the industry standard in the muscle car era.
Paul Williamsen explains:
”An exhaust-driven turbine uses normally wasted heat energy from the exhaust to compress additional air into the engine, delivering more power from a smaller engine. Much more advanced than the turbocharged engines of the 1980s and 1990s, modern turbo engines use smaller, faster-spinning turbochargers coupled with very precise computer control of boost pressure to improve drivability while reducing emissions, improving fuel efficiency, and ensuring durability.”
Today’s cars also have higher compression ratios. Before the days of on-board computers, compression ratios in the typical passenger car were relatively low to prevent the possibility of detonation due to pre-ignition. Compression for the ’66 Corvette big block was 10.25:1, which is relatively high for its time.
But that pales compared to the 13:1 compression ratio in Mazda’s two-liter engine that powers the current MX-5 Miata. Thanks to variable valve timing, engineers can more accurately control spark retard and advance, making technology formerly limited to race cars available in today’s passenger cars.
Compression for the ’66 Corvette big block was 10.25:1, but that pales compared to the 13:1 compression ratio in Mazda’s two-liter engine that powers the current MX-5 Miata.
On-board computers have also improved emissions controls, along with better integration into the engine itself. Early exhaust gas recirculation (EGR) systems were a primary culprit for robbing engines produced during the 1970s of power. The purpose of EGR is to reduce oxides of nitrogen (NOx) emissions by recirculating exhaust gas through the engine to reduce combustion temperatures.
Early systems consisted of valves controlled by manifold vacuum that opened when the engine reached operating temperature. In addition to reducing engine power, these systems were known for causing difficult engine starts and rough idling. In today’s engines, EGR is no longer a stand-alone system. The function is integrated into engine design, so spark timing can effectively compensate for the effects of exhaust gases introduced into the engine cylinders.
Oxygen sensors that more efficiently determine the engine’s need for fuel and air according to operating conditions have reduced the amount of toxic exhausts traveling back to the catalytic converter. Three-way catalytic converters have replaced the single chamber designs of the 1970s, eliminating problems with back pressure that interfered with airflow through the engine.
Big-block engines haven’t entirely gone away, but they’ve been relegated to specialized performance variants like Chevrolet’s 650-horsepower Z06 Corvette.
Weight Matters
While the big-block engines of the 1960s delivered more power than small blocks at the time, they were also heavier. Modern small block engines not only create more power but a much better power-to-weight ratio—the secret sauce of scooting down the highway. Use of aluminum and composite engine components further reduces mass under the hood.
Does all of this mean big block engines have been kicked to the curb? Absolutely not. But production is limited to specialized vehicles such as Dodge’s Hellcat series and Chevrolet’s 650-horsepower Z06 Corvette. Enthusiasts who purchase these cars are willing to pay the gas-guzzler tax for bragging rights on the track.
But in our day-to-day red-light-to-red light society, small is powerful.