I took my ’76 Trans Am out yesterday. I needed a reboot, and it needed exercise.
Drove the orange-painted, screaming, chickened “gas guzzler” around for about an hour, taking my usual route out and back. Full tank when I left. When I got done, I refilled at my local Marathon. I used about 4 gallons to travel about 60 miles, so about 15 miles per gallon, given the car’s 21-gallon fuel capacity.
The 2021 Hyundai Veloster N press car I’ve been driving around all week (reviewed here) averaged 24.3 MPG, according to its computer.
Forty-five years is a long time. But it’s not that much of a difference, particularly when considering everything that has changed over the 45 years that separates a car like my old “gas guzzler” from a new car like the Veloster.
My Trans-Am’s V8 has twice as many cylinders as the Veloster’s four-cylinder engine and is nearly four times the displacement (7.5-liters vs. 2.0-liters).
The Trans-Am’s V8 has a big four-barrel carburetor that literally drips fuel on purpose into the engine, uncontrolled by any computer.
The Veloster’s engine (like almost all new engines) is fed fuel with great precision under extremely high pressure by a computer that controls four injectors, each of them screwed directly into one of the engine’s four cylinders. The fuel doesn’t drip into a warren of runners in a manifold and gets sucked into the cylinders eventually–not all of it–by negative air pressure, as is the case within my Trans-Am’s engine.
The Veloster has a state-of-the-art dual-clutch automated manual transmission with eight forward speeds. Three of them are overdrive gears used to improve fuel economy by reducing engine operating speed at highway speeds.
My Trans-Am has been upgraded with a four-speed automatic transmission with one overdrive gear.
The old Pontiac weighs about 3,800 pounds (or nearly two tons), chiefly because its V8 is made of heavy cast iron and sits on a bolted-in steel subframe–very similar to what you’d find underneath a 4×4 pick-up truck.
None of the front suspension parts are made of aluminum.
The hood and all exterior body panels are made of heavy metal literally. There is a cast iron rear axle out back, perched on steel leaf springs, also like a 4×4 truck’s. Taking off the hood requires at least two strong men and a pair of stamped steel hinges with big coil springs to support it when installed.
All four wheels are steel, too.
The Veloster, a much smaller car, weighs 2,987 pounds, nearly 1,000 pounds less. Its engine is fourth of the physical size and made of aluminum. Many of its suspension components are also made of aluminum, as are all four ultra-lightweight wheels. It doesn’t even have a rear axle since it is a front-wheel drive.
It does not have a bolted-on subframe. Instead, the Veloster has an integrated unibody specifically designed to eliminate the weight of the bolted-on subframe that used to be commonplace in cars (at least, American cars). Its hood is so thin and light a man (just one) could bend it with his bare hands. It is so light that all that’s needed to support its weight is a pencil-thin prop rod, as is commonplace in almost all new cars.
One could go on.
The point here is that despite all of these advantages (much lighter weight, much less engine, and much more in the way of technology, including an engine management system that micromanages fuel/spark and every other parameter to maximize the MPGs), the 45-years-newer car only manages to deliver about ten mpg better than a literal antique car without any of those advantages.
It makes one wonder what a car such as the Trans-Am might be capable of if it had some of those advantages and not even all the way. For example, a basic fuel injection system such as those that can be easily retrofitted to old cars like mine. Not direct injection like the Veloster’s, a hugely complex system that would require redesigning the old Pontiac’s engine to install it. Just a simple, bolt-on throttle body-type system.
The MPG difference would likely decrease to eight mpg and maybe even less.
It makes one wonder why new cars like the Veloster use so much gas relative to the gas used by old gas guzzlers like my Trans-Am.
The answer isn’t mysterious. It’s physics.
My Trans-Am’s engine makes horsepower the old-fashioned way via displacement. Initially, it made just 200 horsepower. I made some upgrades–a performance camshaft the primary difference–that increased its output to around 275 and perhaps 300 horsepower. This happens to be about the same as the Veloster N’s 2.0-liter turbocharged engine makes.
My Trans-Am’s big-displacement V8 can draw in a lot of air with a lot of room inside its coffee-can-sized cylinders.
The Veloster’s little four is force-fed air, stuffed into its much smaller cylinders via the pressure of 20-something pounds of turbocharged boost.
For a small engine like the Veloster’s to make the power of a big engine, its effective displacement must be comparable to that of a physically larger displacement engine.
This makes them bigger, or rather, it enables them to take in more air (and fuel).
No matter how you make your horsepower, in other words, it takes the same energy (fuel and air) to make it.
Hypothetically, the little turbocharged engine can deliver more than a 10 MPG difference vs. a much bigger engine like my Trans-Am’s engine, which is always a big-displacement engine.
My Trans-Am rarely gets more than 15 or so MPGs.
The Trans-Am’s guzzling is more honest in this respect. The Veloster can get as much as 33 or so MPGs on the highway, provided it’s not on boost. But that requires a light foot. As soon as you dial up the boost, down go the MPGs, which means the mileage potential is more hypothetical than actual.
It’s also more relaxed.
That big engine doesn’t have to work as hard to make horsepower, and it is without question under a lot less pressure. Its pistons, connecting rods, bearings, and so on aren’t being stressed nearly as much, not just because they aren’t under as much pressure. The smaller engine’s smaller parts have less material, including the surface area to absorb all of the stress imparted by that boost.
My Trans-Am’s engine has had one rebuild in 45 years. How will these heavily turbocharged engines fare over the next 45 years?
One wonders whether any real gains have been made.
Eric Peters lives in Virginia and enjoys driving cars and motorcycles. In the past, Eric worked as a car journalist for many prominent mainstream media outlets. Currently, he focuses his time writing auto history books, reviewing cars, and blogging about cars+ for his website EricPetersAutos.com.
Editor’s Note: The opinions expressed in this article are those of the author.
