The machine that became the supercharger predates the practical internal-combustion car by decades. Created by brothers Philander and Francis Roots, the Roots Blower was born out of an attempt to make a better water wheel. The brothers developed a mechanism with two lobed impellers meshed together and spun in opposite directions. When testing the machine, so the story goes, it blew someone’s hat off and they realized they’d accidentally made something very good at moving air.
The Roots Blower was patented in 1860 and the original drawings, credited to Philander, show impellers with two, three, and four lobes, but the principles are the same regardless.
Low-pressure fluid—such as air—enters at one end, and the rotation of the two impellers increases the pressure within the system, forcing the fluid out the other end. The rotation of the impellers ensures that no fluid escapes back in the other direction. Initially, this blower was used in blast furnaces, then for mine-shaft ventilation, and even in New York City’s first subway system.
Corky Bell in his book Supercharged! writes that in the 1870s, German inventor Henrich Krigar designed a twin-rotor air compressor of his own. Instead of using two lobed impellers, Krigar’s used two screws, one with concave threads, one with convex threads.
Unsurprisingly, neither was designed with the automobile in mind, or even internal-combustion engines. Soon, however, engineers recognized their potential. Rudolf Diesel used Roots-type superchargers on his eponymous compression-ignition engines of the late 1890s, and around the turn of the century various engineers created the first blown four-stroke gas engines. Per Motor Sport, Louis Renault—yes, that Renault—patented a device to force more air through a carburetor in 1902, and in 1908, American racer Lee Chadwick won a hillclimb with a car featuring a centrifugal supercharger.
The benefits of a supercharger then were the same then as they are now. If you get more air into the combustion chamber, you can make more power. And they operated on the same principles as today’s superchargers, with a belt driven off the engine spinning the supercharger compressor.
While automotive engineers continued to experiment with superchargers in the beginning of the 20th century, the breakout of World War I accelerated their development. BMW—setting a precedent for decades to come—favored naturally aspirated straight-sixes, but Mercedes used Roots-type superchargers in its powerplants. After the war, Mercedes put the first supercharged road cars into production, the 6/25 HP and the 10/40 HP.
A GM engineer writing in a 1926 SAE journal described the supercharged Mercedes thusly:
“The analysis and comparison of power curves show that acceleration from 10 to 30 m.p.h. is much more rapid with the supercharger, in both high and intermediate gear the maximum speed is increased from 40 to 50 per cent, the unsupercharged engine has the characteristics of a low-speed engine and the supercharged engine those of a high-speed engine, the size of the manifolds and valves has been reduced, the supercharger maintains approximately 100-per cent volumetric efficiency at maximum engine speed, and the thermal efficiency is increased. Power required to drive the supercharger is calculated to be 10.1 hp.”
Nearly a century ago, the benefits of the supercharged engine were obvious, but so too was one of its main drawbacks—parasitic loss. Being belt, chain, or gear driven off the engine, the supercharger is always producing a drag on the engine. An exhaust-gas turbocharger, while suffering from lag, doesn’t have this problem. Still, it would be decades before the turbocharger became a viable solution for automotive engines, so the supercharger was the favored power-boosting device.
Following Mercedes, superchargers started showing up on all sorts of high-end sports, racing, and touring cars. In Europe, there was Bugatti, Alfa Romeo, Aburn, Cord, and perhaps most famously, Bentley. The Bentley Blower never won Le Mans, and company founder W.O. Bentley hated the car. Still, the Blower, with its roots-type supercharger sitting ahead of the radiator grille became an icon. Also in the 1930s, Swedish inventor Alf Lysholm developed Henrich Kragar’s twin-screw air compressor into a supercharger.
Later came Nazi Germany’s grand prix cars from Auto Union and Mercedes-Benz, which used supercharging to generate huge horsepower. Naturally, this technology played a huge part in World War II, and as a history from the Pearl Harbor Aviation Museum notes, all combat aircraft relied on forced induction. Even then, engineers knew the advantages of turbocharging over supercharging, but the materials science of the day wasn’t up to the task. So, supercharging ruled.
After the second Great War, supercharging all but disappeared from production road cars. In Grand Prix racing, Formula 1 regulations effectively banned supercharging in 1954, limiting displacement of forced-induction engines to just 750cc. Yet, the supercharger wasn’t dead. California hot rodders used Roots blowers to get huge power out of their Flathead Fords and small-block Chevy. Companies like Judson and Paxton also made centrifugal supercharger kits for all sorts of cars, from Beetles to Mustangs.
Yet only with a handful of exceptions—the Studebaker Avanti, for one—automakers didn’t start offering factory supercharged cars in a major way for another few decades. Lancia, the Italian automaker that always did things differently, came out with the Beta Volumex in 1983, which was likely the first major OEM to re-embrace supercharging. It used a Roots-type supercharger to provide 6 PSI of boost, which was really just to enable better low- and medium-speed performance for an engine with aggressive camshafts meant for high revs. A few years later came the Toyota MR2 Supercharged, which also used a Roots-type blower. Car and Driver noted in a 1988 road test that its performance matched that of the far more expensive and larger-engined Porsche 944S.
By the end of the 1980s, there was also the Ford Thunderbird Super Coupe, which added a Roots blower to Ford’s long running Essex V-6, and VW had launched its own type of supercharger. Called the G-Lader, VW’s blower used two spiral shaped scrolls, one fixed, one rotating on an eccentric shaft to develop boost pressure. It was a novel idea that was in theory more efficient, but unreliable, so VW phased it out in favor of the naturally aspirated VR-6 engine.
In the 1990s, even more supercharged cars came about. Jaguar, and by proxy, Aston Martin introduced supercharged straight-sixes, and Mercedes returned to an old area of expertise with the SLK Kompressor. All the while, superchargers were getting more popular as an aftermarket solution, on everything from Miatas to Corvettes.
At the turn of the millennium, Ford got into supercharging in a big, big way. The blown F-150 SVT Lightning arrived first in 1999, then came the Terminator Mustang. At least partially in response to the controversy over the less-powerful-than-advertised 1999 Cobra, Ford’s SVT division put a Eaton M112 Roots-type blower and four-valve heads on a Mustang Cobra for 2003 and created a 390-hp monster. One year later, Ford’s blown V-8 showed up in the middle of the GT supercar, and with 550 hp, it blew the bloody doors off the Ferrari F430 and all other comers.
For these high-performance applications, the supercharger made sense. You got incredible engine response at all engine speeds, and way more power for a given displacement. And it wasn’t just Ford. Jaguar supercharged its V-8 (which, admittedly, was paid for by Ford), and Mercedes came out with twin-screw compressors for various AMG models.
GM finally entered the fray in 2009 with the Corvette ZR-1 and its 638-hp LS9, and the similar LSA, which was used in the Cadillac CTS-V and Camaro ZR-1. A horsepower war was well and truly underway, with Ford responding a few years later with the evocatively named “Trinity,” a nuclear option if there ever was one. In the 2013 Shelby GT500, this 5.8-liter V-8 used a twin-screw Eaton supercharger for 662 horsepower and 631 lb-ft. Then two years later, came the Hellcat.
Dodge’s 6.2-liter supercharged V-8 arrived in 2014 with 707 horsepower. Car enthusiasts lost their minds. Seven-hundred-plus horsepower out of an American muscle car, available at a local dealer, with a warranty, for well under $100,000. Dodge then put the engine in basically everything, and GM and Ford responded with 700-plus-hp supercharged V-8s of their own.
But, these were beasts out of their time. There’s a reason you see superchargers in high-performance cars, and really nowhere else. A turbocharger does basically the same thing as a supercharger, without a fuel-economy penalty. Sure, if you’re running a turbocharged engine to its maximum, using full boost all the time, it’ll use a lot of fuel. But off boost, there’s no huge downside to having a turbocharger. A supercharger is always draining on the engine, even at idle. Enthusiasts might not mind that, but regulators certainly do.
GM’s supercharged V-8 survives in the Cadillac CT5-V Blackwing, yet it won’t make another, as the next Corvette ZR-1 will likely be turbocharged. Ford has committed to V-8s in the Mustang, and its blown engine will go in the upcoming GTD. Jaguar Land Rover is phasing out its old supercharged V-8 in favor of a BMW-sourced twin-turbo mill. Volvo has a turbo- and supercharged four-cylinder, yet the company is going all electric. Mazda uses a clutched supercharger to generate a lean air-fuel mixture in its innovative SkyActiv-X engine, though that is starting to feel like a technological dead end. And Dodge retired the Hellcat last year.
The pros of turbocharging over supercharging aren’t new either. It’s just that supercharging was the right technology for various points and places in history, when and where fuel economy wasn’t an issue, the supercharger found a home. At this point, however, it’s likely up to enthusiasts and the aftermarket to keep the supercharger going. Will it make its 200th anniversary?
