Features/ Tg-explains/ Superchargers…They seem Fancy!

Superchargers…They seem Fancy!

Most of you remember Dom’s 1970 Dodge Challenger R/T from the Fast and Furious movie franchise. Dom’s Challenger certainly caught my fancy when I first saw it. But what made it different from all the other ’70 Challengers out there? I’ll tell you, it was that bad-a** BDS 8-71 roots-style supercharger that Dom installed onto the engine. The chrome intake and the exposed mechanism of the supercharger that pops out of the hood make that car a beauty to behold. It’s a heartbreak that the vehicle had to be destroyed multiple times during the movie series. I could go on for days about that car, but the point was everyone knows what a supercharger can do to vehicles, whether it’s in terms of performance or simple cosmetic terms. But, do you know what it is and how it works? Read more, and you shall know!

A supercharger is a type of forced induction that is mechanically propelled (often by a belt from the engine’s crankshaft). This energy is used to compress the intake gas, moving more air into the engine and producing higher power for the same displacement. Superchargers are essentially air pumps that suction normal air, compresses it using two rotors, and then jam it into the motor to produce gorgeous clouds of tyre smoke.

What’s the history? 

Using compressed air to improve things has been a concept as old as time, and the idea of a twin-rotor air pump has been around since Francis Marion Roots patented the device in 1860. Many pre-World War II racing automobiles, including those by Mercedes, Alfa-Romeo, Bugatti, Bentley, Sunbeam, Miller, and Fiat, utilised spinning rotors powered by the crankshaft to ram compressed air into engines. On the other hand, Mercedes was the first to introduce the notion of supercharged road automobiles in 1921. 

After World War II, a hot-rodder named Barney Navarro was credited with being the first to grab a supercharger and put it to his V8 to improve engine performance back in 1948. The Italmecanicca “S.C.o.T” supercharger, an Italian-made Roots-style supercharger built for compact European engines that matched the smaller-capacity Flathead engine, was the trendiest way to spice them up these days. These vintage Roots superchargers compress the air using two or three-lobe rotors, but they were never intended to add horsepower. They were used as scavenging pumps on diesel engines earlier. Because they weren’t designed to add horsepower to petrol engines, they have a few drawbacks: first, the rotors require a lot of maintenance to ensure they fit tightly to the case walls and adequately compress the air, and second, they massively heat the air being fed into the motor, which can heat soak the engine.

Fuel was supplied above the superchargers in older engines via carburettors or mechanical injection to keep the rotors cold while simultaneously cooling the compressed charge air. Turning those rotors also took power away from the crankshaft, which is why people who bolt giant blowers onto old engines frequently lose control!

As money poured into drag racing in the 1960s and 1970s, the aftermarket began building its superchargers and race-spec parts. By the late 1970s, Top Fuel dragsters, the fastest accelerating land vehicles on the planet, started using new aftermarket superchargers. 

What are the types of Superchargers?
  • Roots-Style Superchargers: Despite their early introduction, their operating principle is basic but clever. The rotors will grab little air at an inlet, trap it due to its form, and carry it to the outlet by meshing two-lobed rotors in an 8-shaped chamber. The air is not compressed; it is transported like a pump. As a result, this supercharger focuses on airflow and how it can move more air than a naturally aspirated engine. A significant low-pressure space will appear at the inlet, considerably more extensive than the one formed by the engine alone, and the outside air will quickly fill it. As a result, the Roots-type supercharger can generate a big low-pressure area at the inlet, which is so large that the outside air does not have enough time to refill, resulting in decreased performance. Similarly, the Roots-type supercharger is ideal for low RPM applications.
  • Twin-Screw Superchargers: Commonly known as Lysholm superchargers, it is an advancement of the Roots-style positive displacement supercharger. Lysholm blowers differ from Roots blowers in using a male and female screw rotor with varying blade counts to compress the air.
  • Centrifugal Superchargers: Before we get into these superchargers, let’s speak about impellers. An impeller is a fan that draws fluid into its core and expels it outside. Nobody knows when the first impeller was invented. Some believe Leonardo Da Vinci invented the impeller, and they were widely employed to ventilate mines in the 17th century. As a result, the operation of a centrifugal supercharger is straightforward. A spherical housing with an outlet houses an impeller. The impeller draws air from the fan side and directs it into the housing. The impeller slows down as the air is released from it. However, the compressor may gather massive amounts of air, significantly raising its pressure. These superchargers are similar to turbocharger compressors, but instead of being spun by exhaust gases, they are rotated by the engine itself. To function appropriately, Centrifugal superchargers must spin at tens of thousands, if not hundreds of thousands, of RPMs. To do this, the impeller employs a high ratio reduction gear. Nonetheless, these superchargers are only effective at high RPMs.
  • Electrical Superchargers: Electric superchargers are far more recent than any other technology discussed thus far. The superchargers are powered by an electric motor rather than the engines themselves. These motors are controlled electronically by various criteria, including load and RPM. Producers can use any of the superchargers mentioned, but centrifugal superchargers are more typically utilised. Given that electric motors already achieve high speeds, employing a reduction gear to attain the tens of thousands of RPMs stated above negates their disadvantage.

As a rule of thumb, superchargers are mostly found on American-born cars, and very low numbers of supercharged cars are available for sale in India. They look damn fine and can elevate the cars multifold in performance and sheer looks.

Words: Sresht Garg

TopGear Magazine Annual Issue 2024