Turbocharging has taken over the world. Automakers adopted the technology induction in the name of downsizing and efficiency, and it’s quickly become the go-to method of aspiration. The supercharger, meanwhile, is practically extinct.
But it may not stay that way; a supercharger renaissance is brewing.
Photo by: Valeo
Valeo Electric Supercharger
The problem with superchargers is finding the power to drive them. Turbos are powered by energy that would’ve otherwise been wasted by the exit of exhaust gases, which makes them the most efficient option for added boost.
Superchargers, on the other hand, are historically driven from the crankshaft. They take a certain amount of power to spin, which lowers the engine’s total efficiency while increasing output. The solution is mitigating those weaknesses, which means maximizing a supercharger’s base efficiency and getting the most out of the relatively inefficient power it provides.
Sadly, the future doesn’t look all that bright for fans of the traditional roots-type supercharger. Lobe-type air pumps have come a long way from their humble beginnings of ventilating mineshafts and blast furnaces in the 19th century. Outside of a few niche applications like providing metered airflow for hydrogen fuel cells, the juice simply isn’t worth the squeeze.
Photo by: Roush Performance
Ford F-150 Roush Supercharger Kit
But superchargers are part of a larger system, and as the rest of that system improves, we can take advantage of less flexible but more efficient types of superchargers. I’m speaking, of course, about centrifugal blowers.
Centrifugals have been around for a long time, but their historically peaky nature has translated to little relevance outside of motorsports. That said, their maximum efficiency is superior to other types of superchargers, and if you can keep them in that efficient region, they’re your best choice.
This is where the road forks. Keeping a centrifugal near peak efficiency means adjusting the system around it, and there are a few ways to do this.
The more conventional route is combining the supercharged engine with a multi-speed transmission. That’s not unusual. But with the advent of eight-, nine-, and 10-speed gearboxes, this method proves particularly effective. Those automatics keep engines in their most efficient ranges more effectively. This mitigates the peakiness and keeps a centrifugal working optimally.
A continuously variable transmission (CVT) would be even better, but we don’t talk about those.
Centrifugals have been around for a long time, but their historically peaky nature has translated to little relevance outside of motorsports.
While impractical for automobiles, transmissions attached directly to superchargers were very common in piston-driven aircraft during World War II. As the altitude rose and the air thinned, the supercharger needed to spin faster to keep up the boost. These transmissions had a variety of designs, and late in the war, they became essential for high-performance fighters and bombers.
These days, while adding a transmission to a car’s supercharger is not practical—although admittedly tantalizing—engineers have effectively made it happen anyway. I’m referring, of course, to electric superchargers.
Electric superchargers on production cars are centrifugal designs, due to their inherent efficiency advantage. In many ways, they’re far more flexible than turbochargers (for the record, electric turbochargers do exist, but that’s not what we’re talking about here.) An electric supercharger doesn’t require a drive system that leeches off the engine power and there are seemingly endless ways to acquire the energy to run it. If you can get some electricity onboard, you too can enjoy the fruits of forced induction.
Photo by: Mercedes-Benz
Mercedes-Benz Electric Turbocharger
Mercedes-Benz is the biggest proponent of this technology in cars like the C43 AMG. When combined with a hybrid system that gathers waste energy under braking, the setup is extremely flexible and essentially provides free boost on demand. And this tech isn’t just limited to OEMs. There are groups of enthusiasts building their own electric superchargers, and a growing aftermarket.
You don’t even need a proper hybrid system to drive them, either. Some drag racers use a small independent battery bank in the trunk to store the necessary energy. This pack is then recharged between passes. I know, enthusiasts don’t want to charge their cars—but juicing up a supercharger is a different story.
As automakers build more electric cars, they ironically gain the knowledge, resources, and suppliers to develop electric superchargers. Driving an electric motor requires very similar expertise and componentry regardless of what it’s spinning. Likewise, a lower development budget for ICE cars could lead to a push for modularity across platforms. A system that can be easily adapted to several engines would be advantageous, especially one that doesn’t require the hard-tooled plumbing of a turbocharger. With the growing popularity of hybrids, many cars already have the onboard power necessary to support such a system.
As automakers build more electric cars, they ironically gain the knowledge, resources, and suppliers to develop electric superchargers.
Ultimately the key hold-up for this technology is cost. Electric superchargers require their own compact, powerful motors and inverters. Both of these items often require dedicated cooling. In this context, using traditional centrifugally supercharged engines with eight or 10-speed transmissions seems like a better option, especially if the supercharger can be clutched to reduce load when it’s out of boost in day-to-day driving.
We’ll just have to wait and see if the centrifugal can finally take back the performance crown from the ubiquitous turbo. Let’s hope it does, even if other types of superchargers might be relegated to the aftermarket.
Exhaust notes everywhere will be thankful.
