The Ford Mustang Shelby GT500. The Chevrolet Corvette ZR1. The Chevrolet Corvette Z06. The Dodge Challenger and Charger Hellcats. The Dodge Challenger Demon. The Chevrolet Camaro ZL1. All of these cars are top-of-the-line, high performance American muscle cars. And all of them happen to be supercharged. The reason why has less to do with power than with packaging.
There are a variety of ways to make power in an engine. One of them is to make the displacement huge. You know the saying: no replacement for displacement.
Another is turbocharging, rare (outside of Saabs and Porsches) before the days of downsizing but now is extremely common. In these days post-Prius, another route is to add hybrid drive, as in the NSX or the LaFerrari. And then there’s supercharging.
As a quick reminder, a supercharger is an air compressor that crams more air into an internal combustion engine. More air means a greater amount of air and fuel mixture can combust, which produces more work and results in more power. Superchargers are mechanically driven via a belt or a chain that’s connected to the engine’s crankshaft.
A turbocharger, which also crams extra air into the engine’s combustion chamber, does the job with a turbine that is driven by the engine’s exhaust gases. So, because it needs those exhaust gases to pass through first in order to spool up, there is usually a delay in the throttle response. This is known as turbo lag.
The important takeaway here is that superchargers, though lacking any kind of lag, do rely on the engine’s crankshaft to function, so there is some power lost. And turbochargers, though more efficient because they are essentially using spent energy to work, typically come with some turbo lag.
I suspected the lag was part of the reason why the American Big Three decided to take the supercharger route with their cars. What they told me didn’t exactly match my expectations.
Ford
According to Ford, its engineers decided on a supercharger to fit the heritage of the GT500, providing instant throttle response and a high RPM. Since the previous-generation GT500 was also supercharged, it seemed fitting to keep it.
Remember that while a generation of Gen Xers and tuner kids associate turbos with the sounds of power (whether they heard chirping Audi Quattro rally cars or played with boosted Skylines on Gran Turismo), there’s an older muscle crowd that hears the whine of a supercharger as the main calling card of big speed. Think of a massive blower sticking through a hood. Think Mad Max. No surprise that there’s an emotional/heritage side of things for Ford to reference.
The blower gives the 2020 GT500 760 horsepower and 625 lb-ft of torque. It’s quite large.
General Motors
Specifically for Chevrolet and the Corvette, though, superchargers offer a more favorable packaging alternative for the low-hood design.
“A supercharger on a V8 packages very neatly in the valley of the engine. Trying to package turbochargers on V8s in front engine cars is a difficult challenge. There is very little room and it gets complicated very quickly,” Jordan Lee, GM’s global chief engineer of small block engines, explained.
He went on to say immediate throttle response was a desired quality, with the shape of the torque curve defining the character of the engine.
For GM, there really isn’t much of a difference in cost between supercharging and turbocharging. “Both boosting methods are comparably priced on V8s when accounting for all of the ancillaries like exhaust plumbing, intercooling, etc,” Lee continued. “However, on smaller, four-cylinder engines, turbos may be favorable simply because there are not many small-commodity superchargers made for smaller engines.”
Currently, GM’s most powerful car in production is the Chevrolet Corvette ZR1. It makes 755 HP from the LT5 engine, whose supercharger consumes about 100 HP at full boost. “So,” Lee said, “our engine is really making 855 HP at the crank, since 100 HP is used to drive the supercharger.”
Fiat Chrysler
Finally, Jalopnik also got Chris Cowland, FCA’s powertrain director, on the phone to talk supercharging.
He illuminated three driving factors when the company began the Hellcat development program. The first was instantaneous throttle response. The second was a dominant appearance. When you open the hood to a Hellcat engine, you’re greeted by the supercharger sitting wantonly on top of everything. And thirdly, they wanted a signature noise.
“The Apache naturally aspirated 6.4-liter engine has a very recognizable exhaust signature,” Cowland said. “If we were to turbocharge it, the turbine would have taken away some of the pulsations that create the very iconic American V8 sound. We didn’t want that.”
A turbocharger can rob a classic engine’s sound, given that it’s sticking right in the middle of the exhaust. You do get new, exciting turbo sounds, but you lose some of the old-school exhaust note.
“And also the fantastic thing is the supercharger brings a crazy whining noise. We wanted to create an engine... to have this very dominant intake whine. A lot of people think it’s belt noise, but it’s not. It’s from the rotor meshing and pulsations coming from the intake system out of the front of the car. That’s why when it’s coming at you, you hear hear the whine, and when it passes it sounds like a V8.”
For FCA, superchargers are typically “considerably more” expensive than turbochargers. Cowland revealed that a supercharger could cost three times as much as a pair of turbos, and after that you still have to add the front-end drive system. He claims this is why a lot of mainstream cars are turbocharged. It’s more efficient and it’s cheaper.
FCA could have turbocharged the Hemi engine. It would have been easier. The engineers generally get higher boost out of turbocharged units and there would have been no drive loss. As it stands right now, running the Demon’s supercharger at full throttle takes 100 HP. In the Hellcat, it takes 85.
But those engines wouldn’t be what they are if there were turbocharged. Accelerating with one feels like horizontal gravity.
“The Demon has the biggest production supercharger, 2.7-liters per rev,” Cowland told me, “increased from the Hellcat’s 2.38. To get enough air into the Demon, we had to increase the size of the supercharger just to push enough air into the engine.”
Superchargers run hot. In the Demon, there’s a power chiller that uses the car’s air-condition system and refrigerant loop, providing additional coolant ability to drag the temperatures down even further. You can’t run the cabin A/C at the same time that you’re using the power chiller, though. So, you can either be comfortable or you can go fast. This is the Demon way.
It’s interesting that these three companies have decided to keep using superchargers to make power when damn near every other high-performance car has gone either hybrid or turbo. They’re right in that there really isn’t a replacement for the noise and the linear delivery, but these cars aren’t exactly volume-sellers, either.
If it is indeed more expensive to use a supercharger, then I see the logic in only using them for the special stuff and turbocharging all the normal stuff. Probably makes owners feel pretty special, too.
Mercedes-Benz
So let’s move on from America and see how another automaker has treated supercharging over the years.
Everyone’s turbocharging everything now, even Mercedes-Benz, which famously used to supercharge a lot of its engines in the 2000s (the 1.8-, 3.2- and 5.4-liter engines). You always knew a supercharged Benz. It would read Kompressor on it somewhere in blocky silver letters.
When asked why the company made the jump from supercharging to turbocharging, Mercedes senior manager of engine, design and mechanic Ralph Illenberger said,
“Basically, the advantage of a supercharger is the better responsiveness compared to a turbocharger. But, the technology has changed over the last years, so the disadvantage of a turbocharger—the so-called turbo lag—is nearly eliminated.”
“For example, by using the twin-scroll technology or special bearings for the charger, such as we do in our four-liter V8 and in our brand-new four-cylinder as well. Besides increasing the throttle response, one of the main reasons using a turbocharger is its better fuel efficiency. To run a supercharger, a belt is needed, using energy from the crank. The turbocharger just uses the exhaust energy, which at the end is much more efficient by enabling a high power output over a wide range of revs.”
A Mercedes-Benz spokesperson also pointed out the company’s 3.0-liter, inline-six engines in the AMG 53 cars use electric superchargers to supplement the turbochargers, which is neat.
Superchargers are wonderful things. The whine they make is incredible and the provide extremely torquey engine characteristics. And they don’t make the car any quieter.
But as much as I love them, I also think they will soon go in the way of the naturally aspirated engines. They just aren’t efficient enough to keep around, except on the really, really special cars.
Until then, I’ll just sit back and enjoy the whine. It’s the only kind I can stand.