Engine: power, forced induction, cooling
Now that you’ve laid the groundwork, it’s time to pour in the power. There are numerous ways to increase engine output, which could comprise its own article, but I’ll focus on a few popular methods. Forced induction is one of the most common ways to quickly boost engine performance. Superchargers and Turbochargers approach injecting air into an engine in different ways and with unique results.
A turbocharger spins a turbine wheel via exhaust gases that’s connected to a compressor wheel. The resulting pressure is regulated by electronic controllers and a release valve and then funneled back into an engine.
With greater power comes greater…heat, and that’s why performance cars commonly have upgraded cooling systems.
Some automakers choose to use superchargers instead, because they have virtually zero lag time between throttle and boost pressure. This is because a supercharger is constantly spinning to match the engine speed. Why would anyone use turbochargers when a supercharger doesn’t have a delay? One drawback to a supercharger is the fact that it requires engine torque to operate, and therefore robs some power from the engine, and is also not as fuel-frugal.
Presently, automakers either use superchargers on high-horsepower vehicles like the Dodge Challenger SRT Hellcat, or in combination with a turbocharger to create a more efficient setup, like on Volvo’s new 2.0-liter turbocharged and supercharged four-cylinder. There are a few types of supercharger systems. A Roots-style supercharger uses paddles on two rotating drums to push air into the intake. The benefit to this system is that the compressor can produce the same pressure at any engine speed.
Another style of supercharger is the screw-type system, which produces cooler air that a roots supercharger. Finally, there’s the centrifugal style supercharger, which looks like a turbocharger to most people. This system has better thermal efficiency than a roots supercharger, is more compact, and pairs better with an intercooler. Automakers most commonly use twin-screw or “twin-scroll” superchargers which enable instant boost pressure.
With greater power comes greater…heat, and that’s why performance cars commonly have upgraded cooling systems when compared to a standard vehicle. The best method for cooling when using a forced induction system is through an intercooler, which takes the hot air released from a turbocharger or supercharger and cools it (most commonly with liquid) before applying it to the engine. Another method of cooling the engine is through water injection. Water and methanol are mixed and sprayed into the compressed air to not just add power but to cool the system so more air can be funneled in.
Two other common ways to add power are to install a high-flow exhaust system, which lets exhaust gases escape easier and therefore limits back-pressure or an air intake system, which lets cooler air funnel into the engine in greater quantities.
Beyond these methods, automakers employ performance cam shafts, which increase the duration and timing of valve openings during the engine stroke or add upgraded headers, which more efficiently allow exhaust gases to escape (likely to a higher-flow exhaust system). The list of other possible enhancements to an engine or exhaust system is long, but just as important as any power-adding system is proper tuning of the ECU (engine control unit). Whenever something is modified under the hood, tuning the ECU for optimal performance is essential to getting actual output gains.
Transmission: auto or manual, shifting times
Once you’ve leveled up under the hood, it’s time to get that power to the ground. There are several categories of transmissions these days, and while enthusiasts (myself included) will defend the manual transmission to our dying breaths, the fact is that semi-automatic and full automatic transmissions within high performance vehicles shift faster and, in some cases, more intelligently that man ever will with a manual.
Enthusiasts (myself included) will defend the manual gearbox to our last breath, but the fact is that automatic transmissions shift faster than we ever will.
Basic automatic transmissions have been around single the 1920s, but at this stage, they offer eight gears (or more) and can move between those gears incredibly quick. In mid-level performance vehicles, automatics usually come with manual controls, letting the driver toggle between gears via steering-wheel-mounted paddles or via the gear selector. Worth mentioning is the growing popularity of CVT (Continuously Variable Transmissions). While these are almost never used on high performance vehicles, they are more efficient than automatics because they create a virtually limitless range of gear ratios via adjustable pulleys.
The non-manual transmission of choice for performance vehicles is a dual-clutch (DCT) gearbox. Pioneered in race cars, these transmissions combine the control of a manual with the efficiency of an automatic and the precision of a computer. Two clutches are used to change gears by pre-loading half the available gears on one clutch and the other half on the other clutch. This reduces shift times dramatically, whether the driver is shifting via paddles or whether the computer is controlling shifts in fully automatic guise.
Another benefit of this system is that the computer can analyze driver behavior to optimize gear changes based on how it estimates the vehicle will be driven (to the redline or just to an early shift point). Not only is a dual-clutch the fastest automated transmission (shifting in fractions of a second), it’s also the smoothest.
Aerodynamics are critically important in racing, where downforce at high speeds keeps a vehicle planted to the road instead of sailing through the air. As road cars near and sometimes surpass race car performance levels, automakers have needed to incorporate aerodynamic principles in production models.
There are two general types of aerodynamics: static and active. Static aerodynamics are either non-adjustable fixtures like a side skirt or hood, or require manual adjustment like some rear spoilers or front splitters. Active aerodynamics uses sensors to adjust the pitch and deployment of aero elements based on available grip or vehicle speeds. Not only do aerodynamics create much-needed downforce at speed, they help reduce the coefficient of drag on a car to let it slice through the air easier. It’s all about controlling airflow through and around a car.
Both underbody and top-of-body aerodynamics play into how efficiently a performance car moves through the air. Flattened underbodies help channel air quickly beneath the vehicle, as opposed to open sections which gain resistance to airflow as speeds rise. In terms of overall vehicle design, smooth curves and channels (like behind wheels and along a car’s hood) help manage airflow. For a vehicle to be fast straight from the factory, it will have undergone hours of wind tunnel testing to assure its design is as streamlined as possible.
Low-drag designs minimize air resistance, but downforce components keep all four wheels on the ground. That’s where front splitters, rear spoilers, and winglets come in. These “add-ons” manage vehicle lift at speeds (not like 100 mph, more like 200 mph). For this reason, though they look cool, most cars that aren’t engineered with aero elements from the factory don’t need them (sorry, tuner cars).
There are nearly limitless modification options to increase performance, which is why the aftermarket industry is so successful, but these core ingredients are employed by every automaker that develops a performance model. With the fear that this would turn into a novel, I did not mention elements like limited-slip differentials, traction control systems, torque vectoring, steering responsiveness, chassis stiffening methods, and more, but those are impact the driving experience to a certain degree.
Every cocktail has its own flavor profile. Some automakers and enthusiasts like to live dangerously with high-horsepower, oversteer-prone muscle cars, and others develop ultra light roadsters that feel at home on a technical road, but struggle on the straights. There are thousands of recipes to choose from; it’s all a matter of taste.