To reach peak levels of performance and efficiency, elite athletes rely on fuel and oxygen to make their bodies work better, faster and stronger. The engines in your car or truck operate the same way.

But there’s one key difference.

Athletes can rely only on conditioning to boost their performance and efficiency over a lifetime of training, achieving small victories and suffering just as many setbacks along the way. Vehicles have an instant advantage to improve the use of fuel and air: turbocharging.

Turbocharging has been enhancing the driveability of Subaru vehicles since 1983, when the GL Turbo Wagon was introduced. Since then, turbocharging has allowed Subaru cars and SUVs to dominate vehicles with much larger engines, and still return outstanding fuel economy.
Turbocharging has been enhancing the driveability of Subaru vehicles since 1983, when the GL Turbo Wagon was introduced. Since then, turbocharging has allowed Subaru cars and SUVs to dominate vehicles with much larger engines, and still return outstanding fuel economy.
 

Turbocharging allows a smaller engine to produce the kind of driving force typically seen in larger engines, minus the massive fuel economy hit. It offers owners the chance to have a fuel-efficient and lower emission engine most of the time, but with power levels similar to a much larger engine on demand.

“The technologies of turbocharging and direct fuel injection work well together, allowing manufacturers to make a smaller engine for improved performance, better fuel economy or both,” says Todd Hill, the Subaru Carline Planning Manager overseeing WRX and WRX STI. “With a smaller displacement turbo engine, drive it normally and you get good fuel economy. Drive aggressively, it consumes more fuel.”

Turbocharger
Turbocharger. Photo: Iaroslav Neliubov / Shutterstock
 

Subaru was one of the earliest manufacturers to recognize the potential of turbocharging in a mainstream vehicle. Originally, it was a technology reserved for wildly expensive exotic cars. Some conventional manufacturers experimented with it as early as the 1960s, but engine management computers that could precisely monitor and adjust fuel and air mixtures wouldn’t come along until the early ’80s. 

As late as the early 1980s, cars still had carburetors, and turbocharging in mass-market automobiles was almost unheard of. Turbochargers began to make sense as electronic fuel injection and engine management computers took hold. Early on, Subaru incorporated turbocharging in its performance products and daily drivers. Where Subaru really made its reputation, though, was combining turbocharging with all-wheel drive.

And that technology is evolving.

“Where we’re headed, there will be more powertrain choices than you’ve ever had.”
— Todd Hill, Subaru Carline Planning Manager

The 2.4-liter turbocharged engine in the all-new Ascent SUV, for example, is configured to feel punchy and provide maximum torque at low RPM, providing brisk acceleration when merging onto a freeway or towing a trailer. Yet the Ascent can deliver up to 27 mpg1 while still producing 260 hp, all on regular unleaded gasoline.

What lies ahead for turbocharging is just as exciting. For Hill, it comes down to providing a right-sized powertrain for differing applications, from compact, fuel-efficient cars to trailer-hauling SUVs to all-out performance cars. “Where we’re headed, there will be more powertrain choices than you’ve ever had,” says Hill. And turbocharging is positioned to play a more integral component in them than ever.

Turbocharging Process
Turbocharging Process

Turbocharging Explained

Whether you’re driving a high-performance vehicle like the WRX or a family hauler like the Ascent SUV, they share basic technologies to get the job done when you hit the gas.

1. Compressed Air, Cooled

It starts with increasing the air into the cylinder to mix with fuel. Bigger engines rely on volume to produce big power; smaller engines can utilize a turbocharger to make up the difference. A compressor sucks in more air after it’s passed through the air filter. That air is then chilled with an intercooler. Cooler air is denser; this matters in the next step.

2. Bang for Your Buck

The cool and compressed air enters the cylinder. The cylinder has a fixed volume (i.e., space inside the cylinder for combustion), but because the air is denser it has higher mass. This allows for a higher fuel flow rate, resulting in more power being produced during combustion.

3. Gas Power

After the fuel is burned in the cylinder, hot gases are forced into the exhaust manifold, where they’re directed up into the turbine inlet. This rush of pressure into the turbine wheel creates rotational force that powers the air compressor and starts the cycle over again. Two devices are also part of this journey of hot gas toward the turbine wheel: The wastegate can bleed off gas before it reaches the turbine wheel, and the blow-off valve releases excess boost pressure trapped in the system when the throttle closes.

Seeing this cycle in practice helps you to understand how turbocharging maximizes power by utilizing spent exhaust gases, which would normally just exit out the exhaust pipe. Turbocharging lived up to its promise once powerful engine management software was able to take full advantage of its benefits.

1 EPA-estimated fuel economy. Actual mileage may vary.