This is the exhaust turbine side of a turbocharger. Hot, fast moving exhaust gasses enter into the housing at the flange at the bottom of the image above. The gasses flow around and through the pinwheel-like exhaust turbine and exit via the hole in the center of the image. Energy is converted from energy in the exhaust gasses into mechanical energy of the spinning turbine. The exhaust turbine’s center shaft is connected to the intake air compressor on the other side of the turbo. Photo courtesy of Precision Turbo & Engine.

Turbochargers contain two turbines (think two pinwheels) on a common shaft. One turbine is plumbed into the exhaust system and the other into the intake system. Hot exhaust gas flowing at high velocity is routed through the exhaust side turbine and spins the turbo at high speed. On the other side of the shaft another turbine, the compressor, is spinning and compressing incoming air that is then forced into the engine.

This is the intake compressor side of the turbo. The turbine visible in the center is spun at high speed by the spinning exhaust turbine on the other side. Outside atmospheric pressure air enters the compressor in the center of the housing, and pressurized air is collected in the scroll around the outside of the housing and boosted air is fed to the engine via the outlet on the lower left of the image. Photo courtesy of Precision Turbo & Engine.

Auto manufacturers are beginning to have a love affair with turbos for smaller engines. This is due to the efficiency inherent in the turbocharger design. To some degree, the energy to drive the turbo is “free.” The engine is already producing hot, fast flowing exhaust gasses, so capturing some of that exhaust energy to drive a compressor and increase the power production of the engine does not draw a lot of parasitic energy out of the engine. Thus, small engines can produce the power of an engine the next class or size up, yet retain much of the fuel efficiency of the small engine.

In race and hot street engines, when spooled up, turbos can make some awesome horsepower numbers. In 2011 in the Pro Mod classes where you can run turbos, superchargers, or nitrous, twin turbo race cars were the ones to beat.

But turbochargers have a downside: heat, plumbing complexity and lag. You want to locate the turbocharger as close to the engine’s exhaust ports as is practical, which means they’re usually located under the hood. There’s extra exhaust plumbing needed to route exhaust gasses first to the turbine and then somewhere to exit the car. All of this extra tubing introduces heat and can be complicated. And for large engines, like Hemis, you really want two turbos, which just doubles the plumbing issue.