Considering how hard they work in punishing conditions, turbochargers don’t ask for much. Clean oil. Clean air. The correct exhaust gas temperature.
Even with the greater challenges facing turbochargers since being mated with 2002-emissions compliant engines – such as higher operating temperatures and greater boost pressure requirements – these components remain relatively maintenance-free and can last the life of the truck.
“Turbochargers do not normally need any special service,” says Dheyanira Campos, product manager for Cummins Turbo Technologies. “Take care of the engine and its installation, and you automatically take care of the turbocharger.”
This is even more impressive considering the significantly more complex turbochargers being used in heavy-duty trucks. As engine manufacturers look for ways to meet stricter emissions requirements without sacrificing fuel efficiency or performance, turbochargers using variable geometry technology are becoming the norm. While each turbocharger manufacturer brands its variable geometry models differently, they operate with similar principles.
“In some form or another, there’s a variable nozzle inside the turbine, which can tell the turbo to act like a small turbo or act like a big turbo, all in the same package,” says Kurt Henderson, technical sales representative, BorgWarner Turbo & Emissions Systems, which uses Variable Turbine Geometry (VTG). “The technology is not necessarily new; it’s been around for a long time, or at least the idea has. But it was never really adopted by manufacturers for just its improved performance. Now that they need it to meet emissions, it’s driving this technology.”
In addition to helping achieve emissions compliance, variable geometry turbochargers improve driveability and fuel efficiency. The innovative design means the turbocharger adapts to engine operating conditions.
“There are moveable vanes in the turbine housing that direct the flow of exhaust gas into the turbine wheel and, depending on how the vanes are positioned, it affects the velocity of the gas going into the turbine wheel,” says Brian Regnier, Garrett application engineer. “It provides turbo speed and boost control, so at low engine speeds, like pulling away from a stop or moving through traffic, a turbo can act like a much smaller turbo, which gets you to boost pressure faster and helps the driveability. Then when you’re out on the open road and don’t need a lot of boost, the vanes open and it makes the turbo act like a much larger turbo so there is lower exhaust restriction and lower boost.” Garrett’s technology is called Variable Nozzle Turbine (VNT).
