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Turbocharging – Revolution through Evolution

Today’s automotive turbochargers may have their roots in the aerospace industry – but, in many ways, the engine boosting technologies employed in passenger cars and commercial vehicles actually outperform their industry counterparts. For example, the rotating parts of a turbocharger will deliver reliable performance at up to 280,000rpm – speeds much higher than within a jet engine’s moving core.

Early automotive turbochargers were primarily employed to boost the power of gas-powered sports cars. Today—through advances in aerodynamics and high-temperature materials—the focus is on fuel economy, performance and emissions control in gasoline, diesel as well as hybrid engines.

Modern turbos have fewer parts, are smaller, spin faster, offer variable flow solutions, work at pressure rations of around 2-2.5:1 for gasoline and 4-6:1 in diesel engines and are fully interconnected with the engine management system through the latest sensing technology and electronic actuation. Boreless and threaded bore compressor wheels produce high and ultra-high boost pressure, while high-capacity, low-loss thrust bearings enhance performance and durability.

A big step change for turbochargers came in the 1990s with the advent of Honeywell VNT™ (Variable Nozzle Turbine) technology. VNT™ technology matches turbo output to an engine’s air boost requirement. As a result, a turbo can be optimized for both low and high engine speeds, maximizing performance while increasing fuel economy.

Over the past 10 years, there have been significant advances in aerodynamic design that have improved turbo efficiency by 15 percent and yielded an 18 percent increae in turbocharger speed. Exhaust temperature capability has increased by roughly 100°C while at the same time the overall turbo reliability has increased by 10 times thanks to better modeling and advancement in materials.

All of this progress has helped move what was once a specialty technology to a mainstream application that is synonymous with fuel economy, reduced emissions and driveabililty.

Forty Years On – How Do They Compare?
Turbocharging took its first steps into mainstream motoring with the 1962 Oldsmobile F85 Jetfire Turbo Rocket. So how does the original Garrett T05 compare with a modern turbo such as the Garrett GT2560 found in the Ford RS Focus?

Modern turbochargers help engines provide much higher specific output – 107hp / liter for the Ford RS Focus compared to 61hp / liter for the Oldsmobile Jetfire. Today’s turbos are lighter in weight, benefit from better aerodynamic design (which optimizes flow pressure ratio and efficiency), operate at higher temperatures and provide better integration into the powetrain system. As a result, while the turbocharged Oldsmobile Jetfire provided 16 percent performance enhancement compared to its non-turbo version, the boosted Ford RS Focus delivers an impressive 50 percent increase.


Photo Credit: Alain Ernoult