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It wasn’t long ago that turbocharging was something that was done to sports cars and muscle cars. Not anymore. Turbocharging is used on standard models today because it allows manufacturers to use small displacement engines. The advantage to smaller engines is that they offer better fuel economy and tighter emissions than their larger brethren do. Regular, fixed-speed turbochargers are being used but a new breed has appeared: Variable Speed Turbochargers.

How they work

Standard turbochargers are like miniature air pumps that are driven by exhaust gases. They use the pump to drive air into the engine cylinders. Basically, it’s sort of like a small fan with blades at either end; one end is driven by exhaust gases and the other end “blows” air under pressure into the engine.  The result is that engineers can get more power and higher efficiency out of a given size engine. Standard turbochargers are actually pretty old technology that dates back more than 100 years or so.

Very popular today

Considerable emphasis is being placed on turbocharging these days, not just for performance reasons but for increased fuel economy and better emissions. As we mentioned before, turbocharging allows engineers to power cars with smaller engines which are more efficient and pollute less. As a result, Ames Ford of Ames, IA, a Ford and Lincoln dealer, says many manufacturers are using them today.

A new twist

The problem with regular turbochargers is that they spin at a speed that is related to the velocity of the exhaust gases blowing out of the engine. Unfortunately, this may be less than optimal for the engine. This is known as “turbo lag,” the time it takes for a turbocharger to “light up” or produce positive manifold pressure drastically changing the power output of a motor.

That’s why the concept of variable turbocharging is drawing so much attention throughout the industry. With variable speed turbocharging, engineers can optimize the amount of boost that comes out of a turbocharger so maximum power and efficiency are obtained over a wide range.

Who makes variable turbochargers

One of the first to make a variable speed turbocharger is Antonov Corporation. They introduced the world’s first 2-speed supercharger at the 2006 Global Powertrain Congress. It featured an automatic-shifting 2-speed drive system for centrifugal superchargers.

Designed for the aftermarket, ProCharger offered introduced their variable speed i-1 supercharger just a few years ago. This supercharger uses a Continuously Variable Transmission (CVT) between the driven pulley and a centrifugal supercharger shaft. An electric motor is used to alter the pulley sizes, effectively changing the drive ratio between the engine and supercharger.

The Torotrak V-Charge is designed for OEM applications where the vehicles ECU would have complete control over the supercharger with an extremely wide range of RPM and boost capabilities.The  V-Charge leverages Torotrak’s expertise in gearless traction drives to develop a variable-speed drive that turns the supercharger. Company officials say the V-Charge “delivers from 0 to 95 percent of target torque in just 400 milliseconds.”

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