Twin-Scroll Turbine Housing

 Originally developed for commercial diesel applications, 
turbochargers with a twin-scroll turbine housing have now been 
successfully adapted for use with passenger car engines (both 
gas and diesel). By utilizing dual openings, or volutes, into the 
turbocharger's turbine housing, exhaust energy is optimized 
which results in better engine performance at low speeds, 
decreased backpressure at high speeds, and significant gains in 
fuel economy.   



Traditionally, passenger car turbochargers have had only one 
volute through which exhaust gases leaving the engine cylinders 
can enter the turbine housing (where they are used to create 
torque). Unfortunately, this single entry design can sometimes 
lead to combustion inefficiencies, since some cylinders are 
expelling burnt gases while others are inhaling fresh air for 
combustion. What happens is that the hot, dense exhaust gases 
from the first set of cylinders are drawn into the second set of 
cylinders, causing the combustion occurring in those second cyf 
the fuel it's consuming. 

 

Several wastegate solutions were considered to counter this 
problem, with a twin-scroll design ultimately providing the best 
solution. A twin-scroll, or twin-entry, housing allows each set of 
cylinders to release its exhaust gases into a dedicated volute. 
That way, it doesn't interfere with the other set of cylinders, 
which is taking in fresh air at that same time. Of course, 
refinements were necessary to account for the divider between 
the two volutes, but thanks to the dedication of Garrett 
engineers, those challenges have been met. 

As this technology is further developed, even smaller passenger 
car engines will be able to experience the benefits of the twin-
scroll turbine housing design including those fueled by natural 
gas. And, as with all the products Garrett manufactures, twin-
entry turbocharger technology will continue to be developed with 
an eye toward even greater efficiency and maximized performance.