Single Scroll vs. Twin Scroll Turbocharger

There are different kinds of turbo configurations available on the market right now and today we’re going to focus on mainly the single scroll and twin scroll turbos.

A turbocharger works by using exhaust gases from exhaust manifold that propels the turbine wheel which drives the compressor wheel to spin and compress air into the engine. So, for a single scroll turbocharger, all of the gases from the four cylinders go into a collector and feeds the gases into the turbine wheel. While the exhaust gases enter from various pulses, it causes interference when they collide into each other, reducing its efficiency due to turbo lag. As for a twin scroll turbocharger, a turbine housing has two scrolls, this means from the manifold, the pulses already have to be split into two different collectors to enter the two scrolls of turbine housing which reduces interference, leading to better spool and efficiency.

However, a single scroll turbocharger is easier, cheaper to manufacture and install, and its overall size is more compact. It also produces better high rpm performance, and the downside would be poorer low rpm performance as well as a fairly narrow effective rpm range. On the contrary, a twin scroll turbocharger is more efficient due to less turbo lag, producing better low rpm performance, but the disadvantage is having a poorer high rpm performance and it is more complex in manufacturing as well as installation, so the overall cost is higher.

While considering all of the factors above, the general rule of thumb is that if you’re using the vehicle with higher boost, use a single scroll; and if you’re driving it for daily use in the city, a twin scroll turbo would give you better driving experience.