Twin-scroll turbo: What are its pros and cons?

Mitsubishi Twin-scroll turbo
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A twin-scroll turbo is a turbocharger with two exhaust gas inlet channels in the turbine part.

In this article, we will briefly examine the twin-scroll turbocharger's function and advantages and disadvantages.


How does twin-scroll turbo work?

The exhaust pipes from the cylinders lead to one, and the other Twin-turbo channel so that the negative pressure does not take energy from the exhaust gas of one cylinder. In contrast, the exhaust valve of the other cylinder has not yet closed, but its intake valve has already started to open.

If the ignition in the cylinders is in the order 1-3-4-2, the leads from cylinders 1 and 4 will lead to one channel, and the leads from cylinders 2 and 3 to the other channel.

In this case, there will be no loss of exhaust gas energy, because cylinder 3, which would take energy from the exhaust gas from cylinder one is not connected to the same pipe. These two pipes (downpipes) only connect at the turbine.

Advantages of twin-scroll turbo:

  • Better filling efficiency and faster engine response - especially at low speeds

  • Price similar to a simple turbocharger

  • Efficiency similar to a twin-turbo - a different type of turbocharger than a twin-scroll turbo

  • Good reliability

Disadvantages of twin-scroll turbo:

  • Difficult design of exhaust pipes

  • The difficult design solution for engines with a higher number of cylinders

  • The necessity to have an even number of cylinders