Page 93 - Mechanic Diesel - TT

MECHANIC DIESEL - CITS

2 Twin-Turbo
Twin-turbo - types of turbochargers in a twin-turbo turbocharger, the engine has a second turbocharger. V6 or V8
engines, this can be done by allowing a single turbo to operate in each cylinder bank. Alternatively, a smaller turbo
can be applied at lower RPM, with a larger turbo for higher RPM.
The second configuration allows for a wider operating RPM range and gives better torque at low revs (reducing
turbo lag), but also power at higher RPMs. This is known as twin sequential turbocharging. Unexpectedly, having
two turbos greatly increases complexity and cost.

3 twin-scroll turbo
Twin-Scroll Turbo - Types of Turbochargers These types of turbochargers require a split inlet turbine casing and
exhaust manifold that individually connects to the appropriate engine cylinder with each scroll.

For example, in a four-cylinder engine (with a 1-3-4-2 firing order), cylinders 1 and 4 may support one turbo scroll,
while cylinders 2 and 3 feed a separate scroll. This layout gives efficient distribution of gas exhaust energy to the
turbo and helps deliver dense, clean air to each cylinder.
More energy is sent to the exhaust turbine, meaning more power. Repeat, approaching the complexity of the
system requiring complex turbine housings, exhaust manifolds and turbos comes at a huge cost.

4 Variable Geometry Turbo: - Variable geometry turbo
These types of turbochargers are also known as variable nozzle turbines. It is commonly used in diesel engines
because the exhaust gases in diesel engines are low, heat does not damage the vanes.
A variable geometry turbo consists of a ring of aerodynamically shaped vanes in the turbine housing at the turbine
inlet. It is complex in design and requires more cost than other types. VGTs are now limited by cost in petrol
engine applications.

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CITS : Automotive - Mechanic Diesel - Lesson 25 - 28