Have you ever thought about the concept used in sequential turbos? Are you curious to get details about this engine set-up? If your keenness is making you impatient then this article is certainly for you.

The sequential turbos set-up is used where the motor makes use of one turbocharger for the lower engine speeds, while second or both of them at the higher engine speeds.

You should note that the larger high-flow turbochargers do not have impressive efficiency at the low RPMs and this causes low intake manifold pressures in these conditions. The smaller turbos spool up in quick time at the low RPMs although they cannot supply sufficient air at the higher RPMs.

Between low and mid speeds of engine, when the spent exhaust energy available is minimal, just one comparatively small turbocharger (primary) is active. In this period, the engine’s full exhaust energy gets directed to only the primary turbocharger. This gives small turbo advantages like minimal turbo lag, low boost threshold, and more output of power at lower engine speeds.

When the RPM increases, secondary turbocharger gets partially activated to pre-spool before the full utilization of it. When the preset boost pressure or engine speed is achieved, valves that control compressor as well as turbine flow in the secondary turbocharger get open completely. It is interesting to note that in few applications, at this moment primary turbocharger gets deactivated.

The sequential turbochargers help to reduce the turbo lag, and moreover the engine power as well as ultimate boost output is not compromised.