Building On Proven Platforms

The Tier 4 Interim QSB3.3 and QSB4.5 engines build on the proven success of their Tier 3 predecessors by retaining the same displacement and base engine platform that has established an enviable reputation for durability even in the toughest applications.

The QSB3.3 and QSB4.5 engines were 4-cylinder pioneers in the use of a High Pressure Common Rail (HPCR) fuel system with advanced electronic management. This early advantage and experience at Tier 3 now pays dividends for the Tier 4 engine with surprisingly few engine changes needed to achieve low emissions.

The previous wastegate turbocharger is upgraded to a more efficient variable flow turbocharger to drive the EGR system and optimize boost across a wider engine speed.

The variable flow design ensures a simplicity and reliability appropriate for 4-cylinder engines. At low engine speed, the exhaust gas flow is directed to increase boost pressure – acting like a small turbocharger. At high engine speed, the flow is directed to retain the most efficient boost level – acting like a larger turbocharger.

Engine management capabilities of the QSB3.3 and QSB4.5 are upgraded to the latest CM2250 Electronic Control Module (ECM), sharing a common electronic architecture with more powerful Cummins Tier 4 engines. The control module provides three times faster processing and double the memory compared with the Tier 3 module.

The CM2250 module controls a performance-enhanced HPCR fuel system with fast power delivery and low-noise operation. The module also provides a seamless electronic interface to other systems on the equipment.

Engine cooling for the QSB3.3 and QSB4.5 incorporates a stronger drive fan system with auto-tensioning capability. Together with increased water pump flow rates, this will further enhance reliability and help mitigate demands on equipment cooling.

Direct Flow Air Intake

The QSB3.3 and QSB4.5 engines are integrated with the new Direct Flow air cleaner from Cummins Filtration, specifically developed to provide more performance in less space for Tier 4 applications.

Increased dust-holding capacity enables the Direct Flow technology to reduce air cleaner installation space claim compared with conventional cylindrical air cleaners, while achieving equal or better filtration performance. This is achieved by the innovative “V-Block” rectangular configuration of the Direct Flow, which optimizes space normally wasted in the inner diameter of round air filter elements.

The Direct Flow housing features an integral sensor for monitoring temperature and pressure to ensure that optimum airflow is delivered to the engine during all operating conditions. The housing is available with an optional precleaner cover that is able to remove up to 95 percent of particles before they reach the filter, offering significant benefits for high-dust environments. With enhanced filtration efficiency, Direct Flow offers the opportunity to extend filter service intervals and reduce operating costs.