This paper presents the results of a study on the effect of using a continuously variable length intake runner (intake manifold) on Turbocharged multi-cylinder diesel engines. While there is a large amount of data available for naturally aspirated engines, no reliable source was found for the effect of varying the length of intake runner for Turbocharged engines. This study was done for relatively low-speed off-highway diesel engines.The study is based on the results of one-dimensional engine models simulated in AVL BOOSTTM engine simulation software. A simplified engine model has been used for the single cylinder naturally aspirated engine, to demonstrate the effects of varying intake runner effective length. The multi cylinder study is based on validated model of a 12 cylinder 1000hp turbocharged diesel engine. It has been found that multi-cylinder turbocharged diesel engines are more responsive to intake runner length variations than naturally aspirated engines.