ABSTRACT Experiments were conducted to study exhaust emissions of direct injection (DI) diesel engine with different levels of low heat rejection (LHR) combustion chamber such as i) ceramic coated cylinder head, ii) air gap insulated piston and air gap insulated liner and iii) ceramic coated cylinder head along with air gap insulation with pure diesel operation with varied injector opening pressure. Exhaust emissions of particulate emissions and oxides of nitrogen (NO x ) were determined at various values of brake mean effective pressure (BMEP) of the engine. Particulate emissions were measured by AVL Smoke meter, while NO x by Netel Chromatograph NO x analyzer. Engine with different versions of the combustion chamber showed comparable particulate emissions, while they increased NO x emissions drastically at full load operation of the engine, when compared with conventional engine. Engine with air gap insulated piston and air gap insulated liner showed lower NO x levels at 80% of the full load operation. However, exhaust emissions reduced with an increase of injector opening pressure with different versions of the combustion chamber
