Quote:
	
		
		
			 
Compared with petrol-powered engines that most often run with stoichiometric mixtures (that is, the theoretically correct air/fuel ratio for complete combustion, which is about 14.7:1), diesels use very lean air/fuel ratios. The air/fuel ratios for diesel engines under full load are between 17:1 and 29:1, while when idling or under no load, this ratio can exceed 145:1. However, within the combustion chamber, localised air/fuel ratios vary – it is not possible to achieve a homogenous mixing of the fuel with the air within the combustion chamber. To reduce these in-chamber air/fuel ratio variations, large numbers of very small droplets of fuel are injected. Higher fuel pressure results in better fuel atomisation, so explaining the increase in injection pressures now being seen.