Mind the Filters
Diesel engine exhaust can be pretty dirty. Operate the gas analyzer with clean filters. Plan on changing filters (ALL of them) much more frequently than you have to with gasoline or propane engines. Modern gasoline engines (on automobiles and trucks) have catalytic converters on them – so the amount of particulate matter they produce is very small compared to 10 or 20 years ago. Diesel engines are not – and they are much dirtier in general than the gasoline engines were of the same period.
Diesel engines have gotten cleaner – but they are still 10 to 50 times dirtier than a modern gasoline engine – and propane fueled engines are pristine by comparison to them both.
A word to the wise here – change filters often and check the water trap for contamination. If you see dirt in the water trap – it is getting past the input filter.
Engine Loading During Testing
The Higher the true engine load – the closer the exhaust gas values are to undiluted gas. Measuring exhaust gas values under low or idle conditions is pretty much meaningless for a diesel. On the other hand – these engines can produce quite a lot of power.
You need to find some comfortable point of operation – enough power to reduce dilution and produce reasonable exhaust gas levels – but no too much to be unmanageable. Care should be taken to make sure the exhaust conditioning systems are up to operating temperature during the test – but the engine (and drive systems) are not damaged due to stalled running conditions.
Sulfur Compounds in the Exhaust Gas
The testing above will NOT account for all the noxious gases delivered from a diesel engine. You can smell other compounds in diesel exhaust – as even trace amounts of the oxides of Sulfur are very irritating. As these oxides of sulfur are not measured, but may be present and causing a noxious smell – there is not much you can do about this – except mandate that a low-sulfur diesel fuel be used.
(Gasoline and Propane simply do not have this problem due to the refined nature of these fuels.)
Lambda and A/F Ratio on a Diesel
The natural air dilution present in diesel exhaust make the Lambda and A/F ratio calculation in the 4 Gas and 5 Gas Analyzers pretty meaningless. You cannot rely on these values for diagnostic purposes without correcting for the air dilution inherent in the diesel engine.
Combustion Efficiency (CE) on a Diesel
The CE calculation in the 4 Gas and 5 Gas Analyzers is NOT effected by the air dilution present in diesel engines. Combustion Efficiency can be used as a valid diagnostic parameter for diesel engines without modification.
We hope these tips help you out the next time you perform an emissions test on a diesel engine with our 4 or 5 Gas Exhaust Gas Analyzers. Let us know if you have any questions. We would be happy to hear from you at firstname.lastname@example.org