Ed Evans Talks Technical
Do diesel engines have a future?
The usual rumours continue regarding the future acceptability of diesel-powered vehicles in UK cities. Instant views on the fate of diesel engines change almost as rapidly as the prediction of EU emissions regulations. So, to know whether diesel engines have a future, we should not be considering current activity, but instead looking at what is likely to come in future years. In other words, we need to jump ahead of the legislators and look at the science they are likely to employ.
A continual concern with emissions is the tiny particles or particulates that are emitted. These particles are usually associated with diesel engines, and there is no doubt they are harmful to health, entering the bloodstream during normal breathing to potentially damage vital organs. We are all now familiar with Diesel Particulate Filters (DPFS) fitted to diesel engines to collect particles larger than 23 nanometres (nm) which is the currently prescribed limit. That is working fine, but research is showing that these (relatively large) particles are less of a problem than the superfine particles which are not yet regulated.
The reasoning here is that it’s not so much the particulates that cause us harm, but the metal oxides and other chemicals that are carried on the surface of the particles. Simple geometry tells us that small particles will have a larger collective surface area than the same mass of fewer larger particles, and thus carry more toxic chemicals.
Diesel particulate filters are able to capture fine (below 23 nm) particles because they also catch soot, and the soot works as a finer filter to catch these smaller particles. Petrol engines produce less soot, though when fitted with a Gasoline Particulate Filter (GPF) they do control fine particle emission. But, as petrol combustion is further improved, soot levels will fall and the number of fine particulates will increase. This means petrol engines, in their current state, are unlikely to comply with future limitations on the number of finer particles emitted.
So don’t rush out and sell your diesel Land Rover just yet because, in this respect, petrol engines will need to clean up their act, and just how they will do that is still the subject of research.
“Don’t sell your diesel Land Rover just yet, because petrol engines need to clean up their act”