Doctor Diesel

Vorsprung durch gobbledygook?

VOLKSWAGEN POLOI have not come across the term “special auxiliary shell for the oil pan” before, as in Issue 324, page 31, in the new Volkswagen Polo review. Does it mean the engine undertray? Nor have I heard before of a cooler for the exhaust gas recirculation (EGR) valve – Doc Diesel page 83. Would not cooling these exhaust gases make them more liable to deposit their tars and soot than they would when hot?
Peter Duffy

Not my words regarding the Volkswagen Polo, but those of Volkswagen UK, and they seem to owe something to a German-American English translation, since “oil pan” is not a British expression. Apparently this is some kind of noise damping plate which, along with a new design of engine cover, is aimed at further decreasing acoustic emissions – otherwise known as noise. EGR coolers are now in common use, and have been for some years Peter. The latest development (e.g. on the new Golf TDIs) is a twin circuit EGR system, with one uncooled circuit used mostly to reduce particulate emissions when the engine is cold – by recirculating hot gases to achieve a faster warm-up. The cooled circuit is mostly in operation when the engine is hot, and the main objective then is to reduce NOx generation, which increases with combustion chamber temperature. Out of interest, there seems to be some work going on with using NOx to destroy particulates, which would be brilliant if it ever comes off, because they are generated under totally dissimilar conditions and it needs totally different conditions and catalytic processes to remove them both. To use one to eliminate the other would be brilliant. Or am I dreaming!
All the best,
Doc D

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