Engine size - why are diesels 1.9 . . .etc

[Retread]

A silly thing but one that has puzzled me for a while . . .

Why are diesel engines traditionally odd cc sizes (1.7 & 1.9 being the most popular) and petrol engines even cc sizes (1.6, 1.8 etc.) I know recently there are a few 2.0 diesels but it just seems strange that generally speaking it was always odd for diesel, even for petrol.

[saintjohnny]

1.3 petrol engines are pretty common and I know there is a 1.5 petrol engine in some Hyundais. Not an answer I know, but how engine sizes and capacity are decided is indeed a curious one!

[Andyvon]

Many engines are designed in the USA such as Fords and Vauxhalls etc. (US companies). The Americans size their engines in cubic inches and those convert to odd metric equivalents.

I think another reason is that vehicles can be included in a class or group with one particular engine size (say 1.0l - 1.9l) rather than a more expensive higher group such as 2.0l - 2.9l). It's a little like a shop pricing something at �7.99 rather than �8.

[bigboots]

I read somewhere a long time ago about taxation classes in other parts of europe (before the green bandwagon)
diesel's were aloud to be of a higher volume cc to make up for the lack of power they produced

[Retread]

general response . . .

thanks all for your ideas . . . I am well aware that engines come in all sizes and power outputs but my simple query is why, GENERALLY speaking, are diesels often odd sizes whilst very few petrol engines are. if it is just an arbitrary result of other, more important design criteria then so be it . . it just seemed to be more than just a coincidence that many manufacturers use the same sizes (even allowing for the fact that some of them share engines)