2CV mounted engines ranging from 375 cc 9HP to 602 cc 29HP It's a four stroke flat twin (boxer engine). It's far less efficient and I expect it to be more

2CV mounted engines ranging from 375 cc 9HP to 602 cc 29HP It's a four stroke flat twin (boxer engine). It's far less efficient and I expect it to be more polluting than a modern engine, but I don't know how to search for objective measures of such pollution.