Poss numpty question.

[lady topaz]

I have had my 335i now for a month or so and all is fine.I have noticed though on cold morning starts I only get vapour!! from one exhaust, is this the norm? and can anyone explain why?

Cheers Di

[dan101smith]

I'd imagine if that is the case then there's a valve in the exhaust that only opens at high revs, but someone more knowledgable will be along shortly to set us both straight!

[StuB]

It's a valve that helps minimise emissions on startup/warmup. Not an issue.

[MK4 Slowride]

Nothing to worry about. Next time your behind another BMW with two or more exhausts look carefully and you'll see a valve covering one while on idle tickover. If the driver boots it you'll (briefly) see it open.

[lady topaz]

Thanks for quick and helpful replies guys. Put my mind at rest.

Cheers Di