I recently bought a 2006 Boxster S. From time to time on cold start-up, a single cloud of white smoke comes out of the exhaust. Is this a normal occurence with these types of engines...
White smoke on startup is normal. It is caused by oil residue under the pistons heads. Because of the flat six engine design, oil residue remains under the piston heads and burns off at every start up. This can produce white smoke, especially in combination with condensation in the exhaust system. It should only last a few seconds and is nothing to worry about.
Yes, that happened to me with my 2003 Boxster. I had driven most of the day and arrived at my destination at night. The car was parked on slant to the right and I went straight to bed. The car sat there like that for a day and a night. When I started it the following day, wow, it was like a mosquito fogger. But a friend at work that drives a 987 had advised me it would happen sometimes so I just let the smoke clear up and drove on home. It doesn't happen very often. I think it has something to do with parking it on a slant. Or maybe it happens when the pistons come to rest just so...
Let the engine cool down after hard driving, and don't let it sit too long
This is exactly how my Boxey is used and up to now (35 tkm) I never saw the white smoke. Though it shouldn't be a problem - Bluelines already explained it very well
BTW in Germany we refer to this as the "Boxer fart"
A number of factors cause that, condense in the exhaust / cat, lets not forget that cat converters, convert hydrocarbons to water, so depending on how good the cat is and cat / exhaust design may increase water vapour on start up.
White smoke can appear for abit after start up, when the air is cold due to more condense being in the exhaust, you may also notice once the engines fully hot that even after a long drive the fumes appear to be white, but this only accurs in winter when the outside temp is cold technicaly this is just hot exhaust fumes.
Worst case sinario is that water or coolant is getting inside the chamber ie could be headgasket or cracked head.. But that would be very obvious as you be seeing big puffs of dense white smoke plus you'd be losing coolant, so your coolent level is a good indicator of problems.