Can anyone tell me what that sound is when you first start your smart that sounds like a vacuum cleaner? It lasts for about 30 seconds, is quite loud and almost feels like something pressurizing or creating a vacuum somewhere. Could it be the transmission getting ready? I always wait until it stops before I start off. Thoughts???? The whole car is like an adventure so far. I just love it!
The air pump that puts additional air in the exhaust stream is electrically powered and sounds like a vacuum cleaner. This is normal operation and many other vehicles now use an electric air pump instead of a belt driven pump.