A significant amount of the diesel noise (I prefer the term "purr") comes from the direct injection system. Newer diesel engines use a two-stage injection (a small primary pulse of fuel followed by the "real" pulse of fuel injection) to achieve a much quieter sound. Our New Beetle TDI was almost as quiet as a gasoline car when it was brand new, but after the engine got broken in it got a little noisier. It's still silent compared to the Mercedes 616 and 617 engines.

- Nathan
'83 240D "Steiner"
'00 New Beetle TDI