Originally Posted By: Hokiefyd
Does anyone know what gives the classic Beetle it's rattly exhaust note? It has a slight rasp to it under load, somewhat similar to an opened-up Suby boxer exhaust, but the Beetle also has that very high-pitched tinny blee-blee-blee rattle to its exhaust.
Is that mechanical engine noise? I can't imagine exhaust system tuning being able to create a noise like that, but maybe...
Any suitcase engine experts in here?
Also: having been produced from the mid-1930s through the mid-2000s, is this the engine series with the longest running production date span?
The whistly part of it is just the exhaust system itself with the little dual stub pipes out a transverse muffler. The fuel injected Beetles with a larger single outlet didn't make the bleeby-bleeby-bleeby sound from the factory, and neither do any of the bigger outlet aftermarket exhausts.
The fact that there's an underlying burble is the same reason American V8's burble- the firing order doesn't alternate banks. The boxer 4 (ANY boxer 4) fires left-left-right-right. Some aftermarket VW headers or "extractors" have cross-cross pipes and equal length runners which eliminate the burble, too. The American (90-degree crank) v8 fires left-right-left-left-right-left-right-right, regardless of which of the 3 possible firing orders is used. The different firing orders for the v8 just change up where along the length of the crank the sequential firing pulses take place, none makes them alternate banks. That requires a flat (Ferrari, for example) style crankshaft and all the downsides that come with it such as the same inherent 2nd order imbalance that inline 4-bangers have. The flat-crank V8 IS two inline 4-bangers running 90-degrees out of phase, after all. The upside is that despite poorer NVH, the flat crank has lower rotating mass.