If you ask me, far more noise comes out from under the hood than out from the tail pipe on these cars. Just walk around to the back of the car and listen while some one revs thre engine and compare it to the noise at the front. If you want quiet in a diesel your going to have to sound insulate the engine compartment and have good motor mounts IMHO.

If you really think the exhaust system is the source of the noise you can do like Rolls Royce did and run 3 mufflers in series. Mabey you could install one of these new low temp NOx catalytic converters ( after the turbo ) so you can thumb your nose at some of these eco snobs. Of course these options will eat into your mileage and power as well as cost some $.

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green 85 300SD 200K miles "Das Schlepper Frog" With a OM603 TBO360 turbo ( To be intercooled someday )( Kalifornistani emissons )
white 79 300SD 200K'ish miles "Farfegnugen" (RIP - cracked crank)
desert storm primer 63 T-bird "The Undead" (long term hibernation)

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