a good quality diesel i.e. - like the mercedes OM606. or a VW 1.6 turbodiesel Golf, or a Nissan RD28 or even CD20.
The MB 606 is like a refined watch- tick tick tick, vrooom - at partial throttle the engine is dead silent.
the golf turbodiesel is umm.
idle = rattle rattle rattle
off boost = sounds like a regular oldschool 4 cyl OHC engine
on boost = the sound of the turbocharger is NICE, my wife puts its like - jahaaz take off karne waala hai. - hifaazti bund baand lejiye.
The 2C sounds nice at idle - but sounds like a dying tractor at revs, OTOH the nissan CD20 sounds nice both at idle and at revs.
continuing your sentence.
I think thats why the 2.0D corolla interior is the most nicotine stained ones Ive ever seen, the drivers need the smoke to distract them from the noise.