Sunday, 31 May 1998, at 11:57 p.m.
I have had two diesels, a sedan and a wagon in the 200 series. With the diesel is it easy to tell when you have problematic vortex situations at the rear of the car. On both cars I have had problems with diesel soot building up on the back. With white cars, this gets disgusting after a while and it is not very easily removed with washing. THEREFORE, When I had a spare bit of change, I took the cars to the pipe bender and had the "S" pipe out of the rear transverse muffler cut off and an extension put on so that the exhaust pipe pointed to port at the rear corner of the car rather than the stock rear facing arrangement. Once that was done, the soot accretion dropped to between 0 and 1% of what it was, IN BOTH cases.
Now this may not sound like much, but if you don't have the exhaust coiling at the rear of the car, you won't have it entering your vehicle either and this applies to both GAS and DIESEL cars. The only difference is that you can see the one and not the other, well that and the diesel soot is not near as toxic as the gas emissions. I have obtained the air flow data from a Volvo source that I cannot name, and, according to this department, there is not a post 1960 Volvo that would not benefit if modified in the same manner. The main difficulty appears to be from "under car" air being trapped at the rear of the car, including the exhaust pipe area.