[aerohead]

Originally Posted by Christ

I'd think there's a little more involved in it than that, exactly... like legality issues with having exposed sections of exhaust beyond the bumper... illegal in PA.

However, for testing purposes, it might work out... so if it's legal for anyone, maybe a test is in order of different placements of the exhaust flow compared to the dynamic airflow of their particular chassis?

I'm thinking that even light-throttle exhaust flow will counteract a certain degree of wake caused by not having a sharp point to detach flow... plus, on a sedan (full trunk) configuration, having exhaust gasses contaminating that airspace between the upper deck and bumper cover might actually cause a flow extension, allowing the flow to stay attached to an artificial surface far beyond that of the actual sheet metal of the car's chassis.

Obviously, the exhaust gasses are under pressure, so would that not have the added benefit of canceling the vacuum space that traditionally tails an auto? Adding any kind of pressure to that area has to be aerodynamically positive, yes?

You could calculate the volume of exhaust gas exiting the tailpipe in a given unit of time and compare that to the volume of air passing over and around the wake of the vehicle in the same time element.