411 (Series 3-5) Exhaust Tailpipes

[Bellerophon]

Bristol did tests along the runway at Filton on the aero dynes exhausts and
found that if the exit was at the back of the car the fumes became
ingested, hence the cars had an exit on the RHS and thus prevented the problem.
One would need to know how the air flows over the rear of the later cars to
see where to place the pipes, wether Bristol did any aerodynamic work on the
later cars I do not know.
My regards,
Bellerophon

[Rubbond]

Amazing that you should know this!
But how could exhaust fumes get back into the car from the rear of the
vehicle?
Surely there would have to be a leak somewhere in the engine compartment??