[bs0u0155]

I've had an idea, I might be insane but here goes anyway.

If we assume that in normal operation turbochargers recover energy from the exhaust and use it to force more air into the engine creating the opportunity to generate lots more power. If we also assume that our nice efficient high-compression ratio engines, tuned for FE, are not really looking for more power and in fact are really poorly set up for forced induction (advanced ignition/running hot/high compression). However, there is still energy in the exhaust to recover.

So, if we take a turbocharger and mount it to the exhaust of an engine with all of the oil feeds etc, we have a "spare" efficient centrifugal compressor. These flow huge amounts of air in some cases. For a Mitsubushi lancer evo, 300cfm was mentioned and 600cfm for some RX7s. Interestingly they can flow these large amounts even against 15psi+ back pressure.

So why can't this air be taken from a high pressure area at the front of the car and routed out into a low pressure area like behind the car... therefore mitigating the wake.

Now I'm not suggesting you can bolt up a turbo capable of blowing a 600bhp engine to a 1.3l 4 cyl engine. However because there's actually a negative pressure gradient, you may get much larger cfm figures out of a turbo or be able to create a hybrid turbo with a small turbine large compressor to take advantage. Could this be used to mitigate somewhat the hole in the air behind the car? Or directed in some way to improve existing over-car flow?

Given the simplicity of this it could be worth a try, no engine management issues just a turbo/manifold/exhaust/some tubing.