I'm not hugely knowledgeable about forced induction, but I do know that turbocharging and supercharging have different behaviors/characteristics from each other and from natural aspiration.

The main difference, at least for the purposes of the question I am about to ask, is that supercharging has no real effect on the exhaust side, other than producing a much higher volume of exhaust, while a turbocharger "interferes" with the exhaust to make it's power, requiring, among other things; a different camshaft design. If you want the best efficiency that is.


In terms of the following head characteristics:

> Chamber size
> Valve size
> exhaust flow as a percentage of intake flow


What would be the most efficient head designs for turbocharging and for supercharging?

I know the design considerations would be different for each, but different HOW?

 

The answers to these questions are complex and extensive and would be better determined through your own analysis and investigations.

 

Gosh, that was helpful.

 

My $0.02:

Cylinder head flow is much more important on a supercharged head than naturally aspirated.

We'll look at the intake and exhaust strokes separately:

INTAKE: The single largest restriction in the entire intake system is around the intake valve. So, with a supercharger, you're trying to push twice as much air through the same port and valve. This means that the port is twice as restrictive to flow. So, a supercharged engine needs a much better intake port than NA. I know this goes against most accepted logic, but think about it. . . A good NA engine might get 110% VE. A good supercharged engine might get 160% VE at 14 psi boost. Why isn't it 220% VE since you doubled the density of the intake air? Because it can't actually get into the cylinder.

EXHAUST: A low compression supercharged engine retains cylinder pressure much later than a NA engine during the power stroke. Therefore, we must delay exhaust valve opening (EVO) as compared to NA engines. Again, this goes against common logic. But. . . you can pair a delayed EVO with an exceptional exhaust port and achieve more power throughout the curve. Of course, a good exhaust port will help any S/C motor, but the properly matched cam can produce better even better results.

Mike