🚀 go-pugleaf

"Kip C. Anderson" <kca(@)rio(.)com> wrote:
>bryan wrote in message <36CCFAE9.3D38@stuff.com>...
>> Why would you put ram-air on a supercharged engine? [...]
>
>Ram-air is the most efficient form of forced induction available in the
>sense that it doesn't  increase intake temperatures in addition to the
>normal conservation of energy that's unavoidable when compressing a gas.

At normal road speeds, there is essentially no "ramming" going on in 
a ram air system.  The most additional pressure you can get from a 
ram air system is the "stagnation pressure", which is fractions of a 
percent higher than ambient pressure at speeds below 100 mph.  

By the time you put baffles and ducting in to keep water from 
ramming itself into your engine along with the air, I don't think a 
ram air system provides any significant pressure increase at all.  
IMHO, calling ram air "forced induction" is wishful thinking.

What ram air does well is providing a supply of *cool* air, where 
the factory ducting may not.  Any performance benefit from ram air 
systems comes from lowering air temperature, not raising pressure.
     
>I.e. The more air you can force into a supercharger or turbo, the more air
>each can efficiently pump out at higher boost pressures.  The effects of
>ram-air however are not always obvious and tend to be less significant on
>lower powered motors.

Cool air is even more important to blown engines than it is to NA 
engines, so I agree that ram air (oops, cool air) systems can help a 
forced-induction engine.
--
Chuck Tomlinson