🚀 go-pugleaf

"Kip C. Anderson" <kca(@)rio(.)com> wrote:
>
>I agree that ram-air systems aren't too terribly useful at legal road speeds
>in the 55-65 range, however forced induction does not necessarily have to
>mean pressurization.  Ram-air also takes advantage of the mass and inertia
>of air to minimize a drop in intake plenum pressure.  A mere pressure drop
>of 0.5 psi at wide open throttle (a real possibility depending on the motor
>and ducting restrictions) could mean as much as a 3.4% deficit in power.  On
>a motor capable of 200 HP, this works out to 6-7 HP, a significant
>difference.  Merely maintaining the pressure in the intake to atmospheric
>would be worth the effort IMO.

I understand what you're saying, but like I said before, ram-air 
ducting (because of the desire to keep water etc. out of the engine) 
is not necessarily free of restriction, or even less restricted than 
carefully-designed normal ducting.  

>A friend of mine has run A/B tests on his Storm with ram-air type ducting
>and without - all using the original airbox and plenums - and he was able to
>find several tenths quicker 1/4 miles times out of it.

That's... incredible :-)

>Take a look at modern motorcycles as well.  They hardly have a problem with
>getting cool air, yet sport bike makers have gone out of their way to put
>ram-air ducts in the front of the fairings, despite the obvious downside of
>collecting bugs or whatever else should happen to get up that high.

IIRC, bikes without "ram air" ducting pull air from behind/downwind 
of the rather warm engine.  I may be wrong about that, I haven't 
been keeping up on the latest 2-wheeled tech.

>If you're still having trouble swallowing the idea that air is pressurized
>in ram-air systems, stick your head out the window of your car at 100 MPH
>with your mouth open.  I have a feeling you'll swallow that . . if not a bug
>or two. ;-)

I'm not really guessing here.  Maximum ram pressure is determined by 
a pretty simple equation: Pmax = 0.5 * air_density * air_speed^2.  
That's _maximum_ ram pressure.  Normal ram systems will fall short 
of achieving that maximum pressure.
 
>Unlike turbos, which some have been erroneous in calling free horsepower,
>ram-air is free power so long as a person isn't creating more frontal area
>or turbulence to take advantage of it's effects.

Believe me, I'm not disputing the value of cool intake air, as long 
as the cool air ducting doesn't bring other problems along with it 
(water being the biggie for street-driven cars, IMHO).  
--
Chuck Tomlinson