Cheap Horsepower-Ram air

[Stephen Dubovsky]

At 09:19 AM 5/14/97 -0700, you wrote:
>"Ram air" just uses the Dynamic Pressure at the front of the vehicle to
>aid engine breathing.  The formula is simple, 1/2 the fluid density
>times the velocity squared (in suitable units).   This works out to
>about .04 psi boost at 50 mph, .17 psi at 100 mph, and .7 psi at 200
>mph; pretty feeble boost (although not as feeble as the
>previously-mentioned cooling fan), but what the hey it's nearly free. 
>
>Let's see, top speed goes roughly as the cube of engine power; if 0.7
>psi boost gave (.7/14.7) about 5% more power, top speed would go up by
>1.6% or the previously mentioned "few mph".  I'm glad that the UJM has
>done many good things for motorcycle technology over the years (can you
>say 150 street hp per liter!) 'cause this doesn't look like one of 'em.
>
...

  Nope, you completely forgot about aerodynamics.  There is high pressure
on the leading edge of an object (esp. a car bumper or windshield or the
front end of a blunt motorcycle).  I have a bike mag around here somewhere
and they connected a manometer to the ram air intake of a zx-11 and
measured a considerable pressure.  They computed that it would add 10-20
ponies at <100mph which explains why a zx-11 and gsxr-1100 (w/o ram air)
have very similar torque curves (the zx-11 actually gets peak torque later)
yet the zx-11 will walk away from the suzi at the dragstrip.  Ram air means
real ponies at >60mph.  Will try to dig up the article (I never throw them
away;)
SMD