Re: Cheap Horsepower-Ram air (fwd)

[Orin Eman <orin@wolfenet.com>]

>From the diy_efi list...  there is a thread going on about Ram air
there too.  Note the last paragraph!

Orin.

> "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.

> Getting cool air from in front of the car is much more significant for
> street driving; if the radiator exhaust air is 45F warmer that's a 5%
> density (power) loss right there.

> The BMW list has had a sad thread going from a fellow whose 7-series
> hydro-locked during a Miami thunderstorm... if you are thinking ram air,
> think also about the wall of water that hits you when a semi hits a
> puddle in the adjacent lane...

> Ed