I believe the original idea is that exhaust is a high pressure gas, forced
out of the cylinder by compression. If one vented the gas under a panel that
had high speed air rushing over it, it would help with the scavenging of the
exhaust. The air running over the panel would leave a low pressure area
under the panel, high pressure flows toward low pressure and voila ! Of
course theory and practice are two different things.
There is allot more to wave scavenging, (which is what we are really
talking about) then just venting high to low pressure. as the wave of high
pressure runs down the pipe (the eggs), it causes a low pressure area behind
it. Also as the piston is going down on the intake stroke, usually the
exhaust valve is still open and it draws some exhaust (another low pressure
area) into the cylinder diluting the fresh intake charge (YIKES!!!).
Anyhow, I am getting more technical than necessary. the main thing is to
squeeze every drop of help/horsepower out. And scavenging the exhaust better
maybe one free way of doing it.
Dale" chief" Thomas
-----Original Message-----
From: FastmetalBDF@aol.com <FastmetalBDF@aol.com>
To: landspeedracer@email.msn.com <landspeedracer@email.msn.com>
Cc: dferguso@ebmail.gdeb.com <dferguso@ebmail.gdeb.com>;
dhaller@techline.com <dhaller@techline.com>; land-speed@autox.team.net
<land-speed@autox.team.net>
Date: Tuesday, January 04, 2000 4:31 PM
Subject: Exhaust Extraction --- it's exhausting
>John, Dave, Douglas ( --- my son ), and list: The effect we're discussing
>here, the utilization of the air flow past the open ends of either
individual
>pipes from each cylinder, or collecters which team up these runners into a
>large diameter pipe ( if the collector is circular --- some are not ), to
>gain an extraction effort on the exhaust gases --- is known as the
Bernoulli
>principle. We've all probably used spray guns on our cars and other
>projects, and that spray gun, or your wife's or girlfriend's perfume
>atomizer, use this principle to "lift" , or pull, the fluid involved into
the
>airstream which is rushing past a small orifice at the upper end of the
tube
>immersed in that fluid.
> This principle, it would seem, could be used to good advantage to aid
>flow out of the cylinders, thus enhancing the fuel mixture flow INTO the
>cylinder, thereby reducing the TIME required to "change" each cylinder.
This
>results in increased HORSEPOWER, as H.P. is a measurement of work done in a
>GIVEN TIME. One H.P. = 550 foot - pounds of work PER SECOND.
>We know we need LOTS of H.P. to push our racecar --- be it a "brick" or a
>sleek lakester or 'liner --- to really fast speeds. My youngest son
Darrell
>is a great fan of this theory that WAY TOO MUCH HP IS STILL NOT ENOUGH !
I
>often tell him he goes by the " sledgehammer " approach to speed.
> I believe that in order to actually realize any useful gain by
>"extraction", that individual stacks, mounted at 90 degrees to the
airstream
>going along the sides of the car MIGHT work the best, but I think that to
get
>this on pipes of , let's say from 1 3/4" dia or so on a smaller engine, to
3
>1/2" or so on a bigger mill --- that the vehicle would have to be traveling
>at a speed VERY FAR beyond it's ultimate capability. To reduce the
diameter
>to obtain a much smaller cross - sectional area at the pipe end, hoping to
>better its relationship to the flow going past, would obviously be TOTALLY
>Counterproductive, due to the resultant INCREDIBLE BACK PRESSURE created !
>These are just my thoughts --- I can't see any useful application of
>Bernoulli's law here. Maybe Mayf could dope all this out on his
computer ---
>I sure can't. Remember, those exhaust gases are already under tremendous
>positive pressure to escape --- ever stand 10 feet or so from (JUST an
>UNBLOWN smallblock) and feel the " slugs " of air hit your pantslegs from
the
>old " straight out stacks " ?? Many of us have ---that's LOTS of
>pressure, and hard to improve on ! Besides, like Dave Haller likes the
>collectors coming out the front fenders on his altered --- "cool !" he
says
>---well, we ( Doug , Darrell and I ) like the looks of ours - same place -
>on the Black Radon altered, and I, myself, don't care if we lose a few
>horses in the design! MAYBE we can spare a few -----
> Bruce Ferguson Black Radon Engineering Racing Team
>
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