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From: W S Potter <wester6935@attbi.com>
Date: Fri, 25 Jan 2002 07:40:18 -0800
To: "Bryan A. Savage Jr" <basavage@earthlink.net>
Subject: Re: [Fwd: Re: Scoop Openings Revisited.....]
Watching the various scoops used on the streamliners that have been
built/run out of this area ...
Jim Burkdoll has several different scoop/plenum shapes hanging on the wall
in his garage. So do Rick Vesco and Terry Nish. It would be interesting to
hear from Jim his thinking on the latest scoop he built for the new Nish
liner. The air scoop on that car apparently worked well ... the air slowed
in the plenum but had plenty of physical compression to achieve the boost
they were looking for. Top speed at ElMirage on the first event out of the
shop.
Over the years as they experimented on the 444 car they have blown a
scoop/chamber right off the car when the mouth was too large. They went to
a smaller size and it seemed to work. They don't seem to have changed the
size of the opening as they have moved up in displacement size. The one
that is on the new Nish car now and the one on the 444 car both have what
appears to be a relatively small opening but a definite cubic inch size for
the plenum.
The 111 car has to be the test for scoop size with the turbine. Uses more
air as the speed goes up obviously and more critically than an internal
combustion engine would be my guess.
The point I'm working toward is to ask what data acquisition read outs show
about engine efficiency as speeds increase on streamliners with the scoop
size/plenum size changes. The other stuff has to be mostly speculation as
Rich Fox indicates. The educated seat-of-the-pants approach worked for him.
Bryan like Jim Burkdoll was working with a smaller displacement engine that
would arguably require a smaller volume air flow. They were all dealing
with sub-300 MPH speeds which have to require different air management than
the faster special construction bodied cars
Tom Burkland spent 1500 hours on the computer designing their car before
physical construction began. He would have critically considered scoop
opening size and flow for the twin engine configuration. I'd like to have
an idea of what his data acquisition shows on engine performance at various
speeds. Terry has three runs worth of information, I wonder what Marlo
Treit will have when he gets running?
Just questions with no answers but room for lots of speculation.
The next air management I will be watching will be during the Luge
competition at the Olympics.
Wes
on 1/25/02 12:15 AM, Bryan A. Savage Jr at basavage@earthlink.net wrote:
> Wow!
>
> I get a kick out of this mental equivalent of the Chinese water torture:
> Aerodynamics.
> The introductory stuff I read many, many years ago seemed so straight forward.
> Air flow follows the laws of physics. Simple. No problem ..
> Except .. each molecule of Oxygen and Nitrogen follows many different laws
> of physics simultaneously. (Hmmm getting messy here)
>
> Like Rich, many aerodynamically correct things look WRONG to me (F-117) and
> Dick, I casually stuck my hand out into a 145 knot breeze and about lost
> it. Air is very hard stuff at high speed.
>
> mayf, I think the only safe way to use a properly designed scoop is with
> a good EFI system. It might be possible to use an additional fuel pump
> driven by the rear axle to add fuel to a mechanical system but ....
> One new user of a "correct" scoop went 15 steps richer than the tested
> dyno setup and it was still a bit lean at 300 MPH.
> In your carb example, with a scoop, don't you want the air to slow down
> and gain pressure before / while entering the carb?
>
> I don't think that a fast car with an ideal scoop can be jetted to run
> safely without EFI on gasoline.
> With methanol and an excellent ignition system I think acceptable results
> can be produced. You'll be about 20% rich in first gear.
> If you find some pictures of Indy cars before EFI, I don't think you can
> find one with a scoop. They just pulled boundary layer air in from the
> side of the car. That way the induction system was always looking at
> ambient air pressure.
>
> Bottom line for me: I think I can deal with ->basic<- airflow around the
> outside of a car. I think I need to learn much more before trying to manage
> airflow inside a car.
>
> This IS fun and talking about it doesn't burn holes in pistons.
>
> Cheers,
> Bryan
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