I've often wondered how much air flowed through a DCOE with various
chokes fitted. Have never seen such a chart. All of the settings I've
looked at had a choke size fitted that could not act as an actual flow
limiting device. If I understand it correctly, a critical flow Venturi
can only flow a given volume that is limited when the air speed through
the Venturi reaches the speed of sound. That is how they restrict Formula
3 cars in Europe. When the McLaren F-1 coupes were raced their intake was
restricted by two 39 mm Venturies feeding a 6.3 litre V-12, or 2389
square mm, 379 mm2 per litre. Six 28 mm chokes feeding a 2.0 litre
engine, that's 3694 square mm, 1847 mm2 per litre. Almost 5 times more
than the McLaren.
Changing the Venturi / choke size chances the velocity through the carb
for sure and in so doing changes when various circuits perform, but it
seems as though it can't have a great effect on volume. It must though
as there is so much made of limiting the size for an application. I've
also never seen dyno results on an engine fitted with various size chokes
to see how much power is gained and where those gains are made.
Just one of those things I have had trouble resolving in my own mind.
Bill 70 GT-6+
On Wed, 31 Oct 2001 09:42:24 EST EPRacer@aol.com writes:
> Cary:
>
> The only restriction SCCA imposes is the choke size. This is really
> not that
> much of a restriction, as all the rest of the DCOE adjustments are
> open. It
> then becomes an "air pump" question if you can move enough air
> through the
> choke at top RPM to have the cylinder produce max HP, and also can
> the
> exhaust system then discharge that much air. I am sure you engineer
> types
> can also calculate that, but us dumb architects just go by looks,
> and to me
> the DCOE is much sexier than SU's, etc.
>
> Lyn Pollock
> EPRacer@aol.com
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