Daniel1312@aol.com wrote:
> Hi Martyn,
>
> I do not agree that twins are better than singles. What matters is the amount
> of airflow the engine receives (and requires) and with carbs the amount of air
> the carb can flow be it a large single carb or two smaller carbs. Although a
> twin 1.5 SU set up will flow a total of more air, on many A Series engines you
> will get a better result with a single 1.75 (or maybe a single 2.0?). The
> only usual advantage of a twin SU setup over a single is better fuel economy
> (gas mileage).
FWIW, there are intrinsic performance characteristics to each setup that must be
considered for each application.
My perspective is SCCA Solo II (or autocross, etc.). This hobby closely
approximates 'frisky' street driving, which I believe most of us participate in.
Peak torque and not horsepower is king in this arena. Acceleration off the line,
punch at mid-rpms, and acceleration from 20 to 40 are usually better with
smaller
venturis.
The important component here is the *velocity* of the air through the
carburetor.
Carbs are less responsive with the larger venturis, and as you say, fuel mileage
is less. At lower RPM's the cylinders 'pack' better with a greater velocity of
the intake charge - i.e., smaller venturis.
There is no doubt that peak horsepower is greater with a larger carburetor, but
horsepower is not always king.
All of the above IMHO.
Scott Meyers
60 Bugeye
1275 with 45 DCOE with 34mm chokes
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