What you are missing John is that with an IR setup the cylinder only sees the 1
butterfly for airflow. With the carb it sees all 4 so the airflow is not all
that much different for the most part between the systems.
a 2.5 in butterfly has 4.9 square inches as far as my calculator says. a 950
holley if memory serves me right has 1.75 venturi but has 4 of the for 9.62 sq
inches with 2 cylinders on an intake stroke at any one time that gives you 4.8
sq inches per cylinder so the flow increase is perceived not actual.
Dave
"Thomas E. Bryan" wrote:
>
> John,
> Since I am a injector user, I feel the need to respond to your question.
> The last carburetors that I ran were Stromberg "97s" and I don't have a
> clue as to the cfms. It goes without comment that carburetors have
> greatly improved in the last forty years (it has been that long since I
> chose to go with the injectors.) If you discount the electronics,
> injection hasn't changed much during that time, except for getting
> larger in cfms. I do believe that there are advantages and
> disadvantages to either system. Most probably choose injectors because
> of convienent jetting and changing of fuels.
>
> It appears that there is a belief that there is HP in manifolds, for I
> see more systems all the time where injectors are set on top of a custom
> manifold. This also gets rid of a couple of the weaknesses in older
> injection systems, a restricted nozzle or unbalanced air intake to the
> cylinders causing a burned piston, or at least loss of performance.
> With the carburetor system, velocity is key. Fuel delivery is heavily
> dependent on the proper cfms for the engine, particularly at the lower
> rpms. I suspect that either system's need for cfms is controlled by the
> cylinder heads at top rpm. I run the 2 1/2" Crower injectors which give
> the engine an abundance of available cfms, but as someone has already
> said, regardless of the system the engine only uses the cfms it needs.
>
> Tom, Redding CA - #216 D/GCC
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