I have a technical question for the boards engine guru's out there. I understand the principle of venturi action and the positive benefits it has on intake velocity and flow into and engine or anything requiring one. But, is it necessary on our small engines with such short intake manifolds. Is there really any thing to gain performance wise to run one vs. not running one. I still ride a two stroke, as well as a four stroke MX bikes and neither of them have venturi's on the carbs. They too have short intake manifolds that attach to the engine. Thanks for your input to all those that reaply.

Sean

The BLACK intake tube provided by Zenoah with G260s is NOT a venturi, it is only an extended intake tube that increases the intake tract length for increased ram effect. The belled end of it helps pull in air better than the blunt face of the carb does.

In higher rpm mod engine application we generally want the shorter intake tract and in most race type boats we don't have clearance for it's use anyways.

Personally like to use them where I can, but not the OEM Zenoah part, but a shorter and larger version that RCMK markets such as shown. Used along with short intake manifolds the systems overall length downstream of carb is shorter so rpm potential is increased, the intake bell helps bring in more airflow and cuts down a tad on fuel fogging from flow reversal. Dynamics of there use is just another tuners trick one can play with

Thanks for the reply Scott. I didnt realize that the black intake tube didnt have a reducution in diameter. IYO would putting a venturi on the carb provide any performance gain?

Creating a tight spot to form a venturi ahead of actual carb that has it's own venturi would do nothing but restrict air flow entering carb killing intake performance.

Thanks Scott for taking the time to answer my question.