Barrelor sliderthrottles

Barrel and slider throttles work on the same principle as butterfly throttle bodies, but don’t use a butterfly valve mounted on a shaft. Instead, either a roller barrel or slider mechanism is used to control the amount of air allowed to enter the engine.

Roller barrels are basically two tubes inside each other.The outer tube will have holes in either side, which allow air to enter and exit. The inner tube will have exactly the same holes machined in them, but as it rotates inside the outer tube it will blank off the holes.With the throttle closed the inner tube will rotate right round so that the holes in the outer tube are completed blanked off. At full throttle it will rotate so that the holes in both the inner and outer tubes are precisely lined up, allowing the air to pass through uninterrupted. Slider throttles use exactly the same method, but in a linear motion rather than a rotational one.

The main benefit of these type of throttles is that at full throttle there is zero obstruction to the airflow.With a traditional butterfly, even at full throttle the air still has to manoeuvre around the butterfly valve and shaft itself, and this causes some turbulence and ultimately slows the incoming air speed.

There are arguments both for and against barrel/slider throttles and throttle butterflies.The general consensus is that barrel/ sliders work better when at full throttle but can compromise driveability and low-down power. There is another school of thought which suggests that the turbulence caused by the air passing a butterfly actually helps the air and fuel to mix better, too.

Above and below: slider and barrel and systems don’t have any obstructions to airflow when the throttle is wide open.