Why Shaftless?


AT Power developed our patented 'Shaftless' technology in 2005 to overcome the only significant disadvantage of the butterfly throttle design. While the butterfly throttle has always benefitted from excellent idle and part throttle control, it has been limited by the disturbance to the airflow and the blockage to the cross-sectional area of the air passage by the blade and rotating shaft.

One area where traditional butterfly throttle bodies are lacking is that the butterfly valve is held via a thick shaft and two screws. The shaft and screws cause disruption to the airflow, reduce flow velocity and hamper the performance of the engine. To rectify this problem, AT Power developed an award-winning design concept where the blade is supported at each end and has no shaft in the throttle bore. The thickness of the blade is reduced to the minimum achievable, with knife-edged leading and trailing edges and the rotating shaft does not ingress into the airflow passage.

Our patented technology maintains all the benefits of the butterfly throttle system while improving the part and fully open airflow characteristics. Our ‘Shaftless’ system can improve flow by up to 10% on common throttle body sizes. In fact, tests show an AT Power throttle has 99.5% the same flow as having no butterfly at all. The minimal disruption caused by our ‘Shaftless’ blade allows us to specify a smaller throttle bore, resulting in higher airflow velocity resulting in a higher volumetric efficiency.

Inlet geometry is an area critical to engine performance, the way in which the airflow passes through the internal passages of the throttles, over the butterfly valve, and into the inlet port, will make a significant difference to the power output and fuel efficiency of an engine. This is an area in which AT Power has invested significant R&D to provide the optimal solution. Combined with precision CNC machining, AT Power can manufacture small, lightweight throttles offering the same performance as a much larger system.


AT Power Shaftless Throttle: (Left)

Butterfly Knife edge on leading and trailing edges, minimizing air flow separation.

Minimal butterfly thickness, maximizing volumetric efficiency.

No shaft or screws giving 99.5% the same flow efficiency as having no butterfly at all.

Higher airflow velocity resulting in higher volumetric efficiency, horsepower and torque.


Traditional Shafted Throttle: (Right)

Shaft and butterfly fixing screws causing air flow separation and stagnation areas.

Reduced volumetric efficiency.

Reduced airflow velocity resulting in reduced volumetric efficiency, horsepower and torque.