AT Power’s patented Shaftless technology explained and measured. We simulated our own production CAD against a conventional shafted throttle to show exactly what a shaft costs you.
In 2005 we revolutionised butterfly throttle design with our patented Shaftless technology, removing the butterfly throttle’s one real weakness: the shaft sitting in the airway. Butterfly throttles are unbeatable for idle stability, part-throttle control and mechanical simplicity - which is why they run everywhere from club motorsport to Formula One. But a conventional butterfly pays a permanent price for that simplicity, at every throttle opening.
The problem with a conventional butterfly
A traditional butterfly carries its blade on a metal shaft running straight across the centre of the bore while being held in by exposed screws. It sits there whether the throttle is shut, cruising or wide open. Air cannot pass through it, so it has to squeeze around it, accelerate, and then tumble back together on the far side. That tumbling is turbulence which is energy your engine spent pulling the air in is thrown away as churn, instead of being delivered to the cylinders.
What the simulation shows
We took the production CAD for our 50 mm throttle body - ram-pipe, housing and blade - sliced it at the bore centreline and ran a computational fluid dynamics (CFD) simulation of both designs under identical conditions. The only difference between the two cases is the shaft.
- 5x less dead air in the bore core than a shafted throttle
- 29% extra pressure loss a shaft adds across the valve
- 15% extra pressure drop a shaft needs for the same airflow
- 99.5% of open-bore airflow, measured on the flow bench
The Shaftless solution
Our award-winning design supports the blade from its rim, taking the shaft and screws out of the airway completely.
- Ultra-thin blade - knife-edged leading and trailing edges minimise separation
- No shaft or screws in the bore - nothing left in the airway but the blade’s edge
- Near open-bore flow - 99.5% of the airflow of a completely open bore
It matters most on smaller throttles
A shaft’s diameter is set by stiffness, not by bore size - so it eats a proportionally larger share of a small bore. That is exactly where high-performance individual throttle bodies live.
| Throttle bore | Shaft blockage | Added loss across the valve |
|---|---|---|
| 40 mm | ~30% | ~ +43% |
| 50 mm (simulated) | 24% | +29% |
| 70 mm | ~17% | ~ +17% |
Or spend the gain the other way: a Shaftless throttle flows like a conventional throttle one to two sizes larger. You can fit a smaller bore for higher intake velocity and sharper part-throttle response, with no loss of top-end flow.
What this means for your engine
- Up to 10% more airflow than a conventional throttle of the same size
- More usable power - at wide-open throttle, roughly 1% more airflow supports 1% more torque
- Cleaner air delivery - no shaft wake means a more uniform charge into the manifold, better cylinder-to-cylinder distribution and cleaner airflow-sensor signals
- Smaller, lighter throttles that outperform larger conventional systems
Proven where it matters
Combined with our in-house R&D on inlet geometry and precision CNC manufacturing, Shaftless technology is trusted from road-going builds to Formula One, WEC and WRC.
Find Your Throttle Bodies Talk To Our Team
Simulation figures from a 2-D lattice-Boltzmann study of the 50 mm throttle body at the bore centreline, shafted vs shaftless run like-for-like with the shaft as the only variable. Figures isolate the shaft alone and are conservative of the complete Shaftless design. Bore-size figures other than 50 mm are scaling estimates anchored to the simulation. Flow-bench figures (99.5% open-bore, up to 10% airflow) from AT Power product testing.
