Velocity stacks control the speed of the airflow entering into the throttle bodies. Their height, curve and bellmouth radius, even surface roughment determine how efficiently the engine breathes across the RPM range. By refining the geometry, pressure waves inside the intake are altered for improved the cilinder filling. The manufacturer always choose a production method that is low cost (injection molding and 1 single part) and leave some improvement area behind, for raceteams or to sell their own tuning parts. This factsheet compares the stock OEM stack with the improved DK34 low‑ and high‑profiled design, highlighting the improvements in flow behaviour and resonance characteristics.
OEM Triumph 675 2006-2020 velocity stack
This is a section view of the OEM velocity stack used on the Triumph Daytona 675 2006-2020. The exact factory geometry is clearly visible here, including the abrupt transitions, sharp internal edges and the sudden change in curvature near the inlet. These features create turbulence and reduce the efficiency of the airflow entering the throttle bodies.
DK34 low‑profile velocity stack
This is the low‑profile DK34 velocity stack. Note the smooth continuous curve and the enlarged entry radius, designed to reduce turbulence and evenly accelerate the incoming airflow. The low version improves top‑end breathing while maintaining stable flow behaviour across the mid‑range.
DK34 high‑profile velocity stack
This is the high‑profile DK34 velocity stack. The extended length increases intake resonance at lower and mid RPM, improving torque and throttle response. The refined bellmouth radius and controlled taper ensure a clean, stable airflow with minimal pressure loss throughout the entire intake cycle.
The DK34 system uses a staggered intake layout with two low‑profile stacks and one high‑profile stack, creating a 2 Nm torque and 3 hp power increase between the 10000 and 11000 RPM range, on the tested Daytona 675 (no flapper, sportfilter, ECU flash and OEM exhaust system).