Air Valve Bodies / Butterfly Housing
Restoration Work
Bosch D Jetronic
Oversize boring and Bypass
DKG Holley
As with carbs, butterfly valves (throttle-discs) may stutter in the throat (when the spindles are badly worn) causing a small ridge. This prevents the valve closing properly resulting in a higher tickover. Oversize boring (greater air-flow) for race-use (ref air-valve body DB 190 - Ø57mm to Ø61mm) can also be catered for. This is limited, of course, by the body-casting diameter. This mechanical work precedes tuning, either rolling-road or dynamometer, as with normal tuning procedure. Any angle (bypass) can be set, to a tolerance of 0,015mm to compensate for heat expansion. Finally, bodies are tested on a flow-bench rig, to a maximum of 0,25 kg air/h in cold state.
Examples
Air Valve Body mech. injection -
old
old
Air Valve Body mech. injection -
reconditioned
reconditioned