created two or three cycles earlier. This is why exhaust gas sampling on two stroke engines is done with a special valve right in the exhaust port. The gas exiting the stinger has had too much resident time and mixing with gas from other cycles causing errors in analysis. Expansion chambers almost always have turns and curves built into them to accommodate their fit within the engine bay. Gases and waves do not behave in the same way when encountering turns. Waves travel by reflecting and spherical radiation. Turns causes a loss in the sharpness of the wave forms and therefore must be kept to a minimum to avoid unpredictable losses. Calculations used to design expansion chambers take into account only the primary wave actions. This is usually fairly close but errors can occur due to these complicating factors. See also Kadenacy effect Tuned exhaust References Two-stroke engine technology Exhaust systems