At harvesting speeds between about 4 and 6-8 km/hour the machine is moving fast enough for the gathering and feed systems to work well without excessive stool damage. Stool damage can occur at speeds both higher and lower than this optimum range in different crop configurations.
When the flow rate through the cleaning chamber is over about 90 tonnes / hour, the selectivity (ability to extract trash rather than cane) of the cleaning chamber drops rapidly, and the amount of cane extracted to the trash blanket increases significantly. It is important to appreciate that cane extracted by the cleaning system (especially at high rpm) is 'atomised' as it passes through the fan, and not visible in the trash blanket.
In green cane, elevator pour rates over about 150 tonnes/hour generally lead to boiling and spillage, and this increases losses.
Generic high trash variety, Generic modern full sized harvester