Drivewasher. If you don't run a machine (any engine) for what it is designed at, it will do two things. 1) obviously it will not perform as well and 2) most important it will not last as long either.
Whatever the advised optimum revs is suggested should be adhered too. Any reduction or addition will wear out the engine faster than if it is run as it should be.
Best, Dave.
What rubish, sorry but we are talking about a positive displacement PUMP. The pump is designed to give a set pressure by forcing a fixed amount of water through an oriface (nozzle) that is matched by it's hole size so as when the set amount of fluid is FORCED through it it comes out at the pump design pressure.
Because this guy is cleaning wheelie bins with a very high spec machine, he should really change nozzle or reduce the amount of fluid going through it, so he has opted to reduce the amount of fluid forced through the nozzle by REDUCING the engine speed to reduce the flow,thereby reducing noise for the operators, reducing nozzle pressure so they don't get spattered with the remants of his customers bins, and a huge saving in fuel used.
When he goes on to clean drives with a surface cleaner he will have to run machine at the PUMPS optimum speed of 3400rpm engine speed if it's a petrol engine will be 3600rpm NO LOAD so when he triggers up the speed drops to 3400rpm this will be the engines best torque/power band.
So if your cars best power output is say 3000rpm this doesn't mean if you go through side streets in 3rd gear at say 1400rpm you are doing your engine damage cos youre not!