Surprisingly water injection also helps clean the internals of the engine - but it should be shut off well and truly before the engine is switched off otherwise you can be left with water sitting in the bores.

A friend of mine runs a 2500PI Triumph in Targa and he uses a water atomiser from an agricultural supplies company and sprays the water into the injection plenum. He says it helps calm the motor down when they are running it hard at high revs for long periods.

I've planned to do it for ages but not got around to it. My friends have a button half way down the gearstick and just turn it on during races etc when they think they need it.

It has other benefits too - but I'll have to go check my notes.