[nutron]

A few small points,

1) by adding the water/methanol you displace some air and so don't get as much of an increase in efficiency as you might through cooling alone during compression.

2) water and oil get drawn into the turbo all the time, methanol does not. The seals in a turbo are not designed to interact with methanol and over time (I know someone said they had been doing this for a year) the seals could degrade and the turbo might fail at a fraction of it's intended life.

Erosion of the blades is not a major concern as I have said previously, as the breather for the engine feeds back into the intake before the turbo; any oil mist will be going into the turbo in the same way water would and so turbos are designed to withstand this type of particulate flow.

A lot of turbos are water cooled to deal with the high exhaust temps of petrol engines, you could seperate the cooling system from the engine cooling and cool the turbo more effectively. This would allow you to decrease charge temps by not imparting so much heat in the first place.

More small nozzles are better than one large one, as they cause less turbulance.