[hotrod]

If done properly, injection prior to the turbo compressor will work and not destroy the compressor impellers.

There is some debate about the desirability of the various injection points. the common wisdom is if you have an intercooler the injection point should be between the intercooler and the throttle body. If there is no intercooler the injection should be infront of the compressor.

I suspect it is not quite that simple, and if you want to be sure you should run some comparative tests.

By way of example the WWII fighter planes and bombers using the R2800 Pratt and Whitney aircraft engines injected both fuel and ADI (water injection) into the "eye" of the compressor of their superchargers. The trick is the spray into the compressor needs to be set up so no large droplets impact the blades. If it is a very fine mist is appears to vaporize as it enters the inducer due to all shear forces and rapid changes in direction and pressure.

Quite a few of the tractor puller folks use pre-compressor injection on at least one stage of sequential turbos.

There is one user that I know of that places a nozzle so it sprays directly on the tip of the turbo compressor shaft. The water is instantly microatomized on contact with the rapidly spinning shaft before it ever reaches the compressor. Water introduced into the compressor as a solid stream or in the form of a coarse water dropplet spray will quickly "sand blast" the compressor blades.

The ideal may be a combination of both. Spray as much water as you practically can between the IC and the throttle body. If you find you still need more water, I would add an additional injection stage infront of the compressor so it sprays only during the highboost, high heat load part of the boost cycle.

Larry