[hotrod]

Well your comments are interesting, but I feel there is plenty of driving force.

Typical conditions here at the strip or on a hot summer day, outside air,measured well away from the pavement 85 deg F, at 12% humidity. I frequently measure actual intake air temps above 105 deg F.

That puts the intake air humidity as it passes the spray nozzle in the dry air catagory with a dew point of less than -39 deg F.

At dew points like that with pure water your wetbulb temperture would be about 53 deg F. (ie this is the temperature the air would cool to if you raised it to 100% RH by evaporation of water)

This is ignoring the issue of alcohol evaporation or the lower air pressure which makes the water have a higher relative vapor pressure.

The relative air speed between the dropplets and the intake air being in the 100 mph plus range will result in a nearly instantanous evaporation of enough water to drop the air temp by 10's of degrees F.

Its difficult to measure the true air temp because of problems caused by wetting of the surface of the temperature probe, but there is absolutely no doubt that there is a very large driving force for evaporation when the dry air and the rapidly depressurized water dropplets first encounter each other at high relative velocities.


If you want to dig through Perry's or CRC handbooks to figure out the realtive vapor pressures and all that ---- please do ---- I have neither the time or the interest in trying to validate what is obvious to me based on my experience. When going to the pre-compressor water spray, my midrange boost onset was so dramatically improved I had to change my driving style to keep from running over people when accelerating from stop lights. I'd come into boost so quickly I had to change my boost controller settings (turn them down) for daily driving.

Simple proof of driving force for water evaporation when your car is mass flow limited for air by the choke flow capacity of the turbo.

Without water spray in the intake car goes x mph in 1/4 mile, with water spray pre-compressor car goes y mph in 1/4 mile.

x is > than y ----- spray must work!


Larry