I'm a newbie to the turbocharged/IC engine area. I'm used to N/A larger displacement truck engines (and the horrible gas mileage that goes with them). My name's Yoshi. I'm planning on trading in my 2000 Frontier 2wd V6 5spd for a 2005 WRX non-STi.


Anyways, I know that the I/C waterspray cools the intake air under conditions where the intercooler might not get sufficient airflow to do the job. How does this work? Does it spray water directly over the cooling fins on the I/C? How much and for how long? I'm curious about this because I've never heard of it before.

 

Hi Yoshi,

FYI......

The standard (non-STi) WRX isn't equipped with the I/C spray device.

 

Ni3Frontier,

Here's a 4-part article on intercooler and water-spray for ya from autospeed...
http://www.autospeed.com/cms/article.html?&A=0527&P=1

 

That article was pretty good... a little long, but good.

One thing that he completely missed was the actual reasoning behind spraying a a heat exchanger with water. It's not just that water has more "thermal mass" (in engineering it's actually referred to as 'Specific Heat - Cp'). The main reason that it is so effective is that it involves a phase change, i.e. liquid to a gas.

It works on the same principle as when you sweat in hot weather. Your body covers itself in moisture so that when the moisture evaporates, it takes a bunch of heat with it. Phase changes typically require a whole lot of energy to take place. Kinda like boiling water for your noodles: have you ever noticed that it takes no time at all for those first couple bubbles to form on the bottom of the pan, but then is takes another 10 minutes before the water actually boils? This is because the transformation of liquid water to steam (gas) takes a boat-load of energy.

So when you spray a mist of water on the intercooler, the water evaporates and takes a bunch of heat from the intercooler with it. As the article pointed out, there are some limitation to the effectiveness of it. One being that you usually need a substantial amount of airflow. The other being that if you douse it with water, there is too much to evaporate quickly and it will just puddle up and not provide any benefit.

Simple enough?

 

Thanks so much for the info guys! The fact that an intercooler acts more as a heatsink was news to me, but it made good sense. I really enjoyed the article and appreciate the link to it! I'm looking forward to posting here often and learning as much as I can.


-Yoshi