Originally posted by Number47:
it was my understanding that air to air works better because your always running the charged air to the ambiant air temp. example: random numbers to, 150 to 75 there is a greater difference than the water type that is at 90 so your trying to get 150 to 90. but i dont know, thats just how i understood it on our tractors



Not really. Heat transfer into the water from the aluminum core is faster and the water can hold more heat before the temperature raises by 1 degree than air can. Putting it back out into the air means that you still have to think of it the same as an air to air.
Let me better explain: Assume no ice is used and that the water temp operates between intake air temp and ambient temp.

Next, the medium that the heat is going through are as follows:
For air to air IC: Air->Alum->Air
For air to water IC: Air->Alum->water->Alum->Air

The only difference is the water in the middle and since heat transfers between aluminum and water 14x faster than between Aluminum and air, having the water in the middle is negligible. Therefore, without some outside factors such as introducing iced/cold/hot water to the system it will act much like an air to air cooler.
With one or two exceptions. The water temp will respond much slower to ambient temperature differences so if ambient temps cool down or you run through a patch of cooler air then you won't see an immediate benefit in your intercooler efficiency until the water has had time to cool down. On the other hand, if ambient temps raise or you run through a patch of hot air, you won't see the penalty as quick. But counting on the benefits of the last statement are so rare you may as well not include it in the discussion.
This is why you are shooting yourself in the foot if you use a very large capacity coolant system in your water to air intercooler!!!!! Your car cannot cool down the coolant quickly once it is heat soaked without a lot of airflow across the heat exchanger, as in driving down the road for a few minutes. Idle heatsoak will reduce the system efficiency. Also, the more tanks and lines you have running the car the more surface area you have to absorb outside sources of heat, and that is anything higher than the coolant temps. The signficance of this is that putting a bucket of ice water in the cooler and esp. having it in the trunk means it absorbs heat from all across the car, often being too warm by the time you get through the staging lines! Only a drag race team with the container next to the IC core with easy acess to flush with iced water can really see the benefits of a large volume resevoir and ice.

So I come back full circle to the discussions over the past three years that the large trunk mounted tanks are a waste of time, money, space, and of course too much added weight (figure 8#s/gallon)!!
Even though there is a sweet spot in coolant amount for best efficiency, you should think of it as using only enough coolant to fill the lines, cores, and a small resevoir to provide enough coolant for when the water contracts as it cools down.
This improves transient temperature efficiency.

Former owner of '99 CSVT - Silver #222/2760 356/334 wHP/TQ at 10psi on pump gas! See My Mods '05 Volvo S40 Turbo 5 AWD with 6spd, Passion Red '06 Mazda5 Touring, 5spd,MTX, Black