Originally Posted by SPOautos

They only maintain a equilibrium when you have a constant temperature difference. In this case the temperatures are swinging wildly from ambient up to 300 degrees back and forth all the time. My point was if you didnt have a heat exchanger large enough to remove the heat then then the heat is going to keep building higher everytime you get into the boost. Sure if you have a tiney HE you might be ok if you only get into the boost for a few seconds every 20-30 minutes. But what about the situations I mentioned such as taking the car on a road course or tuning session? In those type situations if you want to beat out a air/air then your going to need a LARGE heat exchanger placed in front of the radiator that can remove all the heat. The only advantage a l/a has over air/air is the amout of btu's it can absorb before the water changes temperature above ambient. Once the temperature of the water increases above ambient you wont be able to run ambient charge temps. The water still has to be cooled by the air so either way your removing the heat with air, the liquid just delays that process for a short period of time untill the water heat up.

The only way a liquid air will have temps below ambient is if you get the water below ambient and the only way to do that is by adding ice. By using a heat exchanger and no ice your best temps are going to be ambient temps and to maintain those temps in a situation where your driving the car hard for an extended period of time will require a giant heat exchanger....even then I dont think you could keep ambient.

Originally Posted by edmcguirk

You're right, if you go onto a road course where you are only off boost long enough to brake for a corner, a water/air intercooler will not cut it. When you design a water/air IC system you have to push for the biggest radiator and the fastest pump you can fit/afford.

On the street, it would be unlikely that you could stay on boost for more than 30 seconds. At that point you would be pushing seriously dangerous and illegal speeds. If you go canyon racing you might possibly get the kind of boost times that you might see at the track but even that is kind of pushing dangerous/illegal driving.

As long as you are boosting below the radiator's capacity to reject heat, the water will be getting cooler. When you are boosting more, the water is getting hotter. Bigger is better. A good radiator/pump combination should keep your water reasonably close to ambient for most street driving.

As I said before, the longer you are on boost, the more you want an air/air IC. But most street driving works towards the water/air IC strengths.

Trying to use refrigerant or ice in a water/air IC gets difficult if you try to get water temps below ambient. The radiator starts to fight the cooling system by warming the water up to ambient. You need complicated valves and pumps to make it work well.

ed