I did some analysis awhile back and it indicated that a typical AC evaporator would be quickly overwhelmed by the amount of heat produced by the FI device at high loads (under boost). The BTU absorbing capacity is simply too low for the BTUs produced. Therefore, application as a direct heat exchanger (replacing the IC core) would never work.
However, it would work as a device to simply cool the IC water under light loads and help solve the problem of how to keep light load air temps from slowing raising the intercooler water temp. This makes the intercooler less efficient when you really need it, under boost.
Regarding IC water temp creep, I concluded that a simple pressure switch controlling the IC water pump might work. At light loads the water would not circulate, thus keeping the bulk of the IC water supply from seeing these higher temps and creeping up. On the other hand, this would raise the temp of the local water directly in the IC and to some extent down the feed and discharge hoses as well. The IC housing would soak at a higher temp also. Therefore, when the system sees boost and the water starts to pump it would initially need to overcome this higher soak temp before it could take advantage of the lower overall water temp.
That’s what scared me. This initial “soak down”, even if it only took 10 seconds, might be enough to promote some detonation. So I gave up on the idea. However, having the water cooled at light loads would definitely help intercooler efficiency, for a short time at least (probably 5 minutes or so under track conditions depending on the delta temp and water volume). Under your typical run and gun street conditions it might work pretty well, particularly if the high load periods are short and there’s time to dump some heat between boosted conditions.
It does come at a price (nothings free), as the AC will need to be on putting additional load on the engine. You’ll need to run the system for awhile under light loads to get the bulk water temp lower, the larger the reservoir the more time it’ll take. And you won’t be able to use the AC for cabin comfort, unless it’s a dedicated system. To get something a bit more “free” I was thinking about using exhaust gas temp to feed one of those old fashion refrigeration systems like those used on RVs running propane. It’s a pretty simple concept, just never got around to working the details.
