I just had a brilliant idea. Time to shoot me down!

As you probably know, liquid-air intercoolers do a much better job of cooling down the intake charge than straight air-air intercoolers. That said, instead of lugging around extra water/acetone/hexane/what have you, why not use the gasoline in your fuel tank? Here's what I think it might be like:

Fuel tank > fuel filter > intercooler > injectors.

Of course the part where the fuel flows around the intercooler would be sealed, and you'd have to think of a way to keep pressure high, and adding extra fuel to cool down the cylinders wouldn't work as well, but it might be worth a shot.

What do you guys think?

Usually liquid-air intercoolers have a radiator or heat exchanger to reduce the temperature of the coolant. Otherwise, as you drive the temperature of the liquid coolant would steadily increase ie the temperature in your fuel tank would keep going up with no where for it to go. If you had relatively small fuel loads this could heat up quite rapidly.

Cooling usually requires a large surface area to cool eg a cooling surface. I'd think that in a vehicle this could present some packaging as well as safety issues.

Also heating your fuel presents problems with vaporisation issues and also reduces the density of the fuel being injected.

You can also add the extra weight for the piping to move the gas and more importantly, you'd have to have a minimum amount of fluid at all times. Getting and empty tank would have all sorts of bad repurcussions.

Lastly, gas is a terrible cooling agent.