intercooler

An intercooler is a device which cools the air being drawn into an engine. This cooling increases the air density, and therefore the density of oxygen in the air stream. With more oxygen, there is the ability to burn more fuel - and you get more power. You can go extreme by adding nitrous oxide to the air stream. This is a chemical which breaks down in the heat of an engine to form pure oxygen and nitrogen gases. The best known marketed system (for full size cars) is NOS. A bit over the top for an already way overpowered RC truck.

The heat-exchanger intercooler

The h-e intercooler would comprise a hollow, tubular aluminium part through which the air travelled from the air box to the engine intakes. This would act as a heat exchanger. It would be encased in a tank full of cold material, such as ice water. The finned nature of the heat exchanger gives it a good thermal contact with the ice water, cooling the air passing through the exchanger as much as possible. Extremes could be taken here too, it is possible to fill the tank full of solid dry ice (solid carbon dioxide) which exists at about -80 degrees celcius and below - or for a real chill, liquid nitrogen at about -200 degrees. These two cause problems though as the gas given off as they sublime/boil would have to be released, so the tank could not be sealed. A blow-off valve would have to be fitted. Downsides of the fluid-cooled intercooler are the extra complexity on an already fully packed truck, and the fact that the fuel mixture needles would have to be adjusted for when the intercooler is not used. Supplies of the relevant coolants are not always readily available.
Fitting heat sinks to the air lines is pointless, as a heat sink can not cool below ambient temperature, and that is the temperature of the intake air. It can be beneficial to cool the carburettor intake, and heat sinks are available to cool this potentially hot, air-carrying element. The Hyper-21 engines are equipped with composite carburettors though, which have a low thermal conductivity and will therefore heat the air stream much less than an aluminium carb. For this reason I will not be using carburettor heat sinks.

The injected-vapour intercooler

Another idea, suggested by my Dad, is to inject cool water vapour into the air stream. The latent heat of vapourisation of the water is taken from the air, cooling the air. This of course has the off-set problem of the water vapour possibly displacing any extra oxygen density the air may gain from the cooling process. The trick would be to tune the water vapour rate so that the air was cooled but not saturated with water vapour. The easiest way to do this would be to use an airbrush head to atomise the water vapour, which needs to be driven by a small electric pump operated by a third radio channel. I have a gut feeling that this system would be very hard to put successfully into practise, but it has the extremely cool advantage of being able to supply a burst of extra power upon the flick of a switch. This button would, of course, have to be covered by a bright red surround with a flip-up safety catch.