Intercooling lowers temperature of intake air, reducing the danger of detonation, increasing the efficiency of fuel/air burn and resulting power production.
An intercooler is mounted into the inlet ducting between the turbocharger - which generates intense heat - and the inlet manifold.
There are two different types of intercooler; both designs have their advantages and disadvantages.
ATL (AIR-TO-LIQUID) INTERCOOLING
In this design inlet air is ducted through a vessel containing a cooling body of water. This water has a tendency to absorb a great deal of heat from the inlet air.
The negative aspect of ATL intercooling is that an elaborate system is required to dissipate the heat that inevitably collects in the intercooling liquid, which is generally water. As water cools the inlet air, it starts to rise in temperature, approaching an equilibrium point between inlet air temperature and liquid temperature.
To dissipate this water heat and maintain air cooling efficiency, a radiator system must be used. For basic applications the host car's cooling system and radiator may be sufficient, however for maximal cooling benefit a dedicated cooling system must be used. This will consist of a heat exchanger or radiator to dissipate water heat, combined with a pump to force circulation of liquid through the cooling system. A fan or bonnet vent may be used to maximise cooling effect.
In E15ET Pulsars, a Subaru Liberty RS ATL intercooler can be placed on the passenger side of the engine bay between the strut tower and left headlamp, after relocation of the battery. This setup can provide and almost-factory look, as is evidenced by E15ET list member Paull Charman's install.
ATA (AIR-TO-AIR) INTERCOOLING
A far simpler option is that of ATA intercooling. This involves the placement of a radiator-like baffle in the inlet track within which inlet air is cooled by ambient-temperature airflow.
This method requires clean, cool airflow to be effective, which means front-mounted intercoolers with clear flow through the grille are most common and efficient. Unfortunately, in many ETs and EXAs, such installations require at least some minor, and often major modification of the bodywork around the radiator.
In ATA applications on E15ET's, many different coolers can be considered appropriate. By far the most popular, however, are ex- Mazda RX-7 Series 4/5 (turbo) intercoolers. Nissan 200SX and Mazda MX-6/Ford Telstar TX5 intercoolers are also popular.
Where? How Much?
Subaru Liberty RS ATL intercoolers are available from some wreckers at around $500 for the cooler alone, plus more for radiators and pumps. Shopping around and bargaining down a receptive wrecker could see these peripherals thrown in cheap.
Mazda RX-7 intercoolers are commonly sought items, given their good flow properties, common availability and convenient size. They can be had for around $200.
Piping for intercoolers will vary in price depending upon the installation and the length of piping required. It is possible to get mild steel intercooler plumbing completed for an under-bonnet intercooler at around the $100 mark. Stainless steel will carry a significant premium.