Choosing an intercooler

Intercooling your E15ET engine

The installation of an intercooler to your e15et engine is one of the most important performance modifications you can carry out. Intercooling lowers the temperature of the intake air, reduces the danger of detonation, and increases the efficiency of fuel/air burn which results in better power production.

As standard, the e15et engine running it’s factory boost pressure of 6-7psi has no dramas handling the associated inlet temperatures caused by such a boost figure. However turning the boost up to around 10-12psi may result in detonation which is very harmful to your engine. To remedy this, an intercooler is a must!!

Basically an intercooler is like a radiator for the inlet air and is situated somewhere between the turbocharger and the throttle body.

Choosing an intercooler:

One of the most important decisions you will make regarding the intercooler is what type, and where to place it. The position and the type of the intercooler will have different results on performance and efficiency so you need to take some time to consider which option is best for you.

Basically you have 2 choices of intercoolers, being air-to-air and air-to-liquid intercoolers, and 2 position you can mount them, being top mount or front mount positioning.The following will run through the in’s and out’s of each variety.


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


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 ET’s 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.

Below is a comparison of factory fitted intercoolers from late model Japanese cars: (From

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