Front mount or water to air . Even the gu intercoolers with a thermo fan are shit Most will opt for a crosscountry big top mount and use a big bonnet vent or go water to air . The heatsoak at low rpm on a diesel patrol is horrendous , Does the thermo fan help , yes but the intake temps are still ridiculously when high slow moving already. The gu factory top mount sits in a position that the turbo headers and engine all radiate heat through it.

A subaru has a decent void below the top mount and the heat from the turbo can be reduced with decent shielding . The limiting factor at 400whp is the cfm capabilities and size that the cooler can be made in that position . The cfm limitation causes heat , the intercooler surface area limitation causes heat and as soon as the car stops or does slow driving, increased air flow may be had by fitting a fan to pull air through. But it wont do it at a rate to make a big difference also the radiated heat from the motor and its cooling system increases engine bay temps drastically at low speed.

At 400 whp and above the gains had from that power out weigh the lag and pressure drop of a front mount . Utilising an efficient twin scroll or newer designed billet wheel ball bearing turbo charger negates a large portion of the lag. Turbo technology in the newer twinscroll ball bearing turbos is chalk and cheese compared to the 20 year old technology of a vf series turbo.

Water to air is an option especially if the car is in stop start traffic as water has a much better transference of heat to an air to air intercooler. With the right heat exchange fitted and a decent water to air cooler core size your intake temps remain very constant and only fluctuate 10 degrees up or down even in slow driving . Its inherently more stable by design . So 4wds and heavy stop start driving, or short hard runs such as rally sprint are ideally suited to water to air .

The three limiting factors with water to air are : cost. complexity and weight.

A good quality front mount works very well at the whp you are chasing . You can fit a core very neatly in the front with very minor cutting of the bumper if you plan it out and take your time. Front mounts shine in constant moving air , but also shine in the fact that mounted away from the hot engine components they remain much cooler at slow speeds and rest . The heat soak that they do have is usually experienced with the piping and routing of it . Which again if carefully planed out utilising shields heat wrap and a rotated comp housing on the turbo is much much less of a factor then a top mount.

You can still run a water spray system with the front mount to spray at certain intake temps to lower the heat soak . It actually works much better on a front mount due to the surface area and evaporation takes place faster.
I run Water to air on my Rs its a modified factory intercooler that has a 40 % increase in water capacity and uses a heat exchanger at the front well over double the size . This is set up to work with my new motor combo which will be tuned to over 400 whp.

This was a more cost effective and size friendly package for me to use. I entertained the use of a larger aftermarket water to air cooler but the piping started to be an issue with several tight bends and it also taking up way too much room in the bay making removal and fitment an issue. If I hadn't had an rs with the ability to use its modified water to air cooler I would have gone down the front mount route.

I have fitted many water to air cooler systems to 4wds and can tell you a good setup is over 2500 bucks this was the last system I did from plazmaman in a mates GUhttp://www.perth-wrx.com/vb/offroad-...rol-build.html .

There are cheaper systems on the market but you get what you pay for material and welding wise . A good front mount all plumbed in and routed neatly is at least 1000 bucks less and even cheaper if the core is second hand . Again yes there are cheaper kits but if you dont like lag, pipes blowing off and corrosion dont skimp.

Being a version 6 if you are worried about cutting the front original bar , dont . Get a second bar and trim that nicely , keep all your factory parts intercooler etc . to provide if you do sell the car so it can be retuned to original condition if the purchaser wants it .

I hope this small novel helps