Subaru's Intercooler

Intercooler Duct - by Tim Whiteside

I made mine from 1.5mm thick aluminium sheet as it was nice and easy to cut and shape.

Before making it in Aluminium, I would suggest trying it out in card, as I'm sure that some playing about with the actual dimensions will be needed first.

Apologies for the isometric drawing which is meant to depict the 'as built' shape of the diverter (scoop) !

Some people who got copies of the drawing last night have already been asking questions, so here are some extra points:-

Questions & Answers

You've given dimensions for the holes at the top of your drawing as 2.5mm diam. What diam. are the holes on the bottom of the drawing?

The same, the holes don't need to be exact, just to suit your fixing method (pop rivets or self tappers).

Are the angles for the fold lines critical or is it simply a matter of trial and error ?

The whole thing is trial and error really, the template should ideally help to cut down on the number of times you have to repeat the process! What ever you do please carryout a trial run in card first!

Do these holes pick up on existing bolts/screw on the intercooler/ or do new ones need to be drilled ?

New holes will need to be drilled in the bonnet scoop undertray.

Have you verified your design by rolling road or inlet temperature measurement.

The car went on the rollers at PE, at the last gathering (check out Paul Strong's site) but the duct and my water spray (Allegro parts!) made no noticeable difference. However Rolling Roads are notorious for not 'appreciating' this type of mod on Scoobs, because the fan blows very little air over the bonnet into the intercooler.

I haven't taken any temperature measurements, but it would be interesting to find out what (if any) effect the mods have had to the intake temperature. Just got to work out how to do it!

Just a thought, the duct was designed (!) around a 98 model Impreza, so if going on a Pre 97 modes with the offset intercooler, I've no idea whether it will suit the earlier type!

Hope this helps!

Regards, Tim

Intercooler Splitter - by Tony Stott/Peter McAlpine

We fitted a splitter in the bonnet scoop, which (obviously) splits the intake air to ensure that the front half of the intercooler gets an equal share of the work (he had rightly suspected that most of the airflow hits the rear half, which then has to work twice as much, leaving the front underused). Bingo! This resulted in a further 3 degree C drop in temperature difference from input to output intercooler temperature.

Intercooler and Radiator Protection Grill - by Ian Gray

The mess I used for both jobs was galvanized, sprayed mat black with holes approx. I think..( 6mm x 6mm ) as used for making Rabbit/Pet cages available at garden centers etc.

Not too big as it wont stop anything..not too small as the air will be restricted.

To install the grill in the front rads:- Rough guide ....

Remove front grill . the one with the logo on it ...
Remove inner headlight mounting screw. This is used to hold the mess in place - left and right
Remove / loosen the bonnet latch mounting ( you will need to hold this out of the way while the mesh is installed - a child is ideal for this )
Cut mess to size so it fits between h/light mounting screws and covers all rads top to bottom.
Slid mesh down in front of rads
Refit bonnet latch
Refit light screws holding mess in place between body/light 8) At the bottom of the mesh I used two tie wraps ( to front grill ) to hold it away from the rad and stop it possibly flapping as if not ,this will move it into the rad and possible cause holes ... Defeats the point of installing it...!!!

The Intercooler grill is in the bonnet ......under the black scoop mounting ..between the bonnet and black scoop plate ....can be seen when the bonnet is up better ..held on by approx. 6 screws ....very easy to make mesh up and refit plate...looks good and works very well.

Intercooler Water Spray - by Tony Stott

Actually, waterspray is a great addition (well in Australia anyway...) I bought an aftermarket windscreen washer kit (plastic 2 litre bottle, clear tubing, motor and wiring), fitted it with a short bracket to the front battery retaining rod (had to reverse the horn to increase clearance, wired it to the standard washer wires and joined the tubing to the washers.

I Then Added a pressure switch to the firewall, connected to the rh front corner of the inlet manifold, and sent a wire into a coin holder in the centre console to enable me to disable it in wet weather, and then added vacuum tubing to the rubber skirt around the bonnet scoop, where I placed a couple of nozzles from indoor plant trigger spray bottles (these are best for atomising the water. Now, when boost reaches about 8lbs, a little cloud fills the bonnet scoop. Don't laugh! A recent magazine test on a 200bhp turbo car showed a 12 bhp gain! not too shabby for about $A100!

This weekend I am adding a green LED (ie pressure switch has power), and a bright blue LED (water she is pumping!) all inside the same coin holder.

Call me a geek, but its good DIY fun!

The big one (above) shows the overview. Points to note are:-

Extra small hose leading underneath inner end of right hand ignition leads. This is the pick up point for the pressure switch
Pressure switch can go anywhere - here, it is screwed to the firewall at the back right of the intercooler
The two green water spray bottle nozzles can be seen inside the scoop
The extra hose is ziptied to the washer hoses (care, the washer hose is very thin, and can be closed if the ziptie is too tight.)
New washer bottle (with green anti-smear detergent mixture)attaches in front of the battery (see other photo)

Close up of the bracket which attaches the new water bottle to the battery.

(The ISDC cannot be held responsible for any modifications that adversely effect the warranty of your car.)