Airbox

[b]How to – Make a cold air box.[/b]

Yes I`ve been at it again....another How To - Enjoy .........

This is a pretty easy one to be honest and I`m shocked that I havnt done this before now. The cost is potentialy very cheap, but it depends upon your design and needs of the cold air box. The cold air box below I made for £30, this price includes all materials, specialist tools I had to buy etc but will probably cost you more as I doubt many people will have a spare roll of heat reflective material lying around. This stuff is very expensive at £90 a rolll, but in this roll you will have enough material to lag 3 chargecoolers and line your cold air box, so if you went halves with someone that would reduce your costs.

Tools and Materials

Alloy sheet (20” squared) from B&Q £15 ish there is a larger sheet availablle for those who are designing a larger cold air box, but obviously the price doubles.
Cardboard
Pen/pencil
Ruler
Pop rivet gun (£15 from B&Q)
Pop Rivets (£1.50 from B&Q)
Tape (I used large width masking tape but cellotape will do)
Heat resistant material (expensive)
A straight edge
Alloy Tape (£4 from Halfords)

Designing your cold air box –

Your cold air box has two requirements, one – it needs to defend your intake air from the heat of the bonnet, two – It needs to have a supply of cold air. To this end, in my mind you need to make your cold air box as big as you possibly can...this isnt easy as there isnt alot of space under the bonnet of a GT4, those of you with straight intakes and battery relocation kits will have the best set up as you can make the maximum sized airbox.
My engine bay by comparisson has all sorts of bits in the way, so the airbox is quite small.

First off you need to get a large piece of cardboard, some tape, a pen and a ruler, (its like being back at school) Blue Peter here I come.........
Remove your existing airbox or induction kit so you can have plenty of access space.

I started with the bottom of the cold airbox, this isnt reall a neccessary part to do, but it does offer more heat protection from rising hot air but be warned, there are alot of wires to concider, you need to note the position of these, alter them if you can to give you a better space, but if you cant then you`ll need to make sure that your cold air box is allowing for them.

WATCH OUT FOR SHARP EDGES, these can over time rub through your wires and cause all sorts of havoc.

When you have measured the base, make a rough outline on your cardboard and cut it out. Offer the cut out to the engine bay and make any adjustments needed so that it is a perfect fit. Label up its position and set to one side.

You need to do this for all the sides of the box, Now I left the forward facing face of the box (next to the battery) open so that forward motion of the car allows cold air in, and obviously I left the face open near the wing/cold air feed. You could make a fully enclosed box with just an input from the cold air feed, but you would have to be confident that your cold air feed is big enough to supply enough air.

Once all the sides are done you are ready for the top, particular attention needs to be payed here as this is the bit your going to see, nice smooth curves etc will make the top more atractive to look at. You also have to make sure of the clearance between the bonnet and the top of the cold airbox, I had to angle the top of my cold airbox down slightly to make enough clearance, not really a big issue, but it would be slightly annoying to complete the manufacture of your cold airbox to find that you couldnt shut the bonnet....now this would dramaticaly reduce underbonnet temps, but you wouldnt be able to see where your going too well.

Now you should have a selection of shaped pieces of card....its time to put them together, Make yourself a cuppa and start putting the little cardboard jigsaw together.

Once your done you should have something that looks like your cold airbox...but cardboard.

Back to the car and position the template cold airbox where you want it, make sure that its not going to catch on any wires, block any access to fuses and obviously fit correctly. Position it in the engine bay...now your ready to cut the hole into the side where the airfilter pipe will go, cut the hole slightly bigger than you need it but not too much, Make sure you have allowed for the temp sensor and other pipework (idle up valve feed etc) Once your happy with the set up/fit your ready to convert the cardboard cold air box into an alloy version.

This is where you`ll need to use a bit more brain power than you might usually....... For the best results the cold airbox should idealy be made from one piece of alloy like a carboard box, but it also has to fit on the piece of alloy sheet, you need to cut the joins of the cold airbox template in such a way that it will achieve this.....confused??? well you will be. I found to best to make the face with the hole in it for the airfilter the middle bit and radiate the other sections off it.

Mark your finished shape onto your alloy sheet, arrange it anyway you can so that it fits.

Sorry about the blurryness...I was drunk when I took these pics.