Induction  

Induction, the process where by the piston travelling on a downwards stroke attempts to create a vacuum within the combustion chamber. Air will then attempt to fill the combustion chamber to counteract this vacuum.

 

So with this in mind you would have thought the simplest and easiest way to improve induction would be to just remove all the filters and piping in front of the inlet valves would you not?

Well its never ever that simple, manufacturers utilise a variety of different methods to allow for things like smoother running, better fuel economy. On the AE111 corolla you can find two tanks attached to the air intake system, one of which is a resonantor (acts similar to a capacitor in an electrical circuit) and the other is a resevoir (beneath the battery and hidden n the wing) this catches any large particles that find its way into the intake.

Right, now thats the explination out of the way

 

We can now move onto the fun stuff...

Modfiying your air intake system

 

-- Disclaimer --

All information regarding modification has not been officially sanctioned by anyone! All research is a result of trial and error, any alterations to your vehicles are at your own risk and i will not be held accountable!

I personally like the idea that an aftermarket induction kit can, theorectically, add 5-8 BHp to you car, but in reality you need to get AEM Cold Air Intake or K&N 57i Gen II in order to get anywhere near those figures. They start at £150 so that was way out of my budget then, so i experimented with the exsisting pipes and a Ripspeed induction filter from Halfords, cheap and cheerful.
   
here is the basic induction setup
I have experimented with various different lengths of intake pipe and found that placing the filter on the throttle body itself is not really very beneficial (this is all measured by the bum dyno! of course) Below is with an itake pipe that is too short:

The above intake pipe setup consists of a sort length of Silicone hose, a Ripspeed air filter and a 45 degree bend from B&Q, the plumbing section (one end diameter 60mm or close the other end around 76mm) This was very cheap to manufacture
on the left is a pipe with the correct length however i went a bit overboard on the cooling ducts.
Whilst cooling is a good idea there were far too many ducts there not really helping. However the large duct served two purposes, i) divert cold air to the filer, ii) minimise warm air from the radiator/exhaust getting into the filter. There was a noticeable difference when the duct is removed, not so much the cooling air but restricting hot air entry. The design of the engine bay leads to most of the hot air from the radiator blowwing straight onto the air filter, so if you can prevent this you should see a notable difference in performance (most likely at higher speeds eg. the motorway). Below is my current setup  
 
Below is my custom built Cold Air Induction kit. This didn't cost too much and you could do the same cheaply, it totalled aroun £80 for everything from the filter to the sheet of aluminium. The key factor is this setup is to move the battery from behind the headlight, further into the engine bay. This will allow you to place the filter closer to inwards rushing air and move it out of the path of hot air travelling from the exhasut/radiator. Also removing the air resevoir in the O/S wing (you'll have to remove the front bumper or pull it through the passenger side wheel arch) you can duct cold air in straight from the front bumper, lowering intake tempratures further. The heat shiled is quite important to reduce temperatures and you'll need to remeber that warm ir will come at the filter from all side. This setup is very hand at the drag strip as removing the headlight lets cold air directly onto the filter.
 

4A-FE power!