Cold air vents and CAI kits

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Cars are more lively and perform better when it is colder, you’ll also notice that you make more power and your fuel economy is lower in cold weather.  This is due to the effects of air temperature and the fact that cold air carriers more oxygen than warmer air.  An intake vent will help to address this problem, and can be a stylish addition to your car by providing an easy route for cold air to enter the engine.

Therefore for performance applications you really want to be sucking cold air into the engine.  The problem we will encounter though is that an engine produces a lot of heat and the engine bay is not an ideal palce to be sucking in air from although after a mile or so the temperature drops a fair bit. 

The more power you are producing the more heat will be released by the engine which is a simple fact of life so in a performance car it become more important to have cold air coming into the engine. 

The job of the radiator is to take call and from the engine exposing the is too cold outside air and therefore reducing the temperature of the engine.  The problem with this arrangement is that the temperatures under the bonnet of the car rise to very high levels in a relatively  short period of time. 

One way of reducing the under bonnet temperature is to put insulating lagging or a heat resistant coating like ceramic around the exhaust, particularly the headers.  As a side effect the catalyst will typically reach operating temperature more quickly.

It is no surprise then that motor sport teams make good use of vents in the bonnet and wing of the car.  These allow additional air flow through the engine bay and help to dissipate the high temperatures. 

Ideally you want your air intake to be sucking in the fresh air from outside of the engine bay, and one way of achieving this is quite simply to have a vent cuts in the bonnet just the above the intake area.  You will need to avoid sucking in water to the air intake and need to think about this when cutting a vent and citing your intake. 

The best applications we have seen include a cold air induction kit fed from a vent on the bonnet with the induction kit housed in a box to separate it from the hot air in the engine. An intercooler may also be used to help reduce the temperature of the intake charge,  in typical high pressure turbo and supercharged applications.  Citing the intercooler behind a vent will be substantially better than mounting it near the radiator, where the hot air around the radiator will reduce the effectiveness of the intercooler.

You cannot just cut holes in the bonnet if you look underneath the bonnet and remove the sound deadening material you will notice that there are sets of reinforcement bars usually in the pattern of triangles.  You should not cut through any of these bars, unless you want to reduce the rigidity of the bonnet or risk it bending and flexing as you drive along.  When creating vents you also have to be conscious that you are not exposing any electrical components to the possibility of water ingress.  A shield or scoop may help to minimize this risk.

The addition of a carbon fibre bonnet with integral vents will help also as this will be more effective at dissipating the heat  compared to a steel unvented bonnet.

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