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Induction kit guide and the effect on performance.

"Induction kits - the real story."

Cars like us need to breathe. You couldn't run very far if your nose was blocked up and a car with a restrictive intake will not perform very well. In this article we will look at the performance advantages of fitting induction kits and see if they are really worth fitting to your car.

The air filter is a very necessary part of the engine, it keeps out particles that would burn leaving harmful deposits and clog up the engine as well as harmful particles that would increase engine wear. The actual act of running air through a filter slows up the air flow but do standard airboxes really restrict a cars intake? Those that assume it does would look to fitting an induction kits or high flowing sports panel air filter.

But do induction kits and high flow air filters always add power to the engine?

There are different types of induction kits and filters. There are Ram, Cone, Panel and round and dome shaped filters. Another important consideration is the material used. Engine bay temperatures can also affect performance so we will suggest the best approach for a variety of different engine sizes and types.

TorqueCars have looked at the various types of filter materials available today and we have concluded that the best filters for flow rates use lightly oiled cotton gauze as their filtration medium.

90% of standard factory fitted airboxes work fine and do not restrict the airflow. The filter is much larger than the intake pipe and although there is a little turbulence caused it does nothing to diminish performance.

When cars are tuned up and the requirement for air is increased you may start to hit a restriction which is when you should look to fitting a better flowing filter. Manufacturers also design air boxes to deaden intake noise and give a wide power band. If you want to focus on a narrow power band or love the intake noise then an induction kit is the way to go.

Most performance filters have a slight coating of oil which will aid filtration. We have not seen any evidence to suggest that lightly oiled filters cause any issues.

Sports panel filters

The bigger the surface area of the filter the better the air flow will be. Mainstream cars today can be fitted with an air induction kit which completely replaces the air intake box and these offer a greater surface area for filtration.

Performance induction kits, a cheap way of making the most of induction roar and freeing up a little top end power.

The plus of any performance filter is youy get a better air flow, particularly at higher revs. Things are only improved though if there was a restriction to start with.

Smaller engined cars will generally lose power when an open induction kit is used instead of the OEM air box. This is mainly due to the kit sucking in warm air. You need to deliver COLD air (which carries more oxygen) to the engine from outside the engine bay. The temperature under the bonnet can get quite high and and a 20 degrees rise in temperature can rob you of up to 3% of your power!

Under bonnet temperatures can quickly rise to double this if you are driving the car enthusiastically. On forced induction (turbocharged) engines) an intercooler can be added which reduces the temperature of the air intake.

It should be noted that in many small engined non turbo applications the car will feel less powerful with an induction kit due to a noticeable lack of low end torque.

In these instances the best option is a direct replacement panel air filter which goes in the standard airbox giving the best compromise.

Sucking warm air in from the engine bay is a great way to lose power. Site your intake as far away from the exhaust as you can and wrap the exhaust to keep those temps down.

Make sure you have a cold air feed pipe to get cool air from outside of the engine bay - cold air carries more oxygen.

Intake air temperatures

It is also good practice to enclose the induction kit sealing it off from the engine with a box of some description.

Recently one of our members (Claymore) ran some tests with and without an airbox and came up with the following interesting results with a performance cone induction kit.

1) With an air box the intake temps dropped to ambient within 1/4 of a mile of driving.
2) Without an air box, the car had to be driven for 2 miles before the intake temperatures dropped.

If you are doing a quarter mile run or short sprints, an open cone filter is next to useless. Without a cold air feed the engine bay air will be quite hot for the entire run, even with a heat shield and you'll lose power.

If you had a cold air feed from the outside via a vent then intake temps would be  substantially lower and you wouldn't need to run the car any distance to clear out the engine bay temperatures.

So the best air induction kits come with a cold air feed pipe and are fitted in an air box which shields the intake air from the high under bonnet temperatures. Some kits have a long pipe which the filter sits at the end nearest the bonnet which really does help cut down the noise and improves the intake temperature. We've seen drivers remove lights to make space for the intake. Adding vents to the bonnet or front of the car will also be useful in citing your intake feed.

We should also mention RAM air Induction kits that protrude under the front bumper which claim to get more air forced in. The intake is now cited on the pressure front on the front of the car as it cuts through the air. Do these work any better?

Other than the benefit of the cold air from outside the engine bay, - the RAM effect will require speeds of over 100 mph before any benefit is realised. These kits are however a great way to collect many botanical specimens of flies, moths and bugs in the air filter and requires more cleaning than a conventionally cited intake!

NB: Be very careful where you site the cold air feed - the last thing you want is to be sucking water into the engine every time you splash through a puddle. We've seen a few engines killed due to poorly located intake pipes!

If the induction kits air filter is enclosed in a box with a cold air feed, then more power can be obtained avoiding the hot under bonnet air (Carbon fibre boxes are very good for their heat shielding and durability). It also good to wrap a the exhaust manifold with a heat resistant material to keep the under bonnet temperatures down and tasteful vents can be added to the bonnet to take away the heat.

So to summarise standard airboxes work fine on most cars. Fitting a performance filter will make little difference. However if the engine has been tuned and requires more air you'll probably find an induction kit overcomes any restriction in the OEM airbox.

If you have a large engined car, turbocharged or highly tuned engine fit an induction kit with a cold air feed. If you have a small engined car or one with little power in the lower rev band fit a direct replacement sports panel air filter or just stick with the standard paper filters.

Please join us in our friendly tuning forum where you will find 1000's of common sense car specific tuning tips and recommendations.

Just don't expect to see noticeable power gains from an induction kit alone and you won't be disappointed. The best reasons for getting one is to experience the induction roar sound.

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