Back What they actually do Replacement filters Induction kits The kit
Can a replacement air filter really give me more power ? There seems to be 100's of different types of air filter available for whatever you drive, varying from replacement air filters which take the place of the factory one to direct air induction kits as pictured below. But what do they do and how effective are they ?
Well they clean the air before it goes into the engine. The theory is that
the more cold air you can get into the engine the more power it will produce as
long as the fueling is adequately proportioned. It follows then that if you
replace the standard air filter with one that will allow more air to flow
through it you can gain power ... just don't expect miracles !
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We'll start with replacement filters. They come in all different flavours but
will all look basically the same in shape as each other for your particular car.
They replace the standard one in the standard air filter box and have the
advantage that they can usually be cleaned using a special solution giving you a
re-usable filter that can outlast the engine. They will normally give you a
little bit more induction noise and a couple of bhp. Yes that's right : maybe 2
bhp if you are lucky. People that tell you more can be had are talking shite,
the main restriction here is the standard air cleaning system. Remember this air
filter will only have the same amount of air being fed to it as the standard one.
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K&N 57i, Ram-Air, Piper etc are all familiar direct air induction systems that can be bought for your car and will require a bit of fitting. I have a K&N 57i kit fitted to my Pug 309 and although it's difficult to measure the performance difference I feel that there are several advantages to be gained by fitting such a kit as follows :
Looks - the filter looks impressive under the bonnet, in the case of the K&N there are many components removed such as the air box for the standard air filter and the rubber ducts that feed the air box. This makes for a cleaner look under the bonnet and the air filter itself looks the business.
Power - there is some extra brake horsepower to be had from this type of filter particularly if complimented by other mods that help the engine breathe or the engine requires more air. These would include performance exhaust systems and gas flowed heads. Just how much can be gained is difficult to establish because measuring the power output of the engine is best done on a dyno or rolling road. In these circumstances the car or engine is stationary which means that the usual abundant supply of cool air is not available so rolling road results may be disappointing. There is a few bhp to be had here though in most cases.
Re-useable - again these filters can be cleaned and re-used like most replacement high performance filters which means that the filter theoretically need not be ever replaced which in the long term has to save money. I would warn that it is worth using the recommended manufacturer cleaning materials and oil because this prolongs the life of the filter.
Induction noise - this now isn't as subtle as the replacement filter, you can
actually hear your engine breathing ! I love it but appreciate that it may not
be everyones desire, coupled with a good aftermarket exhaust system to maximise
engine throughput results in some reasonable power gains for not a huge amout of
cash. As far as I know the fuel economy of the car remains fairly unaffected.
The mixture must be adjusted though on some filters because the extra air being
drawn into the engine would lean out the mixture if the fuelling wasn't
increased accordingly and could also affect emissions.
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Usually consists of little more than the filter, a fitting pipe to attach it to the air-flow metering unit and maybe a retaining bracket and cold air feed pipe if required. The K&N 57i kit i used is a DIY fit but a word of warning - make sure you purchase the exact kit for your car ! Buying a Pug 205 gti one like i did caused me real problems. Most cars use the same idea though so fitment time really depends on the access you have in the engine bay. If there is no kit for you car it's possible to buy these cone filters in different bore sizes and you could make your own induction kit. The idea is that the cone filter can allow a more direct path for the air flow into the engine and cold air pipes/ducts canm be used to feed more air to that part of the engine bay.
On nearly all these kits the standard air cleaner box will need to be removed.
Once this is done some kits attach the new filter to the air feed pipe that
connects to the standard air box, in the case of the K&N the air box and all the
feed pipes are removed, the battery is then moved back on it's tray and a new
pipe is provided that fits to the throttle body. The air flow meter is then
turned through 90 degrees and fits onto that bracket I mentioned earlier that is
provided. The new air filter is then fitted directly behind the passenger side
headlight. A cold air pipe is then fed from the front valance up to the filter.
On the 309 i simply moved the power steering reservoir around and made a bracket
to attach it to the battery, there was no need to remove or chop any of it's
pipes. That's all there was to it. The mixture is best adjusted by a garage who
can use a gas analyser for better results. I know it all sounds a bit of a
nightmare but the results ARE worth it and full instructions are provided.
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Back What they actually do Replacement filters Induction kits The kit