Induction kits, eg K&N - what exactly do they do and do they do it better than the standard air filter?

Ta

 

An inducation kit is an alternative type of air filter. It doesn't use the resonator box which the standard panel filter uses, and is typically more free-flowing.

"Does it do it better?". If you're asking about the effectiveness of cleaning the air -- no, not necessarily. Some will not clean as effectively. If you're asking about throughput of air -- yes, some will flow more air. However, this isn't always necessary. Some high power Imprezas (I understand) use the original airbox. To be honest, I'm not sure of the limit (power-wise) beyond which the airbox is the constriction.

Bear in mind that some induction kits can damage the MAF sensor, either through oil contamination or through excessive vibration. The K&N seems to be one of the less MAF-harmful choices. This might depend on the particular model of car you're considering, though. Hope this helps.

 

Ahh this old chestnut again. You will hear alot of different opinons on this.

What they do is allow air to flow more freely into the engine as the restriction of the standard panel filter and airbox is removed. A good thing you might think however....

The induction kit draws warm air in from the engine bay, unless you isolate it and fit a cold air feed system. The standard setup already gets its air from a cool source. Warm air in = higher exhaust temperatures, greater detonation risk etc.

Induction kits are known to cause premature MAF failure, especially on the more recent models fitted with the film type MAF. Failing MAF = lean mixture = detonation = melted pistons

They can also cause the MAF to misread due to the increased airflow... problems as above.

So personally I wouldn't bother. They don't make much difference power wise. A free flowing panel filter (e.g. Green Cotton, STI) is a much better idea. If you are going for big power and need the airflow then an induction kit may be necessary but is usually combined with an ECU that does not use the MAF sensor. The standard air intake should be okay for 300bhp+.

 

Thanks for that. I've a MY95 classic, so I don't think it's troubling 300bhp! I don't reckon I'll need to get one, but interested to know what the deal was, cheers.

Second beginner's question - What's the MAF?

 

MAF = Mass Air Flow (sensor). It's sat just behind the filter in the inlet pipe. It measures the air passing through the inlet, and some induction kits can cause them to misread. Then there's the potential damage to the MAF, mentioned above.