Do Performance Air Filters, Cold Air Intakes & Induction Kits Work?
Get ready to wheeeeeelspin!!
Brum Brum. Squeeeal. Waheeeey!
At some point when owning a performance car, or if you're young, a slow car that you'd like to squeeze more performance from, the question comes up. How can I get more power out of this thing? How can I burn people off at the lights and generally feel like more of a boss, while attracting the attention of beautiful women?
Well one of the ways that you can do this, or at least so the marketing people tell you anyway, is to fit a performance air filter, or a full induction kit. A K&N or Pipercross, or something that looks like that but is unbranded, which you can get on ebay. Hey you can always put a K&N badge on the back of your car and get the respect of the rest of the barry boy racers so it's all good.
What's the difference between an induction kit and an air filter?
An induction kit usually comes with pipework, the idea being that you'll have the filter, which is usually cone shaped, situated somewhere it can suck in cold air, usually at the front of the bumper or somewhere close to air flow anyway. A filter without the induction kit is usually just put in place of the airbox and sits in the engine bay. Or there is the other type, the drop in filter, which is made of foam/gauze and sits in the air box, in the place of the standard paper version.
So, do these performance air filters work? The marketing bumph tells you that they will. I remember when I was a young man, with a low powered car and my friend told me that his friend had told him that you could get an extra 40bhp out of your engine with performance spark plugs and a K&N filter. I soiled myself on the spot obviously, that would have meant 50% more performance from my measly engine for practically no money. What a bargain. So I got the plugs and filter.
How do they work? What is an engine?
These filters do work on a fairly simple principle. Engine power is created from fuel and air being mixed. If you put more of both in, then you'll get more powwwwwwwwwer. So the idea is, get a filter that doesn't restrict the air flow, or is less restrictive anyway and engine will then suck in air easier, the engine management system will provide more fuel and then the power/women will follow. Yeehah!
So, what's the problem? Is there one?
After driving cars with and without performance filters and noticing that the ones with the performance filters were louder, then I thought I'd do some reading. These filters do let a bit more air through. A bit anyway, in an independent real world test the top performing air filter on the market, the K&N filter let through 0.14% more air than a standard paper filter. Letting more air into your engine isn't what they're really good at though, they're good at letting more dirt into your engine. They don't really give you any more performance though which is the downside. Well I say no performance, that's not really true as you'll get 0.14% more. WOOO!
If you have the filter unshielded in the engine bay like this, then you'll lose, not gain performance
Hot air? Cold air? What's the difference?
The downside is that a lot of these filters come in a cone shape and requre you to remove the factory air box. Because of this they then suck air in directly from the engine bay which is hot. As you will no doubt remember from your physics lessons, air expands as it heats up, which means hot air contains less oxygen than cold air.
Less oxygen is not what you want from your air as this means that the air is less combustible, cold high oxygen air is what your engine craves and is the reason that turbo charged engine use intercoolers, you need to get that air cold before your engine gulps it down if you want to extract maximum power from it.
If you have an unshielded cone filter, then you will only be getting good cold air flow to the filter when you are going very fast, so there is a lot of air flowing into the engine. It's not practical to be driving at 100mph+ just to get a cold air flow, most of the time anyway.
You should hear it roar now I've fitted the induction kit. Aiight Ladies..
What this can mean is that until the air is flowing into your engine quickly enough to negate the heat soak from the engine, then you'll actually lose performance with a performance air filter. This will happen at low speeds and especially from a standing start. If you've been idling at traffic lights for 20 seconds, the air under the bonnet is very warm. You pull away and your car is down on power, until enough air has flowed in to replace the hot air. Not really what you want from a performance upgrade.
A drop in type that replaces your paper air filter directly in the air box won't suffer from this problem, but a cone will. Pretty much the opposite effect you're looking for when you buy one of these is less power, but if it's unshielded that's what you'll get.
They do make a louder noise though. Brum Brum!
This isn't fully shielded, but the bonnet sort of makes up the top of the box.
If you want to maintain the same level of performance that you get now, but have a louder noise, which to be fair can sound pretty good, then you'll need a full shielded induction kit.
I have included a picture of a filter that has been shielded to some degree, the bonnet closes off the box it sits in and it probably doesn't suck in too much of the hot air from the engine, or at least less than an unshielded cone.
Have you ever fitted or used an performance air filter / induction kit and how did you find it?See results without voting
Something like this will give you the noise.
Here's the conclusion.
Although there is a lot of good marketing bumph out there, it is all unfortunately just bumph.You'd be far better off not getting a 'performance' air filter / induction kit and instead losing some weight from the car if you want a bit more performance. With an induction kit you will only get a louder noise and no noticeable performance increase, just your engine getting dirtier internally and if using an unshielded cone, then you'll have less power than standard.
My advice is just keep your paper filter regularly changed and don't worry about a high flow filter if you're after performance. If you must fit one, then make sure you don't leave the cone air filter exposed and instead fit a fully shielded induction kit to ensure that the air that goes in is as cold as possible. Only do it if you want the noise though, not as a performance enhancing modification as you just won't get noticeable performance increase, despite what K&N, Pipercross etc all claim.
Remapping, well that is a different story and something that will actually give you some real performance gains, rather than imagined ones with louder noise. If you want to read about that, take a look at the linked article below.
Thanks for reading, please leave any comments below!
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