Welcome to the Big Induction thread
First off I claim to be no expert but I hope this thread will answer some of the new members questions on ALL things airfilter'y
Why do I need a Airfilter?
It might seem obvious but you need a airfilter to 'Filter' out all the muck in the air otherwise it would enter into your engine and do alot of damage, so straight away you can forget that idea about removing the filter all together to get more air into the engine!
Whats wrong with the one already on the Car?
Nearly all cars barring Super Super cars like Zondas and the like are all built to a budget. Also cars have to have a big enough service gap as to still get done when its needed but not so you feel your getting ripped off by the Main Dealer who says 'Your car needs 3 services a year'.
Low noise levels, good fuel return, performance and emissions also come into the the mix so the 'Factory Airfilter system' has to meet all these required needs without adding too much of a extra cost to the build value and running/servicing cost of the car when you buy it.
Ok, So how can I improve my cars performance?
Right, does a aftermarket airfilter actually improve performance?
The simple answer is
Yes, but depending on what one you go for will greatly change how much of a gain you will see!
A performance airfilter is made of higher quality material allowing for better filtration and airflow, the more air the more performace! Factory elements and pattern parts are made of cheaper materials design to do the job like the designers designed the car to perform to a low cost then thrown away, where as aftermarket filters are constructed of better materials and are designed to increase performance, hence being alittle more expensive.
The Golden rule of airfilters regardless of how much you spend is
Colder the Better! Cold air is more dense so more air can be forced into the engine to be ignited with more fuel, ergo more performance.
So what one do I buy and what one is Best?
Ok, the easiest way is to work from a budget point of view so we will start with the cheapest and work upwards in terms of money.
The Panel filter
A panel filter is a direct replacement for the cars standard element and is made from the same materials as in open cone filters which offers better filtration and airflow. These are cheap at between £30-£40 depending on brand.
Beacuse they are limited to the restrictive factory airbox you wont see much of a gain if any at all but they do offer a better Filtration than a pattern part if you are looking just to keep the car standard but buy 'Better Quality' items
Panel Filters might slight increase induction noise but not so you would notice
The Open Cone filter
These have been around almost as long as EFi which replaced the Carb in the late 70's and early 80's. They offer a greatly improved sureface area compaired to the panel filter and are open to all atmosphere, so the improvements in airflow over the factory airbox are noticable straight away and will make the car more free reving.
But because of their 'open to atmosphere' design they are subject to 'Heat Soak' where the filter draws in warm air from the engine bay and 'Possibly' losing performance rather than gaining it. This can be 'Slightly' over but not totally over come by using a 'Cold Air Feed' to direct cold air to the filter of using a 'Heat Shiel' these two solutions will 'only work to a point'. A Open cone filter will set you back anywhere between £50-£200 depending on type and brand, gains? Well this is open to debait. Its fair to say a well installed, well located Open filter should give a gain in performance but performance claims by the items producer or supplier should be taken with a pinch of salt.
Open filters should really be seen as a Styling item as much as a performance item. The biggest gain will be in noise.
Open cone
Open cone with Heat Shield
Open filters whether they be Cotton, Foam or Stainless Steel will Greatly increase induction noise, giving a loud roar under hard accelration, like mentioned above, this is one of the main reasons people buy Open filters for pure induction noise.
The Scoop filter
This filter incases the cone filter in a protective case, there by solving the problem of 'Heat Soak' to a point. These are the next step in the link of performance filters as they offer the best of both worlds in ref to Panel filters and Open filters at a good price. Air is forced into the Scoop through the Slam Panel at the front of the car and is feed by forward motion of the car, the filter inside draws in what is requireds when required.
These types of filter will see a better gain over a longer period of use ie long drives compaired to Open filters as the air is always cold, where as with a Open filter the air starts cold but will get warmer as the engine gets warmer so will the induction air. You should see a noticable difference in performance compaired to a Open filter and pick up on the move will be very good as the cold air will be constantly being forced into the scoop by the cars forward motion
A Scoop filter will increase the noise under hard accelration as it is still a Open filter all be it abit smaller and incased in a Plastic or Carbon Fibre Scoop, it will not be as loud as a Open filter for that same reason tho.
Totally Enclosed filter
These filters in 'Theroy' are really the best of the best, as they offer a totally enclosed filter being feed through a direct Cold Air Feed directly into the filter itself. The only problem with these filters is that because of their single entery they can suffer abit unless always being feed or in other words always on the move. So on stop start driving these kinds of filters may be starved of cold air.
These are the most expensive in the list of filters here costing anywhere between £100-£250+ again like the Panel filter there are long debaits as to if they are worth the extra money or not. In theroy like mentioned they do offer the best solution but like most performance items you improve one area and slightly worsen another area.
This filter will give a increase throttle noise under hard accelration probally on par with the Scoop filter as again the casing acts as a sound barrier.
Depending on what brand of filter regardless of type the element or cone will be one of three main materials Cotton, Foam and Stainless Steel. The material slightly effects the noise generated under accelration but on the hole it has not been proven that anyone is better than the other in terms of out right performance as rolling roads do not 100% replicate real road driving conditions. Most people tend to go on trusted brands.
Look out for Leading Brands which have been around for a long time like the ones below:
K&N - Cotton,
Green - Cotton,
Pipercross - Foam,
BMC - Cotton,
Quickshift - Stainless Steel
This is only a selection of what is now a huge list of brands making aftermarket filter or induction kits. Cheaper kits can be bought from places from
www.eBay.co.uk but there is it is still slightly unclear as to if the filters are as good at filtration as the leading brands mentioned above and there by effecting the life of the engine by allowing more dirt into the engine causing engine wear.
The best advice is to make the choice yourself. If you are happy with spending alot of money on a airfilter because of performance claims or just the name then do so, if you are on a budget and feel the risk is worth taking buying a slightly cheaper unbranded item again do so. There is no right or wrong in terms of what you should or shouldnt buy.
Important notes - Please Read
Its worth pointing out that all gains if any at all depend on far too many variables to be spot on and may vary from application to application. I think its fair to also say No one filter will give you anymore than 4bhp-5bhp tops regardless of brand or type.All the information and views on the items above are my own personal views, many different people will recommend different products due to personal tastes or views. I in no way suggest to anyone 'you should buy one other the other' this is just a collection of information to try and help inform people who are not as informed in the world of airfilters.
On their own any form of Induction kit will totally transform the way your car drives or performs but combined with a decent 4branch manifold and exhaust package you could see a good gain of somewhere between 10bhp-15bhp.
Most people like to say it simply as
Open Filters = Noise
Closed Filters = Performance
and to a point this is very true.
There are so many different brands, designs, types of filter these days it would be almost impossible to list. But I hope this is a step in the right direction to helping people look in the right direction.
Thank you
The Big INDUCTION Kit Thread - Please read if you need advice on airfilters
al have a hunt for it!
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