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FAQ - Air Filters

In here you will find answers to commonly asked questions about verious modifications. You will also find some great DIY's for doing mods to your Isuzu. If you have a mod to add here, please contact a member of the FAQ Team.

FAQ - Air Filters

Postby Pissy » Tue May 19, 2009 1:52 pm

(Part numbers will follow soon)

In a year, your car can draw in approx 20,000L- 40,000L of air, to be mixed with fuel. As a result of this need for air, an air filter is essential to deliver clean, dust and insect free air. Driving without a filter will soon, in no time, cause major engine problems.

Air Filters can be divided into few categories, Paper, Foam and Cotton gauze. These 3 types can all look similar in appearance no matter what style or shape,.......Eg, panel, column, pod oval etc.

Paper Filters
The Paper type is usually the standard filter that comes with the car from the factory. These filter are sold under many brands of which Repco and Ryco are the most well known.
Paper filters are regarded as having the best filtration properties and therefore, more and finer dust particles are trapped by the cellulose in the paper. So in dusty conditions it’s recommend/deemed better to use Paper. The draw backs of this, is that the engine has to suck harder through paper which tends to lead to a small drop in power and fuel economy.
Another draw back is that these filters usually are only good for a set distance before you should replace it with a new units which cost from $30-$60. The MU manual suggests a new filter every 40,000kms but it all depends on your areas conditions. To clean out and extend the paper filters, compressed air can be used. Spraying from the inside of the filter will blow out some of the dust and particles but this is not a true clean, as there no such thing and therefore recommended replacing with new filters.

Foam and Cotton gauze.
I will discuss these 2 types together as they are both similar in the pros and cons.
Foam filters and are made from Foam, while Cotton gauze are made from,…well you guessed it Cotton Gauze in an aluminum netting/cage . Both filters require an oil additive mixed within its structure to attract/entrap dust and other particulates. The most common brand names for these filters are Uni filter for Foam and K&N filters for Cotton gauze and both retail for around $90-$140.
There is much debate over these filters and their effectiveness in filtering the finer particles as they are made to allow an engine to breathe better. But there is no doubt about their abilities in allowing an engine to breathe more freely and therefore a small power and fuel economy gains. Plus a change and exhaust tone may occur as well.
Another positive is that these filters are made to be reusable and therefore cleaning kits can be purchased for around $30-40 for kit which could do 5 – 10 cleans.
I would recommend checking these filters every yearly and maybe a re-oil, a total clean and re-oil every 20,000kms, again depends on your areas conditions.
Besides the obvious environmental and performance benefits, a reusable air filter will save you a lot of money in the long run.


Pod Filters
These styles of filters and can be made from Paper, Foam or Cotton gauze. A pod filter is said meant to contain more surface area thus enabling a vehicle to breathe easier, thus more power and better economy,…IN THEORY.
Pods usually don’t fit into an air box and are therefore are subjected to sucking in hot engine air and potentially when off road, WATER in deep water crossings. Pods are usually just placed in the open with no box within the engine bay. I would not recommend using this set up if you intend to go off road, city only driving in fine.

So, the decision is your personal preference as to what type of air filter to use , but you should take into consideration your areas driving conditions.

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94 3.1L MU,2.5"suspension lift,2"body Lift,33"Bighorns,F&R Autolockers,Rock Sliders,winch bar,240 lightforces,UHF,120amp alternator,dual batteries,snorkel,turbo timer etc
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