trinituner.com

Ask anybody with a "gas-brains" about aftermarket air-filters and you'll hear words like "performance", "horsepower", "mileage", "economy". It's a general consensus that aftermarket air-filters like K&N or ACDelco have a distinct advantage over the factory paper-filters when it comes to improving the performance on your vehicle.



Some reviewers suggested that such air-filters don't really give as much of a horsepower increase in naturally-aspirated engines as one might think. Independent reports suggest only a 1-2hp gain in overall power with an aftermarket filter, while other areas such as fuel economy would show greater relative increases. This makes sense in that in order to make an explosion, a certain amount of fuel and oxygen is required. If you have more oxygen than fuel, then you need less fuel to create the same amount of power, hence less overall consumption and better fuel economy.


But when it comes to forced-induction engines, such as our beloved Turbo-charged diesel engines, that's when power-gains become more pronounced. And this isn't hard to fathom, if you apply a little bit of basic physics to the concept.

Simply put, a forced-induction engine would have more air being rammed into the combustion chamber than a naturally aspirated engine. If you have freer-flowing air coming from a less restrictive filter PLUS a turbo-charger compressing and ramming the air into the intake, then you can get a larger amount of oxygen into the combustion chamber.

Because of the higher compression pressures within a diesel engine's chambers, more oxygen mixed with the same amount of fuel per stroke would mean more fuel would be burnt, thus we get a much more powerful detonation and less residual fuel left over. Thus you get more power, and better fuel economy. In a naturally aspirated engine, there is no benefit of extra air being pumped into the combustion chamber.


So how are K&N and similar filters different from paper filters? K&N filters are made out of foam material (similar to surgical gauze, laid out in overlapping layers) that are coated in a special oil. Foam has larger air-spaces than paper. However this oil helps to trap particulate matter within the foam, while still allowing the larger air-spaces to breathe freely. This is how K&N filters are able to achieve up to 50% better air-flow rates while keeping dirt and dust out of the engine.

Besides that, K&N filters have the benefit in that they can be washed and re-used many times over. Though initially expensive (the filters aren't as cheap as paper-filters), this would save you money in the long-run.

K&N boasts that their filters have a "million mile warranty", in that, once they are used and maintained properly, the filter should outlast the life of the engine & vehicle. They also recommend that their filters not be washed more than 25-times, to keep the maximum efficiency of the foam. Also, being that the foam filter is more durable than paper, K&N suggests that the service intervals can thus be longer than with paper filters, i.e. 50,000KM with K&N vs. 10,000KM with paper.


So, what's the final verdict? Should you use an aftermarket performance air-filter?

Why the heck not?



Here's a few tips to get the best out of a K&N Filter:

- Get the CORRECT filter for your vehicle. Some filters are interchangeable, eg. the 3.0L D4D hilux uses the same filter as the Ranger & BT-50 (Part # E2296)
- Make sure to follow all installation instructions properly. If the filter doesn't fit or isn't mounted properly, then you lose the filtration effect.
- CLEAN THE FILTER REGULARLY. The recommended intervals for cleanings are between 25,000KM - 50,000KM. These intervals are longer than paper-filters, however you still shouldn't forget to clean your filter. This depends on the vehicle make as well as your regular driving conditions.
- If you're taking the vehicle off-road or drive in dusty areas often, consider cleaning the filter more often than usual. Remember the foam is more porous than paper-filters, so once they're saturated with dirt, the filtration effect is lost and you'll end up fouling the engine.
- Use ONLY K&N cleaning supplies & filter oil, DO NOT replace it with DIY or other brands of solutions
- The best gains in horsepower come from a combination of: K&N FILTER + COLD-AIR INTAKE PIPING. You'll gain more power when sucking in colder, denser air away from the engine instead of hot air close to the engine. Consider some shielding or relocating the filter away from the engine block & exhaust headers (once the engine bay has space).





Here are some links for further reading about K&N Filters:

- K&N's official website & FAQ section

- A detailed overview of K&N's performance air-filter (*this is an interesting read*)

- A review on the performance of K&N Filters

- How to clean your K&N and similar-styled air filter

- How to get cleaner air from a K&N Air Filter

i think they should make you min. of information.. ..good stuff bro

^^ LOL thanks dude. This is all learning for me too, so I like to share whatever I read.

Does K&N make a cone-filter for the D22 ZD30T frontier? I can't seem to find it.

donno dude - but i love my k&n in my ranger - you feel it breathe better and the turbo never sound this sweet

civic minded wrote:i think they should make you min. of information.. ..good stuff bro

i totally agree - this man does have real solid articles

in light of the informative article above...for those who have K&N drop in..how often do you clean them...do you wait for the 25,000 miles?

I cleaned mines when i got it initially at 5000kms interval...mostly highway driving....read that article posted above on a website...thus far im doing 10,000kms since last clean...

Given the volum of air used by diesel do you guys think its safe to wait for 25,000 miles?

The general rule of thumb with K&N is that if your vehcile is driven often in dusty conditions, you should clean the filter more often, like 10K or 15K km's. Also their recommended no. of cleanings is 25 per filter, they can't guarantee the filtering efficiency of the filter after that.

I saw on another tuner magazine that there's a one-way valve you can install for water-trapping, esp if you do a lot of off-roading. It usually drops into the cold-air intake piping, should be no problem to install once you have the space. AEM makes it, not sure if K&N does too though.

Saw on the forum that teknet brings in K&N filters, so does Auto Image in valpark. Carboutique in st james is also a good place to check. They all should do their own installation for you too.

The installation is easy... only if you're blond, you'd ask the dealer to put it in
The filter comes pre-oiled, sealed in plastic in the box. Just have to open it up, rip off the plastic and drop it in.

The last two cleanings on my K&N was at 5000km and 7000km. Was noticing black smoke out the back at higher speeds. Cleaned the filter and the problem was solved.

^^^ Lol, well my hair black so I guess I can do eet :O).

Actually, I was looking through a PDF of a D22 Frontier service manual I found online, and from the engine setup it looks pretty easy. I checked out the filter housing and saw that it's conical shaped, so it shouldn't be a problem to install a cone-shaped K&N or AEM-brand filter.

What about the oxygen sensor though, any modifications to be done to that? I saw a couple wires leading to the filter box, so I was wondering if maybe a drop-in filter would be better?

Bought & installed a K&N drop-in filter for the Frontier. Had some difficulty trying to find the one to fit the frontier, only two places carried it - Auto Image in Valpark & TekNet, French St. Ariapita Ave.

Got a better price at TekNet for the K&N. Fits tightly into the airbox of the Frontier, and somehow the lower clip holding the air-hose assembly to the box has gone missing so only the two (out of three) upper clips are holding the whole box together now. I'm concerned whether this will affect the filter's ability to keep dirt out of the intake.


Noticed a significant difference in performance, specifically when the turbo is spooled up at 2400 RPM and the boost kicks in. The torque has increased and I'm getting much better acceleration. Eg. running at 2500 RPM, 5th gear, 100km/h, accelerating to 120Km/h to overtake on the highway is MUCH faster now.
Can overtake other vehicles quite easily when the boost kicks in. Was able to keep up with a fully-loaded BMW X5 in moderate traffic, as the dude kept trying to pull off whenever traffic broke and an opening came up.

This is rather interesting...

*Phoenix* that video (Automotive Air Filter Test) is a good find. I knew my K&N does flow more air but I was concerned on how often I had to clean it (every 5000 - 7000km)...... performance of the K&N obviously dropped off when it really starts to get really dirty and the performance (when dirty) seemed similar to a paper filter in my van.


I still enjoy hearing the turbo spooling up when I accelerate while using the K&N


Will have to look into a local dealer for the foam filter to run my own tests.

I still enjoy hearing the turbo spooling up when I accelerate while using the K&N

Forced induction FTW.

SO the turbo sound with and without a K&N is a big difference???

Yeah it's a bit louder now, and it almost sounds like the van is breathing easier. Like as if you gave it a halls cough drop and it throat get cleared

"Ffffwwwiiiiissssssssssssshhhhhhh"

^^lol - for true - from standstill on any sort of pavement - i getting tires ripping when i mash out - i try to avoid this as my rear tires looking more worn already than the front...lol

lighthammer wrote:The general rule of thumb with K&N is that if your vehcile is driven often in dusty conditions, you should clean the filter more often, like 10K or 15K km's. Also their recommended no. of cleanings is 25 per filter, they can't guarantee the filtering efficiency of the filter after that.

I saw on another tuner magazine that there's a one-way valve you can install for water-trapping, esp if you do a lot of off-roading. It usually drops into the cold-air intake piping, should be no problem to install once you have the space. AEM makes it, not sure if K&N does too though.

Saw on the forum that teknet brings in K&N filters, so does Auto Image in valpark. Carboutique in st james is also a good place to check. They all should do their own installation for you too.

Had one of these one way valves in my vitara. Was an AEM. Works great. If you have a 'cone' filter and do a lot of driving in wet areas, its great.

I recently installed one of the drop in kn filters in my frontier, and i really did not get any difference.
same speed and not much difference in sound

DJ_Bee,

What kind of conditions were u driving in? Usually the best improvements are in the early morning or night, when the air is slightly cooler and denser.


When I driving to work in the morning around 7am, I notice that the engine runs smoother, revs faster and the power comes faster.

When driving in the hot sun at lunchtime or after lunch, the engine's performance isn't as good.


I'll have to compare the performance between the k&N and the factory filters in the frontier at these two different times of day

ok ok. like at 1 - 2 in the morning wouldnt lie, it works better, engine really runs smoother

Finally got the K&N Filter for the Nissan Navara D40 LE.

Part no - 33-2198
Search for it on the K&N website.


Noticed a significant difference in the performance. Top Speed was basically the same, but the power delivery was much quicker and more responsive. Acceleration is much quicker too, the truck hardly makes any effort to accelerate at all. It feels like the engine breathes a lot better too.

Of course hearing the turbo spooling up into a turbine-whine is fakking awesome was well

Just dropped in a K&N filter in the Nav.

Top speed is the same. Acceleration in faster and the sound is definitely different.
Sounds like there is an additional fan in the engine.

Will record fuel usage and will post an update.

lighthammer wrote:DJ_Bee,


When driving in the hot sun at lunchtime or after lunch, the engine's performance isn't as good.

i notice this also.. and my engione is naturally aspirated.. i was thinking if i cud re route the air inlet of the the filter housing to somwhere outside of the engine bay area it may solve this problem... a DIY project i might attempt early next year if time permits....