Interesting discussion on stock air filters

[Genie47]

I refer to this discussion in BITOG.

 

The most interesting post is the one below by crossbow:

Just to drop an interesting note to the conversation.

 

I recently had my stock airbox flowbenched from the Mazda 6.

 

This included...

 

1) Airbox

2) Filter

3) Accordian hose

4) Tuba

5) Tray

6) Resonator

 

Here's a photo of the evil contraption.

 

 

With the stock intake flow benched, it generated 8 hg/inch of resistance.

 

By completely removing the stock filter, 7.5 hg/inch of resistance was exerted.

 

By leaving in the filter, but removing the entire resonator @ the bottom... 7.0 hg/inch of resistance was exerted.

 

The filter was found to have almost zero effect on the incoming air, as other components of the airbox were far more constrictive.

 

For those who car, I also had the Mazda 6s Injen CAI flow benched, which had a whopping 0.1 hg/inch resistance to the incoming airflow with a 6 inch powerstack S&B filter.

 

So there you have it. It is not the filter usually. It is the components in the filtration system. The resonator and all those bendy parts. Keep to your paper filters. Cheap, no need to clean and oil and if you want CAI, remove resonator and use some ducting to replace it. Position it so that it has the least restriction for air to come in.

[Worker]

Interesting !

What gadgets did you use to do the bench checks ?

Was it done "on" the engine or "off" ?

I wonder the 1" difference in pressure will make any difference to power or FC .

 

Anymore ideas coming up ?

 

Rgs

[Slowpoke156]

The bench test on the intake is useless. I wonder why that guy bothered to do it in the first place. If it were as simple as flow benching, cars will be made with super small resonators and a straight pipe.

 

There are other things to consider when you change to sponge or other types of washable filters. Those filters pay for themselves after a few servicings, and they do not obstruct the pulsating effect required for resonance in the intake tract to maximise power.

 

A very simple test, you take 2 filters, one sponge and the other paper and try forcing air through, then see which one has more airflow. Doesn't take a rocket scientist to figue out

[Genie47]

High airflow = more dirt. Performance enthusiasts pay more than the dollars and cents when the engine needs overhauls sooner than expected.

 

All performance filters can never match the paper filter when it comes to protection regardless of what K&N and others of the ilk have to say. Day to day driving does not require gulps of air. Only on the track. If need be, attach the SRI or CAI when tracking. Else, leave the paper filter.

[Slowpoke156]

Higher airflow does not equal more dirt. It's the efficiency of the filter that counts. A more efficient filter does the job just as well (or better) without obstructing airflow.

 

You are sadly mistaken if you think day to day driving does not require gulps of air. There is such a thing called a tuned intake pipe which provides air in gulp like phases. Paper filters are there for many reasons, that they are replaceable, cheap, and something which the car manufacturer can control without complicating other factors. If manufacturers were to provide washeable air filters, they would have lost a source of renewable income, increased complications for servicing (workshops that take short cuts in servicing the filter) and most of all, make the car much less smoother than if a less efficient filter was used. Smoother and larger airflow equates directly to a more responsive throttle, the masses don't like it if the car jerks forward each time they stab the accelerator. This is the same reason why large resonators are mated with the intake, so that inefficient paper filters have a buffer of air to draw from when required, providing more torque and drivability in the lower revs.

[Ghostrider]

High airflow does not have to come at the expense of more dirt.

 

Paper filters is damn effective in filtering off dirt...in fact so well that it the cause of blockage. Its more like a miss and hit thing. Either air go thru or it does not.

 

Let's face it, filter manufactuer ain't fooling people that their filters is so darn effective that your engine breaths clean room quality air. It merely filters off larger particles while allowing more flow of air to the engine.

 

CAI or SRI...you do not need to be on the track to enjoy its benefits. More air flows encourage better combustion.

[Esky]

I did a quick and simple search in the bobistheoilguy.com forum, and even over there they had the same argument over K&N filters like the one here in MCF. Some claimed their intake tract was very clean after using K&Ns, while others said their used oil analysis (UOA) had higher dirt content in it after using K&Ns.

 

Also found an interesting artile here: http://www.thedieselstop.com/contents/geti...%20The%20Editor which claimed although the K&Ns have pin holes under the light, there are also hundreds of microscopic fibres spanning within these holes, i.e. small fibres which can't be seen with the naked eye but are doing the job of holding fine dirt particles in place.

[Ghostrider]

I thought that K&N uses the oil as the medium to trap the dirt ? The sugical cloth is merely the medium to hold the oil and dirt in place ?

 

Most people who end up with oily throttle body usually have serviced their filters before and most of them over oil the filters.

[Phochem]

Yup, happen to me once when i started using K&N, oily TB. Now aft 3years, oiling "kungfu" improve liao and the problem gone..

 

i prefer K&N over stock filter.... life too short 2 worry abt such thing... i chose to enjoy the benefits....

[Bigfatbear]

agree that more air equals better combustion but isn't the air/fuel ratio controlled by the ECU esp for fuel injection cars?

so was wondering if changing to higher air flow filter or modifying air intake without changing the fuel rate has any impacts and vice versa.

these mods are very subjective even if you go dyno because the ambient air temperature also affects the dyno tests.

[Genie47]

I'm already receiving the benefits from just removing my resonator and i didn't have to spend (actually removed) on K&N or anything.

 

The car now jerks forward each time the gas is stepped on. Its my stock setup. The whole thing acts like an SRI but the resonator is the undoing.

 

$10 for a filter every 10k worth it? You bet! I don't oil and and I don't worry. I just drive and enjoy.

[Genie47]

Well, Slowpoke156 has argued that bench flow testing isn't accurate. Well, it might as well be true but who has better testing equipment? The car makers themselves. What this guy did is pretty laudable knowing he is a hobby motorhead and with the limited budget he has, he has done a pretty good job.

 

Any hypothesis stands until someone destroys it with evidence from practical tests.

 

Hypothesis here is that high airflow = better performance. Nobody can disprove it.

Aftermarket oiled cotton filters offer high airflow. Nobody can disprove it.

Aftermarket oiled cotton filters allow more dirt. There are some that disproved it so the battle still rages.

Stock paper filters offer cleaner intake air. Nobody can disprove it.

Brand new to 10k used stock paper filters offer as high a flow as oiled cotton filters. Nobody can disprove this.

Resonators = lower airflow. Thus removal of the resonator will restore airflow. Nobody can disprove this.

 

From the above, I can get the best of both worlds w/o spending time to oil and maintain a cotton filter. Use throw, install new one. Go.

[Ghostrider]

Your ECU will compensate for the fuel rate. Your injectors ain't working at a 100% duty cycle. Its more like 70-80% only at normal driving.

 

So with higher airflow, your air flow sensor will sense more flow hence will allow the ECU to adjust your fuelling to be leaner.

 

Changing the air filter alone will not yield any bhp gains. Its all about helping the engine to breath better to help it work more effecient.

 

You are rite about ambient temp effect dyno reading. But in SG context where the air temp is a constant average of 32degree...the diff is little. More cooler air contains more O2 than hot air....hence the want to let your engine breath cool air instead of hotair from your engine bay.

[Vtim]

I refer to this discussion in BITOG.

 

The most interesting post is the one below by crossbow:

Just to drop an interesting note to the conversation.

 

I recently had my stock airbox flowbenched from the Mazda 6.

 

This included...

 

1) Airbox

2) Filter

3) Accordian hose

4) Tuba

5) Tray

6) Resonator

 

Here's a photo of the evil contraption.

 

 

With the stock intake flow benched, it generated 8 hg/inch of resistance.

 

By completely removing the stock filter, 7.5 hg/inch of resistance was exerted.

 

By leaving in the filter, but removing the entire resonator @ the bottom... 7.0 hg/inch of resistance was exerted.

 

The filter was found to have almost zero effect on the incoming air, as other components of the airbox were far more constrictive.

 

For those who car, I also had the Mazda 6s Injen CAI flow benched, which had a whopping 0.1 hg/inch resistance to the incoming airflow with a 6 inch powerstack S&B filter.

 

So there you have it. It is not the filter usually. It is the components in the filtration system. The resonator and all those bendy parts. Keep to your paper filters. Cheap, no need to clean and oil and if you want CAI, remove resonator and use some ducting to replace it. Position it so that it has the least restriction for air to come in.

how come he never replace the paper filter with K & N/Green filter & test again

[Vtim]

i prefer K&N over stock filter.... life too short 2 worry abt such thing... i chose to enjoy the benefits....

I also say so

[Yansen]

so the resonator acts like an air reservoir? is it right to say because of this trapping of air in it, air flow is impeded? if i remove the resonator, i would have created better air flow but this would offset the advantage of a large pool or air when u need it, right?

[Slowpoke156]

I'm not sure I understand your second question.

 

The resonator does act like a reservoir, a very small one in fact. This is good for low speed driving where the trapped air in the resonator provides a ready supply of air under low suction rates. However, the resonator itself will be a flow obstacle under larger air flows (under load when you require more air) because air has to first enter the resonator, move through the various chambers (and lose momentum as a result) and then finally come to the open chamber where it will be sucked in.

 

Imagine yourself sucking through a straw that has been inserted into a coke can with half the ring pull opening size versus sucking through the straw from open space itself. if you suck hard enough (try the bubble tea straws), you will find yourself fighting against the airflow in the can .

[Bigfatbear]

i think our main concern is not how much air to feed the engine but whether it is the cool air from outside the engine bay- by flexible tube extention to retrofit into bumper or the hot air from inside our engine bay.

 

what is the point of removing the resonator and end up sucking in more hot air which retards the engine performance?

 

to ans genie47 concerns; i think it is better to change to a performance filter like K&N after you done this mod. I personally have done this mod on my CRV before- resonator box removed and flexible tube extend from engine bay and fix in to bumper where the fog lamps are. when i step on the gas, you can feel the sucking power at the mouth of the extended tube. the induction sound is louder and my engine is breathing cool air from outside.

but when i check my air cleaner box every month, there are lots of sand, small leaves trapped below my K&N.

 

so my point is ordinary air filter may not be good enough to filter or cope with the excess air flow so it is better to fit a performance filter and not worry every time. wonder what will happen if those fine sand got suck into our throttle???