Want to replace the filter in the stock air box?

[Pecker]

According to this article....

Original Article can be found here: AUTOSPEED ARTICLE

Don't Bother Changing the Factory Filter

We’ve been saying it for years but it’s a message that doesn’t seem to have widely got through. Nine times out of ten, dropping an aftermarket filter into the standard factory airbox is not going to get you any more power.

None.

Zilch.

Bugger-all.

Factory airfilters have excellent flow and they’ve also got filtration that matches the car manufacturer’s stringent criteria. Put a different filter in the box and not only will there be almost certainly no improvement in flow, there’ll also be an unknown decrease in filtering efficiency. That’s a pretty dumb combination to pay money for.

The way that you can easily assess the flow capability of the filter is to measure the pressure drop across it. No flowbench is required – just your normal car breathing in lots of air. (Which flows more than all but the hugest of flowbenches, anyway.) A sensitive pressure gauge with two ports that’s plumbed to either side of the filter will measure the difference in pressure at times of high flow. That difference in pressure shows how much flow restriction there is.

More pressure drop = worse flow.

Suitable pressure gauges for this application include the Dwyer Magnehelic gauges (they’re big but beautifully built and very accurate) or the smaller Dwyer Minihelic gauges (not so well built but still fine in this application).

The gauges can also be used to show the restriction of the whole intake system, just by plumbing the low pressure port to the intake before the throttle body (or turbo) and leaving the other port open to air.

In the case of the guinea pig car being used in this story – a 1988 Toyota Crown Supercharger - a 0-20 inches of water Minihelic gauge is mounted permanently on the dash. The car was bought and the gauge installed before any other changes were made to the standard car. In normal cruise, the gauge shows a pressure drop through the whole intake of 5 inches of water – very little.

At full-load, full revs, that rises to 20 inches of water, which is getting too high for max power development. (Any pressure drop will harm power, but usually getting the maximum intake pressure drop down to below 5 inches of water isn’t worth it for the amount of effort involved.)

Given that the car was bought secondhand, it was likely that the factory airfilter was dirty. And an inspection revealed that oh, boy was it ever filthy. In fact, the amount of dirt that came out when it was tapped on a surface was mind-boggling.

And just compare the dirty old filter and the clean new one...

So whack in the new filter and the total pressure drop through the intake will drop by a helluva lot, right? Like, maybe it will now be only 10 inches of water?

In went the new filter and onto the road went the car. And at maximum power the intake restriction remained exactly the same – 20 inches of water.... The brand spankers new clean filter made no difference to intake flow over the old, filthy filter. Y’see, that old filthy filter still flowed very well...

But aaah, you’re saying. What about without the factory filter in the box at all? Well, we did that test as well and if we were paid for imagining things, we might have seen a fractionally lower peak pressure drop – say, 19.5 inches of water...

To put it as simply as possible, there’s no problem with the flow of the factory filter – even when it’s dirty.

And we’ve seen the same story on everything from an Audi S4 to a Subaru Liberty RS to a Nissan Maxima V6 Turbo to a Commodore VL Turbo to a....

In nearly all cases it’s not the factory filter element which is causing the restriction. Instead, it’s likely to be the snorkel going into the airbox, or even the shape of the airbox itself.

Don’t start off by changing the filter; start off by altering the intake flow into the box.

[imek]

Oh really?

Check this out:

Stock:

http://www.forum.corollaclub.org/album_pic.php?pic_id=54

190hp + 191 Nm

K&N Drop-in:

http://www.forum.corollaclub.org/album_pic.php?pic_id=53

195hp + 195 Nm

At some revs the increase was as much as 7hp!!!!

These are my measurements, so I know what I'm talking about.

Detailed tables to find at www.corollaownersclub.com/forums

Just look for my early posts.

[DANZZT231]

K&N Drop is noticable for me. Power? dunno, but sure is better throtlle.

[influx]

they statement that the filtration will drop is the biggest load of you know what i have ever heard esp if the drop in filter is more efficient and not a like a HKS super power flow which is only really good for filtering pieces of gravel.

[grimlock]

i couldn't stop myself from laughing at the comment about the gravel.

funny stuff.

How is everyone?

[xTiGeRx]

I'm sorry to say, but i have already taken out the stock filter and placed it on a flow bench. seen the results...and then placed a k&n panel filter on the bench too.

The increase in flow between the stock and k&n was VERY VERY noticable.

it was also noticeable in drivability and pick up.

a lot smoother.

[Pecker]

very interesting, i wonder why auto speed would write such an article then...

whats a K&N worth?

Do you mind giving me the K&N part number to suit the stivo tiger.

Cheers...

[E-Gene]

Personally I may got the the TOM's one that we saw on Sat instead. It looks pretty good and cost about the same as the K & N one.

[Pecker]

i gotta say the toms filter looked pretty hot...

[DANZZT231]

The paper filter on corolla is very, well, at least it look very restricted. The K&N looks more acceptable if you ask me :) What your might want to do is to also get some piping done for better induction, if you're not planning to get cold air intake kit that is. You just need to get the pipe that connects to the air box out, and get some exhaust shop to make a piping that replace it and lead it down where the TRD or AEm or Injen cold air intake finishes. Actually I might do that too :)

[DANZZT231]

Oh, not to mention if u get the piping done u can also stick a pod in! Stealth mode just like TRD141 stylez! Many honda owners did this too.

[CAP]

Having gone from paper to a K&N and then back to paper at the moment, There's certainly a difference - not only can you feel the difference, you can see it in the fuel consumption.

I'm soon going to be buying a BMC panel filter. They're 'supposed' to be better than K&N at high end for N/A engines with the same level of filtration.

[stauff]

..

So that's how kcorro is getting his posts up..

Posts: 347

- Matthew

[kcorro]

learned that trick from sport1vo. but seriously there is no way to delete a reply.

[E-Gene]

learned that trick from sport1vo. but seriously there is no way to delete a reply.

Deleted...see how easy that was

[xTiGeRx]

very interesting, i wonder why auto speed would write such an article then...

whats a K&N worth?

Do you mind giving me the K&N part number to suit the stivo tiger.

Cheers...

i'm in darwin at the moment...thus i can't check the box for the part number.

when i get back (next week) i'll post up the Part Number.

[ZEEROLLA]

very interesting, i wonder why auto speed would write such an article then...

whats a K&N worth?

Do you mind giving me the K&N part number to suit the stivo tiger.

Cheers...

i'm in darwin at the moment...thus i can't check the box for the part number.

when i get back (next week) i'll post up the Part Number.

The part number is 33-2252 i think and it is made in USA. That is the number i had on my K&N box. I paid $130 for it. It is the same filter used in 1ZZFE Corollas so should be easy to get.