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Air Induction, one more time.

22K views 86 replies 23 participants last post by  cooljustin 
#1 · (Edited)

Working as an Air Induction Designer for 6 years for a few of the worlds automotive companies, (Ford, VW, Aston Martin, Jaguar, Saab, Opel etc.) has given me a good insight into what does
and doesn't make a good induction system. I recently removed my air box and after quite a lot of research I decided to go for an M's system. This is just two aluminium adapter funnels, the same as Blitz, with K&N's.

My logic behind this decision is as follows:

HKS type foam filters allow a lot of dirt to enter the engine, especially if they aren't changed
regularly. As they use an open cell foam the dirt particles rattle around in the foam structure,
as the air does, and eventually finds a way through.

Blitz Mesh filters boast the filter down to 20 microns. I have extensive engine wear data showing
that particles down to 3-8 microns actually wear big ends and the rings. Being only a thin filter
medium there is no where to trap the dirt and it only takes a little effort to such it through. It may
be good for flow, although I seriously doubt this, but you want this power and the engine to last.

K&N type oil treated cotton filters do offer better filtration by virtue of the oil sticking and
trapping the dirt particles. Our suppliers of air filters have done a lot of work on oil migration
to the air flow sensor and have found little proof of this. I know people will claim that theirs
was effected by the oil, but as long as the filter isn't soaked in oil, there is little evidence.
We only treat ours with only 10-20 grams of oil. So be warned when cleaning yours. The use of
oil on a filter can not only improve its efficiency but can also triple the amount of dust it can hold.
This is why we only use oil when the vehicle only has room for a small filter and/or works in a
dusty environment, (e.g. S/America, Africa etc.).

Apexi's cone filter has a combination of all the others virtues with NONE if the down sides.
It has the bell mouth and other air flow aids, and the filter medium they use is recognised in
our business as the best. It has good flow characteristics as well as exceptional filtration
capacity down to the real fine stuff. The only down side for myself as a designer is the fact
it 3 times the price of paper, and making 1 million air box's a year we tend to look at price first.
But for us as an after market item the expensive price of the filter isn't as important and there
is only pennies in it. In my opinion they are the BEST filter on the market.

So why did I chooses the M's system. Well not wanting to sound like a tart, but the M's system
looked a lot neater and factory fitted look when compared to the Apex'i, and the performance
isn't that far behind the either. So for me K&N offered adequate protection as well as aesthetics.

All/most aid induction kit should offer lower restriction as long as it is clean and in good order.
But there is the problem of under hood heat. As long as the is some baffling and cool air ducted
in this shouldn't be an issue. The worst condition is actually when stationary, but this isn't a
problem as no power demand is being made on the engine. As soon as you do move off then
cool air will purge the system quite quickly.

Well I hope this has help in some way clear up some of the misleading quotes and claims
these manufactures put out.



Just one last nugget of information: at 7500 rpm and standard boost the air filters
have to clean 232 litres of air a second and 325 litres at 1 bar, No mean task.



STOP PRESS:

For more infomation and to see what I mean go to: www.mkiv.com/techarticles/filters_test/1/index.html
 
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#3 ·
HKS

Guy,

As long as you keep them changed reguarly, you'll may never know the difference.
Engine WILL wear, but that may mean a rebuild will be due @ 100k miles rather than 130k.
I recon you'll be onto a R35 by then anyway.
;) ;)
 
#4 · (Edited)
Just for Glen


I have been getting a few worried E-mails.

So let me try to put this to bed.

Here is one of my replies:


With regard to the foam filters, as I said to Guy yesterday, yes they do let a lot more dirt in,
especially when compared to the factory fitted paper filter, and yes this will lead to premature
wear. But when this will raise its head as a mechanical problem, no one can tell. All I'd say
is that it won't do say 130,000 miles before a rebuild, it may only do 100k now. I don't know.
Is this a problem? You probably won't own it then, so don't worry. Its only if your car is a
long term thing, you intend on keeping it forever it may be worth using something else.
But it won't die tomorrow.

As for oil additives, you can buy spray on oil to serves filters for K&N etc. But I would NOT
recommend putting it on some foam filters. Oil can do some horrible things to foam.
Besides the whole idea is for some foam is to be dry. An oiled one may just completely clog
up into a oily sludgy mess. Foam filters use their thickness to contain the dirt, where as
paper/fabric and mesh hold it on the surface, and the oil helps this. Apex'i filters do a
combination of the two but are dry.

My experience, (in the motor industry), we can not afford in the field failures, it buggers up the
small profit margin you see. We need every car to do 100,000+ mile regardless in all conditions
and environments, hot, cold, wet, and dry around the world. So our standards are very tight.

Quality is also an issue. If you talk a close look at a K&N filter, (which is one of the better ones),
you will see measurable gaps in the fabric. And when I say measurable, I mean with a good ruler.

As a comparison I have just got hold of some test data:

........................................Standard.............K&N..................Jetex...............Green............Pipercross
Type:.................................Paper..........Oiled Fabric......Oiled Fabric.....Oiled Fabric.....Oiled Foam
No. of pleats:......................89.....................22.......................25......................34.....................n/a
Media area m2:................0.87..................0.09....................0.06..................0.08...................0.04
Face velocity m/min:.........8.0...................75.8..................107.2.................86.7..................194.4
Initial restriction kpa:........2.91...................2.51...................2.46..................2.48....................2.7
Dust capacity g:................88.7..................51.2...................26.2..................22.1..................155.4
Initial efficiency %:.............99.2................90.77.................51.84................93.91.................61.29
Final efficiency %:..............99.5...............95.86..................55.35................94.31.................39.59

This test was done on a Ford Focus air box with after market panel filters fitted.
The Japanese brands don't make any for this vehicle, but it show the typical characteristics
for the filter type. I would expect Blitz mesh to be as pipercross but with the lowest dust
capacity due to no oil and very thin media.

Notice the face velocity, High velocitys can suck dirt off of the element
Also note the differance in restriction. Not much in it concidering the down sides.

Now you can all see for your self where I am comming from.
 
#8 ·
My mistake.


Sorry gents, wasn't familuar with the HKS. :rolleyes: :rolleyes:

But saying that I have also made another mistake, the Pipercross we tested was oiled. :( :(

I'll edit my chart, (Above).
 
#12 ·
Scott...does the fact that you just found out that HKS filters are oiled change what you said about them??:confused:
My understanding is that you thought that the HKS were not very good because the foam lets small particles through(dry). But if the oil is present wouldn't it stop those little buggers getting in??
 
#13 ·
#15 ·
Scott,

Sorry to bring this up again but I would be grateful if you could help me with one question.

I notice (unless I'm being dumb) that you don't ever mention panel filters as an option, only cone induction systems.

Would you not agree that panel filters offer infinitely better protection at a negotiable loss of power? Say 5bhp?

Cem
 
#17 ·
Cem...
in the factory box the restrictive bit is the box itself rather than the filter...i've witnessed no considerable gain on the dyno from changing the paper filter to a K&N...
on the other hand a pair of pod type filters really made a difference especially up the top end... surface area of two pods are far greater than a panel filter therefore able to suck in more air... and for protection i put a pill in the tank everytime i fill her up....:D
 
#19 ·
Cem and other,

My original note was only a comparison between the different types of filter media alone.

All the filters tested were actually panel filters, tested in a Ford Focus air box, (as thats our designed).

I do agree, and may have written at the time, most air filter boxs have a far higher restriction than any filter.
Hence it is the box, not the filter bunging things up. That's why people do away with it and fit a cone.

But this has the down side of warm air injestion.

There is no real point in adding a panel filter to a box as there will be no decernable difference,
just more dirt getting into your engine.

The whole note was just meant as a reminder, not of the possible lower restrictions out there,
but an indicartion as to how much crap will enter your engine with different types of filter media.:eek:

Hope this helps.:)
 
#20 ·
Panel v Cone

Still not clear what you're getting at - with a similar filter medium, I can't see why the simple absence of the box will make any real difference to what the engine ingests.

As an aside, I'm also not convinced about the cold air with a box (good), hot air without (bad) argument. I'd imagine that this could only be an issue when driving at very low speeds, and hence not relevant.

Phil
 
#22 ·
Phil,

I said nothing about the deletion of the box will lead to injesting dirt, just warmer air.
Fitting a bad quility aftermarket filter to a box (or in cone form), WILL lead to engine wear.

Will it help if I sum it up like this:

Box & Standard paper filter = Cool air, High restriction & Good filtering.
Box & 'Sporty' panel filter = Cool air, High restriction & Bad filtering.
Cone filter = Warmer air, Low restriction & Bad filtering.
Cone filter in paper would = Warmer air Low restriction & Good filtering


Unfortunatly nobody makes a cone filter using quality paper. :mad:

As surgested by most, and I agree, the warm air issue isn't a big one, only a few degrees in it.

All I was doing is helping people:
1. Realise the trade off.
2. Help them to decide the best protection out of the after market brands.
 
#24 ·
Dino,
My notes arn't meant to be what I think of them,
so much as how well they preform under our lab tests.

And these tests show a trend for each type of filter media regardless of brand.
I was first unaware that the HKS was oiled, but this was pointed out by a few people.
But this does'nt change much, its still foam with big holes.

From what we have seen in after market filters:

The Apexi type of cotton wool filter performs very well, with lower restriction than paper,
but with lslightly lower filtering capability.

After that I'd say go for trusty old K&N.

I wouldn't, myself, go for either foam of a mesh.

Look at the numbers yourself on the first page of this thread.

The decision is yours.;)
 
#26 ·
OS GIKEN 3litre.

Guy is that what you`ve ordered? ;)
Henry:smokin:

The Blitz Supra doesn`t have "filters" just fine stainless steel mesh! I`m into HKS Purple foam on the R33.

Henry.:smokin:
 
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