Talking about Air Filters...

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jondee86
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Talking about Air Filters...

Postby jondee86 » Sun Jun 28, 2015 3:57 am

Removed this from another thread as it went a bit far off topic.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

As a matter of interest I did this (right click > view image)...

Image

... with and without the filter mounted. It made a difference of 1Nm (0.6%)
and 2kW (2.0%). That is with the filter clean and dry. The element is supposed
to be oiled, but it then gets a bit messy to handle, so I am leaving that for later.
Your filter has more surface area so I would expect it to have even less effect
on the engine output. By comparison, I have seen figures of 10-15% reduction
in power quoted for "sock" filters.

Cheers... jondee86

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
To which YoShImUrA replied...

Crazy difference with and without filters (2KW~2.7Hp!!), let alone if they're socks (25-30hp loss, wuuuut?!?!)...

Great to know. Thanks for that insight, Jondee!
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Re: Talking about Air Filters...

Postby jondee86 » Sun Jun 28, 2015 3:58 am

Going off-topic for a moment to add a bit of information about sock filters. Air
filters generate their fair share of myth and legend, so I think it is worthwhile to
try and put a few facts down straight.

Image

Sock filters are a compromise solution when filtration is mandatory because of
the engine operating in dirty/dusty (off-road) conditions. If there is no room to
fit an airbox or a better flowing type of filter, then sock filters will do a job. To
avoid choking the engine airflow (and power) the sock must be long enough to
have decent surface area, and it must be internally supported to prevent collapse.

Here is a picture of a typical sock filter installation, and without wishing to offend
the vehicle owner, this setup has several failings. When you look at the position of
the bulge caused by the end of the bellmouth, you can see that it is very close to
the flat end of the filter. The active surface area is small and the filter restriction
will be high. At high rpm the engine will try and suck the flat end into the engine.

Image

Image

This picture shows what happened when the socks slid up the trumpet until the
flat end of the filter was the only part letting in air. The engine suction was high
enough to tear the end out of the filter (not the same engine as above).

Image

A well thought out sock filter setup will hurt engine performance a littl bit. A poor
installation will hurt it A LOT. A large foam filter covering all the trumpets will
always be a better solution. Oiling foam filters makes them better at catching and
holding dust, but it will cause a little bit more restriction. If you live in a "clean"
location where dust/grit/sand is not a problem, then running a quality double-layer
foam filter dry is OK.

Cheers... jondee86
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Re: Talking about Air Filters...

Postby jondee86 » Sun Jun 28, 2015 4:01 am

The fundamental problem is a poor understanding of fluid dynamics and
filtration in general. If you want good filtration to protect your engine, you
need filter media with high efficiency (basically more smaller, finer holes that
let air thru but keep the dirt particles out). How small ? Small enough to
capture particles around the 20 micron range, which are known to cause the
greatest wear to engine internals. They are small enough to pass thru low
quality filters, but not small enough to pass thru the close tolerances inside
an engine without causing abrasive wear.

Chicken wire will keep vermin out. Screen door mesh will keep flies and
rocks out. Fine wire mesh and coarse fabrics or foams will keep out sand.
But none of these will protect your engine from the fine particles that cause
the most damage. To keep them out you need a quality filter material. The
factory generally fits a paper filter that is a great compromise providing
decent filtration with low pressure drop.

Aftermarket filter suppliers provide alternative materials and designs that
often trade off decent filtering to get a higher flow rate (=lower pressure
drop and theoretically, more power). These aftermarket suppliers are not
always too concerned with the fact that their fancy colored filters are letting
more crap into your engine to wear out your rings and bearings. The actual
power increase (if indeed there is any increase at all) is usually ngligible.

Don't let the advertising BS fool you into believing that car manufacturers
are so dumb that they leave a bunch of power on the table by fitting a crap
filter. Many actual tests have shown the factory filter to flow just as well, if
not better, than expensive big name aftermarket filters. Caveat emptor !!!

But I digress :D There are many different designs of sock filter, and when
mounting them onto a tapered trumpet, you need to take care to secure
the sock to stop it moving. The internal spring that sits in the mouth of the
trumpet will help make sure the flat end of the sock stays at least one trumpet
diameter away from the trumpet mouth opening. Then a zip tie or clamp will
help hold the open end of the sock tight on the trumpet taper.

The more active surface area you can get in the sock, the lower the pressure
drop and the better it will work (<=== this here is the bottom line :mrgreen: )

Cheers... jondee86
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Re: Talking about Air Filters...

Postby jondee86 » Sun Jun 28, 2015 4:01 am

I'm pleased you stayed away from the wire mesh screens. I've added a bit
of information explaining why they are not a substitute for an air filter.

Here are some details of Market Grade Wire Cloth in plain weave...
- 14 mesh uses 0.508mm dia wires and has an opening width of 1.30mm.
- 40 mesh uses 0.254mm dia wires and has an opening width of 0.38mm.
Wire mesh domes or caps for carburettor or ITB bellmouths would likely
use something within this range. And being nicely made out of shiny
stainless wire, you might think that this is an easy way around the filter
in a small space problem :)

Image

But think again. That little 0.38mm opening is 380 microns, and the fine
20 micron particles that wear your engine out will pass thru that mesh like
it was not even there. Worse still, the open area of the 40 mesh wire cloth
is only 36% :shock: That means the mesh is going to strangle your engine by
creating a big pressure drop as the air squeezes thru the small openings.
Forming the material into a dome helps increase the surface area, but
wire cloth domes or bits of screen cloth sandwiched between the trumpets
and the ITB's, are BAD ideas.

Making the opening width of the mesh bigger and the wire diameter thinner,
helps to make the free area better... this design might have 50% free area.

Image

And respected Japanese tuner parts supplier Jubiride offers this screen for
inserting between trumpet and ITB. They choose a mesh with larger openings
to keep the pressure drop down.

Image

This is not a filter. It is a screen to keep out rocks and It will hurt engine
performance
. But if it makes you feel better and you don't mind losing a
bit of power at the top end, use a wire mesh screen. I would probably just
run open trumpets for racing, and put these in for driving to the track.

Cheers... jondee86
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Re: Talking about Air Filters...

Postby jondee86 » Sun Jun 28, 2015 4:03 am

The design and application of automotive air filters is a balancing act. The various
factors that govern the performance of the filter dictate the end result. You can have
a small filter that does not work very well, but is easy to fit in the engine bay. Or you
can have a large filter that works well and takes up a lot of space under the hood.

Basically, the more effective the filter material (cloth, mesh, paper etc), the
higher the resistance to airflow per unit area. So to get the required surface area
necessary to keep the resistance low enough to avoid hurting performance, some way
of stacking more surface arae into a small space is needed. This is usually done by
folding the material (pleating) and can be seen in factory paper filters, inside oil
filters, and in industrial air filter. Here area couple of examples...

Image

Foam air filters use a somewhat different approach to obtaining increassed surface
area. They do it by using a thicker layer of material with a larger pore size. This
allows lower pressure drop and increased dirt holding capacity, while keeping the
filter size relatively compact. Take a look at pretty much any dirt bike you can find,
and you will see a foam filter installed.

Image

Ahhh... but the larger pore size means the efficiency will be crap... right ? Well
you might think that, but foam filters are designed to be used oiled, and operate
on the viscous impingement principle. In short, by forcing the dirt particles to
change direction many times within the thickness of the foam, inertial separation
occurs and the particles come into contact with the tacky oiled surface of the foam.
The oil holds and eventually saturates the dirt, allowing fresh dirt to stick to the
previously captured dirt.

So even tho the foam has a larger pore size than a "strainer" type filter, it still
has a high capture efficiency. By putting a coarser outer layer of foam on the filter,
the larger particles of dirt are prevented from reaching and clogging the inner
finer foam layer. The downside is that oiled foam filters need washing and re-oiling
from time to time... not something you would want to do wearing a suit :D

Cheers... jondee86
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Re: Talking about Air Filters...

Postby saiGone » Tue Jun 30, 2015 12:24 pm

Hey Jondee,

What do you think about the popular HKS Mushroom style foam filter. There are many Ebay knockoffs circulating as well.

Image

http://www.ebay.com/sch/i.html?_from=R40&_trksid=p2053587.m570.l1313.TR0.TRC0.H0.Xhks+mushroom+filt.TRS0&_nkw=hks+mushroom+filter&_sacat=0
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Re: Talking about Air Filters...

Postby Deuce Cam » Tue Jun 30, 2015 12:38 pm

^If you search around online you'll find that they have a bad reputation.

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Re: Talking about Air Filters...

Postby jondee86 » Tue Jun 30, 2015 3:47 pm

saiGone wrote:What do you think about the popular HKS Mushroom style foam filter.

If you look at the pics I posted further up, you will see a double layer foam
filter that might be fitted to a 400cc dirt bike. So you might expect that a
foam mushroom filter fitted to a 1600cc car engine would have four times
the surface area. But obviously this is not the case.

So the only way that the mushroom filter can flow enough air for the car
engine is by using a low restriction filter material, which by definition will
not have a high filtration efficiency.

Filter Type....................Filtration ................Maintenance .... HP Gains
Blitz Sus
Image;Image
Dry Metallic Mesh Type Filter Poor.......... Zero Maintenance, Lifetime Use............. 13.9 bhp

HKS Mega Flow
Image;Image
Wet, Foam type filter. ......Very Poor Throw away. Change Filter every 10,000 Miles. 13 bhp

Apexi Power Intake
Image;Image
Dry, Mesh type filter. Excellent Zero Maintenance - Lifetime Use. 14 bhp

K & N Filtercharger
Image;Image
Wet, Mesh type filter. Good Lifetime Usage - Inspect every 30,000 Miles or 12 Months
Clean and re-oil, if appropriate. 13 bhp

These pics are from tests carried out some years ago on filters sitted to Supras, and
are only included for educational purposes. The Ebay mushroom filter linked above is
described as "HKS Style" which is market speak for counterfeit, so it is likely that the
performance would be worse than a genuine HKS filter. Which filter people use on their
car is a matter of personal choice. It is not a safety item so pick the one that suits
your requirements for price, style, color, size, maintenance and performance.

This is the one I chose :D

Image

Cheers... jondee86
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Re: Talking about Air Filters...

Postby yoshimitsuspeed » Wed Jul 01, 2015 12:02 pm

This is a good thread on air filters.
http://www.mr2.com/forums/threads/10030 ... ilter-work

A good article linked to from that thread.
http://www.nicoclub.com/archives/kn-vs-oem-filter.html


IMO the only time any one should give half a f about 2 KW is if they are racing competitively. If not then it's not something you will ever notice by the seat of your pants or messing around.
Choose a good filter that does it's job well and isn't a ridiculous restriction. If you want more power do things that actually make significantly more power.

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Re: Talking about Air Filters...

Postby jondee86 » Thu Jul 02, 2015 5:00 pm

Some interesting reading there !! The criticisms of K&N are well known,
but the power of marketing prevails, and human nature continues to prove
the old adage... There is a sucker born every minute :D

I should have deleted the reference to power gains, as the tests outlined
above were done on a big power turbo Supra, so quite irrelevant to the
average AE86. However, it is reasonable to expect some small increase
in top end power when using a freer flowing filter and intake duct. With
the Apexi setup I noticed that the engine pulled a little better from about
4500rpm... butt dyno of course ;)

My philosophy with a car that is relatively low powered, and has a small
displacement engine, is that you need to take advantage of every small
gain that you can. If you can make a few simple modifications and gain a
few hp from each one, before you know it you are up 10hp :) Here is the
list I started off with...
- replace OEM intake with Apexi intake and filter kit
- replace OEM thermofan with junkyard electric fan
- replace rusted out exhaust with new custom exhaust
- full engine service and tune-up with semi-synthetic oil

Then I got carried away and swapped in a smallport engine, and my list
suddenly got a higher price tag. That's the problem when you start modifying
your car... it's addictive... there is always something more you must have :P

Cheers... jondee86
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Re: Talking about Air Filters...

Postby yoshimitsuspeed » Thu Jul 02, 2015 5:36 pm

It would take a lot of small mods like that to get 10 hp.
Maybe if you used the freest flowing intake/filter and the exhaust with one specifically engineered and tuned for your application, maybe you might make 5. The problem is that half the time anyone dynos any non engineered, tested and developed parts it seems people loose power or at least gain in areas and loose in others. So then you might gain 3 here and loose one there. I'm not trying to bash your build or approach but I just don't understand it. I personally couldn't be bothered for 10 hp. You might feel it in the pants but in a blind test I'd be willing to bet most wouldn't.
Yes keeping your car in good order, tune up, oil etc I'll never argue against that.

Just because it starts out low displacement low power doesn't mean it has to stay like that. Personally I would save up for mods that actually made a difference. Cams and pistons for a 50% gain in power. That you will feel and notice. Yes it costs more but the $/hp ratio would be 5 times better. Boost will cost more still but the $/hp ratio will be even better. I just don't feel like 5 hp is worth worrying about unless you are racing competitively. I definitely don't think it's worth sacrificing longevity of your motor with something like a bad filter or none at all which I think was one of your main points.

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Re: Talking about Air Filters...

Postby jondee86 » Thu Jul 02, 2015 6:40 pm

I guessif I had to have a main point when it came to modifying cars, it would
be that there is no "one size fits all". A bone stock AE86 GTS that is restored
to factory condition will be fun to drive and have enough performance for many.
Others will not be happy until they have 250hp or more, and in the process change
the character and looks of the car into something quite different from factory. In
between these two extremes, there will be people like me who just enjoy making
"improvements" to satisfy their own curiosity, learn something, and see what
difference it makes :D

As I have said before, I admire anyone who puts serious effort into modifying their
car be it for drag racing, customising, drifting, rally or show. If I had a big shed
there would be a dozen cars inside... or at least as many as needed to cover all the
aspects of car modification and forms of motorsport that make me happy 8-)

Cheers... jondee86
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Re: Talking about Air Filters...

Postby oldeskewltoy » Tue Jul 07, 2015 7:41 am

It is also good to make sure the filter you use can filter the volume of air needed... In my particular case I'm using a filter housing originally intended for an engine nearly twice the size of mine....
OST Cyl head porting, - viewtopic.php?f=22&t=300

Building a great engine takes knowing the end... before you begin :ugeek:

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Re: Talking about Air Filters...

Postby jondee86 » Tue Jul 07, 2015 3:51 pm

For sure. When it comes to filters, bigger is always better :D More surface
area = lower restriction and greater dirt holding capacity. If I could have fitted
a bigger filter to my engine I would have done, but I ran out of space (talking
about the ITG "sausage filter" on the ITB's here, not the Apexi).

Image

RHD cars are a bit cramped for space for getting a filter on the back ITB.

Cheers... jondee86
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Re: Talking about Air Filters...

Postby ae86714 » Mon Jul 13, 2015 5:07 pm

Now what about the addition of a venturi to whatever filter type you may choose? My very limited understanding was that most of the gains (if any) from and aftermarket intake was due to more air velocity than volume...? I'm far from any sort of an expert on the matter, just trying to learn a little more on the theory side of things. I know the numbers we are talking about with these little motors is pretty much meaningless, but I'm with Jondee in that somestimes you just wanna try things and see what happens.

This is my homemade setup:
Image
Image
Image

I like to tell myself that this improved throttle response, but meh who knows lol.

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Re: Talking about Air Filters...

Postby jondee86 » Tue Jul 14, 2015 1:03 am

Interesting topic, and one that probably warrants its own thread. But we
will leave it here for now and see what develops :)

Here is a picture showing the construction of an Apexi filter...

Image

As you can see the filter has a bellmouth built-in to improve flow from the
filter to the intake. By the look of your pic, you have essentially installed
a filter with a bellmouth on top of a second bellmouth. In so doing you have
created a "step" which will interrupt the airflow and create turbulence. The
good thing about your setup is that you have used an oversize filter, so your
resistance to flow will be low. The lower velocity over the "step" will also
reduce the impact of the turbulance created.

Unfortunately, you also appear to have an abrupt change of section where
the round throat of the bellmoth meets the square opening for the AFM.
This will cause a lot of turbulence and disruption to the smooth airflow from
the bellmouth. I can't say what the overall result would be... better or worse
than a correctly sized filter and matching intake ?? However, I suspect worse.

In airflow engineering the square to round transition is one of the basic
components when connecting ducting together...

Image

Soory about the big pic, but this illustrates perfectly how the change from
square to round is designed to avoid any abrupt changes to the direction or
velocity of the air. The transition should be as long as space allows, and the
included angle between opposite side should be as small as possible, preferably
less than 15 degrees.

Image
Image

The idea is to avoid flow separation where the airflow pulls away from the
wall of the duct or pipe, creating an area of turbulence. Turbulence absorbs
energy from the flow and in so doing reduces the net flow rate. Therefore all
changes of direction or cross section should be as smooth and gradual as
possible for best flow.

Image

The design of a bellmouth should channel air down a tube of decreasing
diameter with the curve shaped to avoid flow separation at the entrance,
and a smooth transition to the intake. The above pic shows a bellmouth
with a parabolic curve which is said to be the most efficient. If the bellmouth
is to match with a tapered bore ITB (20V ITB's for example) the exit tube
should also have a similar taper to the ITB throat, to avoid an abrupt change
in angle at the entrance to the ITB.

More info than you need, but it is useful to understand what you need to
do to get the best airflow with the lowest pressure drop ;)

Cheers... jondee86
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Re: Talking about Air Filters...

Postby ae86714 » Tue Jul 14, 2015 10:12 am

Yeah I kinda figured those flat surfaces around the square opening weren't going to help much. i suppose i could have another adapter plate machined up that funneled to a size hole that would fit the inside measurements of the AFM opening. That would look more like those transition pieces you have pictured. I will have to wait for another good extra chunk of aluminum to show up around the shop first, before I mess with it anymore. Cool info tho Jon, thanks.

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Re: Talking about Air Filters...

Postby Deuce Cam » Tue Jul 14, 2015 1:51 pm

jondee86 wrote:Unfortunately, you also appear to have an abrupt change of section where
the round throat of the bellmoth meets the square opening for the AFM.
This will cause a lot of turbulence and disruption to the smooth airflow from
the bellmouth. I can't say what the overall result would be... better or worse
than a correctly sized filter and matching intake ?? However, I suspect worse.


IMO, the small square inlet on the afm pretty much makes any aftermarket intake pointless from a performance standpoint. It's a fixed restriction and poorly shaped for airflow. Curse Toyota NA and the EPA for not getting the MAP management...

A stock intake without the snorkel will perform the same (if not better) than any aftermarket replacement unit. You won't get the excessive induction noise though due to the intake box.

The real benefit to the aftermarket setup is durability. The stock rubber intake tube that goes between the afm and throttle body is prone to cracking since they're 30 years old. (I've cracked a few just pulling the hose off the throttle body when working on the engine.) They're discontinued, and it's a very odd shape /angle. I've yet to find anything aftermarket that will fit with the stock airbox.

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Re: Talking about Air Filters...

Postby ae86714 » Tue Jul 14, 2015 3:24 pm

Ya i have a stock airbox too, I looked for an oem intake hose but got impatient quickly and just slapped this together. Those hoses are pretty hard to come by now it seems.

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Re: Talking about Air Filters...

Postby jondee86 » Tue Jul 14, 2015 4:01 pm

It is quite strange that no-one seems to have made a simple square to round
MAF adapter available for the the AE86. Here is a pic of a long transition which
would be nice if you had the room, and another pic of a cast adapter that is
getting closer to something that would be useful on an AE86.

Image

Image

Now if one was to use the replacement filter without the flange adapter that
is usually attached to the filter, and fix this directly to a flange that was part
of the square to round adapter... and the other end was a square flange to
match the MAF intake ? Then calculate the area of the MAF intake, add say
10% to the area, and find the equivalent circle diameter, one could get an idea
of how long the adapter needs to be to keep the internal taper within the 15
degree included angle guideline.

Image

Check out the available filters sizes and recommended rating for the 4AGE, and
you have all the information you need to design an adapter ;)

Cheers... jondee86
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Re: Talking about Air Filters...

Postby Deuce Cam » Tue Jul 14, 2015 4:35 pm

The one with the long transition looks great actually, but unfortunately there's just no room.

The average ebay adapter looks like this :( :

Image

However when looking for that ^ picture I stumpled across this thread: http://forums.club4ag.com/zerothread?id=79223 . Not cheap but seems like a much better option.

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Re: Talking about Air Filters...

Postby jondee86 » Tue Jul 14, 2015 5:21 pm

I'm thinking the Apexi one is most likely one of these...

Image

Just round to round on the inside, and really only a more expensive
version of the Ebay adapter. Something like this would be better if
it was made more round to square instead of round to rectangle. Put
the bolts outside on the flange and you could be cooking :)

Image

Cheers... jondee86
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Re: Talking about Air Filters...

Postby Deuce Cam » Tue Jul 14, 2015 7:50 pm

Image

It would be interesting to know what the inside looked like since they do appear to make some for different models with castings that go from round to square / rectangle on the inside. It does appear to taper down from filter to afm. If it tapered to the shape of the gasket / inlet (or very close to) that would be good enough for me. Unfortunately there's just no room for anything longer (unless an opening was cut into the fender), and the intake tube/adapter/filter are about as short as it can get without using junk parts.

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Re: Talking about Air Filters...

Postby ae86714 » Wed Jul 15, 2015 8:46 am

http://forums.club4ag.com/zerothread?id=92111

I always loved that Apexi setup, so clean and simple. IDK why I didn't remember that when I was messing around making my intake. doh!

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Re: Talking about Air Filters...

Postby assassin10000 » Sun Jul 19, 2015 5:33 pm

Apexi & k&n filter adapters have a radius into the afm mouth. Iirc apexi unit was originally for the miata which uses the same style afm.

Andrew

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Re: Talking about Air Filters...

Postby oldeskewltoy » Tue Jul 21, 2015 12:30 pm

http://www3.telus.net/mako/rolla/kn1.jpg

The K&N FIPK at least was designed correctly... or as correctly as the minimal space would allow for... note the square opening has bell shaped curves heading into the square shaped opening.
OST Cyl head porting, - viewtopic.php?f=22&t=300

Building a great engine takes knowing the end... before you begin :ugeek:

Enjoy Life... its the only one you get!

Deuce Cam
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Re: Talking about Air Filters...

Postby Deuce Cam » Wed Jul 22, 2015 9:29 am

That looks decent.

I used to have the Injen intake system but I can't remember what it's like at the afm inlet. It's probably just like the cheap ebay adapter, but they might crimp the pipe somewhat to shape at that end. At least with that one gets a full intake kit that won't wear out over time, and it cost the same as K&N / APEXi kits. The filter they include is garbage, but that's easy enough to change.

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shadowwolf151
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Re: Talking about Air Filters...

Postby shadowwolf151 » Wed Aug 12, 2015 1:20 pm

So a little off topic, and a little on topic. I want to put something like what is pictured below on my 20v BT. but I can't seem to find anywhere that sells this type of setup. I am posting this here because I feel it would be a waist to create a whole other thread for this.
Image

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jondee86
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Re: Talking about Air Filters...

Postby jondee86 » Fri Aug 14, 2015 12:03 am

The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore, all progress
depends on the unreasonable man.

ritz
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Re: Talking about Air Filters...

Postby ritz » Fri Aug 14, 2015 8:32 am

I know a lot of people don't like them but I recently acquired an ARC Magic air box.

It feels quite amazingly compared to the OEM Japan air box on the butt dyno as well as track.

Unfortunately it does get rather hot after 30 minutes.

Image

Image
It has two velocity stacks. One inside the primary box, and one inside the secondary box.