2. 1 | P a g e
PROPOSAL
What are we attempting tofind?
We are going to find out whether or not we can improve the airflow of an engine by changing the air
filter and air filter design on a 2003 Mitsubishi Eclipse 2.4L. We will first test the air flow in cubic feet
per minute (CFM) on the factory air filter and set it up as the control experiment. Then we will switch
out the airflow design to an aftermarket air filter set up, cold air intake system. This will determine if
the change of air filter will affect the air flow within an engine.
There is a total of 3 air flow tests that we willaccomplish.
The stock air intake system, the aftermarket air intake system without the hyper-shield, and the
aftermarket air intake system with the hyper-shield. Then we will compare the results and determine
potential gain or loss of horsepower, the effects of the torque curve, and overall impression of the
aftermarket intake system.
We want to use this information to judge if the gain that is advertised is true or not. This project
enables us to see the difference in the amount of air that flows through the filters.
3. 2 | P a g e
UNDERSTANDING
The internal combustion engine requires oxygen in order to effectively burn. In an ideal world, having
unrestricted air flowing into the throttle body would be the best. However, this is not possible since the
air contains particles; such as dust, pollen, and dirt. In addition, the location of the air intake is vital to
engine horsepower and torque. If the air that is pulled into the combustion chambers is hot air, it
reduces the density of oxygen, whereas if cold air is pulled in the chamber the density of oxygen is
greater. In conclusion, we found two important factors regarding air intake: the type of air and quality of
air.
Currently, there are 4 different materials used in the automotive industry: paper or other fibrous
materials, foam, cotton gauze, and steel mesh. Very few companies continue to use steel mesh filtration
since it requires to be bathed in oil but was commonly used in the 1960’s (Bobtheoilguy, 2007). We used
paper filtration and cotton filtration during our testing.
The goal of the test is to determine if the change of air filter material/style will enhance the air flow that
is going into the engine. Due to the design of the vehicle we tested on, the intake manifold would be too
large and tedious to include in our testing. In addition, we are using same air temperature during our
testing to ignore any air density changes that would normally occur with the change ofintake air
systems.
4. 3 | P a g e
DESCRIPTION
2003 Mitsubishi Eclipse
Engine: 4-Cylinder Inline
Engine Size: 2.4L
Engine: 2351 CC or 143CID
Compression Ratio: 9:1
Bore: 3.41”
Stroke: 3.94”
Cam Type: Single Overhead Cam
Valves: 16
Horsepower: 147hp @5500rpm
Torque: 158 ft-lbs @4000rpm
Transmission: 5-speed Manual
TESTING EQUIPMENT
Company: Superflow
Model: SF-600
FIGURE 1
Capabilities: up to 600CFM at 25in. of water testpressure
TEST
Manufacturer air filter set-up (See Figure2)
Company: Mitsubishi
Material: Pleated Paper filter
Particulate Size: >5µm
FIGURE 2
5. 4 | P a g e
Class: G1 (European Normalizationstandards)
Aftermarket Cold-Air Intake Set-up (see figure 4)
Company: Injen Technology
Material: Foam
Particulate Size: Unknown
Class: Unknown
Hydro-shield: Waterproof protective material
TESTING RESULTS
FIGURE 4
Aftermarket w/
Cover
Aftermarket
w/o Cover
Stock
Diameter Intake 3” 3” OEM size
Air filter Diameter 3” 3” OEM size
Test Pressure
(H20)
10" 10" 10"
Flow Range 5 5 4
CFM 270.1CFM 272.2CFM 202.3CFM
FIGURE 5
FIGURE 3
6. 5 | P a g e
√
√
√
CALCULATIONS
Estimated CFM and RPM for peak power on Vehicle
147
= 36.75 HP/Cylinder
4
143
= 35.75 CID/Cylinder
4
36.75
= 136 CFM/Cylinder Needed
0.27
1265×1.1 ×136
= 5293 RPM35.75
Converting the 10” H2O to 25” H2)
Aftermarket w/ Cover
10
× 270.1 = 170.83 CFM
25
Aftermarket w/o Cover
10
× 272.2 = 172.15 CFM
25
Stock Air filter
10
× 202.3 = 127.95 CFM
25
Estimated Horsepower from Air Filter CFM valuesfound.
HP per Cylinder
HP of All 4 Cylinders
0.27 × 170 × 1 = 45.9HP/Cylinder
45.9 × 4 = 183.6 HP
7. 6 | P a g e
Stock Versus Aftermarket (without cover)
Approximately there is 44.2 CFM difference between the stock air filter and the aftermarket with the
cover. It would be estimated to give an additional 47.73HP by changing the air filter. Considerations
must be made in regards to the flow that goes through the air filter to the volume of flow that reaches
within the combustion chamber. Such as: wave pulses, valve sizes, volumetric efficiencies of the engine.
However, the testing that we did doesn’t take these factors into consideration. Therefore, we will just
use the information as a comparison based onhorsepower.
It appears based on these assumptions that the change of air filter alone would give the vehicle extra
horsepower. The aftermarket set-up has a
finished surface on the inside, which is more for
esthetic appearance rather than performance
purpose. As the boundary layer created within a
CFM vs Horsepower
Air Filter w/ cover
183.6
170.83
Air Filter w/o Cover
185.92
172.15
Stock Air Filter
138.19
127.95
0 20 40 60 80 100 120 140 160 180 200
Horsepower CFM
8. 7 | P a g e
finished surface doesn’t improve when the surface is extremely smooth. It is more ideal to have
some bumps within for more flow.
However, the bends allow air movement to be more laminar compared to factory induct set-up. As
stated earlier, during our testing we choose to ignore the air density changes based on hot or cold air.
But the design of the Ingen air induct system puts the head of the filter in direct range of cold air which
would improve air density.
9. 8 | P a g e
ARTICLES
http://www.knfilters.com/filter_facts.htm#DEAL
AIR FILTER FACTS
Paper vs K&N
To meet minimum filtration standards, paper air filters must be thick and/or the fibers must be tightly compressed and
dense. Therefore paper elements that provide adequate filtration are more restrictive to air flow by design.
Additionally, as a paper filter becomes more and more clogged, the pressure inside the filter drops while the
atmospheric air pressure (approximately 14.7 psia at sea level) outside the filter remains the same. It’s like using your
lungs to draw the air out of a plastic milk bottle. When the pressure differential becomes too great, the bottle will
collapse. The same thing could happen to your paper filter, although it is unlikely. But what will happen could be just
as severe. An excessively high pressure differential created by a restricted filter can literally pull dirt particles through
the paper medium. In other words, the performance of a paper filter, i.e. air flow through the filter and its ability to
protect your engine, DECREASES near the end of its service interval.
Disposable Paper Air Filter
1. Pleated wood pulp bonded together.
2. As dirt builds, passages are plugged and filter must be replacedin
approximately 10,000 miles.
3. Irregular passages filter out dirt on a go/no go basis.
4. As fibers swell from moisture or oil blow-by vacuum pressure increases and
airflow decreases.
5. Turbulent filtered air.
10. 9 | P a g e
Typical Foam Air Filter
1. Lack of surface area hinders air flow and dirt holding capacity. Open cell
foam usually saturated with oil.
2. Dirt builds on outside and blocks the openings.
3. Higher vacuum pressures distort the cells drawing dirt deeper into thefilter.
4. Airflow is reduced as cells become blocked.
5. Turbulent filtered air.
The K&N air filter is somewhat more complex. The unique design features multiple layers of oiled cotton fabric which
captures the airborne dirt particles. These dirt particles cling to the fibers of the filter and actually become part of the
filtering media. This process, known as depth loading, allows the K&N air filter to retain significantly more dirt per
square inch than a paper filter. The cotton fabric is sandwiched between pleated aluminum screen. Pleating
increases surface area which in turn prolongs service intervals. Pleating exposes substantially more surface area
compared to a flat element like foam.
The dirt particles collected on the surface of a K&N element have little effect on air flow during much of its service life
because there are no small holes to clog. Particles are stopped by layers of crisscrossed cotton fibers and held in
suspension by the oil. As the filter begins to collect debris, an additional form of filter action begins to take place
because air must first pass through the dirt particles trapped on the surface. That means a K&N air filter continues to
exhibit high air flow throughout the life of the filter while it is accumulating dirt. At the same time, the air flow for an
average paper air filter can decrease dramatically as the paper element gets dirty. So as dirt accumulates, the
performance advantages of a K&N air filter can increase! Tests performed by an independent laboratory commonly
known as the Frazier Permeability Test have shown that the Medium used in K&N air filters flows more than 300%
more air than paper air filter medium when compared on a square inch per square inch basis. A Square inch
comparison is not directly proportional to the increase you can expect from installing a K&N air filter in replacement of
a paper air filter due to the effect of such things as filter size, number and depth of pleats. However, you can be
assured a K&N air filter will provide dramatically more air flow which can enhance engine performance.
11. 10 | P a g e
This is a contribution from AnthonyS Member # 1824 of our forum board. showing some interesting results on air filtration/ flow tests. I want to thank
AnthonyS for all the great work in taking the time to perform these tests. Of course these are not standard ASTM tests and by no means represent any
scientific certainty. He explains on how he performed his test and what he found as a result. This information is to be taken as nothing more and is not to
endorse , promote, or imply which is better but to share some interesting results.
Air Filtration and Flow Test
As automotive enthusiasts, we are always looking for ways to increase the power output of our
motors. Many aftermarket companies now manufacture and offer high performance air
filters. Most all claim a power gain through increased airflow and some claim better filtration as
well. In this test, many air filters will be compared. I personally have owned various makes of
performance automobiles. This particular test is being conducted using a 1992 Mazda Miata
with a bone stock engine (can't wait to modify it personally). I have many different turbocharger
parts and components collected waiting to modify the Miata. The air filters tested include a
Napa Gold, Amsoil two stage foam, Jackson Racing two stage foam, a Baldwin fiberous, a
K&N, and a Mazda factory replacement.
The air filters will be mounted in the stock air box and filtration tested by placing a 2nd filter
(after filter if you will) just before the airflow meter. A picture, as you will soon see, is worth a
thousand words and shows this setup. A water manometer will be used to test pressure drop
across each filter. Obviously the filters with lower pressure drop flow better, and have the
potential to yield more power given the engine actually needs the airflow increase. The pressure
drop across each filter will be measured in inches of H2O (water). The pressure drop will be
from atmosphere using the stock Miata induction system to the air box just after the filter. 1 psi
of pressure = 27.7 inches of water for reference.
I have a degree in mechanical engineering and am currently pursuing a master's in engineering
management. I have been around the automobile all my life, and will be obtaining certification as
an ASE certified mechanic this fall (for fun). My father worked in the automotive test industry
my entire adolescent life. I've also spent much of my life at the race track, either racing as an
amateur or with my father who was a crew chief for a stock car racer many years. He also was a
crew chief at the 24 hours of Daytona and LeMans twice. I regret not being able to go to LeMans
to this day. I'm a certified gage calibration technician, certified quality assurance inspector,
certified as a refrigerant worker by the EPA, and work in the Navy as a mechanic in nuclear
12. 11 | P a g e
propulsion. I like to think I know a few things about machines including automobiles, but there is
always something to learn.
I choose to conduct this test because of the conflicting information I see in advertisements and
have read on the internet. Everyone claims that their filter flows the best, and removes the most
dirt. If you think about it, flow and filtration ability are actually linked. A solid piece of metal
would prevent any particles from entering the engine, but it wouldn't flow any air at all. On the
other hand, the screen used on a window screen will flow well, but won't filter well at all. So if
you think about it, the best flowing and best filtering is really contradictory in claim. I wanted to
find out which filter really does filter the best, and which one really does flow the best. I have
used almost every brand and type of air filter over the years including K&N. I had not used a
foam filter until conducting this test. I have used every manner of off the shelf fiberous or paper
filter.
There are basically four types of filtration materials currently in use for automobiles: paper or
other fiberous (some appear much like fiberglass), foam, cotton gauze and stainless steel mesh.
This test has used the first three, but not stainless steel mess. Steel mesh bathed in oil is some of
the very first filtration materials ever used in an automotive application. There is a reason they
were abandoned for paper in the '60s. I find it surprising that some aftermarket manufacturers are
touting them now. In the links at the end, there is an interesting test of a stainless mesh filter.
The filters in this test were tested for both flow and filtration. The pressure drop across a filter is
a good indication of its ability to rob the engine of needed airflow and hence power. Obviously
the air filter with the least pressure drop is the highest performing. For the filtration test, I used a
secondary filter after the filter being tested to catch any particles that passed through the first
filter. The secondary filters were made by cutting apart an off the shelf Fram carburetor filter.
The particles passing through the filter being tested leave a deposit on the secondary filter. The
lightness or darkness on the secondary filter is an indication of how much dirt is getting through
the filter being tested.
The differential pressure test was performed using a water manometer where one psi of pressure
is equivalent to 27.7" of water. The differential pressure was measured between atmospheric and
the pressure drop after the air filter in the stock airbox. The max pressure drop in this test was
seen at only 7.0 inches of water or 0.25 psi. The factory airbox and piping with no filter yielded a
pressure drop of 5.0 inches of water or 0.18 psi. That means that the worst filter in this test only
caused a pressure drop of 0.07 psi. In my opinion, this means that if you are picking an air filter
based on performance, you probably aren't doing your car any favors. For the record, the K&N
was the best flowing filter. Of the 3 types of media tested, the cotton gauze type filters flow best.
There are other brands besides K&N for sale, of which most are probably made by K&N for
resellers. Foam air filters flowed marginally better than paper.
The filtration test has been the cause of much argument and debate in some circles. Many
contend that a color comparison (comparing shades of gray) is not scientific or appropriate.
Again, this is a very low budget test, and there are other scientific analyses where color
comparison is valid. In water chemistry a color comparison is often used to determine
concentrations as low as parts per billion. Search for information on titrations (of which some are
14. 13 | P a g e
CONCLUSION
What we have found during this research project is that there is a potential gain by changing the air
filter design. The aftermarket that was chosen to test on has a greater volume and area that can be
utilized during the flow of air. In addition, the design of the Ingen filters or other cotton foam material
can be beneficial since it does provides a great surface/volume area for air flow but still allows the
filtration process that is needed for the engine. The stock air filter has an area of 9in2
, volume of 27in3
where the aftermarket air filter has 42.41in2
and volume of 21.21in3
. But the improvement isn’t solely
gained on the filter paper type. Instead the improvement would be due to the density change from
cooler air, dimensions of the air filter, and lower restriction caused by bends/silencers. There are
different types and styles of aftermarket air filters. The wrong choice of aftermarket air filter could be
detrimental to the engine performance and health. If the air filter doesn’t filter the air properly then it
could damage the engine. However, if the filtration clogs then the engine will not breathe well (or at all
in extremely situations) resulting in a decrease in engine performance. Changing the style and design of
the air filter could give a slight gain of air flow into the engine cylinders and would be a great first step
for adding performance at a lower cost compared to changing intake/exhaust manifolds. However,
understanding airflow and its effects is very important to properly gainingperformance.
