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2005-01-1139

SAE TECHNICAL
PAPER SERIES

Performance and Benefits of Zero

Maintenance Air Induction Systems
Neville J. Bugli and Gregory S. Green
Visteon Corporation

Reprinted From: New SI Engine and Component Design 2005

(SP-1966)

2005 SAE World Congress

Detroit, Michigan
April 11-14, 2005

400 Commonwealth Drive, Warrendale, PA 15096-0001 U.S.A. Tel: (724) 776-4841 Fax: (724) 776-5760 Web: www.sae.org
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2005-01-1139

Performance and Benefits of Zero Maintenance Air Induction

Systems
Neville J. Bugli and Gregory S. Green
Visteon Corporation

Copyright © 2005 SAE International

ABSTRACT

Engine air filtration technologies currently used in air Accelerated field evaluations are also presented to
induction systems typically utilize pleated paper or felt support the new Visteon technology using Long Life
type air filters. These air filter designs have been used Filtration System. These studies show the viability and
for many years in panels, cylindrical or round (pancake flexibility of multi-layer foam designs.
type) type air cleaners. Pleated air filters are specifically
designed to be serviceable and hence their performance Keywords: Long Life Filters, Long Life Air Cleaners,
is inherently limited by vehicle under-hood packaging Reticulated Foams, Multi-layered Foams, non-
and manufacturing constraints. Due to these constraints, serviceable, zero maintenance.
majority of air cleaner designs are not optimized for
engine filtration and air flow management under the
hood. NOMENCLATURE
Studies show that use of low performing serviceable
aftermarket air filters significantly affect the performance
AIF = Air Induction Filters
and durability of engine air cleaners [9]. High mileage
AIS = Air Induction Systems
studies confirm that engine durability, service issues,
CARB = California Air Resource Board
warranty field returns and customer satisfaction was
DHC = Dust Holding capacity
affected by use of aftermarket filter brands.
EAC = Engine Air Cleaners
EIS = Engine Induction Systems
Innovative air cleaner designs are required to maximize ISO = International Standards Organization
filtration performance, improve flow management, LLF = Long Life Filtration
extend air cleaner service life and improve engine MAFS = Mass Air Flow Sensor
durability. Filtration characteristics of reticulated porous NA = North America
foams were studied and evaluated as a potential NVH = Noise Vibration and Harshness
solution. Reticulated foam media has a very open OEM = Original Equipment Manufacturer
structure, which allows it to have a relatively high dust PPI = Pores Per Inch
holding capacity (DHC) and capture efficiency. The PZEV = Partial Zero Emission Vehicle
potential benefits of reticulated foam filters are longer
life, competitive cost and flexibility in packaging. A foam
filter model was also developed to predict performances
of multi-layer reticulated foam filters. Model predictions INTRODUCTION
for a four layer foam filter design have been presented
and discussed. Foam filters have been used in the aftermarket for
motorcycle and high performance vehicle air intake
A new Long Life Filtration System was developed for systems with limited success. Most foam filter designs
OEM (Original Equipment Manufacturer) applications are super-saturated with viscous oils or tackifiers to
(2003/2004 Ford Focus Vehicle) and requirements. This improve their filtration performance levels. This is further
new technology uses a unique multi-layered reticulated evidenced by the oil puddle that collects in the plastic
foam media which does not need servicing or
maintenance for the life of the vehicle [150K+ miles].
This technology also provides some unique advantages
over the traditional serviceable air induction filters.
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bag used to package these foam filters. Most of the Engine Air cleaners [EAC] are designed to effectively
foam aftermarket filters exhibit high oil migration, remove airborne contaminants in order to protect the
contamination of downstream sensors, contamination of engine throughout its service life [12]. The engine
moving parts, poor service life and poor engine requires that the ingested air meet a minimum level of
protection. However, the successful use of OEM foam cleanliness to reduce engine wear, improve engine
filters for engine intake has been reported previously efficiency and protect electronic sensors [12]. However,
[1, 2, 3, 4, 5, 8]. in actual service when aftermarket components
(especially air filters) are used the OEM design integrity
This paper describes a new Long Life Filtration (LLF) is generally compromised. The majority of the air filters
System technology developed for OEM applications available in the aftermarket exhibit poor performance
using a unique multi-layered reticulated foam media and levels [9]. Use of low performing aftermarket filters may
air cleaner design. Filtration characteristics of reticulated lead to excessive engine wear and system
porous foams were studied and evaluated. Multilayered contamination [6, 9, 10]. A robust engine air cleaner
reticulated foam media were designed having high should meet and exceed the following parameters.
filtration performance levels. The multi-layered
reticulated foam maximizes the dust holding capacity 1. Maximize the available package space
and efficiency due to its depth/deep-bed filtration 2. Improve filtration performances;
properties. This technology also provides some unique a. Higher fine dust efficiency &
advantages over the traditional serviceable air induction b. Higher fine dust capacity
filters. A filter model was developed to predict 3. Accommodate higher engine flow rates and
performances of multi-layer reticulated foam filters. The media face velocities
model can accommodate multiple foam layers in various 4. Reduce overall engine wear
thicknesses. The model also allows for the foam layers 5. Improve engine power/torque
to be dry or treated to improve performance. 6. Improve MAFS performance
Comparisons of experimental data to foam predictions 7. Allow competitive costs
show good correlation [1]. 8. Meet evaporative emissions over 150K miles
9. Improve sealing to meet LEVII, ULEV & PZEV
Based on the LLF technology, an innovative ‘Zero 10. Withstand higher under-hood temperatures
Maintenance’ Long Life engine air cleaner system was 11. Extend filter service life
developed for 2003 ½ and 2004 Ford Focus Vehicle. 12. Improve engine durability to 150K+ miles
Previous papers [1, 2] discuss details of the Ford Focus 13. Reduce parts complexities
long life air cleaner development that meets all OEM 14. Improve Recyclability
requirements. This new system is completely sealed and
does not require any service for 150K+ miles. This paper ENGINE AIR INDUCTION SYSTEMS AND
presents further performance enhancements to the AFTERMARKET AIR FILTERS
original design [1, 2].
OEM (original equipment manufacturers) air induction
With the long life system, OEM's will enjoy substantially designs are optimized to meet required levels of
reduced warranty costs associated with air filter service. performances using a systems approach and synergy
Consumers will no longer need to worry about using for the vehicle. Invariably, when aftermarket components
sub-standard replacement filters and additional are used the design integrity and durability of the OEM
installation problems that can damage engines [9, 10]. system is compromised. Use of aftermarket air filters in
This new technology can save consumers between $100 OEM air cleaners presents a very challenging dilemma.
and $300 over the life of the vehicle. Higher cost savings High mileage studies conducted by Ford Motor
may be realized for dedicated fleets and rental Company in 2000 - 2002 clearly indicated that; a)
companies. aftermarket air filters and b) mis-assembly of the air
cleaner parts significantly contributed to field returns and
higher warranty issues. Their high mileage studies
ENGINE AIR INDUCTION SYSTEMS yielded the following issues;

Engine air induction systems are designed to meet - OEM air cleaner design integrity could be
engine protection requirements, engine durability compromised
requirements, air flow management, horse-power - Broken and cracked air cleaners were observed
targets, achieve desired torque tuning, water/snow - Air cleaners had severe leakage issues
ingestion management, NVH targets, vehicle sound - Aftermarket air filters were very difficult to service
tuning and more recently managing evaporative - Mis-assembly of parts during service was highly
emissions. Tradeoffs in performance requirements are probable even when no tools were required.
often made in designing air induction systems based on - Majority of the air filters were pre-maturely
OEM customer requirements [10, 11, 12, 13]. serviced.
- Engines exhibited stalling and starting issues.
- Mass Air Flow Sensor contamination was high.
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Figure 1 shows pictures of OEM engine air cleaners loss, allows the filter to achieve its highest efficiency
from high mileage fleet evaluations. The air cleaners thus providing maximum engine protection. Frequently
exhibited filter seal tear and filter collapse into the tray. servicing the air filter, especially within the first 30% of
Figure 2 shows typical aftermarket air filter for a light its service life can significantly increase engine wear [7].
truck application. These aftermarket filters exhibited filter
warpage and loss of performance. Additional information
on performance of aftermarket filters can be found in
reference [9, 10]. The filters could exhibit pleat collapse,
pleat separation, torn seals and permanent compression
set on seals.

Figure 2: Typical examples of warped aftermarket

filters.

In reality, engine air cleaners are pre-maturely serviced

by the end customer. As a result the customer never
utilizes the full value of the air filter. This is due to the
Figure 1: Typical examples of air cleaner field returns fact that the engine air filter never achieves its highest
from high mileage study using aftermarket filter brands. efficiency levels, thus reducing overall engine protection
by increasing the rate of engine wear [7, 11, 12]. Figure
3 shows the efficiency of a typical engine air cleaner
using a pleated paper filter design. Data for figure 3 was
ENGINE AIR INDUCTION SYSTEMS AND FILTER generated from benchmark studies on air induction
SERVICE LIFE systems. Figure 3 shows that the air filter never reaches
its full efficiency (illustrated by dash line). The customer
Estimating service life for a particular engine size or is also throwing away a perfectly good filter, which
vehicle can be complex. However, understanding increases the cost of vehicle ownership.
service life requirements is crucial for optimum engine
protection. Engine air cleaners should be serviced after
they have reached or surpassed an allowable restriction SERVICE LIFE CRITERIA - Service life expectations for
rise due to contaminant loading [11]. Further, the point at light, medium & heavy-duty vehicles are different.
which the engine air cleaners are serviced affects both, Typical service interval for light/medium duty vehicles
filtration performance and overall vehicle performance. under normal driving conditions is about 30K miles.
Engine air cleaners having excessive restriction values Engine performance for light and medium vehicles
can significantly degrade overall engine performance. It generally requires that most EAC should be serviced,
has been well demonstrated that the filtration efficiency once the restriction rise has reached or exceeded about
of the AIF improves with contaminant loading [7, 12]. 2.5 kPa beyond initial restriction [10, 11].
With an increase in efficiency, the engine wear
significantly decreases [7]. Servicing air filters at the Service life expectations are generally recommended for
recommended (design intent) restriction rise or pressure normal driving conditions. Typically, that includes the
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97th percentile customer profile. Service life representative of the typical field environment
expectations for severe/dusty driving conditions are [10, 11,12]. Using ISO Coarse test dust yield higher dust
significantly shorter compared to normal conditions [10, capacities, but have very little correlation to real world
11]. environment. Table 1 below shows the summary of the
extensive field evaluations performed on various
customer fleets and on proving grounds.
Cumulative Gravimetric Efficiency vs. Dust Fed For a
Serviceable Filter Using Traditional Designs
100.0 Contaminant Expected Expected
Design Intent Loading Min. Dust Min. Dust
Vehicle
C umulative Eff., % using

Service Interval g/1000 miles Capacity** Capacity**

ISO Fine Test D ust

99.5 at 30K miles at 150K miles

service, g Service, g
Small /
99.0 Medium 2 60 300
Passenger
Cars & SUVs
98.5 Large/Full
Size 3.5 105 525
Passenger
98.0
Cars, SUVs,
0 100 200 300 400 500 600 Minivans &
Dust Fed, Gms
Lt. Trucks
Figure 3: Efficiency performance of a typical pleated Medium/
5 150 750
engine air filter challenged with standard ISO fine test Large Trucks
dust. The dotted line indicates the performance
benefits not realized by the OEM customer.
** Dust capacity expectations based on ISO Fine
Test Dust

Table 1: Estimated Minimum ISO Fine Dust Capacity

FACTORS AFFECTING SERVICE LIFE – Service life Required for Vehicle Segments. Data derived from
primarily depends on the application and end use. extensive field studies [10, 11, 12].
Factors affecting service life can be complex and
multivariate in nature. Some key factors are listed below; ZERO MAINTENANCE LONG LIFE ENGINE AIR
INDUCTION SYSTEM FOR ENGINE INTAKE
- Air cleaner housing design
- Inlet (dirty) tube location Engine air induction systems (AIS) typically use paper or
- Outlet (clean) tube location felt type air filters [10, 11,12]. The filtration
- Air Filter design characteristics for these media are well understood and
- Filter media type modeled. However the model applications are fairly
- Filter media area limited. These designs have limitations as discussed in
- Filter dust holding capacity previous sections above. Due to these constraints,
- Filter dust loading characteristics majority of the air cleaner designs frequently do not
- Driving conditions provide optimal filtration and flow management under-
- Type of contaminant hood. However, the current OEM air cleaners are
- Contaminant Shape/Size/Concentration designed and suited for serviceability.
- Environmental conditions
- Customer awareness OEM automakers are constantly striving to provide
- Cost of ownership more product value to the end customer. OEM
manufacturers are constantly improving their products
Various studies have been performed to predict or and systems to reduce both development time &
estimate Air Cleaner Service Life with limited success manufacturing process time, and also warranty and
[6, 10, 11, 12]. Generally lab or bench studies are maintenance costs. The zero maintenance Long Life
conducted to measure the performance (DHC, Filtration (LLF) System makes it possible for the vehicles
gravimetric efficiency, restriction, fractional efficiency to operate using the same air cleaner for at least 150K
etc.) of the air filter. These studies are performed using miles or more without requiring any maintenance or
standard test procedures and standard test dust, service, under normal driving conditions.
providing limited information regarding filter service life.
Use of porous foam filters for engine intake and related
Analysis of extensive Real World field evaluations air filter applications have been reported previously
indicated that using ISO Fine Test dust is most
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[1, 2, 3, 4, 5, 6]. For developing Visteon’s zero The pentagon is formed by struts or strands. A whole
maintenance Long Life Filtration System, reticulated matrix of these cells make up the foam giving it a very
(open cell) foam structures were studied ranging from 20 high permeability and surface area, ideal for depth or
ppi (pores per inch) up to 110 ppi (pores per inch). By deep bed filter design. Porous foam media have been
designing multi-layered reticulated foams using the used in various filtration applications to remove airborne
appropriate pore sizes, the usage of viscous treatments particles for low efficiency filtration applications. Porous
(oils) can be significantly reduced. foams when used in a multi-layered configuration can
effectively be used for medium to high efficiency filtration
The reduction of viscous treatment usage was one of the applications [1, 2, 3]. All known filtration mechanisms are
key goals of the development team. Experience and present within the foam structure to collect particles. The
analysis of field failures have demonstrated that the reticulated foam filter media provides the following
migration of viscous treatments from a filter element can benefits:
lead to contamination and subsequent failures of the
Mass Air Flow Sensor, and other critical engine sensors. ¾ Reticulated 'open cell' foam is about 96%-98%
The use of multiple layers in the filter allowed the porous.
development of a control for migration of the viscous ¾ High surface area for contaminant collection.
treatments out of the filter element. New control methods ¾ Foams can be accommodated in multiple shapes
for applying viscous treatments were utilized in the and sizes.
Visteon Long Life Filtration system. Specific amounts of ¾ Foams are durable materials resistant to water
oils are added to the foam, and additional processing and snow and solvents.
was utilized to distribute the oils into the center of the ¾ Available in multiple pore sizes.
foam matrix. The multi-layer construction allows the ¾ Fairly uniform pore size distribution.
¾ Selective layers can be treated with viscous oils
arrangement of the layers to provide a barrier to oil
to improve filtration performances.
migration into the air stream.
¾ High dust capacities and efficiencies are
possible.
An additional benefit afforded from the use of multi-layer ¾ Cost effective
foam construction is that reticulated foam can be coated
with activated carbon. The resulting structure functions For reticulated foams the pore size and strand (fiber)
as both a collector of dust particles and an adsorber of diameter are important parameters to control filtration
hydrocarbon vapors. A filter that contains such an performance levels. Figure 4 shows an example of a
adsorbing layer, and designed with DHC to exceed 150K clean reticulated and dust loaded ( light and heavy)
miles, provides an OEM with an integrated solution to air foam. The dust loading clearly shows the dendrite
filtration and under hood evaporative emission control. formation of the dust around the strands within the pore.

The new sealed zero maintenance LLF air cleaner FOAM FILTER MODEL - A semi-empirical model has
design can provide an attractive package as a stand- been developed to predict pressure drop, collection
alone or a complementary system to support a full PZEV efficiency, dust loading behavior of foam filters and
solution. PZEV development as it relates to AIS is estimate service life. Model can be applied to any Pore
discussed in a separate technical paper [13]. The next count between 20 and 110 pores per inch using multiple
generation of engine air induction systems will have to layers. The model is suited for reticulated foam having a
support and meet United States Tier 2, California LEV-II basis weight in the range of 24 – 32 kg/m3 (1.5 – 2.0
(low emission vehicle) and PZEV vehicle emission lb/ft3). The pressure drop model applies to face
requirements. The California Air Resources Board velocities in the range of 75 to 300 m/min. Overall
(CARB) is mandating the LEVII and PZEV requirements accuracy of model predictions is about ± 20% for
for 15 years/150K miles. It has already been established collection efficiencies, pressure drop and dust holding
that hydrocarbon vapors flowing and/or diffusing out capacities. The model predictions are based on uniform
from the inlet manifold and engine will have to be flow conditions.
reduced or removed to meet the new LEV-II and PZEV
requirements. For PZEV designated vehicles, OEM The model can accommodate up to 12 layers of foam,
automakers have determined that the use of aftermarket dry or selectively treated to capture dust. The model
components may seriously compromise the design and predicts pressure drop, dust capacity, initial and overall
functional integrity of the air cleaner system. gravimetric efficiencies at selectable pressure drop rises
of up to 5 kPa beyond initial restriction.
MULTILAYERED FOAM MEDIA - Open cell
polyurethane foams are engineered in various pore In addition, the model also predicts performance of
sizes ranging from 20 to 100 ppi (pores per inch). The individual layers in terms of restriction rise, dust loading
pore sizes are defined based on a pressure drop method and cumulative gravimetric efficiency. The performance
(MIL-PRF-87260A {UASF} 1998). Polyurethane foams predictions of individual layers are critical in designing
have a very unique 12-sided three-dimensional structure the multi-layer foam filter. The model also predicts the
also known as a Pentagonal Dodecahedron structure. fractional size efficiency of the multi-layer foam. Model
Each of the 12 cell sides is pentagon in shape [1,3,4,5]. input/output parameters are briefly listed below.
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dust under normal driving conditions. Efficiency curves

show that the design optimal face velocity for the 4 layer
foam design is in the range of 100 to 200 m/min..

Example of Multilayer (4-layer) LLF Model Predictions

Face Velocity vs. Pressure drop
2.0
1.8
1.6

pressure drop, kPa

1.4
1.2
1.0
0.8
0.6
y = 0.0003x1.6003
0.4
0.2
0.0
0 50 100 150 200 250 300
Figure 4: Example of a clean and dust loaded foam Face Velocity, m/min.
filter. Figure 5: Pressure drop vs. Face Velocity prediction for
a 4 layer long life filter.
Input Parameters
i Number of layers
i Thickness of each layer
Example of Multilayer (4-layer) LLF Model Predictions
i Dry or Treated
Face Velocity vs. Dust Capacity
i Face velocity through media 700
i ISO coarse or fine test dust
650
dust capacity, g w/ISO

i Terminal pressure drop rise

i Assumes uniform flow distribution 600
Fine test dust

550
Output Parameters 500
o Initial clean pressure drop
o Initial mass efficiency 450
o Differential dust distribution on each layer 400 y = -1.5795x + 833.8
o Cumulative dust distribution on each layer 350
o Total Dust mass loading
o Fractional size efficiency 300
o Service life prediction 0 100 200 300
Face Velocity, m/min.
The model was used to predict the performance of a Figure 6: Predicted Dust Holding Capacity vs. Face
high capacity 4 layer ‘zero maintenance’’ long life foam Velocity for a 4 layer long life filter.
filter. The 4 layer foam design would meet or exceed
performance levels typical of current filtration
Example of Multilayer (4-layer) LLF Model Predictions
technologies used on engine air cleaners [2, 9, 10, 12].
Face Velocity vs. Gravimetric Efficiency
The foam media was about 63.5 mm in thickness with a 100.0
footprint of about 600mm2. The prediction curves that initial overall
99.5
dust capacity, g w/ISO

follow illustrate the modeling capabilities of foam filters. efficiency efficiency

Figure 5 shows the predicted pressure drop vs. face
Fine test dust

99.0
velocity of the 4 layer foam. The pressure drop
increases can be approximated by a power function. 98.5
When the face velocity is doubled the pressure drop
increases by about a factor of three. Figure 6 shows the 98.0
predicted dust holding capacity vs. face velocity. In the
range of 100 to 250 m/min., the dust DHC can be 97.5 targets
linearly approximated. For example the dust holding
capacity dropped by about 30% when face velocity was 97.0
doubled. 0 50 100 150 200 250 300
Face Velocity, m/min.
Figure 7 shows the predicted initial and overall efficiency Figure 7: Predicted Gravimetric Efficiency vs. Face
of the 4 layer media. Figure 7 also shows the target Velocity for a 4layer long life filter.
minimum efficiencies required when using ISO fine test
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As expected the efficiency increases with increasing Example of Multilayer (4-layer) LLF Model Predictions
face velocity, as the dominant particle capture Media Depth vs. Pressure drop
mechanism is by interception and inertia [8]. The 1
efficiency drop off at higher face velocities may be y = 0.3232x
0.2234
0.9

pressure drop, kPa

attributed to particle bounce and re-entrainment.
Multilayer foam filters can be designed for a range of
0.8
velocities. Depending on the number, type and size of
multilayer foam filters the optimal face velocity range
0.7 Initial Gravimetric Eff.= 99.11%
may be different.
Overall Gravimetric Eff. = 99.84%
0.6 Face Vel = 150 m/min
Figure 8 shows the estimated service life of the 4 layer
foam for a large passenger car application. The service
0.5
life varies almost linearly with face velocity. Based on
0 50 100 150
the optimal design face velocity of 100 – 200 m/min., the
Media Depth, mm
service life can range from 148K to 190K miles.

Example of Multilayer (4-layer) LLF Model Predictions Figure 9: Predicted Restriction Rise vs. Media Depth for
Face Velocity vs. Service Life a 4 layer long life filter.
200000.0
Service Life, miles

175000.0
Example of Multilayer (4-layer) LLF Model Predictions
Media Depth vs. Dust Capacity
150000.0 1200
y = -431.77x + 234677
1100
125000.0 Dust Capacity, g w/ISO
1000
Fine test Dust y = 9.8175x
900
100000.0 800
0 50 100 150 200 250 300 700
Face Velocity, m/min. 600
Initial Gravimetric Eff.= 99.11%
500 Overall Gravimetric Eff. = 99.84%
400 Face Vel = 150 m/min
Figure 8: Estimated service life for a 4 layer foam 300
designed large passenger car. 0 50 100 150
Media Depth, mm

Figures 9 and 10 show the effect of increasing thickness

Figure 10: Predicted Dust Capacity vs. Media Depth for
of multilayer layer foam filter. The foam filter was
a 4 layer long life filter.
designed to operate at a face velocity of 150 m/min. For
each increasing thickness the foam layers were
designed to maintain the same initial and overall
removal efficiencies. The end effect was to offer the
same engine protection with increasing dust capacities LONG LIFE FILTER REAL WORLD FIELD
and service life. Figure 9 shows the effect of increasing STUDIES
thickness on restriction rise. The pressure drop can be
approximated by a power function. However in the range A production prototype air cleaner was developed for a
of interest, the pressure drop increase was almost linear large passenger car application equipped with a 4.6L 2-
with increasing thickness. valve engine at a rated flow of 9.91m3/min. Figure 11
shows the location of the Long Life filtration System in
Figure 10 shows the effect of thickness on dust holding fleet vehicles. The Long Life filtration System was
capacity. The dust capacity can also be closely packaged outside the engine compartment and behind
represented by a liner function. It is interesting to note the front bumper below the driver side headlight. Figure
that doubling the thickness only increased the restriction 12 shows a cut-away view of the air cleaner showing the
rise by about 20%. However doubling the thickness foam multilayered filters.
increased the dust capacity by about 90% (almost
double).
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Total Mileage and Restriction Rise For All Vehicles

250000 4.0
Miles Restriction Rise
3.5
200000
3.0

R e s trictio n , k P a
2.5

D is ta n ce , m ile s
150000
2.0
100000 1.5

1.0
50000
0.5
Figure 11: Long Life AIS used in Fleet Study. The
system was packaged outside the engine compartment. 0 0.0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38

Vehicles

Figure 13: Miles accumulated and restriction rise on

fleet study.

The data for contaminant loading and restriction rise was

also plotted in Figure 14. There is an increasing trend of
restriction rise with contaminant loading. On average we
can expect about 500g of contaminant collected at a
2.5kPa restriction rise.

Figure 12: Cut Away View of the Long Life Air Cleaner Dust spot efficiency was also measured on random LLF
used in Fleet Study. air cleaners returned from the field. The spot efficiency is
measured after feeding 20g of ISO fine test dust on the
filtration stand using maximum rated flow conditions.
Extensive field evaluations were performed on the above Figures 15, 16 and 17 all show increasing efficiency
Long Life filtration System using multi-layer foams over a levels with contaminant loading, miles accumulated and
2- 3 year period at four different locations in North restriction rise. These increasing trends are desirable as
America (NA). Field evaluations were performed at; 1) it demonstrates the reliability of the LLF filter after
New York City, 2) Orlando, 3) Las Vegas and 4) Phoenix contaminant loading and with time. On average the dust
- Maricopa County [1,2]. Additional information can be spot efficiency increased from about 98.85% to 99.3%
found on the fleet studies in ref. 1 and 2. with contaminant loading.

All fleet vehicles operated on a single long life filtration Overall Contaminant Loading vs. Restriction Rise
system for 2 to 3 years without any customer complaints All Fleet Data
or engine performance degradation. These systems did 8.0
not require any maintenance or service actions during 7.0
Restriction Rise, kPa

the entire study period. Customer satisfaction with 6.0

engine and filter performance was high [1, 2].
5.0

Figure 13 shows the mileage accumulated and the 4.0

restriction rise for all fleet vehicles (38 vehicles). The 3.0
restriction rise was measured on a bench test before 2.0
and after the fleet tests were concluded (2 to 3 1.0
years).The restriction rise does not show a continuous 0.0
increasing trend with mileage. This was expected as the
100 1000
vehicles were operating in four different environments Contaminant Loading, g
and driving conditions. The dash line shows the
restriction rise trend. On average the vehicles Figure 14: Contaminant loading and restriction rise for
accumulated about 109K miles with a restriction rise of fleet study.
0.94kPa.
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Contaminant Loading vs. Measured Dust Spot Restriction Rise vs. Measured Dust Spot
Efficiency - All Fleet Data Efficiency - All Fleet Data
100.0 100.0
99.8 99.8

Dust (gravim etric) S pot

D u s t (g ra v im e tric )
S p o t E ffic ie n c y , %

99.6 99.6
99.4

E fficiency, %
99.4
99.2
99.2
99.0
98.8 99.0
98.6 98.8
98.4 98.6
98.2 98.4
98.0 98.2
0 100 200 300 400 500 600 0 1 2 3 4
contaminant loading, g Restriction rise. kPa
Figure 15: Contaminant loading vs. dust spot efficiency.
Figure 17: Restriction rise vs. Dust spot efficiency

Mileage Accumulated vs. Measured Dust Spot

Efficiency - All Fleet Data Overall Contaminant Loading Data Including
100.0
All Fleet Vehicles
99.8 4.0
Dust (gravim etric) Spot

contaminant collected, g/1000 miles

99.6
3.5
99.4
Efficiency, %

99.2 3.0
99.0 2.5
98.8
2.0
98.6
98.4 1.5
98.2 1.0
0 50000 100000 150000 200000 250000 300000
0.5
Vehicle Miles
0.0
avg 95% confidence 99% confidence
Figure 16: Vehicle miles accumulated vs. Dust spot
efficiency
Figure 18: Normalized Contaminant loading.

Figure 18 shows the overall normalized contaminant

loading based on data from all fleet vehicles. On
average we can expect about 2.1g/1000 miles. Based Long life
Long life filtration
on confidence limits we can expect about 3.5g/1000 filtration system
system
miles of contaminant loading at 99% confidence. Hence, Model
Experimental Data
at a service life of 150K miles we can expect about 525g Predictions
of total contaminant to be ingested. Dust Capacity, g 333g 287 g
Initial Gravimetric
Table 2 below compares the lab bench measurements 98.41% 98.47%
Efficiency, %
to model predictions for the Long Life Filtration systems
Overall
used in the taxicab fleet study. The dust capacity
measurements based on model predictions were within
Gravimetric 98.83% 99.35%
±20%. The efficiency predictions were within ±0.5%. Efficiency, %
Based on these measurements the LLF for the taxicab Flow rate= 8.0 m3/min. constant
fleet may not require any service for 95K miles. Test Dust = ISO fine

Table 2: Experimental data compared to model

predictions for Long life filtration used in Taxicab Fleet
Study.
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BENEFITS OF ZERO MAINTENANCE LONG LIFE AIR contaminants. The use of multi-layer reticulated foam
INDUCTION SYSTEMS - The zero maintenance LLF air accommodates complex geometries, which further aids
cleaner design offers some unique and significant the LLF in packaging flexibility, freeing up valuable real
advantages to OEM automakers and end usage estate under the hood and around the engine. The
customers. Some of the performance benefits have performance of the LLF can be tuned to meet normal
been discussed above. Additional key design benefits driving conditions using proprietary CAE models.
include the following;
Figure 20 shows the complete Long Life Air Induction
1. Increases air filter service intervals over 150K system removed from the vehicle. This system was
miles. initially developed for the 2003 Ford Focus PZEV
2. Improves robustness and durability of air vehicles. For the 2004 MY all Ford Focus have adapted
induction systems. this system across the board.
3. Provides OEMs and end customers a complete
solution ‘hassle free design’.
4. Allows a variety of geometric shapes to be
packaged.
5. Allows increased packaging flexibility.
6. Reduces vehicle lifetime service cost.
7. Reduces the impact of serviceable filters
occupying landfills.
8. Minimizes the possibility of using substandard
aftermarket filters during the warranty period.
9. Allows manufacturing complex geometries
compared to traditional paper and felt type
filters.
10. Allows ease of filter design tuning to local
market requirements.
11. Enables incorporation of evaporative emission
controls to meet PZEV and LEVII vehicle
requirements for the sealed air cleaner design
12. Allows use of a proprietary filtration to quickly
design LLF system performances.
Figure 19: Zero Maintenance Sealed Long Life Air
Cleaner System for 2003/4 Ford Focus. The Long Life
A PRODUCTION ‘ZERO MAINTENANCE’ LONG Filtration System is covered by one or more Visteon
LIFE ENGINE AIR INDUCTION SYSTEM FOR Patents. Additional patents are currently in progress.
SMALL PASSENGER CAR ENGINE

A sealed production Long Life Filtration System was

designed and developed for a small passenger car
application [2003/2004 Ford Focus]. Additional
information on the Long Life Filtration System design
and performance can be found in Bugli N et. al [1,2]. The
Long Life Filtration System requires zero maintenance
and service for 150K miles under normal driving
conditions. The Long Life Filtration System is packaged
outside the engine compartment. Figure 19 shows the
LLF design as installed in the vehicle. The air cleaner is
completely sealed and packaged outside the engine
compartment behind the front bumper on the driver side.
The inlet tube was packaged in the fender area for
improved water protection and lower restriction as
shown in Figure 19. The outlet tube uses a slot-in MAFS
design for improved performance. The large plenum
downstream of the air cleaner includes a sound
attenuating resonator and a hydrocarbon emissions
arrestor for vehicles requiring PZEV compliance [1, 13].
Figure 20: Production Long Life Air Induction System
The new Visteon Long Life Filtration System uses a
shown from inlet tube to throttle body inlet.
unique multi-layered reticulated foam media and
construction for OEM applications to trap and remove
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Figure 21 shows a cross-section of the sealed LLF Average Dust Capacity Measured Using ISO Fine Test Dust @
design. The cross-section shows the multi-layered 2.5 kPa Restriction Rise
reticulated foam used for achieving higher filtration 1100
performance. Selective layers of the reticulated foam are 1000
treated with commercially available chemicals, to 900 Target capacity for Ford Focus = 300 g

D ust C apacity, Gms

enhance the contaminant trapping efficiency of the LLF. 800
The foam layers are also trapped and held rigidly 700
600
between two plastic screens. The plastic screens are
500
designed to be part of the air cleaner cover and tray
400
assembly and are necessary to achieve the desired
300
filtration performance levels.
200
100
0
Dry Paper Treated Synthetic Felt 2003/4 Ford Long Life
Technology Paper Technology Focus Long Technology
Technology Life Capability
Technology

Figure 22: Dust Holding Capacity Performance of Long

Life Technology compared to Traditional designs.

Figure 23 compares the average initial gravimetric

efficiencies measured on traditional technologies to a
clean LLF using ISO fine test dust [10]. The initial
gravimetric efficiency target was set at 98% min. using
ISO fine test dust. The target efficiency was calculated
based on OEM benchmark data covering over 150
vehicle types [10]. On average the LLF achieved an
initial efficiency of 99.5%. Compared to traditional
technologies the Long Life filter initially allows about 4
times lower dust penetration to the engine. This can be
Figure 21: Details of Multilayer Foam For Zero significant for engine wear, protection and durability [7].
Maintenance Sealed Long Life Air Cleaner System
Average Initial Gravimetric Efficiency Measured @ 20 Gms of
ISO Fine Test Dust
ZERO MAINTENANCE LONG LIFE FOAM FILTER 100.0
PERFORMANCE – Long Life air cleaners were 99.5 Target capacity for Ford Focus
extensively tested in the lab and in real world field
In itia l G ra vm e tric E ff., %

99.0 = 98% minimum

environments. ISO fine test dust was used for all
evaluations to more closely represent actual field loading 98.5
[11]. The production LLF air cleaner design meets or 98.0
exceeds known customer OEM engineering
97.5
specifications as applied to conventional air cleaners.
More details on air filter testing and specifications are 97.0
covered in reference [14]. 96.5
96.0
Figure 22 compares the average dust capacity
Dry Paper Treated Synthetic Felt 2003/4 Ford Long Life
measured on traditional technologies and a clean Long Technology Paper Technology Focus Long Technology
Life filter using ISO fine test dust [10]. The target dust Technology Life Capability
capacity was set at 300g using ISO fine test dust [2]. Technology
The target capacity was calculated based on field
evaluations and specific engine size for this application Figure 23: Initial Efficiency Performance of Long Life
[2, 10, 11]. On average the LLF holds about 500g of ISO Technology compared to Traditional designs.
fine dust at a 2.5 kPa restriction rise. This target
capacity represents a service interval of 150K miles for Similarly Figure 24 compares the average overall
the Ford Focus application based on normal driving gravimetric efficiencies measured on traditional
conditions [Table 1]. Compared to traditional technologies and a clean LLF using ISO fine test dust
technologies the Long Life filter achieves about 2.5 to 5 [10]. The overall gravimetric efficiencies were measured
times higher dust capacity. at a 2.5kPa restriction rise. The overall gravimetric
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efficiency target was set at 98.5% min. using ISO fine Figure 26 shows the restriction rise of the Ford Focus
test dust. The target efficiency was calculated based on Long Life Filter with dust loading. The restriction rise rate
OEM benchmark data covering over 150 vehicle types was very linear with dust loading and is predictable. This
[10]. On average the LLF achieved a high overall trend is significantly different when compared to
efficiency of 99.5. Compared to traditional technologies traditional filter designs where a prominent change over
the Long Life filter allows about 1.5 to 3 times lower dust point is present when dust cake formation takes over.
penetration to the engine. Again, this can be significant This was expected as the foam filter behaves like a
for engine wear, protection and durability [7]. depth media.

Average Overall Gravimetric Efficiency Measured @ 2.5 kPa

Terminal Restriction Rise Using ISO Fine Test Dust Restriction Rise vs. Dust Fed
100.0
Ford Focus Long Life Filter
Target capacity for Ford Focus 4.0
O v e ra ll G ra v im e tric E ff.,%

R e striction R ise, kP a
= 98.5% minimum 3.5
99.5
3.0
2.5
99.0
2.0
1.5
98.5
1.0
0.5
98.0 0.0
Dry Paper Treated Synthetic Felt 2003/4 Ford Long Life
Technology Paper Technology Focus Long Technology 0 100 200 300 400 500 600 700 800
Technology Life Capability Dust Fed, g
Technology

Figure 24: Overall Efficiency Performance of Long Life Figure 26: Pressure drop rise vs. dust loading for the
Technology compared to Traditional designs. Ford Focus Long Life Filter.

Figure 25 shows one of the primary advantages of using The measured performance of the Ford Focus Long Life
the Long Life Filter Technology. Figure 25 compares the Filter was also compared to model predictions. Table 3
high efficiency level of the Long Life filter to traditional shows the comparisons. The model predictions compare
serviceable filters [Figure 3]. Clearly, the Long Life fairly well. The capacity predictions are within ±20%. The
technology offers better engine protection throughout the efficiency predictions were within ±0.5%. The restriction
vehicle life. predictions were within ±25%.

Cumulative Gravimetric Efficiency vs. Dust Fed comparing LLF

LLF Model
Serviceable Filters and Long Life Technology Experimental
100.0 Predictions
Data (average)
Design Intent Ford Focus AIS
Service Interval Ford Focus AIS
Cumulative Eff., % using

Dust Capacity, g 499g 609g ± 130g

ISO Fine Test Dust

99.5
Initial Gravimetric
99.52% 98.9%
Ford Focus Long Efficiency, %
99.0 Life Technology Overall Gravimetric
99.48% 99.51%
Efficiency, %
Filter Restriction,
98.5 1.13±.315 0.94 ±0.125
kPa

98.0 Flow rate= 6.4 m3/min. variable

0 100 200 300 400 500 600 Test Dust = ISO fine
Dust Fed, Gms

Figure 25: Efficiency increase of Long Life Filter Table 3: Experimental Long Life filter performance
compared to traditional pleated filter. The dashed compared to model simulations
line indicates the performance benefits not realized
by the OEM customer.
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SUMMARY CONCLUSIONS

Field evaluations and laboratory analysis successfully OEM’s and vehicle owners can realize numerous
demonstrates the viability and flexibility of Long Life benefits from the elimination of maintenance to the
Filtration System designs. vehicle, as has been demonstrated with 100,000 mile
spark plugs, long life coolants, and electronic ignition
Model predictions correlate with experimental data for systems. The Long Life Filtration technology developed
filter performance levels. Capacity and Restriction by Visteon Corporation provides a method for minimizing
predictions using the model are within ±20% and the the requirements to replace or clean engine air filters.
efficiency predictions are within ±0.5%. Zero maintenance filtration for engine air cleaners have
been modeled, tested and validated in vehicle fleets for
The multi-layer foam technology provides superior durability and robustness. The multilayer foam filtration
filtration, and therefore engine protection, as compared technology is a cost effective method to eliminate engine
to standard OEM filters designed for regular air filter maintenance while improving engine durability,
replacement. The multi-layer foam filter technology also reducing evaporative emissions, and reducing overall
provides improved performance when compared to filter material usage.
media that are serviced by cleaning at regular intervals.
The greatest areas of improvement are in filter efficiency REFERENCES
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Exposition, Reno, Nevada, June 17-20, 2003.
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customer some very unique advantages and value over Polyurethane foam for small engine filters", SAE
the life of the vehicle. technical paper 951811.

a. Improved system reliability and robustness over the 4. Curti C. M," Reticulated Polyurethane Foam",
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$300 over the life of the vehicle (Higher cost paper 970673, also in SAE special publication SP-
savings may be realized for dedicated fleets and 1252 pp. 103 - 112, presented at the SAE
rental companies). International Congress and Exposition, Detroit, Feb.-
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9. Bugli N. J and Leffel J. (2001), "Engine Air Induction

Filtration Systems- Design challenges for the Next
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March 2, 1995.

ACKNOWLEDGMENTS

The authors would like to sincerely thank Mr. Brian

Condron, Mr. Michael Adams, Ms. Celine Jee Dixon, Mr.
Ryan Grimes, Mr. Jeffrey Leffel, Mr. Scott Flora, Ms
Grace Alent and Mr. Scott Dobert of Visteon Corporation
for their help and support in developing the ‘zero
maintenance’ Long Life Air Cleaner.

CONTACT

Neville Bugli
Technical Fellow
Visteon corporation
734-710-4751
734-736-5600 fax