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2005-01-1139

Performance and Benefits of ZeroMaintenance Air Induction Systems

Neville J. Bugli and Gregory S. GreenVisteon Corporation

Reprinted From: New SI Engine and Component Design 2005(SP-1966)

2005 SAE World CongressDetroit, MichiganApril 11-14, 2005

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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 induction systems typically utilize pleated paper or felt type air filters. These air filter designs have been used for many years in panels, cylindrical or round (pancake type) type air cleaners. Pleated air filters are specifically designed to be serviceable and hence their performance is inherently limited by vehicle under-hood packaging and manufacturing constraints. Due to these constraints, majority of air cleaner designs are not optimized for engine filtration and air flow management under the hood. Studies show that use of low performing serviceable aftermarket air filters significantly affect the performance and durability of engine air cleaners [9]. High mileage studies confirm that engine durability, service issues, warranty field returns and customer satisfaction was affected by use of aftermarket filter brands.

Innovative air cleaner designs are required to maximize filtration performance, improve flow management, extend air cleaner service life and improve engine durability. Filtration characteristics of reticulated porous foams were studied and evaluated as a potential solution. Reticulated foam media has a very open structure, which allows it to have a relatively high dust holding capacity (DHC) and capture efficiency. The 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 for a four layer foam filter design have been presented and discussed.

A new Long Life Filtration System was developed for OEM (Original Equipment Manufacturer) applications (2003/2004 Ford Focus Vehicle) and requirements. This new technology uses a unique multi-layered reticulated 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.

Accelerated field evaluations are also presented to support the new Visteon technology using Long Life Filtration System. These studies show the viability and flexibility of multi-layer foam designs.

Keywords: Long Life Filters, Long Life Air Cleaners, Reticulated Foams, Multi-layered Foams, non-serviceable, zero maintenance.

NOMENCLATURE

AIF = Air Induction Filters AIS = Air Induction Systems CARB = California Air Resource Board DHC = Dust Holding capacity EAC = Engine Air Cleaners EIS = Engine Induction Systems ISO = International Standards Organization LLF = Long Life Filtration MAFS = Mass Air Flow Sensor NA = North America NVH = Noise Vibration and Harshness OEM = Original Equipment Manufacturer PPI = Pores Per Inch PZEV = Partial Zero Emission Vehicle

INTRODUCTION

Foam filters have been used in the aftermarket for motorcycle and high performance vehicle air intake systems with limited success. Most foam filter designs are super-saturated with viscous oils or tackifiers to improve their filtration performance levels. This is further evidenced by the oil puddle that collects in the plastic

bag used to package these foam filters. Most of the foam aftermarket filters exhibit high oil migration, contamination of downstream sensors, contamination of moving parts, poor service life and poor engine protection. However, the successful use of OEM foam filters for engine intake has been reported previously [1, 2, 3, 4, 5, 8].

This paper describes a new Long Life Filtration (LLF) System technology developed for OEM applications using a unique multi-layered reticulated foam media and air cleaner design. Filtration characteristics of reticulated porous foams were studied and evaluated. Multilayered reticulated foam media were designed having high filtration performance levels. The multi-layered reticulated foam maximizes the dust holding capacity and efficiency due to its depth/deep-bed filtration properties. This technology also provides some unique advantages over the traditional serviceable air induction filters. A filter model was developed to predict performances of multi-layer reticulated foam filters. The model can accommodate multiple foam layers in various thicknesses. The model also allows for the foam layers to be dry or treated to improve performance. Comparisons of experimental data to foam predictions show good correlation [1].

Based on the LLF technology, an innovative ‘Zero Maintenance’ Long Life engine air cleaner system was developed for 2003 ½ and 2004 Ford Focus Vehicle. Previous papers [1, 2] discuss details of the Ford Focus long life air cleaner development that meets all OEM requirements. This new system is completely sealed and does not require any service for 150K+ miles. This paper presents further performance enhancements to the original design [1, 2].

With the long life system, OEM's will enjoy substantially reduced warranty costs associated with air filter service. Consumers will no longer need to worry about using sub-standard replacement filters and additional installation problems that can damage engines [9, 10]. This new technology can save consumers between $100 and $300 over the life of the vehicle. Higher cost savings may be realized for dedicated fleets and rental companies.

ENGINE AIR INDUCTION SYSTEMS

Engine air induction systems are designed to meet engine protection requirements, engine durability requirements, air flow management, horse-power targets, achieve desired torque tuning, water/snow ingestion management, NVH targets, vehicle sound tuning and more recently managing evaporative emissions. Tradeoffs in performance requirements are often made in designing air induction systems based on OEM customer requirements [10, 11, 12, 13].

Engine Air cleaners [EAC] are designed to effectively remove airborne contaminants in order to protect the engine throughout its service life [12]. The engine requires that the ingested air meet a minimum level of cleanliness to reduce engine wear, improve engine efficiency and protect electronic sensors [12]. However, in actual service when aftermarket components (especially air filters) are used the OEM design integrity is generally compromised. The majority of the air filters available in the aftermarket exhibit poor performance levels [9]. Use of low performing aftermarket filters may lead to excessive engine wear and system contamination [6, 9, 10]. A robust engine air cleaner should meet and exceed the following parameters.

1. Maximize the available package space 2. Improve filtration performances;

a. Higher fine dust efficiency & b. Higher fine dust capacity

3. Accommodate higher engine flow rates and media face velocities

4. Reduce overall engine wear 5. Improve engine power/torque 6. Improve MAFS performance 7. Allow competitive costs 8. Meet evaporative emissions over 150K miles 9. Improve sealing to meet LEVII, ULEV & PZEV 10. Withstand higher under-hood temperatures 11. Extend filter service life 12. Improve engine durability to 150K+ miles 13. Reduce parts complexities 14. Improve Recyclability

ENGINE AIR INDUCTION SYSTEMS AND AFTERMARKET AIR FILTERS

OEM (original equipment manufacturers) air induction designs are optimized to meet required levels of performances using a systems approach and synergy for the vehicle. Invariably, when aftermarket components are used the design integrity and durability of the OEM system is compromised. Use of aftermarket air filters in OEM air cleaners presents a very challenging dilemma. High mileage studies conducted by Ford Motor Company in 2000 - 2002 clearly indicated that; a) 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 yielded the following issues;

- OEM air cleaner design integrity could be compromised

- Broken and cracked air cleaners were observed - Air cleaners had severe leakage issues - Aftermarket air filters were very difficult to service - Mis-assembly of parts during service was highly

probable even when no tools were required. - Majority of the air filters were pre-maturely

serviced. - Engines exhibited stalling and starting issues. - Mass Air Flow Sensor contamination was high.

Figure 1 shows pictures of OEM engine air cleaners from high mileage fleet evaluations. The air cleaners exhibited filter seal tear and filter collapse into the tray. Figure 2 shows typical aftermarket air filter for a light 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 1: Typical examples of air cleaner field returns from high mileage study using aftermarket filter brands.

ENGINE AIR INDUCTION SYSTEMS AND FILTER SERVICE LIFE

Estimating service life for a particular engine size or vehicle can be complex. However, understanding service life requirements is crucial for optimum engine protection. Engine air cleaners should be serviced after they have reached or surpassed an allowable restriction rise due to contaminant loading [11]. Further, the point at which the engine air cleaners are serviced affects both, filtration performance and overall vehicle performance. Engine air cleaners having excessive restriction values can significantly degrade overall engine performance. It has been well demonstrated that the filtration efficiency of the AIF improves with contaminant loading [7, 12]. With an increase in efficiency, the engine wear significantly decreases [7]. Servicing air filters at the recommended (design intent) restriction rise or pressure

loss, allows the filter to achieve its highest efficiency thus providing maximum engine protection. Frequently servicing the air filter, especially within the first 30% of its service life can significantly increase engine wear [7].

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 fact that the engine air filter never achieves its highest 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 generated from benchmark studies on air induction systems. Figure 3 shows that the air filter never reaches its full efficiency (illustrated by dash line). The customer is also throwing away a perfectly good filter, which increases the cost of vehicle ownership.

SERVICE LIFE CRITERIA - Service life expectations for light, medium & heavy-duty vehicles are different. Typical service interval for light/medium duty vehicles under normal driving conditions is about 30K miles. Engine performance for light and medium vehicles generally requires that most EAC should be serviced, once the restriction rise has reached or exceeded about 2.5 kPa beyond initial restriction [10, 11].

Service life expectations are generally recommended for normal driving conditions. Typically, that includes the

97th percentile customer profile. Service life expectations for severe/dusty driving conditions are significantly shorter compared to normal conditions [10, 11].

Cumulative Gravimetric Efficiency vs. Dust Fed For a

Serviceable Filter Using Traditional Designs

98.0

98.5

99.0

99.5

100.0

0 100 200 300 400 500 600Dust Fed, Gms

Cum

ulat

ive

Eff.,

% u

sing

IS

O F

ine

Test

Dus

t

Design Intent Service Interval

Figure 3: Efficiency performance of a typical pleated engine air filter challenged with standard ISO fine test dust. The dotted line indicates the performance benefits not realized by the OEM customer.

FACTORS AFFECTING SERVICE LIFE – Service life primarily depends on the application and end use. Factors affecting service life can be complex and multivariate in nature. Some key factors are listed below;

- Air cleaner housing design - Inlet (dirty) tube location - Outlet (clean) tube location - Air Filter design - Filter media type - Filter media area - Filter dust holding capacity - Filter dust loading characteristics - Driving conditions - Type of contaminant - Contaminant Shape/Size/Concentration - Environmental conditions - Customer awareness - Cost of ownership

Various studies have been performed to predict or estimate Air Cleaner Service Life with limited success [6, 10, 11, 12]. Generally lab or bench studies are conducted to measure the performance (DHC, gravimetric efficiency, restriction, fractional efficiency etc.) of the air filter. These studies are performed using standard test procedures and standard test dust, providing limited information regarding filter service life.

Analysis of extensive Real World field evaluations indicated that using ISO Fine Test dust is most

representative of the typical field environment [10, 11,12]. Using ISO Coarse test dust yield higher dust capacities, but have very little correlation to real world environment. Table 1 below shows the summary of the extensive field evaluations performed on various customer fleets and on proving grounds.

Vehicle

Contaminant Loading

g/1000 miles

Expected Min. Dust Capacity**

at 30K miles service, g

Expected Min. Dust Capacity**

at 150K miles Service, g

Small / Medium

Passenger Cars & SUVs

2

60

300

Large/Full Size

Passenger Cars, SUVs, Minivans & Lt. Trucks

3.5

105

525

Medium/ Large Trucks

5

150

750

** Dust capacity expectations based on ISO Fine Test Dust

Table 1: Estimated Minimum ISO Fine Dust Capacity Required for Vehicle Segments. Data derived from extensive field studies [10, 11, 12].

ZERO MAINTENANCE LONG LIFE ENGINE AIR INDUCTION SYSTEM FOR ENGINE INTAKE

Engine air induction systems (AIS) typically use paper or felt type air filters [10, 11,12]. The filtration characteristics for these media are well understood and modeled. However the model applications are fairly limited. These designs have limitations as discussed in previous sections above. Due to these constraints, majority of the air cleaner designs frequently do not provide optimal filtration and flow management under-hood. However, the current OEM air cleaners are designed and suited for serviceability.

OEM automakers are constantly striving to provide more product value to the end customer. OEM manufacturers are constantly improving their products and systems to reduce both development time & manufacturing process time, and also warranty and maintenance costs. The zero maintenance Long Life Filtration (LLF) System makes it possible for the vehicles to operate using the same air cleaner for at least 150K miles or more without requiring any maintenance or service, under normal driving conditions.

Use of porous foam filters for engine intake and related air filter applications have been reported previously

[1, 2, 3, 4, 5, 6]. For developing Visteon’s zero maintenance Long Life Filtration System, reticulated (open cell) foam structures were studied ranging from 20 ppi (pores per inch) up to 110 ppi (pores per inch). By designing multi-layered reticulated foams using the appropriate pore sizes, the usage of viscous treatments (oils) can be significantly reduced.

The reduction of viscous treatment usage was one of the key goals of the development team. Experience and analysis of field failures have demonstrated that the migration of viscous treatments from a filter element can lead to contamination and subsequent failures of the Mass Air Flow Sensor, and other critical engine sensors. The use of multiple layers in the filter allowed the development of a control for migration of the viscous treatments out of the filter element. New control methods for applying viscous treatments were utilized in the Visteon Long Life Filtration system. Specific amounts of oils are added to the foam, and additional processing was utilized to distribute the oils into the center of the foam matrix. The multi-layer construction allows the arrangement of the layers to provide a barrier to oil migration into the air stream.

An additional benefit afforded from the use of multi-layer foam construction is that reticulated foam can be coated with activated carbon. The resulting structure functions as both a collector of dust particles and an adsorber of hydrocarbon vapors. A filter that contains such an adsorbing layer, and designed with DHC to exceed 150K miles, provides an OEM with an integrated solution to air filtration and under hood evaporative emission control.

The new sealed zero maintenance LLF air cleaner design can provide an attractive package as a stand-alone or a complementary system to support a full PZEV solution. PZEV development as it relates to AIS is discussed in a separate technical paper [13]. The next generation of engine air induction systems will have to support and meet United States Tier 2, California LEV-II (low emission vehicle) and PZEV vehicle emission requirements. The California Air Resources Board (CARB) is mandating the LEVII and PZEV requirements for 15 years/150K miles. It has already been established that hydrocarbon vapors flowing and/or diffusing out from the inlet manifold and engine will have to be reduced or removed to meet the new LEV-II and PZEV requirements. For PZEV designated vehicles, OEM automakers have determined that the use of aftermarket components may seriously compromise the design and functional integrity of the air cleaner system.

MULTILAYERED FOAM MEDIA - Open cell polyurethane foams are engineered in various pore sizes ranging from 20 to 100 ppi (pores per inch). The pore sizes are defined based on a pressure drop method (MIL-PRF-87260A {UASF} 1998). Polyurethane foams have a very unique 12-sided three-dimensional structure also known as a Pentagonal Dodecahedron structure. Each of the 12 cell sides is pentagon in shape [1,3,4,5].

The pentagon is formed by struts or strands. A whole matrix of these cells make up the foam giving it a very high permeability and surface area, ideal for depth or deep bed filter design. Porous foam media have been used in various filtration applications to remove airborne particles for low efficiency filtration applications. Porous foams when used in a multi-layered configuration can effectively be used for medium to high efficiency filtration applications [1, 2, 3]. All known filtration mechanisms are present within the foam structure to collect particles. The reticulated foam filter media provides the following benefits:

Reticulated 'open cell' foam is about 96%-98% porous.

High surface area for contaminant collection. Foams can be accommodated in multiple shapes

and sizes. Foams are durable materials resistant to water

and snow and solvents. Available in multiple pore sizes. Fairly uniform pore size distribution. Selective layers can be treated with viscous oils

to improve filtration performances. High dust capacities and efficiencies are

possible. Cost effective

For reticulated foams the pore size and strand (fiber) diameter are important parameters to control filtration performance levels. Figure 4 shows an example of a clean reticulated and dust loaded ( light and heavy) foam. The dust loading clearly shows the dendrite formation of the dust around the strands within the pore.

FOAM FILTER MODEL - A semi-empirical model has been developed to predict pressure drop, collection efficiency, dust loading behavior of foam filters and estimate service life. Model can be applied to any Pore count between 20 and 110 pores per inch using multiple layers. The model is suited for reticulated foam having a basis weight in the range of 24 – 32 kg/m3 (1.5 – 2.0 lb/ft3). The pressure drop model applies to face velocities in the range of 75 to 300 m/min. Overall accuracy of model predictions is about ± 20% for collection efficiencies, pressure drop and dust holding capacities. The model predictions are based on uniform flow conditions.

The model can accommodate up to 12 layers of foam, dry or selectively treated to capture dust. The model predicts pressure drop, dust capacity, initial and overall gravimetric efficiencies at selectable pressure drop rises of up to 5 kPa beyond initial restriction.

In addition, the model also predicts performance of individual layers in terms of restriction rise, dust loading and cumulative gravimetric efficiency. The performance predictions of individual layers are critical in designing the multi-layer foam filter. The model also predicts the fractional size efficiency of the multi-layer foam. Model input/output parameters are briefly listed below.

Figure 4: Example of a clean and dust loaded foam filter.

Input Parameters ii Number of layers ii Thickness of each layer ii Dry or Treated ii Face velocity through media ii ISO coarse or fine test dust ii Terminal pressure drop rise ii Assumes uniform flow distribution

Output Parameters

oo Initial clean pressure drop oo Initial mass efficiency oo Differential dust distribution on each layer oo Cumulative dust distribution on each layer oo Total Dust mass loading oo Fractional size efficiency oo Service life prediction

The model was used to predict the performance of a high capacity 4 layer ‘zero maintenance’’ long life foam filter. The 4 layer foam design would meet or exceed performance levels typical of current filtration technologies used on engine air cleaners [2, 9, 10, 12]. The foam media was about 63.5 mm in thickness with a footprint of about 600mm2. The prediction curves that follow illustrate the modeling capabilities of foam filters. Figure 5 shows the predicted pressure drop vs. face velocity of the 4 layer foam. The pressure drop increases can be approximated by a power function. When the face velocity is doubled the pressure drop increases by about a factor of three. Figure 6 shows the predicted dust holding capacity vs. face velocity. In the range of 100 to 250 m/min., the dust DHC can be linearly approximated. For example the dust holding capacity dropped by about 30% when face velocity was doubled.

Figure 7 shows the predicted initial and overall efficiency of the 4 layer media. Figure 7 also shows the target minimum efficiencies required when using ISO fine test

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

y = 0.0003x1.6003

0.00.20.40.60.81.01.21.41.61.82.0

0 50 100 150 200 250 300Face Velocity, m/min.

pres

sure

dro

p, k

Pa

Figure 5: Pressure drop vs. Face Velocity prediction for a 4 layer long life filter.

Example of Multilayer (4-layer) LLF Model Predictions

Face Velocity vs. Dust Capacity

y = -1.5795x + 833.8

300

350

400

450

500

550

600

650

700

0 100 200 300Face Velocity, m/min.

dust

cap

acity

, g w

/ISO

Fine

test

dus

t

Figure 6: Predicted Dust Holding Capacity vs. Face Velocity for a 4 layer long life filter.

Example of Multilayer (4-layer) LLF Model Predictions Face Velocity vs. Gravimetric Efficiency

97.0

97.5

98.0

98.5

99.0

99.5

100.0

0 50 100 150 200 250 300Face Velocity, m/min.

dust

cap

acity

, g w

/ISO

Fine

test

dus

t

targets

overall efficiency

initial efficiency

Figure 7: Predicted Gravimetric Efficiency vs. Face Velocity for a 4layer long life filter.

As expected the efficiency increases with increasing face velocity, as the dominant particle capture mechanism is by interception and inertia [8]. The efficiency drop off at higher face velocities may be attributed to particle bounce and re-entrainment. Multilayer foam filters can be designed for a range of velocities. Depending on the number, type and size of multilayer foam filters the optimal face velocity range may be different.

Figure 8 shows the estimated service life of the 4 layer foam for a large passenger car application. The service life varies almost linearly with face velocity. Based on the optimal design face velocity of 100 – 200 m/min., the service life can range from 148K to 190K miles.

Example of Multilayer (4-layer) LLF Model Predictions

Face Velocity vs. Service Life

y = -431.77x + 234677

100000.0

125000.0

150000.0

175000.0

200000.0

0 50 100 150 200 250 300Face Velocity, m/min.

Ser

vice

Life

, mile

s

Figure 8: Estimated service life for a 4 layer foam designed large passenger car.

Figures 9 and 10 show the effect of increasing thickness of multilayer layer foam filter. The foam filter was 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 and service life. Figure 9 shows the effect of increasing thickness on restriction rise. The pressure drop can be approximated by a power function. However in the range of interest, the pressure drop increase was almost linear with increasing thickness.

Figure 10 shows the effect of thickness on dust holding capacity. The dust capacity can also be closely represented by a liner function. It is interesting to note that doubling the thickness only increased the restriction rise by about 20%. However doubling the thickness increased the dust capacity by about 90% (almost double).

Example of Multilayer (4-layer) LLF Model Predictions Media Depth vs. Pressure drop

y = 0.3232x0.2234

0.5

0.6

0.7

0.8

0.9

1

0 50 100 150Media Depth, mm

pres

sure

dro

p, k

Pa

Initial Gravimetric Eff.= 99.11%Overall Gravimetric Eff. = 99.84%

Face Vel = 150 m/min

Figure 9: Predicted Restriction Rise vs. Media Depth for a 4 layer long life filter.

Example of Multilayer (4-layer) LLF Model Predictions Media Depth vs. Dust Capacity

y = 9.8175x

300400500600700800900

100011001200

0 50 100 150Media Depth, mm

Dus

t Cap

acity

, g w

/ISO

Fine

test

Dus

t

Initial Gravimetric Eff.= 99.11%Overall Gravimetric Eff. = 99.84%

Face Vel = 150 m/min

Figure 10: Predicted Dust Capacity vs. Media Depth for a 4 layer long life filter.

LONG LIFE FILTER REAL WORLD FIELD STUDIES

A production prototype air cleaner was developed for a large passenger car application equipped with a 4.6L 2-valve engine at a rated flow of 9.91m3/min. Figure 11 shows the location of the Long Life filtration System in fleet vehicles. The Long Life filtration System was packaged outside the engine compartment and behind the front bumper below the driver side headlight. Figure 12 shows a cut-away view of the air cleaner showing the foam multilayered filters.

Figure 11: Long Life AIS used in Fleet Study. The system was packaged outside the engine compartment.

Figure 12: Cut Away View of the Long Life Air Cleaner used in Fleet Study.

Extensive field evaluations were performed on the above Long Life filtration System using multi-layer foams over a 2- 3 year period at four different locations in North America (NA). Field evaluations were performed at; 1) New York City, 2) Orlando, 3) Las Vegas and 4) Phoenix - Maricopa County [1,2]. Additional information can be found on the fleet studies in ref. 1 and 2.

All fleet vehicles operated on a single long life filtration system for 2 to 3 years without any customer complaints or engine performance degradation. These systems did not require any maintenance or service actions during the entire study period. Customer satisfaction with engine and filter performance was high [1, 2].

Figure 13 shows the mileage accumulated and the restriction rise for all fleet vehicles (38 vehicles). The restriction rise was measured on a bench test before and after the fleet tests were concluded (2 to 3 years).The restriction rise does not show a continuous increasing trend with mileage. This was expected as the vehicles were operating in four different environments and driving conditions. The dash line shows the restriction rise trend. On average the vehicles accumulated about 109K miles with a restriction rise of 0.94kPa.

Total Mileage and Restriction Rise For All Vehicles

0

50000

100000

150000

200000

250000

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

Dis

tanc

e, m

iles

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

Res

trict

ion,

kP

a

Miles Restriction Rise

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.

Dust spot efficiency was also measured on random LLF 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. Figures 15, 16 and 17 all show increasing efficiency levels with contaminant loading, miles accumulated and restriction rise. These increasing trends are desirable as it demonstrates the reliability of the LLF filter after contaminant loading and with time. On average the dust spot efficiency increased from about 98.85% to 99.3% with contaminant loading.

Overall Contaminant Loading vs. Restriction Rise All Fleet Data

0.01.02.03.04.05.06.07.08.0

100 1000Contaminant Loading, g

Res

trict

ion

Ris

e, k

Pa

Figure 14: Contaminant loading and restriction rise for fleet study.

Contaminant Loading vs. Measured Dust Spot Efficiency - All Fleet Data

98.098.298.498.698.899.099.299.499.699.8

100.0

0 100 200 300 400 500 600contaminant loading, g

Dus

t (gr

avim

etric

) Sp

ot E

ffici

ency

, %

Figure 15: Contaminant loading vs. dust spot efficiency.

Mileage Accumulated vs. Measured Dust Spot

Efficiency - All Fleet Data

98.298.498.698.899.099.299.499.699.8

100.0

0 50000 100000 150000 200000 250000 300000Vehicle Miles

Dus

t (gr

avim

etric

) Spo

tEf

ficie

ncy,

%

Figure 16: Vehicle miles accumulated vs. Dust spot efficiency

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 on confidence limits we can expect about 3.5g/1000 miles of contaminant loading at 99% confidence. Hence, at a service life of 150K miles we can expect about 525g of total contaminant to be ingested.

Table 2 below compares the lab bench measurements to model predictions for the Long Life Filtration systems used in the taxicab fleet study. The dust capacity measurements based on model predictions were within ±20%. The efficiency predictions were within ±0.5%. Based on these measurements the LLF for the taxicab fleet may not require any service for 95K miles.

Restriction Rise vs. Measured Dust Spot Efficiency - All Fleet Data

98.298.498.698.899.099.299.499.699.8

100.0

0 1 2 3 4Restriction rise. kPa

Dus

t (gr

avim

etric

) Spo

tEf

ficie

ncy,

%

Figure 17: Restriction rise vs. Dust spot efficiency

Overall Contaminant Loading Data Including All Fleet Vehicles

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

avg 95% confidence 99% confidence

cont

amin

ant c

olle

cted

, g/1

000

mile

s

Figure 18: Normalized Contaminant loading.

Long life filtration

system Experimental Data

Long life filtration system

Model Predictions

Dust Capacity, g 333g 287 g Initial Gravimetric

Efficiency, % 98.41% 98.47%

Overall Gravimetric

Efficiency, % 98.83% 99.35%

Flow rate= 8.0 m3/min. constant Test Dust = ISO fine

Table 2: Experimental data compared to model predictions for Long life filtration used in Taxicab Fleet Study.

BENEFITS OF ZERO MAINTENANCE LONG LIFE AIR INDUCTION SYSTEMS - The zero maintenance LLF air cleaner design offers some unique and significant advantages to OEM automakers and end usage customers. Some of the performance benefits have been discussed above. Additional key design benefits include the following;

1. Increases air filter service intervals over 150K miles.

2. Improves robustness and durability of air induction systems.

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.

A PRODUCTION ‘ZERO MAINTENANCE’ LONG LIFE ENGINE AIR INDUCTION SYSTEM FOR 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].

The new Visteon Long Life Filtration System uses a unique multi-layered reticulated foam media and construction for OEM applications to trap and remove

contaminants. The use of multi-layer reticulated foam accommodates complex geometries, which further aids the LLF in packaging flexibility, freeing up valuable real estate under the hood and around the engine. The performance of the LLF can be tuned to meet normal driving conditions using proprietary CAE models.

Figure 20 shows the complete Long Life Air Induction system removed from the vehicle. This system was initially developed for the 2003 Ford Focus PZEV vehicles. For the 2004 MY all Ford Focus have adapted this system across the board.

Figure 19: Zero Maintenance Sealed Long Life Air Cleaner System for 2003/4 Ford Focus. The Long Life Filtration System is covered by one or more Visteon Patents. Additional patents are currently in progress.

Figure 20: Production Long Life Air Induction System shown from inlet tube to throttle body inlet.

Figure 21 shows a cross-section of the sealed LLF design. The cross-section shows the multi-layered reticulated foam used for achieving higher filtration performance. Selective layers of the reticulated foam are treated with commercially available chemicals, to enhance the contaminant trapping efficiency of the LLF. The foam layers are also trapped and held rigidly between two plastic screens. The plastic screens are designed to be part of the air cleaner cover and tray assembly and are necessary to achieve the desired filtration performance levels.

Figure 21: Details of Multilayer Foam For Zero Maintenance Sealed Long Life Air Cleaner System

ZERO MAINTENANCE LONG LIFE FOAM FILTER PERFORMANCE – Long Life air cleaners were extensively tested in the lab and in real world field environments. ISO fine test dust was used for all evaluations to more closely represent actual field loading [11]. The production LLF air cleaner design meets or exceeds known customer OEM engineering specifications as applied to conventional air cleaners. More details on air filter testing and specifications are covered in reference [14].

Figure 22 compares the average dust capacity measured on traditional technologies and a clean Long Life filter using ISO fine test dust [10]. The target dust capacity was set at 300g using ISO fine test dust [2]. The target capacity was calculated based on field evaluations and specific engine size for this application [2, 10, 11]. On average the LLF holds about 500g of ISO fine dust at a 2.5 kPa restriction rise. This target capacity represents a service interval of 150K miles for the Ford Focus application based on normal driving conditions [Table 1]. Compared to traditional technologies the Long Life filter achieves about 2.5 to 5 times higher dust capacity.

Average Dust Capacity Measured Using ISO Fine Test Dust @ 2.5 kPa Restriction Rise

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s Target capacity for Ford Focus = 300 g

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 significant for engine wear, protection and durability [7].

Average Initial Gravimetric Efficiency Measured @ 20 Gms of ISO Fine Test Dust

96.0

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Figure 23: Initial Efficiency Performance of Long Life Technology compared to Traditional designs.

Similarly Figure 24 compares the average overall gravimetric efficiencies measured on traditional technologies and a clean LLF using ISO fine test dust [10]. The overall gravimetric efficiencies were measured at a 2.5kPa restriction rise. The overall gravimetric

efficiency target was set at 98.5% 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 a high overall efficiency of 99.5. Compared to traditional technologies the Long Life filter allows about 1.5 to 3 times lower dust penetration to the engine. Again, this can be significant for engine wear, protection and durability [7].

Average Overall Gravimetric Efficiency Measured @ 2.5 kPa

Terminal Restriction Rise Using ISO Fine Test Dust

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Figure 24: Overall Efficiency Performance of Long Life Technology compared to Traditional designs.

Figure 25 shows one of the primary advantages of using the Long Life Filter Technology. Figure 25 compares the high efficiency level of the Long Life filter to traditional serviceable filters [Figure 3]. Clearly, the Long Life technology offers better engine protection throughout the vehicle life.

Cumulative Gravimetric Efficiency vs. Dust Fed comparing

Serviceable Filters and Long Life Technology

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Figure 25: Efficiency increase of Long Life Filter compared to traditional pleated filter. The dashed line indicates the performance benefits not realized by the OEM customer.

Figure 26 shows the restriction rise of the Ford Focus Long Life Filter with dust loading. The restriction rise rate was very linear with dust loading and is predictable. This trend is significantly different when compared to traditional filter designs where a prominent change over point is present when dust cake formation takes over. This was expected as the foam filter behaves like a depth media.

Restriction Rise vs. Dust Fed Ford Focus Long Life Filter

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Figure 26: Pressure drop rise vs. dust loading for the Ford Focus Long Life Filter.

The measured performance of the Ford Focus Long Life Filter was also compared to model predictions. Table 3 shows the comparisons. The model predictions compare fairly well. The capacity predictions are within ±20%. The efficiency predictions were within ±0.5%. The restriction predictions were within ±25%.

LLF

Experimental Data (average) Ford Focus AIS

LLF Model Predictions

Ford Focus AIS

Dust Capacity, g 499g 609g ± 130g Initial Gravimetric

Efficiency, % 99.52% 98.9%

Overall Gravimetric Efficiency, % 99.48% 99.51%

Filter Restriction, kPa 1.13±.315 0.94 ±0.125

Flow rate= 6.4 m3/min. variable

Test Dust = ISO fine Table 3: Experimental Long Life filter performance compared to model simulations

SUMMARY

Field evaluations and laboratory analysis successfully demonstrates the viability and flexibility of Long Life Filtration System designs.

Model predictions correlate with experimental data for filter performance levels. Capacity and Restriction predictions using the model are within ±20% and the efficiency predictions are within ±0.5%.

The multi-layer foam technology provides superior filtration, and therefore engine protection, as compared to standard OEM filters designed for regular replacement. The multi-layer foam filter technology also provides improved performance when compared to filter media that are serviced by cleaning at regular intervals. The greatest areas of improvement are in filter efficiency and the elimination of filter oil migration.

The Long Life Filtration System challenges the customer and after-market perceptions that the air filter needs to be replaced every 5K to 30K miles, especially under normal driving conditions. The LLF design minimizes the possibility of using substandard aftermarket filters during the warranty period.

Zero Maintenance Long Life Filters can be very effectively designed to meet and exceed customer requirements for the life of the vehicle (150K miles)

Long Life Filtration System designs offer the OEM customer some very unique advantages and value over the life of the vehicle.

a. Improved system reliability and robustness over the life of the vehicle

b. Reduced operating, design and warranty costs.

c. Improved packaging benefits.

d. Improved tuning filter design to local market requirements using the proprietary filtration model.

e. Reduced landfill waste. The VLLF is constructed from 100% polymers, easy to recycle. There are no used filters to be disposed to landfills.

f. 'Sealed for life' to provide the required resistance to consumer tampering with emission controls in the AIS.

g. Added hydrocarbon trapping layer to achieve reduced evaporative emissions for LEV II Tier2 compliance, or to achieve 'zero' evaporative emissions for PZEV certification.

h. Low cost of ownership compared to more traditional air cleaner designs, saving consumers $100 to $300 over the life of the vehicle (Higher cost savings may be realized for dedicated fleets and rental companies).

CONCLUSIONS OEM’s and vehicle owners can realize numerous benefits from the elimination of maintenance to the vehicle, as has been demonstrated with 100,000 mile spark plugs, long life coolants, and electronic ignition systems. The Long Life Filtration technology developed by Visteon Corporation provides a method for minimizing the requirements to replace or clean engine air filters. Zero maintenance filtration for engine air cleaners have been modeled, tested and validated in vehicle fleets for durability and robustness. The multilayer foam filtration technology is a cost effective method to eliminate engine air filter maintenance while improving engine durability, reducing evaporative emissions, and reducing overall material usage.

REFERENCES

1. Bugli N. J and Green G. S, " Air Induction Systems Using Long Life Reticulated foam Media", Technical Paper Presented at the World Filtration Congress and Exposition, New Orleans, , Louisiana, April 19 - 22, 2004.

2. Bugli N. J and Dixon C. J, " Long Life Engine Air Cleaner Technology For Automotive Passenger Cars, SUVs and Light Trucks", Technical Paper Presented at the American Filtration and Separations Society, 16th Annual Conference and Exposition, Reno, Nevada, June 17-20, 2003.

3. Pizzirusso J. F., "The Unique Properties of Polyurethane foam for small engine filters", SAE technical paper 951811.

4. Curti C. M," Reticulated Polyurethane Foam", Technical paper, Automotive Engineering International Publication, Vol. 109 No. 6, June 2001, pages 88 –92.

5. Rucker J.," reticulated Polyurethane Foam For the Filtration Industry", Technical Paper presented at INDA Filtration 2001 Conference.

6. Nouis R., (1993), " Predicting the Ninety-Fifth Percentile Dust Environment for Passenger Vehicles in the Continental United States," SAE technical paper 930018, presented at the SAE International Congress and Exposition, Detroit, March 1-5, 1993.

7. Barris M., (1995), "Total Filtration: The Influence of Filter Selection on Engine Wear, Emissions, and Performance," SAE technical paper 952557, Fuels & Lubricants meeting and exposition, Toronto, October 16-19, 1995.

8. Poon W. S., Liu B. Y. H and Bugli N. J, (1997), "Fractional Efficiency and Particle Mass Loading Characteristics of Engine Air Filters", SAE technical paper 970673, also in SAE special publication SP-1252 pp. 103 - 112, presented at the SAE International Congress and Exposition, Detroit, Feb.-Mar 1997.

9. Bugli N. J and Leffel J. (2001), "Engine Air Induction Filtration Systems- Design challenges for the Next Generation", Advances in Filtration and Separation Technology, Volume 15, American Filtration and Separations Society Annual Conference, Tampa, Florida, 2001.

10. Bugli N. J, (2001), "Automotive Engine Air Cleaners – Performance Trends", SAE technical paper, 2001-01-1356, presented at the SAE International Congress and Exposition, Detroit, March 5 –8, 2001.

11. Bugli N. J, (1998), " Service Life Requirements For Engine Air Induction Filters", Advances in Filtration and Separation Technology, American Filtration and Separations Society, 1998 AFS annual conference, Vol. 12, pp. 38 - 49.

12. Bugli N. J, (1997), " Filter Performance Requirements for Engine Air Induction Systems ", SAE technical paper 970556, also in SAE special publication SP-1252 pp. 55-69, presented at the SAE International Congress and Exposition, Detroit, Feb.-Mar 1997.

13. Leffel J. and Green G. S.,” Development of Evaporative Emissions Filter for Automotive Applications”, Technical Paper Presented at the American Filtration and Separations Society, 16th Annual Conference and Exposition, Reno, Nevada, June 17-20, 2003.

14. Bugli N. J, Puckett R., and Lanier V., “Filtration Challenges and Conical Filter Development for Engine Air Induction Systems,” SAE technical paper 950941, presented at the SAE International Congress and Exposition, Detroit, February 27 - 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