buct nitrogen inflation of tires for pdf.813.ppt · inflation of tires . 2 one example of reported...

Walter H. WaddellPolymers TechnologySeptember 19, 20132008.1603; 2007 PYBA 21

presented to

Beijing University of Chemical TechnologyBeijing, China

EVALUATION OF NITROGEN INFLATION OF TIRES

2

One example of reported claims for inflating tires with nitrogen gas:• Constant pressure: “Nitrogen molecules are four times larger than air and

as a result will not seep through the casing of the tyre like air, which would normally result in pressure loss. Nitrogen is also a more stable gas than air and as such will not give high fluctuations in temperature and therefore pressure within the tyre”.

• No oxidation: “As normal compressed air passes through the casing of the tyre, oxidation is caused within the tyre belts, reducing the life of the casing and increasing the risk of blow outs. As nitrogen is clean and dry, there is no moisture and the larger nitrogen molecules will not pass through the tyre casing like air”.

• Lower running temperature: “Fluctuation in pressure means increased temperature resulting in increased tyre wear. As the pressure in the tyre is more constant, you will not get the increase in temperature and pressure like you get with tyres inflated with normal compressed air”.

• 3 per cent saving on fuel costs: “As the tyre loses pressure, the tyre surface on the road increases. With a 10 per cent reduction in tyre pressure, research has shown that you will get a 3 per cent increase in fuel usage”.

Background: Reported Benefits of Nitrogen

Ref: Bowen Independent (Australia), March 7, 2007, Pg. 17

3

• Constant Pressure Inflation Pressure Loss Rate

• No Oxidation Age Resistance

• Reduced Risk of Blow Outs Durability/Endurance

• Lower Running Temperature Rolling Resistance

• Savings on Fuel Costs Vehicle Fuel Economy

Key Points

4

• Constant Pressure– Gas Diffusion in Rubber

– Experimental Tires

– ASTM F11112 Test

– Literature Results

• Oxidation

• Roadwheel Durability

• Rolling Resistance

• Vehicle Fuel Economy

• Summary

Agenda

5

Constant Pressure: Gas Diffusion in Rubber

• Nitrogen (0.10977nm) molecule is similar size to oxygen (0.12074nm)(Ref: Handbook of Chemistry and Physics, 78th Edition, The Chemical Rubber Co., New York, 1997)

• Nitrogen is 50% less soluble in natural rubber than is oxygen gas(Ref: van Amerongen, “Diffusion in Elastomers”, Rubber Reviews, 37, 1065 (1964)

• Nitrogen gas calculated to be 30% - 40% less permeable in rubber than is oxygen gas

– Natural Rubber @25oC N2 = 6.12 O2 = 17.7 (10-8cm2.sec-1.atm-1)

• For Natural Rubber QAir ~ 1.4 QNitrogen 70% of Air Value

– Butyl Rubber @25oC N2 = 0.247 O2 = 0.99• For Butyl Rubber QAir ~ 1.63 QNitrogen 60% of Air Value

Nitrogen Less Soluble Less Permeable than Oxygen

6

• Compounds prepared in 2-step factory mix– GK400 sheeted out on extruder with roller die– GK160 sheeted out on two-roll mill

• Experimental summer tires made on full automatic building machines– 205/60 HR15– 205/60 SR15 (no nylon cap ply)– Cured innerliner gauges of 1.0 mm

Constant Pressure: Production of Expt Tires

1.251.251.25Accelerator, MBTS

0.50.50.5Sulfur

111Zinc Oxide

111Stearic Acid

888Processing Oil, TDAE

444Processing Aid, SP1068

606060Carbon Black, N660

777Processing Aid, 40MS

4020Natural Rubber, SMR 20

6080100ExxonTM Bromobutyl 2222

321Ingredient

1.251.251.25Accelerator, MBTS

0.50.50.5Sulfur

111Zinc Oxide

111Stearic Acid

888Processing Oil, TDAE

444Processing Aid, SP1068

606060Carbon Black, N660

777Processing Aid, 40MS

4020Natural Rubber, SMR 20

6080100ExxonTM Bromobutyl 2222

321Ingredient

ExxonMobil Chemical Company Data

7

Constant Pressure: Inflation Pressure Loss Rate

00001.965

00002.150DigitalMonitor

Computer

Atmospheric pressure

• ASTM F-1112 (modified)• Use of sensitive pressure

transducers with computer allowssignificant shortening of test

• Two weeks equilibration at 21°C before starting the 4-week test

• Tire start pressure = 2.2 bar(220 kPa or 32 psi)

• Computer automatically recordsmeasurement every second

• Test duration as short as 42 days

P

Time

Time

% Loss

8

Constant Pressure: Fill Gas Effects on IPLR

Tire IPLR Reduced 40% Using

Dry, Pure Nitrogen Gas Inflation

Used ASTM F-1112 (modified) to study Inflation Pressure Loss Rates of 205/60 SR15 tires built with different innerliners• Tires purged 3X in order to obtain pure fill gas: dry 99.4% nitrogen


Inflation Pressure Loss Rate of 100-phr BIIR

1.45

0.79

0

0.5

1

1.5

2

Air Nitrogen

Filling Gas

%-L

oss/

Mon

th

Inflation Pressure Loss Rate of 80/20 CIIR/NR

1.84

1.01

0

0.5

1

1.5

2

Air Nitrogen

Filling Gas

%-L

oss/

Mon

th

9

Constant Pressure: Fill Gas Effects - LiteratureConsumer Reports (Ref: Petersen, “Consumer Reports Tire Testing. A Consumers Perspective”, ITEC 2008, Akron, OH, 9/16-18/2008)

• Studied 31 H- and V-rated, all-season tires – Filled with nitrogen / deflated 3X to purge air out of tire– Oxygen analyzer used to ensure 95% nitrogen purity – One-year test showed nitrogen reduces pressure loss over time.

From initial 30 psi, 3.5 psi air pressure loss, while nitrogen-filled tires lost average of 2.2 psi: 37% lower for tires inflated with nitrogen gas

National Highway Traffic Safety Administration (NHTSA)(Ref: MacIsaac, Evans, Harris, Terrill, “The Effects of Inflation Gas on Tire Laboratory Performance”, ITEC 2008, 9/16-18/08)

• Studied nitrogen (94 to 99%) inflation of 25 passenger or LT tires – 34% lower IPLR for tires inflated with nitrogen gas– Tire type also a statistically significant variable

In agreement with claims:

Tire IPLR Reduced ~35% Using Nitrogen Inflation

10

• Constant Pressure

• Oxidation– Oven Aging od Tires

– Component Testing of Aged Tires• Roadwheel Durability



• Summary

Agenda

11

Oxidation: Tire Oven Aging Study

205/60 SR15 tires aged in air-circulating oven: 4 weeks @ 70oC• 100-phr Bromobutyl rubber, and 80/20 and 60/40 BIIR / NR liners• Tires inflated with dry nitrogen (99.9%), dry air, or 50/50 O2 / N2 mixture

Oven-aged tires tested on a 1.7-m laboratory roadwheel according to the NHTSA Federal Motor Vehicle Safety Standards• FMVSS 139 Endurance / Stepped-Up Load to failure

New and oven-aged / road wheel tested tires cut and analyzed by contract lab: Akron Rubber Development Laboratory• Tensile Properties: 100% Modulus, Elongation at Break• Crosslink Density• Fixed Oxygen• Peel Strength• Laser Shearography


12

Oxidation: Fill Gas Effects on Tensile Properties

Tensile Changes of Oven-Aged Tires:

Increases with Increasing Oxygen

%-Retained Elongation0.83

0.58 0.58

R2= 0.7381

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

N2 Air O2/N2

%-Change 100% Modulus

1.03

1.431.57R2= 0.9309

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

1.80

N2 Air O2/N2


13

Oxidation: Fill Gas Effects on Crosslink Density

Crosslink Changesof Oven-Aged Tires:

Increases withIncreasing Oxygen

Total Crosslinks: S-Rated Tires

1.17

1.21

1.28R2 = 0.9733

1.081.101.121.141.161.181.201.221.241.261.281.30

N2 Air 50/50 O2/N2

Fill Gas in 80/20 BIIR/NR Liner

Rat

io to

New

Tire

Skim Coat Linear (Skim Coat)

% Sulfur Crosslinks in Skim Coat

100.0

79.9

58.6

R2 = 0.9997

0

20

40

60

80

100

120

N2 Air 50/50 O2/N2

Fill Gas

%

%-Change due to oxidative aging can be calculated• Air: 20%• O2/N2 (50/50): 40%


14

Oxidation: Fill Gas Effects on Fixed Oxygen

Fixed Oxygen Changes of Oven-Aged Tires:


Fixed Oxygen: Skim Coat

3.363.43

3.61

R2 = 0.9442

3.03.13.23.33.43.53.63.73.83.94.0

N2 Air 50/50 O2/N2Fill Gas

%-O

xyge

n

Fixed Oxygen: Shoulder Wedge

3.46

3.68

3.86

R2 = 0.9956

3.0

3.1

3.2

3.3

3.4

3.5

3.6

3.7

3.8

3.9

4.0

N2 Air 50/50 O2/N2

Fill Gas

%-O

xyge

n

ExxonMobil Chemical Company Analysis

Fixed Oxygen is covalently bonded oxygen content measured for natural rubber wire coat and shoulder wedge compounds• Leco CHNS-932 uses elemental analysis technique to determine

%-Oxygen by weight denoting covalently bound Oxygen in sample• Pyrolyze mg sample in tin cup in high-carbon environment at 1050oC toform CO, then convert to CO2, and detect via its infrared absorption

15

Oxidation: Fill Gas Effects on Belt Peel Strength

Peel Strength Changes of Oven-Aged Tires:


%-Retained Skim Peel Strength0.76

0.63

0.54

R 2= 0.992

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

N2 Air O2/N2


Peel Strength conducted per ASTM D 413 Type A, 180 peel

16

Relating Shearography to Tire Defects

Belt-1 edgeBelt-2 edge

Progression of belt edge defects along the two belt edges

Belt-1 edgeBelt-2 edge

Progression of belt edge defects along the two belt edges

17

VisibleDamage: 35.5 hrs

1x1-inch region of 205/60 SR15 passenger tire withBromobutyl / NR (80/20) innerliner, Tire IPLR = 2.0

Example Optical Micrograph of Aged / Tested Tires

18

IPLR=2.00

19

Oxidation: Fill Gas Effects on Shearography Cracks

Cracking of Aged Tires Significantly

Reduced by Reducing Oxygen

Shearography

642

12,729

25,344

0 0 5000

5000

10000

15000

20000

25000

30000

100 BIIR 80/20 BIIR/NR 60/40 BIIR/NR

Cra

cks,

mm

2Air Inflated Nitrogen Inflated


20

Oxidation: Impact of IPLR on Shearography Cracks

Shearography Cracking Quantitatively Correlates to

Tire Inflation Pressure Loss Rates

Shearography Crack Area

0 0 571

12729

25344

R2 = 0.9862

0

5000

10000

15000

20000

25000

30000

0.79 1.10 1.45 2.00 2.65

Inflation Pressure Retention

mm

2


21


• Oxidation

• Roadwheel Durability– FMVSS 139 Endurance of New Tires

– FMVSS 139 Endurance / SUL of Aged Tires



• Summary

Agenda

22

Roadwheel Durability: Impact of IPLR on FMVSS 109205/60 SR15 tires made compositions tested to FMVSS 109 Endurance standards (80 km/h), but running until the tire fails

Excellent Correlation of Hours to Failure to Tire IPLR

Modified FMVSS 109 Endurance: S-Rated Tires319.6

273.9

171.4

R2 = 0.9533

050

100150200250300350

1.45 2.00 2.65

Inflation Pressure Loss Rates, %-loss/month

Hou

rs to

Fai

lure

23

Roadwheel Durability: Impact of IPLR on FMVSS 139205/60 HR15 tires made with different innerliner compositions tested to FMVSS 139 Endurance standards (120 km/h), running until tire fails

Good Correlation of Hours to Failure to Tire IPLR


Modified FMVSS 139 Endurance: H-Rated Tires

539.4

384.8349.9

R2 = 0.8827

0

100

200

300

400

500

600

1.45 2.10 2.75Inflation Pressure Loss Rates, %-loss/month

Hou

rs to

Fai

lure

24

Roadwheel Durability: Fill Gas Effects on Endurance

FMVSS 139 Endurance to Failure

97.0 100.790.190.8

117.0101.9

0

20

40

60

80

100

120

140

100 BIIR 80/20 BIIR/NR 60/40 BIIR/NR

Hou

rs to

Fai

lure

Air Inflation Nitrogen Inflation

FMVSS 139 Endurance to Failureof CIIR / NR (80/20)

118.6 110.8

020406080

100120140

Air NitrogenFilling Gas

Hour

s to

Fai

lure

No Effect of Nitrogen on Lab Roadwheel Testing:

Performance of New Tires Comparable

FMVSS 139 Endurance test modified by • Running at final test conditions until the tire fails• Using dry 99.9% nitrogen as the fill gas 99.4%


25

Roadwheel Durability: Impact of IPLR on FMVSS 139FMVSS 139 Endurance test modified by following-up with a Stepped-Up Load test until failure

• Temperature: 38oC, Speed: 120 km/h, Pressure: 180 kPa dry air• Load: 4 hr @85% / 6 hr @90% / 24 hr @100% of rating• Stepped-Up Load: increase 10% @ 4-hr intervals until the tire fails

Roadwheel Performance of New Tires Comparable


FMVSS 139 Endurance, Step-Up Load

46.149.5 48.1

0

10

20

30

40

50

60

1.45 2.00 2.65

Inflation Pressure Loss Rates, %-loss/month

Hou

rs to

Fai

lure

26


FMVSS 139 Endurance, Stepped-Up-Load

44.0 42.738.6

47.3 44.5 43.6R2 = 0.9422R2 = 0.9272

0

10

20

30

40

50

100/0 80/20 60/40

BIIR / NR

Hou

rs to

Fai

lure

Air Inflated, Oven Aged N2 Inflated, Oven Aged


Roadwheel Endurance of Aged Tires Improved

using Dry 99.4% Nitrogen Gas Inflation

27


Roadwheel Endurance Quantitatively Correlates to

Tire Inflation Pressure Loss Rates

FMVSS 139 Endurance, Step-Up Load

47.344.5 43.8 42.7

38.6

R2 = 0.9376

0.05.0

10.015.0

20.025.030.0

35.040.0

45.050.0

0.79 1.10 1.45 2.00 2.65

Inflation Pressure Retention

Hou

rs to

Fai

lure

Red = Nitrogen Purple = 1 Nitrogen and 1 Air-filled Tire Blue = Air


28


• Oxidation


• Rolling Resistance– SAE J1269, SAE 2452

– Temperature

– Coefficient


• Summary

Agenda

29

• Rolling resistance measured at Smithers Rapra on 1.7-meter indoor roadwheel at 24oC– 205/60 SR15, 100-phr BIIR innerliner with cured gauge of 1.0 mm– Six inflation pressures requested: 32, 31, 30, 28, 26, 24 psi

• Single Point Inflation– Measured at 50 mph, 70% load and one inflation pressure

• Repeated six times: 32, 31, 30, 28, 26, and 24 psi hot inflation – Tire Footprints obtained and areas determined

• SAE J1269 – Current recommended practice used to evaluate tires by tire industry– Measured at constant 50 mph speed at 50% and 90% of maximum

load and two inflation pressures

• SAE J2452– Current recommended practice used to evaluate tires and effect on

vehicle fuel economy• Many vehicle manufacturers use this technique to generate CAFE predictions

– Measured at speed of 71 mph coasting down to 9 mph at two loads and two inflation pressures

• Rolling resistance values calculated from regression curve

Rolling Resistance: Characterization Tests


30

• Three tests run: Single-point inflation, SAE J1269 and SAE J2452– Tests on experimental tires: 205/60 SR15

• Rolling resistance (RR) measured experimentally– Excellent reproducibility between methods: Mean = 10.754, SD = 0.045

Rolling Resistance: Comparison of Tests


Rolling Resistance vs Inflation Pressure

10.25

10.75

11.25

11.75

12.25

12.75

22 24 26 28 30 32 34Inflation (psi)

RR

(lbs

)

single point #1478 modeled 2452 #1478 modeled 1269 #1478

Test Methods Comparison

31

• Three tests run: Single-point inflation, SAE J1269 and SAE J2452– Tests on experimental tires: 205/60 SR15

• Rolling resistance (RR) measured experimentally– Excellent reproducibility between tires: Mean = 10.754, SD = 0.20

Rolling Resistance: Repeatability of Tires


Rolling Re sista nce vs Infla tion P re ssure

10.25

10.75

11.25

11.75

12.25

12.75

22 24 26 28 30 32 34Infla tion (ps i)

RR

(lbs

)

Mode led 1269 #1478 Mode led 1269 #1479 Mode led 1269 #1480

Tire Reproducibility

With 25% Pressure Loss, Footprint Area Increases 20%

Bead area

Sidewall

Crown

Inflated Tire

25% Under-inflated Tire

221 kPa, Area = 236 cm2

166 kPa, Area = 282 cm2

Rolling Resistance: Effect of Tread Footprint

33

Rolling Resistance: Fill Gas Effects on Temperature


Cavity Gas Temperature

R2 = 0.9708

3536373839404142

165 172 179 186 193 200 207 214 221 228 234 241 248 255 260

Inflation Pressure, kPa

Deg

rees

C

Air Linear (Air)

Cavity Air Temperature Dependent Upon Inflation Pressure

34

Rolling Resistance: Fill Gas Effects on Temperature

Cavity Air Temperature Does Not Change using Nitrogen Gas


Cavity Gas Temperature

R2 = 0.9708 R2 = 0.9782

3536373839404142

165 172 179 186 193 200 207 214 221 228 234 241 248 255 260

Inflation Pressure, kPa

Deg

rees

C

Air Nitrogen

35

Rolling Resistance: Fill Gas Effects on Coefficient

Tire Rolling Resistance Dependent Upon Inflation Pressure


Rolling Resistance Coefficient

R2 = 0.9716

0.0100

0.0105

0.0110

0.0115

0.0120

0.0125

0.0130

24 25 26 27 28 29 30 31 32 33 34 35 36 37 37.7

Inflation Pressure, psi

RR

CAir Linear (Air)

36

Rolling Resistance: Fill Gas Effects on Coefficient

Tire Rolling Resistance Does Not Change Using Nitrogen


Rolling Resistance Coefficient

R2 = 0.9716 R2 = 0.9737

0.0100

0.0105

0.0110

0.0115

0.0120

0.0125

0.0130

24 25 26 27 28 29 30 31 32 33 34 35 36 37 37.7

Inflation Pressure, psi

RR

CAir Nitrogen

37

Rolling Resistance: Fill Gas Effects from Literature

In Agreement with NHTSA Results:

Tire Rolling Resistance Equivalent Using Nitrogen Gas

National Highway Traffic Safety Administration(Ref: MacIsaac, Evans, Harris, and Terrill, “The Effects of Inflation Gas on Tire Laboratory Performance”, ITEC 2008, 9/16-18/08)

• Studied rolling resistance of 24 tire types and ASTM F2493-06 SRT

• SAE J1269 test procedure

• Filling with nitrogen gas or air inflation gave essentially identical results

RRAir 12.80+/-0.38 lbs RRN2 12.65+/-0.44 lbs

38


• Oxidation



• Vehicle Fuel Economy• Summary

Agenda

39

Vehicle Fuel Economy: In-Service Equipment

New tires were tested on four vehicles driven under normal city driving conditions using dry air or dry 99+% nitrogen gas inflation from purchased cylinders• Tires were purged and refilled three times in order to obtain pure dry

nitrogen gas inflation (99+%)


Vehicle 1 2 3 4

TypeLuxury

PassengerCar Small Light TruckFull-size

Passenger Car Small SUVYear 1998 1998 2000 2007Engine 8 cylinders 4 cylinders 4 cylinders 4 cylindersTransmission Automatic Manual Automatic Automatic

Tire A B C DType All Season M+S All Season M+S All Season M+S All Season M+SSize P215/60R16 94V P215/65R15 95H P205/60R15 91H P215/70R16 99HIPR* 1.4 2.2 2.3 2.5* = ASTM F1112-06

40

Vehicle Fuel Economy: Tire Pressure Loss Rates

Tire Inflation Pressure Loss Rates (%-month) dependent upon tire type and measurement type• ASTM F1112 measured at 21oC for unloaded, static tire• In-service IPLR measured at ambient temperatures for tires on vehicles

In-Service Loss Rates Increased Significantly: 50 – 125%


Tire IPLR Loss Rates

1.42.2 2.3 2.5

2.1

3.3

5.2

4.2

0.0

1.0

2.0

3.0

4.0

5.0

6.0

A B C D

% -

Loss

/Mon

th

ASTM F1112 In Service

41

Vehicle Fuel Economy: Tire Pressure Loss Rates

Inflation pressure was measured directly for each tire on the vehicle, and the average value for all four tires was used to calculate tire IPLR monthly loss rates based on 10 weeks of data• Inflation cycle: Air, Nitrogen, Air, and Nitrogen

Loss Rates are Reduced Using Nitrogen to Inflate Tires


Tire IPLR Loss Rates

1.42.2 2.3 2.5

2.1

3.3

5.2

4.2

1.21.6 1.8 1.6

0.0

1.0

2.0

3.0

4.0

5.0

6.0

A B C D

% -

Loss

/Mon

th

ASTM F1112 In Service-Air In Service-N2

42

Vehicle Fuel Economy: In-Service Miles Driven

Vehicle miles driven under normal city/highway conditions• Gallons of gas consumed recorded for each fill-up during the four

10-week time periods: 45,961 total miles driven


VehicleAir N2 Air-2 N2-2 Total

1 4030 4115 2720 3677 145432 2726 2537 3388 3381 120323 2328 2317 1984 2371 90004 3449 2860 4078 10387

Miles Driven

Vehicle Miles Driven

0

1000

2000

3000

4000

5000

Air N2 Air-2 N2-2

Mile

s

Vehicle 1 Vehicle 2 Vehicle 3 Vehicle 4

43

Vehicle Fuel Economy: Gasoline ConsumedAverage miles per gallon was obtained under normal city driving conditions in order to determine the effect of nitrogen inflation on vehicle fuel economy


Vehicle 2 MPG: Air vs N2

141618202224262830323436

8 31 54 70 96 114

146

168

187

209

229

242

278

Days

MPG


141618202224262830323436

8 23 44 70 78 90 101

113

141

164

193

204

225

240

258

280

300

Days

MPG


141618202224262830323436

8 21 32 56 69 102

123

138

171

193

217

234

269

289

Days

MPG


141618202224262830323436

3 28 39 60 88 109

129

162

179

195

213

236

Days

MPG

44

Vehicle Fuel Economy: Miles per Gallon of GasolineAverage miles per gallon was obtained in order to determine the effect of nitrogen inflation on vehicle fuel economy


VehicleAir N2 Air-2 N2-2 Average

1 20.1 20.3 19.9 19.6 20.02 23.1 22.2 22.2 23.7 22.83 21.7 22.2 22.8 23.0 22.44 28.5 28.1 28.9 28.5

MPG

Vehicle Fuel Economy

0.0

5.0

10.0

15.0

20.0

25.0

30.0

Air N2 Air-2 N2-2 Average

MPG

Vehicle 1 Vehicle 2 Vehicle 3 Vehicle 4

45

Vehicle Fuel Economy: Tire Effects on Gas Mileage


Inflation Gas Not Statistically Significant: Prob>|t|=0.9

Nominal factors expanded to all levelsContinuous factors centered by mean, scaled by range/2

InterceptVehicle[1]Vehicle[2]Vehicle[3]Vehicle[4]GAS[A]GAS[N]Test[1]Test[2]IPRTEMPBAROMETERTire KPa

Term23.476592-3.563654-0.723551-1.1080915.3952963-0.1630090.1630093-0.0718430.071843

0.08442430.0303879-0.169403-0.191698

Scaled Estimate0.1172680.30291

0.2046610.2822860.1951290.2705480.2705480.1067050.1067050.4521260.2586820.3210290.381145

Std Error200.20-11.76-3.54-3.9327.65-0.600.60

-0.670.670.190.12

-0.53-0.50

t Ratio<.0001*<.0001*0.0005*0.0001*<.0001*0.54780.54780.50180.50180.85210.90660.59850.6157

Prob>|t|

Scaled Estimates

1620242832

MP

G19

.678

08±0

.753

549

1 2 3 4

1Vehicle

A N

AGAS

1 2

1Test

1 2 3 4 52.3459

IPR15 20 25 30 35

27.171TEMP

100.

5

101

101.

5

102

102.

5

101.8115BAROMETER

210

220

230

240

250

230.832Tire KPa

Prediction Profiler

Vehicle Type is Only Statistically Significant Variable, Prob>|t|<0.1

46

Vehicle Fuel Economy: Effects of Different Vehicles


No Statistical Difference Using Air or Nitrogen to Fill Tires

Vehicle 1

16

17

18

19

20

21

22

23

MP

G

A N

GAS

Each PairStudent's t0.05

Excluded Rows 107

AN

Level2129

Number20.002419.9690

Mean0.243640.20733

Std Error19.51319.552

Lower 95%20.49220.386

Upper 95%

Std Error uses a pooled estimate of error variance

Means for Oneway Anova

Oneway Anova

Oneway Analysis of MPG By GAS

0.15% Decrease

47ExxonMobil Chemical Company Data


20

21

22

23

24

25

MP

G

A N

GAS


Excluded Rows 118

AN

Level2118

Number22.608122.9978

Mean0.226100.24421

Std Error22.15022.503

Lower 95%23.06623.493

Upper 95%



Oneway Anova


Vehicle 2

1.7% Increase




Vehicle 3

20

21

22

23

24

MPG

A N

GAS


Excluded Rows 129

AN

Level1414

Number22.199322.5914

Mean0.307660.30766

Std Error21.56721.959

Lower 95%22.83223.224

Upper 95%



Oneway Anova


1.7% Increase




24

25

26

27

28

29

30

31

32

33

MP

G

A N

GAS


Excluded Rows 117

AN

Level1426

Number29.007128.7685

Mean0.442740.32489

Std Error28.11128.111

Lower 95%29.90329.426

Upper 95%



Oneway Anova


Vehicle 4

0.8% Decrease


50

Vehicle Fuel Economy: Pressure Effects on Gas Mileage


Tire Inflation Pressure and Tire IPLR are Statistically Next Most Important Variables

( g )

Nominal factors expanded to all levelsContinuous factors centered by mean, scaled by range/2

InterceptGAS[A]GAS[N]Test[1]Test[2]IPRTEMPBAROMETERTire KPa

Term23.272876-0.7196820.71968210.2685351-0.2685352.3090921-0.7127660.90409062.8965046

Scaled Estimate0.2640820.5598370.5598370.2614990.2614990.7604930.5828970.7841050.733452

Std Error 88.13 -1.29 1.29 1.03 -1.03 3.04 -1.22 1.15 3.95

t Ratio <.0001 0.2006 0.2006 0.3061 0.3061 0.0028 0.2233 0.2507 0.0001

Prob>|t|

Scaled Estimates

MPG

32.29

16.47

22.82173

GAS

A N

Test

1 2

IPR

1.1

5.2

2.34586

TEMP17

.2

35.627.1707

BAROMETER

100.

5

102.

4

101.811

Tire KPa

209.

5

252.

75230.832

Prediction Profiler

51

Vehicle Fuel Economy: Effects of Air vs. N2 Inflation


No Statistically Significant Difference in Vehicle Fuel Economy Using Air or Nitrogen

16

18

20

22

24

26

28

30

32

34

MP

G

A N

GAS


AN

Level7087

Number23.024423.6474

Mean0.433800.38912

Std Error22.16722.879

Lower 95%23.88124.416

Upper 95%



Oneway Anova


2.7% Difference

52

Vehicle Fuel Economy: Effects of Air vs. N2 Inflation


No Statistically Significant Difference:Using Means gives +2.7%, Using Averages gives -2.3%

16

18

20

22

24

26

28

30

32

34

MP

G

A N

GAS


AN

Level7087

Number23.024423.6474

Mean0.433800.38912

Std Error22.16722.879

Lower 95%23.88124.416

Upper 95%



Oneway Anova


Avg Air = 23.66Avg N2 = 23.13

- 2.3%

53

Vehicle Fuel Economy: Temperature Effects - N2


Temperature Effect of Using Air Conditioner inSummer Months during Nitrogen-1 Measurements

18

20

22

24

26

28

30

32

MP

G

1 2

Test


Excluded Rows 70

12

Level4245

Number23.318623.9542

Mean0.585450.56560

Std Error22.15522.830

Lower 95%24.48325.079

Upper 95%



Oneway Anova

Oneway Analysis of MPG By Test

2.7% Difference

54

Vehicle Fuel Economy: Temperature Effects - Air


Temperature Effect of Using Air Conditioner inSummer Months during Air-2 Measurements

16

18

20

22

24

26

28

30

32

MP

G

1 2

Test


Excluded Rows 87

12

Level4228

Number24.092921.4218

Mean0.491360.60179

Std Error23.11220.221

Lower 95%25.07322.623

Upper 95%



Oneway Anova

Oneway Analysis of MPG By Test

11.1% Decrease

55

Summary

Use of dry 99.4% nitrogen as the fill gas

• Reduces oxidation of the natural rubber wire coat compound– Linear decrease in peel strength of skim with increasing

oxygen in the fill gas during laboratory oven aging

• Reduces tire IPLR by 40%

• Does not have primary affect on Cavity Gas Temperature– Cavity gas temperature dependent upon tire pressure: IPLR

• Does not have primary affect on Tire Rolling Resistance – Rolling resistance dependent upon tire inflation pressure: IPLR


Reducing Tire IPLR and Reducing Oxidation are the

Primary Effects of Using Nitrogen Gas Inflation

56

Summary• Tire IPLR measured in-service is much greater than when

measured using ASTM F1112 test protocol at room temperature– 50 - 125% increase in monthly loss rates– Use of dry 99+% nitrogen to inflate tires for in-service testing on

vehicles shows 50% lower tire IPLR

• Tire type is only statistically significant variable using Prob>|t|<0.1– Inflation gas type is not statistically significant: Prob>|t|=0.9

• No statistical difference in fuel economy using air or nitrogen to inflate tires during 46,000-mile in-service 4-vehicle study

• Effect of ambient temperature observed on vehicle fuel economy since measured mpg lowest in summer months– Up to 11% decrease in vehicle mpg when air-conditioning is turned

on during summer months


57

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Evaluation of Nitrogen Inflation of Tires

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