Ministry of Land, Infrastructure, Transport and Tourism

Progress of Studies on Vehicle Fuel 　Economy Measurement Method with the Effect of Air Conditioner Taken into Account

Masato OKUTSU

Environment Division

Road Transport Bureau

MLIT, JAPAN

Working Paper GRPE-MACTP-02-02

ConsumersConsumersAutomakersAutomakers

GovernmentGovernment

Fuel/EnergyFuel/EnergySuppliersSuppliers

Divergence Between Mode FE and Actual FE; Comprehensive Approach

* AC

* Driving method

* Traffic congestion

* Status of inspection, etc.

Source: JAMA

Low carbon policyLow carbon policySubsidiesSubsidiesIncentivesIncentivesInfrastructureInfrastructure

High fuel efficiencyHigh fuel efficiencyNext gen. vehiclesNext gen. vehicles

Diversified fuel/energyDiversified fuel/energy

Eco-drivingEco-drivingWider use ofWider use of low-carbon low-carbon vehicles vehicles

Driving SustainabilityDriving Sustainability through an through an Integrated ApproachIntegrated Approach

Fiscal Year

Owned-vehicle mode FE

Actual driving FE

8.0

9.0

10.0

11.0

12.0

13.0

14.0

15.0

1990 1993 1996 1999 2002 2005 2008Av.

Fue

l Effi

cien

cy（

km/L

）

Measurable divergence exists between mode FE and actual driving FE. Comprehensive approach is taken, including measures not only on the

vehicle itself but also on infrastructure building, traffic flow, fuels, better driving method such as eco-driving, and more efficient logistics.

The Purpose of Research and Current Situation

MLIT aims to develop a vehicle FE measurement method that takes into account the effect of AC use, rather than the evaluation on the AC itself. Currently, studies conducted by government and industry have begun.

The method for evaluating the AC efficiency/effect on FE(1) Should represent the effect on FE in the real world.(2) Should be able to evaluate different AC systems fairly.(3) Should be able to be incorporated into the vehicle FE test method.(4) Should improve the AC efficiency and the resultant FE through its

incorporation into the FE test method.(5) Should be cost-effective.

International harmonization of standards is needed.

Overview of the Test

Overview of the test1) Test vehicle: Vehicle A: Passenger car A (1.5L, 5AT) Vehicle B: Passenger car B (1.5L, CVT)2) Time: July and October 20093) Test conditions: 20 – 30C, 40 – 75% RH4) Test mode: JC08 mode (Hot)5) Insolation condition: N/A6) Blower level: Max./Min.7) Air: FRS8) Main measurement parameters:Vehicle speed, engine speed, coolant temperature, engine oil temperature, test cell temperature/humidity, temperature/humidity at A/C filter, temperature/humidity in vehicle compartment (behind front passenger seat, air vent), compressor working condition, exhaust gas, FE

Env. conditions

Temp. HumiditySpecific enthalpy (kJ/kg)

Env. A 25C 50% 50

Env. B 20C 40% 35

Env. C 30C 75% 82

Env. D 21C 75% 51

Env. E 28C 60% 65

A/Ccondi-

tion

ON/OFF

Set-ting

Temp. set

Blowerlevel

Circula-tion

method

Vent direc-tion

AC0 OFF - - - - -

AC1

ON

Ma

nu

al

Lowest Max.

Fre

sh a

ir in

take

Fa

ce

AC2 Min.

AC3 Mid Max.

AC4 Min.

Environmental conditions AC settings

Regarding the effect of AC on the vehicle FE, the following study was conducted in fiscal 2009.

Main Test Results

Relation Between Test Cell Specific Enthalpy and FE Deterioration Rate

Relation Between Compressor Working Ratio and FE Deterioration Rate

Source: JAMA

y = 0.138x + 22.065

R2 = 0.7475

y = 0.203x + 1.0608

R2 = 0.9955

y = 0.2759x - 2.6635

R2 = 0.9926y = 0.124x + 18.918

R2 = 0.991

0

5

10

15

20

25

30

35

40

30 40 50 60 70 80 90Specific enthalpy in the test cell (kJ/kg(DA))

Det

erio

ratio

n ra

te a

gain

st s

tand

ard

cond

ition

* (%

)

Vehicle A, AC Setting: Temp. Lowest, Blower Max, FRS, FACE

Vehicle A, AC Setting: Temp. 25℃, Blower Min, FRS, FACE

Vehicle B, AC Setting: Temp. Lowest, Blower Max, FRS, FACE

Vehicle B, AC Setting: Temp. 25℃, Blower Min, FRS, FACE

（*）Standard condition: A/C OFF, Test cell temp. 25℃, Humidity 50%RH

JC08H

y = 0.2607x + 0.8086

R2 = 0.9536

y = 0.3004x + 2.8532

R2 = 0.9927

0

5

10

15

20

25

30

35

40

0 20 40 60 80 100 120Compressor working ratio (%)

Det

erio

ratio

n ra

te a

gain

st s

tand

ard

cond

ition

* (%

)

Vehicle A, AC Setting: Temp. Lowest, Blower Max, FRS, FACE

Vehicle A, AC Setting: Temp. 25℃, Blower Min, FRS, FACEVehicle B, AC Setting: Temp. Lowest, Blower Max, FRS, FACEVehicle B, AC Setting: Temp. Lowest, Blower Min, FRS, FACEVehicle B, AC Setting: Temp. 25℃, Blower Max, FRS, FACEVehicle B, AC Setting: Temp. 25℃, Blower Min, FRS, FACE

（*）Standard condition: A/C OFF, Test cell temp. 25℃, Humidity 50%RH

JC08H

Summary of Test Results

To set the appropriate representative values, we need to study in detail how the FE would change when the AC settings (Blower level, circulation method, etc.) and/or environmental conditions (fresh air temperature, humidity, insolation condition, etc.) are changed.

The effect needs to be grasped for vehicles using power-saving technologies, such as automatic AC control and variable capacity compressor, as well as vehicle equipped with multiple AC units.

Effect of the AC use on FE- The higher the test cell specific enthalpy, the higher the compressor

working ratio and the more deteriorated the FE.- Compressor working ratio varies depending on the AC setting, which

affects the FE.- Compressor working ratio and FE value are highly correlated by linear

regression .- The relation between AC settings and compressor working ratio differs

between vehicles.

Future Tasks

Test Schedule

1) Test vehicle: Vehicle A: Passenger car A (1.5L, 5AT) Vehicle B: Passenger car B (4.0L, 5AT)2) Time: Scheduled for January 20113) Test conditions: 25C-50%RH, / 30C-40%RH4) Test mode: JC08 mode (Hot/Cold)5) Insolation condition: N/A6) Blower level: Auto/Mid/Max.7) Air: FRS/REC8) Main measurement parameters:Vehicle speed, engine speed, coolant temperature, engine oil temperature, test cell temperature/humidity, temperature/humidity at A/C filter, temperature/humidity in vehicle compartment (behind front passenger seat, air vent), compressor working condition, exhaust gas, FE

To study in detail the effect of AC settings and/or environmental conditions on the FE, it is scheduled to measure data under various conditions.

Overview of the test scheduled to be conducted by MLIT in fiscal 2010

MLIT’s Stance (Proposal)

MLIT aims to develop a vehicle FE measurement method that takes into account the effect of AC use, rather than the evaluation on the AC itself.

The method for evaluating the AC efficiency/effect on FE that we need to establish

(1) Should represent the effect on FE in the real world.(2) Should be able to evaluate different AC systems fairly.(3) Should be able to be incorporated into the vehicle FE test

method.(4) Should improve the AC efficiency and the resultant FE through its

incorporation into the FE test method.(5) Should be cost-effective.

Therefore, it should be studied carefully without hasty discussions.