G1_Oota

The advantage of CVTin the real world

Yoshikazu OotaSenior Engineer

Powertrain Engineering DivisionNISSAN MOTOR CO.,LTD.

Contents Introduction Transmission performance Competitiveness of CVT and DCT Driving Pattern in the Real World Summary

Introduction There are mainly 3 types of 2 pedal transmissions such

as AT, CVT and DCT. They have each advantages and disadvantages.

Continuously Variable Continuously Variable TransmissionTransmission

(CVT)(CVT)

Dual Clutch TransmissionDual Clutch Transmission(DCT)(DCT)

ConvenConventtionalional StepStep--ATAT(AT)(AT)

Introduction Many Nissans vehicles have CVTs. Because CVTs have some advantages for fuel

consumption comparing to other transmissions.

Powertrain Fuel Consumption The powertrain fuel consumption depnends on 3

characters.

Transmission

(2) Engine Operate Efficiency

(1) Engine Efficiency

(3) Transmission Efficiency

Engine

Transmission Peformance Transmission performance can be expressed with

engine operate efficiency and transmission efficiency.


(2) E

ngin

e O

pera

teEf

ficie

ncy

bette

r

100%

100%

Transmission Efficiency

Vehicle Speed

020406080

0 100 200 300 400 500 600 70005101520

km/h

Input energyOutput energy

kW

1.5L-Engine+4AT

Energy

Measurement4ATs transmission efficiency is approximately 75 on 10-15 test cycle.

Transmission efficiency [%] Output energy [kW]dtInput energy [kW]dt

= 100

Engine Operate Efficiency

Optimal fuel consumption curve

1.5L-Engine

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

0 5 10 15 20Engine Output energy [kW]

Fuel

Con

sum

ptio

n[c

c/kJ

]

3600rpm

2800rpm

2400rpm

2000rpm

800rpm1200rpm

1600rpm

3200rpm

Better


Minimum fuel consumption = 0.10 [cc]

1.5L-Engine

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20


3600rpm

2800rpm

2400rpm

2000rpm

800rpm1200rpm1600rpm

3200rpm

Engine operate efficiency = 0.10/0.12 = 83 [%]

Acrual Fuel Consumption = 0.12 [cc]

Engine Operate Efficiency [%]Minimum fuel consumption [cc]dtActual fuel consumption [cc]dt

6

= 100

Fuel

Con

sum

ptio

n[c

c/kJ

]


1.5L-Engine+4ATon 10-15 test cycle

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20


3600rpm

2800rpm

2400rpm

2000rpm

800rpm1200rpm1600rpm

3200rpmMeasurement


4ATs engine operate efficiency is approximately 80 on 10-15 test cycle.

Fuel

Con

sum

ptio

n[c

c/kJ

]

Transmission efficiency & Engine operate efficiency

DCTs Transmission efficiency is the highest. CVTs Engine operate efficiency is the highest.

Transmission efficiency [%] Engine operate efficiency [%]2.5L-Engine Simulation

CVTCVT

ATAT(6speed)(6speed)

DCTDCT(6speed(6speed

Wet)Wet)

This simulation was performed with existing transmissions specification.But the final gear ratio was adjusted in order to have the same driving forces.

100% 95% 90% 85% 80% 75% 75% 80% 85% 90% 95% 100%

Highway cycleLA4 cycle

Transmission Efficiency CVTs transmission efficiency is lower than ATs or

DCTs because CVTs equip with lager oil pump for higher oil pressure.

0%

20%

40%

60%

80%

100%

120%

CVT 6AT 6Speed Wet DCT

Tran

smis

sion

Ene

rgy

Loss

[%]

Torque Converter or Starting Clutch

Oil Pump

Inertia

Others

2.5L-Engine Simulation

CVT AT(6speed) DCT(6speed Wet)

US-Combined test cycle

Engine Operate Efficiency DCTs engine operate efficiency is lower because DCTs

run at the stepped gear ratio.

Engine Output energy [kW]

Fuel

Con

sum

ptio

n [c

c/kJ

]

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

0 5 10 15 20 25 30

3600rpm

2800rpm

2400rpm

2000rpm

600rpm1200rpm

1600rpm

3200rpm

CVTDCT(6speed Wet)

LA4 test cycle2.5L-Engine Simulation


Transmission performance CVTs are better at engine operate efficiency. DCTs are better at transmission efficiency.

bette

r

DCT

AT

CVT


(2) E

ngin

e O

pera

teEf

ficie

ncy

Contents Introduction Transmission performance Competitiveness of CVTs and DCTs Driving Pattern in the Real World Summary

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0 20 40 60 80 100 120 140 160

Fuel Consumption of ATs Fuel consumption of emission test cycles is worse than

that of constant speed condition.

Average of vehicle speed [km/h]

Fuel

Con

sum

ptio

n [L

/km

]

Constant speed

US0610-15

AT(6speed)NEDC

2.5L-Engine Calculation

HighWay

JC08

LA4B

etter

144%

Fuel consumption ratio(vs Constant speed)

VSF (Vehicle Speed Fluctuation)VSF(Vehicle speed fluctuation) [%]

Standard deviation of vehicle speed () [km/h]Average vehicle speed () [km/h]

time[sec]

0

20

40

60

80

100

120

140

0 200 400 600 800 1000 1200

Vehi

cle

spee

d [k

m/h

]

Time frequency [%]

+

-

VSF =/= 29.5 / 43 = 69 [%] on NEDC cycle

100

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0 20 40 60 80 100 120 140 160

Fuel Consumption of ATs The larger VSF is, the worse fuel consumption is.

Fuel

Con

sum

ptio

n [L

/km

]

123%

140% AT(6speed)144%


US06(VSF=36%)10-15(VSF=60%)

NEDC(VSF=69%)

Average of vehicle speed [km/h]

Constant speed

Fuel consumption ratio(vs Constant speed)

100%

110%

120%

130%

140%

150%

0% 10% 20% 30% 40% 50% 60% 70% 80%

Fuel Consumption Ratio of ATs VSF and Fuel Consumption Ratio are linearly correlated.

Vehicle speed fluctuation [%]

Highway

JC08AT(6speed)

LA4

10-15

NEDC

Fuel

Con

sum

ptio

n R

atio

[%]

(vs

Con

stan

t spe

ed)

US06

Constant Speed


Acceleration & Deceleration

100%

110%

120%

130%

140%

150%

0% 10% 20% 30% 40% 50% 60% 70% 80%

Fuel Consumption Ratio of ATs,CVTs and DCTs

The slope of CVTs is smaller than that of DCTs and ATs.


CVT

DCT(6speed Wet) AT(6speed)

Constant Speed


Fuel

Con

sum

ptio

n R

atio

[%]

(vs

Con

stan

t spe

ed)

100%

110%

120%

130%

140%

150%

0% 10% 20% 30% 40% 50% 60% 70% 80%


The smaller the slope is, the higher engine operate efficiency is.


CVT

DCT(6speed Wet) AT(6speed)

engine operate efficiency


Fuel

Con

sum

ptio

n R

atio

[%]

(vs

Con

stan

t spe

ed)

Constant Speed

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0 20 40 60 80 100 120 140 160

Fuel Consumption of constant speed condition

The fuel consumption of DCTs are better at the constant speed condition.

Vehicle speed [km/h]

Fuel

Con

sum

ptio

n [L

/km

]

CVTAT(6speed)

DCT(6speed Wet)


Better

6%

100%

110%

120%

130%

140%

150%

0% 10% 20% 30% 40% 50% 60% 70% 80%


DCTs intersects with CVTs in the Vehicle speed fluctuation about 40%.


DCT(adjustmed)

Transmission

efficiency


Fuel

Con

sum

ptio

n R

atio

[%]

(vs

Con

stan

t spe

ed)

CVT

DCT AT

Constant Speed

94%

100%

110%

120%

130%

140%

150%

0% 10% 20% 30% 40% 50% 60% 70% 80%

Competitiveness of CVT and DCT


CVT

DCT(adjustmed)

CVT is betterDCT is better

Constant Speed

Highway

JC08

LA4

10-15

NEDC

US06


VSF 40% is the turning point of the fuel consumption.Fu

el C

onsu

mpt

ion

Rat

io [%

](v

s C

onst

ant s

peed

)

94%

Driving Pattern of real world Driving patterns are different at every markets. We classify various driving patterns into 6 patterns.

EuropeEuropeUSAUSA

JapanJapan

BRICsBRICsother...other...

3.Suburb3.Suburb2.Urban2.Urban

1.Heavy traffic1.Heavy traffic

4.Mountain4.Mountain5.Highway5.Highway

6.High speed in mountains6.High speed in mountains

Driving Pattern in Japanese market Over VSF=40% share more the 75% frequency in market.

VSF=59%

VSF=58%

VSF=40%

VSF=32%

VSF=30%

VSF=22%

Time freqencyin Japan

VSF > 40%

0 200 400 600 800 1000 1200 1400 1600

0 200 400 600 800 1000 1200 1400 1600

0 200 400 600 800 1000 1200 1400 1600

0 200 400 600 800 1000 1200 1400 1600

0 200 400 600 800 1000 1200 1400 1600

0 200 400 600 800 1000 1200 1400 1600

1.Heavy Traffic4.High speed in mountains

2.Urban

3.Suburb6.Mountains

5.Highway

0%

20%

40%

60%

80%

100%

0% 10% 20% 30% 40% 50% 60% 70%

Driving Pattern in Japanese market In Japanese market, the time frequency at VSF=40% is

76%.


Cum

ulat

ive

Freq

uenc

y [%

]

Constant Speed

76%

Measurement

Tim

e fre

quen

cy in

Jap

an [%

]

1.Heavy Traffic

3.Suburb

2.Urban

6.Mountains

5.Highway4.High speed in mountains

Acceleration & Deceleration

0%

20%

40%

60%

80%

100%

0% 10% 20% 30% 40% 50% 60% 70%

Driving Pattern of USA and China In the USA and China, the time frequency at VSF=40% is

more than 60%.


JapanUSAEuropeChina

Cum

ulat

ive

Freq

uenc

y [%

]

Constant Speed

Measurement

Tim

e fre

quen

cy in

eve

ry c

ount

ries

[%]

0%

20%

40%

60%

80%

100%

0% 10% 20% 30% 40% 50% 60% 70%

Driving Pattern of Europe In Europe, the time frequency at VSF=40% is 40%.


JapanUSAEuropeChina

Cum

ulat

ive

Freq

uenc

y [%

]

Constant Speed

MeasurementTim

e fre

quen

cy in

eve

ry c

ount

ries

[%]

0%

20%

40%

60%

80%

100%

0% 10% 20% 30% 40% 50% 60% 70%

Driving Pattern of Europe In Europe, at VSF=40% time share is 40%.


JapanUSAEuropeChina

Cum

ulat

ive

Freq

uenc

y [%

]

Constant Speed

Measurement

In Japan, USA and China, CVTs are better because the time frequency at VSF=40% is larger.

In Europe, DCTs are better because the time frequency at VSF=40% is smaller.

Summary CVTs have an advantage of fuel consumption in many markets

because CVTs have much higher engine operate efficiency than DCTs and

ATs. Higher engine operate efficiency could alleviate additional fuel

consumption caused by vehicle speed fluctuation. Vehicle speed fluctuation is large in the real world.

However, CVTs would lose the advantage if Driving pattern in the real world changes greatly. Transmission efficiency of DCTs greatly improves.

Thank you for your attention.

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