© Ricardo plc 2005RD. 05/52402.1

Gasoline Engine Performanceand Emissions

Future Technologies andOptimization

Paul Whitaker - Technical Specialist -Ricardo

8th June 2005

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Contents

Fuel Economy Trends and Drivers – USA and Europe

Production Advanced Gasoline Technologies

Boosting for Downsizing Technologies

– Lean Boost Direct Injection

– EGR Boost Direct Injection

– 2-stroke / 4-stroke Switching

Optimization of Advanced Gasoline Combustion Systems

– Example: Optimization of a CAI enabled flexible valvetrain engine

Summary and Conclusions

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Fuel Economy Trends and Drivers – USA and Europe

Significant improvements since 1995:

– Increased diesel fleet (25% to 45% in last 5 years)

– Some improved gasoline engines

2002 & 2003 data shows levelling off

Diesels near saturation

OEMs currently face significant commercial challenges

Further improvements in gasoline powertrain efficiency will be required

that are cost effective and attractive to consumersSource: EPA Light-Duty Automotive Technology and Fuel Economy Trends: 1975 Through 2004

Overall fleet fuel economy deteriorating

Significant Truck market share increase (now 48%)

Significant increase in vehicle weight

Emissions legislation limiting dieselization

Increased pressure for improved fuel economy

– CO2 legislation? stricter CAFE? High Fuel Prices?

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Production Advanced Gasoline TechnologiesStratified Charge SIDI

Failed to deliver fuel economy promise

Work continues on central injection (2nd generation)

NOx challenge difficult to overcome in US

Homogeneous =1 SIDI

Fuel economy, emissions & performance benefits

Synergies with many other technologies

Less complicated/expensive than stratified, lowerrisk

Cylinder Deactivation

Fuel economy potential similar to Stratified SIDI

Relatively easy and inexpensive to implement

Particularly suitable for OHV engines

Easier to apply to V8 than V6 engines

Advanced NVH technologies required for full benefit

Fully Mechanical VVA

Unthrottled operation, throttled across intake valve

Potential friction reduction from reduced valve lift

Complex mechanical system

Only in production with BMW

Continuously Variable Cam Phasing

Most widely adopted advanced gasoline technology?

Fuel economy, emissions & performance benefits

Best benefits are from dual independent phasing

Phaser speed/controls can limit benefits

Baseline: V8 PFI Gasoline Engine WithoutEGR, Cost of $2,000, 500,000 units p.a.

Cost Benefit vs HSDI

Better

Worse

Stratifi

ed SIDI

Fu

ll V

VA

PFI

Ho

mo

ge

ne

ou

s S

IDI

DualVCP

Cylin

de

r D

ea

cti

va

tio

n

Emissions and performancebenefits must also be considered

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Contents

Fuel Economy Trends and Drivers – USA and Europe

Production Advanced Gasoline Technologies

Boosting for Downsizing Technologies

– Lean Boost Direct Injection

– EGR Boost Direct Injection

– 2-stroke / 4-stroke Switching

Optimization of Advanced Gasoline Combustion Systems

– Example: Optimization of a CAI enabled flexible valvetrain engine

Summary and Conclusions

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Lean Boost DI (LBDI)

Ignition retard

stability limit

Lean stabilitylimit

Increasing MAP

Naturally aspirated

0

20

40

60

80

100

120

140

160

180

200

1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9Excess Air Factor

IME

P [

%]

Ignition retardstability limit

Lean stabilitylimit

Increasing MAP

Naturally aspirated

Control Octane requirement by

– direct injection

– lean operation at full load

– enables high compression ratio

Stratified operation at part load

Fuel economy approaching diesel

Lower cost and weight

Real world fuel economy benefit

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Lean Boost DI demonstrator has delivered downsizing benefits - Fullylean operation at all conditions delivers the fuel economy of a dieselwith gasoline NVH and lower cost

VCR

HCCI

SIDI LBDI

Camless EMV

Boosted DI

MPI Base1

1.5

2

2.5

3

3.5

1 1.05 1.1 1.15 1.2 1.25 1.3 1.35 1.4

Benefit Index

Ris

k In

de

x

VCR

HCCI

SIDI LBDI

Camless EMV

Boosted DI

MPI Base

1.1l LBDI maximises hardware value:

– Higher power than 1.6 l (+5%)

– Higher torque than 1.6 l (+20%)

– Higher economy NEDC >20% better

• 132 g/km EUDC CO2

– Matched or better acceleration

– Economy over wide operating range

LBDI delivers fuel economythrough downsizing, boosting &lean operation with highcompression ratio

Octane requirement controlled by:

– direct injection

– lean operation at full load

– stratified lean DI operation atpart load

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EGR Boost Direct Injection

EGR Cooler

SIDI V6 Engine

EGR Valve

EGR Boost

Fixed GeometryTurbocharger

Fixed GeometryTurbocharger

Intercooler

Intercooler

Throttle3-way Catalyst

EGR Cooler

SIDI V6 Engine

EGR Valve

EGR Boost

Fixed GeometryTurbocharger

Fixed GeometryTurbocharger

Intercooler

Intercooler

Throttle3-way Catalyst

Uses cooled EGR as a dilutant to reduceoctane requirement

Enables high CR boosted operation

Lambda=1 operation with Three-wayCatalyst

Cost penalty 30%

Fuel economy benefit 12%

Technical risk medium/high

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DI Gasoline 2 / 4 Stroke Switching Concept improves efficiencythrough extreme downsizing – 2 stroke operation provides enhancedlow speed torque

Very high low speedtorque - 220 Nm/litre

Ultimate fun to drive(torque and revs)

HCCI at part load ?

LNT required for 2 strokemode only

(not required for typicalurban or motorwaydriving)

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Cost/FE Benefit Trade-off Advanced Gasoline Technologies

Baseline: V8 PFI Gasoline Engine Without EGR, Cost of $2,000, 500,000 units p.a.

Cost Benefit

vs HSDI

Better

Worse

Str

ati

fie

d S

IDI

Fu

ll V

VA

PFI

Homogeneous SIDIDualVCP

Cylin

de

r D

ea

cti

va

tio

n

Emissions and performancebenefits must also be considered

HSDI diesel

2s / 4s Switching SIDI

LBDI

EGR Boost

Downsizingtechnologies offerthe greatest fuel

economy potential

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Contents

Fuel Economy Trends and Drivers – USA and Europe

Production Advanced Gasoline Technologies

Boosting for Downsizing Technologies

– Lean Boost Direct Injection

– EGR Boost Direct Injection

– 2-stroke / 4-stroke Switching

Optimization of Advanced Gasoline Combustion Systems

– Example: Optimization of a CAI enabled flexible valvetrain engine

Summary and Conclusions

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Increased variability requires a mathematical optimisation technique– DoE provides an efficient, robust analytical solution

New powertrain configurations haveincreased challenges in optimisation:

– More variables

– More interactions

– More non-linear responses

– More emphasis on robustness

Design of Experiments can create a“virtual” engine or powertrain andreduce experimental work leading to:

– Shorter development times

– Better, more robust solutions

– Increased engineering understanding

DoE is now essential for many engine development and calibration tasks

Two requisites for successful DoE

– Good tools, especially for modeling and optimisation

– Intelligent implementation of DoE process

• Planning Design Testing Modeling Validation Optimisation

2

4

6

8 34

56

78

9101

0

2

3

4

5

6

EVL [mm]BMEP [bar]

BS

HC

[g

/kW

h]

2

4

6

8 34

56

78

9101

0

2

3

4

5

6

0

2

3

4

5

6

EVL [mm]BMEP [bar]

BS

HC

[g

/kW

h]

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Example – Optimisation of a Controlled Auto Ignition enabledgasoline engine using a flexible valve train providing variablelift & phasing on intake & exhaust

BMW Valvetronic systemapplied to intake andexhaust system on 4cylinder engine

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A Design-of-Experiments (DoE) approach using Stochastic ProcessModelling (SPM) and optimiser tools identified variable settings forbest fuel economy

Data sets obtained for inlet valve throttled, load ranges1000-3500 rev/min with inlet throttle wide open.

– Control variables IVP, EVP, IVL, EVL, MAP

Source:

Variables

Inlet valve phasing (IVP)

Exhaust valve phasing (EVP)

Inlet valve lift (IVL)

Exhaust valve lift (EVL)

Manifold air pressure (MAP)

Responses Modelled

BMEP

Fuel consumption

HC

NOx

CO

COV (Net IMEP) (stability)

50% Mass Fraction Burned

Ignition to 10% MFB

10 – 90 % MFB

PMEP

Optimum spark timing (MBT)

Model qualityassessment

Model quality

assessment

Estimation of ranges ofeach variableeach variable

Estimation of ranges of

each variable

Design experimentDesign experimentDesign experimentDesign experiment

Test corner pointsof experiment on engine

Test corner points

of experiment on engine

Run test sequenceon engine

OK

Run test sequenceon engine

OK

ReRe--definedefine

corner pointscorner points

unsuitable

Re--define

corner points

Re define

corner points

unsuitable

Optimise

-with constraints

PASS

Optimise

-with constraints

PASS

Test engine to validate

optimum points

Test engine to validate

optimum points

EndEnd

OK

EndEnd

OK

Poor validation

Generate modelsGenerate models

Definition of variables under investigationDefinition of variables under investigationDefinition of variables under investigationDefinition of variables under investigationObjectivesObjectivesObjectivesObjectives

FAIL

Modelimprovement

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Comparison of model output and measured data shows goodcorrelation – Data shown at minimum fuel consumption

200

250

300

350

400

450

500

550

600

1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0

BMEP [bar]

BS

FC

[g

/kW

h]

DoE model - variable inlet and exhaust liftand phase - unconstrained optimum BSFC

Validation test results

200

250

300

350

400

450

500

550

600

1.0 2.0 3.0 4.0 5.0 6.0

BMEP [bar]

BS

FC

[g

/kW

h]

DoE model - variable inlet and exhaust liftand phase - unconstrained optimum BSFC

Validation test results

200

300

400

500

600

700

800

900

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0

BMEP [bar]

BS

FC

[g

/kW

h]

DoE model - variable inlet and exhaust lift andphase - unconstrained optimum BSFC

Validation test results

1000 rev/min valve lift controlled

2000 rev/min valve lift controlled2000 rev/min throttled

3500 rev/min valve lift controlled

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Validated optimum settings show that CAI combustion providessignificant BSFC gains compared with normal SI operationResults shown for 2000 rev/min load rangeVCP=Variable Cam Phasing VVL=Variable Valve Lift

250

275

300

325

350

375

400

425

450

475

500

1.5 2.0 2.5 3.0 3.5 4.0 4.5

BMEP [bar]

BS

FC

[g

/kW

h]

SI - Dual VCP

SI - Dual VCP + Dual VVL

CAI - Dual VCP + Dual VVL

Baseline – fixed maximumlift and variable inlet andexhaust cam phasing

Variable inlet and exhaustphasing and lift – SI operation

Variable inlet and exhaustphasing and lift – CAI operation

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Typical pressure/volume characteristics for CAI operation showrecompression in exhaust stroke

Negative valve overlap createsrecompression cycle

Recompression largely reversible

Higher trapped mass due to high residuals –higher pressures

Lower losses across intake valve – reducedthrottling due to high residuals

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0

2

4

6

8

10

12

14

16

18

20

1.5 2.0 2.5 3.0 3.5 4.0 4.5BMEP [bar]

Fu

el C

on

su

mp

tio

n B

en

efi

t [%

]

Fuel Consumption benefitversus Dual VCP

CAI combustion provides significant BSFC gains compared withnormal SI operation mainly due to pumping work reductionResults shown for 2000 rev/min load rangeVCP=Variable Cam Phasing VVL=Variable Valve Lift

Dual VCP + Dual VVLwith SI combustion

Dual VCP + Dual VVLwith CAI combustion

-1.0

-0.9

-0.8

-0.7

-0.6

-0.5

-0.4

-0.3

-0.2

-0.1

0.0

1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

BMEP [bar]P

ME

P [

bar]

SI - Dual VCP

SI - Dual VCP + Dual VVL

CAI - Dual VCP + Dual VVL