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Baltimore, February 25th, 2014

Two-Stage Variable Compression Ratio

(VCR) System to Increase Efficiency in

Gasoline Powertrains

2014 CRC Advanced Fuel and Engine

Efficiency Workshop

Henning Kleeberg, Dean Tomazic, Steve Bowyer, FEV NA Inc.

Juergen Dohmen, Bernd Haake, FEV GmbH

 Andreas Balazs, RWTH Aachen University

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Content

Introduction and Motivation

Layout of FEV’s Two-Stage VCR System

CO2 Reduction Potential

Combination with Future Technologies

Summary and Conclusion

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Introduction and Motivation

Principle Influence of Compression Ratio on Fuel Consumption

3

Compression ratio (CR) [-]

   B   S   F   C   [   %

   ]

high

100

low

 CRbase

2000 rpm / WOT

2000 rpm / BMEP = 2 bar 

148

VCR

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Introduction and Motivation

Classification of VCR Systems

Variable piston

TDC position

 min

 max

Unconventional

cranktrains

Variable distance

head - crankshaftVariable

kinematic lengths

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Layout of FEV’s Two-Stage VCR System

Working Principle: Conrod

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Layout of FEV’s Two-Stage VCR System

Working Principle: Mechanical Actuation

6

Cam disc carrier 

View from top

horizontal

movement

valve body

functional surface

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Layout of FEV’s Two-Stage VCR System

Transition Time During Load Step

7

actual CR ideal CR

high

low-0.2 0.0 0.2 0.4 0.6 0.8 1.0

2500

2000

1500

1000

500

0

   C   R   [  -   ]

   A  c  c  e   l  e  r  a   t  o  r   P  e   d  a   l    [  -   ]

M ani    f    ol     d  

  pr   e s  s  ur   e  [   m b   ar    ]   

Time [s]

Full Load

Part Load

n = 2000 rpmOil temp. = 90°C

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Layout of FEV’s Two-Stage VCR System

Influence of Oil Temperature

8

0.0 0.2 0.4 0.6 0.8 1.0

high

low

   C   R   [  -   ]

Time [s]

n = 2000 rpm

BMEP = 8 bar 

Oil temp.:

0°C 90°C

CR ‘low   high‘ CR ‘high low‘

     = 

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US Emission Cycles based Simulations – Boundary Conditions

Large Passenger Car (Vehicle Weight = 1670 kg)

7-speed Wet Dual-Clutch Transmission

2.0L-I4 Turbocharged GDI Engine

Max. Power = 180 kW

Max. Torque = 350 Nm (BMEP = 22bar)

Base CR

 –  10.5 with Premium Fuel

 –  10.0 with Regular Fuel

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Two-Stage VCR System

CO2 Reduction Potential

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Two-Stage VCR System

CO2 Reduction Potential

US Emission Cycles based Simulations – FTP 75 Results

FTP 75Full size sedan

Baseline CR = 9/12 CR = 9/13 CR = 9/14 CR = 10/12 CR = 10/13 CR = 10/14

   C   O   2   E  m   i  s  s   i  o  n  s   [  g

   /   k  m   ]

170

175

180

185

190

195

200 Premium Fuel Regular Fuel

-4.8%-3.9%-2.8%

-4.5% -5.3% -6.0% -4.8% -6.5%-5.6%

-2.8% -4.0% -4.8%

   C   R

  =   1   0

 .   5

   C   R

  =   1   0

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Two-Stage VCR System

CO2 Reduction Potential

US Emission Cycles based Simulations – FTP 75

Fuel sharein FTP75 [%]

   B   M   E   P   [   b  a  r   ]

0

2

4

6

8

10

12

14

1618

20

22

24

Engine Speed [rpm]

1000 2000 3000 4000 5000 6000

Turbocharged DI 2.0L CR=10/14

CR = 14

CR = 10

6

5

4

3

2

1

0

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Two-Stage VCR System

CO2 Reduction Potential

US Emission Cycles based Simulations – US06

   B   M   E   P   [   b  a  r   ]

0

2

4

6

8

10

12

14

16

18

20

22

24

Engine Speed [rpm]

1000 2000 3000 4000 5000 6000

Turbocharged DI 2.0L CR=10/14

CR = 14

CR = 10

8

7

6

5

4

3

2

1

0.8

0.5

0.3

0

Fuel sharein US06 [%]

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Two-Stage VCR System

Combination with Future Technologies

 Alternat ive Fuels

Gasol ine Controlled

 Auto Ignit ion (GCAI)

13

‘Extreme

Downsizing’

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Combination with Future Technologies

Two-Stage VCR Combined with GCAI - Gasoline Controlled Auto Ignition

14

Base vehicle: 1372 kg, 1.8L -4% CO2 in NEDC

Fixed CR = 9.8

GCAI operation area

Load too low for GCAI

Two-stage VCR CR = 9.8/13-12% CO2 in NEDC

Load too high for GCAI

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Two-Stage VCR System

Combination with Future Technologies

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Two-Stage VCR Potential for Alternative Fuels

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Two-Stage VCR System

Summary and Conclusions

VCR can help to resolve the conflict between part load and full load CR layout

especially for boosted downsized gasoline engines

The presented two-stage VCR system is based on a variable length conrod with

eccentric piston wrist pin suspension and can be adapted with moderate effort to

existing engines Various CR settings can be chosen with small conrod design changes

The transition duration of the system with 0.6 seconds is sufficiently short

especially for boosted engines and is almost independent from oil temperature

CO2 reduction potential for moderately downsized GDI engines 5 – 7% within the

FTP75 cycle Operating area of GCAI technology can be significantly enlarged resulting in up

to 12% CO2 reduction in combination with two-stage VCR in NEDC

The higher knock resistance of alternative fuels can be used via adaptation of the

VCR shift line in the map

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2014 CRC Advanced Fuel and Engine Efficiency Workshop

Two-Stage Variable Compression Ratio (VCR) System

Thank you for your attention!

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