Investigation of Potential Fuel Economy Improvements of a ... · IMOP 108.5°ATDCNF EMOP...
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Investigation of Potential Fuel Economy Improvements of a SOHC Engine via Independent Inlet and Exhaust Cam Timing Controlg
2008 GT-SUITE Conference
Mike Bassett, Steve Simmonds, David Gurney,
Rob Lynn Hugh BlaxillRob Lynn, Hugh Blaxill
MAHLE Powertrain, UK
Falk Schneider
© MAHLE
MAHLE Valvetrain, Germany
ContentContent
IntroductionMAHLE CamInCam® System OverviewMAHLE CamInCam® System OverviewBaseline Engine Testing Engine Simulation– Baseline Model Correlation
– CamInCam® WOT Performance Optimisation
– CamInCam® Part Load Fuel Consumption Optimisation
Cam Timing Selection and Cam Phaser ConsiderationsCamInCam ® Engine Testing– Comparison with Engine Modelling ResultsComparison with Engine Modelling Results
Vehicle PerformanceConclusions
2MAHLE Powertrain Ltd., 14-October-2008 © MAHLE
IntroductionIntroduction
Fuel economy legislation for new vehicle fleets demands high engine efficiencyVariable Valve Timing (VVT) allows simultaneous improvementsVariable Valve Timing (VVT) allows simultaneous improvements– Wide Open Throttle (WOT)
– Part Load Fuel Economy and Emissions
Combustion stability– Combustion stabilityTraditionally VVT is achieved with camshaft phasers– Independent phasing of inlet and exhaust valves readily achieved for double overhead
camshaft (DOHC) enginescamshaft (DOHC) engines
– 2-valve per cylinder single overhead camshaft (SOHC) or overhead valve (OHV) engines
Advantages of cost and packaging
Single camshaft engine limited to dual equal phasing onlySingle camshaft engine limited to dual equal phasing onlyNew mechanical device – CamInCam®
– Allows inlet only, exhaust only or dual independent VVT on a single cam engine
Thi k d ib th li ti f th d i t E SOHC i
3MAHLE Powertrain Ltd., 14-October-2008 © MAHLE
– This work describes the application of the device to a European SOHC engine
MAHLE CamInCam® SystemMAHLE CamInCam System
Exhaust Lobes permanently fixed to Exhaust Cam Lobes
Slots for Inlet Pinsp y
outer tube (1)Inlet lobes fixed to concentric inner shaft (2) with pins (3)
2
1Exhaust Cam Lobes
22
CamshaftBearing
Slotted T be3Inlet Cam Lobes
Slotted Tube
MoveableCam Lobe
Once assembled Inlet lobes have sliding fit over outer shaft
Fixed Cam Lobe
4MAHLE Powertrain Ltd., 14-October-2008 © MAHLE
Manufacture similar to conventional assembled camshafts
Fixed Cam LobeInner Shaft Pin
Baseline TestingBaseline Testing
European production engineIndicating measurements Test Engine DetailsIndicating measurements – Water cooled cylinder pressure
sensors (Kistler 6041type)
– High speed inlet / exhaust pressures
Capacity / Layout 1.2L / 4 cyls InlineValvetrain 8v, SOHC, Direct actingCompression Ratio 9.8:1
224° (Top of Ramps)g p pWide Open Throttle (WOT) testing– manual AFR & ignition timing
optimisation
In / Exh Cam Profile 8mm peak lift
Valve TimingIMOP 108.5°ATDCNFEMOP 110.5°BTDCNF
Variable Cam Phasing FixedInlet / Fuel Fixed Inlet / MPI
Part Load– Test Points selected from vehicle drive
cycle
Inlet / Fuel Fixed Inlet, / MPIExhaust Manifold 4 into 2 into 1External EGR No
– Warm and Cold idle tested for stability Charge Dilution Tolerance– Inlet air sampled for CO2 dilution in the inlet runners
5MAHLE Powertrain Ltd., 14-October-2008 © MAHLE
Part Load Test Point SelectionPart Load Test Point Selection
Part Load Test Points
Test Point Speed BMEP( ) (kP )
100
(rpm) (kPa)3rd hill 2500 150100km/h Cruise 3000 500WW Map point 1500 262
60
80
ure
[kP
a]
120km/h
p pWW Map point 2000 200
40
60
Man
ifold
Pre
ssu
3rd HillIdle
70km/h100km/h
0
20
M
1st Hill2nd Hill
Idle
50km/h
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0 1000 2000 3000 4000
Engine Speed [rev/min]
Residual Gas Fraction Dilution ToleranceResidual Gas Fraction Dilution Tolerance
Tolerance to Residual Gas Fraction (RGF) has large influence on fuel consumptionFor engine simulation, combustion stability assumed proportional to RGFFor engine simulation, combustion stability assumed proportional to RGF– Ignores effects of charge motion and effective compression ratio
– Good correlation reported by othersBaseline engine only available with fixed cam timingBaseline engine only available with fixed cam timing– Effect of RGF was replicated by addition of CO2 into inlet system
– Inlet air sampled in inlet runner for dilution measurementMaximum CO tolerance was defined for 0 15bar SDIMEPMaximum CO2 tolerance was defined for 0.15bar SDIMEP– Internal RGF calculated with engine simulation
– Gives an estimate for acceptable total RGF limit
Speed Load CalculatedRGF
Measuredmaximum CO2
Maximumtrapped residuals
(rev/min) (kPa) (%) (%) (%)3000 500 6.9 12.0 18.02500 150 12 3 7 0 18 4
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2500 150 12.3 7.0 18.42000 200 11.7 8.5 19.21500 262 11.5 13.0 23.0
Baseline GT-Power Model Correlation at WOTBaseline GT Power Model Correlation at WOT( ) ( ) ( )
100
110
8
90
bar]
60
rque
[N
m]
80
90
100
effic
ienc
y [%
]
75
80
85
der p
ress
ure
[
45
50
55
Bra
ke to
60
70
MeasuredGT-Power model
Vol
umet
ric
65
70
axim
um c
ylin
d
35
40
Wiebe comb stion model sed ith meas red phasing (50% MFB) and d ration (10
50
Engine speed [rev/min]1000 2000 3000 4000 5000 6000
GT-Power model
60
Engine speed [rev/min]1000 2000 3000 4000 5000 6000
M
30
Engine speed [rev/min]1000 2000 3000 4000 5000 6000
Wiebe combustion model used with measured phasing (50% MFB) and duration (10-90% MFB) data – Maximum cylinder pressure indicates combustion is well modeledTorque correlation within 3%
8MAHLE Powertrain Ltd., 14-October-2008 © MAHLE
Torque correlation within 3%Volumetric Efficiency within 4%
Baseline Model Correlation - WOTBaseline Model Correlation WOT
Pressure wave activity in the inlet runner well modeled
1.10Inlet Runner Pressure - 2500rpm
re [b
ar]
1.00
1.05
Pres
su
0.90
0.95
MeasuredGT P d l
0.85
Crank angle [°CA]0 90 180 270 360 450 540 630 720
GT-Power model
TDC firing
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Part Load CorrelationPart Load Correlation
0.55
0.60
[bar
]
35
40
475
500 MeasuredGT-Power model
ic e
ffici
ency
0.40
0.45
0.50
der p
ress
ure
[
25
30
35
[g/k
Wh]
400
425
450 GT-Power model
Vol
umet
r
0.25
0.30
0.35M
axim
um c
ylin
d
15
20 BS
FC
300
325
350
375
Part Load Test Points
0.20
Engine speed [rev/min]1000 1500 2000 2500 3000 3500
M
10
Engine speed [rev/min]1000 1500 2000 2500 3000 3500
275
300
Engine speed [rev/min]1000 1500 2000 2500 3000 3500
4 part load test points investigated for fuel consumption optimisationBrake Specific Fuel Consumption (BSFC)
Part Load Test Points
Test Point Speed BMEP(rpm) (kPa)
3rd hill 2500 150100km/h Cruise 3000 500
10MAHLE Powertrain Ltd., 14-October-2008 © MAHLE
p p ( )correlation within 1%
100km/h Cruise 3000 500WW Map point 1500 262WW Map point 2000 200
Model WOT Performance OptimisationModel WOT Performance Optimisation
Torque contours for valve-timing variation using standard camshaft profiles
T [N ]1500 rev/min - standard cam profiles
-80
-70
-60
95956565105105
100105110
Torque [Nm]
[°C
A]
-100
-90
808080
8585
100100 7070 80859095
EM
OP
-130
-120
-110
7575
9090
65655560657075
Locust of standard cam phasing Standard timing Dual equal phasing optimum Dual indepedndent phasing optimum
-160
-150
-140 60605555
40455055
Locust of standard cam phasing Standard timing Dual equal phasing optimum Dual indepedndent phasing optimum
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IMOP [°CA]50 60 70 80 90 100 110 120 130 140 150
1500 rev/min
Model WOT Performance OptimisationModel WOT Performance Optimisation
Torque contours for valve-timing variation using standard camshaft profiles
T [N ]2000 rev/min - standard cam profiles
-80
-70
-60
9595100105110
Torque [Nm]
[°C
A]
-100
-90
80
8080
9090
7070100100
80859095
EM
OP
-130
-120
-110
7575
85857070
5560657075
-160
-150
-140 65656060
40455055
Locust of standard cam phasing Standard timing Dual equal phasing optimum Dual indepedndent phasing optimum
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2000 rev/min IMOP [°CA]50 60 70 80 90 100 110 120 130 140 150
Model WOT Performance OptimisationModel WOT Performance Optimisation
Torque contours for valve-timing variation using standard camshaft profiles
T [N ]2500 rev/min - standard cam profiles
-80
-70
-60
9090 7070100105110
Torque [Nm]
[°C
A]
-100
-90
80
7575
85859595
80859095
EM
OP
-130
-120
-110
9090
6565
100100
5560657075
-160
-150
-1408080
7070
6565
6060
40455055
Locust of standard cam phasing Standard timing Dual equal phasing optimum Dual indepedndent phasing optimum
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2500 rev/min IMOP [°CA]50 60 70 80 90 100 110 120 130 140 150
Model WOT Performance OptimisationModel WOT Performance Optimisation
Torque contours for valve-timing variation using standard camshaft profiles
T [N ]3000 rev/min - standard cam profiles
-80
-70
-60
75758585 100
105110
Torque [Nm]
[°C
A]
-100
-90
808080
8585
9090 9595
80859095
EM
OP
-130
-120
-110
8585
9090
100100
5560657075
-160
-150
-140
656570707575
40455055
Locust of standard cam phasing Standard timing Dual equal phasing optimum Dual indepedndent phasing optimum
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3000 rev/min IMOP [°CA]50 60 70 80 90 100 110 120 130 140 150
Model WOT Performance OptimisationModel WOT Performance Optimisation
Torque contours for valve-timing variation using standard camshaft profiles
T [N ]4000 rev/min - standard cam profiles
-80
-70
-60
6565 9090 100105110
Torque [Nm]
[°C
A]
-100
-90
80 7070
8080
85859090
80859095
EM
OP
-130
-120
-110
7070
75758585
9595
5560657075
-160
-150
-140
5050 55556060 6565
7575
40455055
Locust of standard cam phasing Standard timing Dual equal phasing optimum Dual indepedndent phasing optimum
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4000 rev/min IMOP [°CA]50 60 70 80 90 100 110 120 130 140 150
Model WOT Performance OptimisationModel WOT Performance Optimisation
Torque contours for valve-timing variation using standard camshaft profiles
T [N ]5000 rev/min - standard cam profiles
-80
-70
-60
50505555
7575 100105110
Torque [Nm]
[°C
A]
-100
-90
80
858580859095
EM
OP
-130
-120
-1105555 6060
6565
7070
8080
5560657075
-160
-150
-1404040
45455050
40455055
Locust of standard cam phasing Standard timing Dual equal phasing optimum Dual indepedndent phasing optimum
16MAHLE Powertrain Ltd., 14-October-2008 © MAHLE
5000 rev/min IMOP [°CA]50 60 70 80 90 100 110 120 130 140 150
Model WOT Performance OptimisationModel WOT Performance Optimisation
Torque contours for valve-timing variation using standard camshaft profiles
T [N ]6000 rev/min - standard cam profiles
-80
-70
-60
6060100105110
Torque [Nm]
[°C
A]
-100
-90
804040
5050
555580859095
EM
OP
-130
-120
-110
4545
5555 6565
5560657075
-160
-150
-140
40455055
Locust of standard cam phasing Standard timing Dual equal phasing optimum Dual indepedndent phasing optimum
17MAHLE Powertrain Ltd., 14-October-2008 © MAHLE
6000 rev/min IMOP [°CA]50 60 70 80 90 100 110 120 130 140 150
Model WOT Performance OptimisationModel WOT Performance Optimisation
Valve event durations and timings optimised for several VVT strategies– Increased inlet and exhaust durations selected– Increased inlet and exhaust durations selected
– ‘Dual equal’ – single camshaft with single phaser
– ‘Dual Independent’ - independent inlet and exhaust valve timing with CamInCam® device
N d ti f t t dNo reduction of torque at any speedValve timing range limited to allow part load optimisation with 60° phaser
m] 14
rove
men
t [N
68
1012 Dual independent
Dual independet - limited timing range Dual equal
Torq
ue im
pr
0246
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0
Engine speed [rev/min]1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 6000 6500
Part Load Fuel Consumption OptimisationPart Load Fuel Consumption Optimisation
Carried out using GT PowerCamshaft profiles retained from WOT optimisationCamshaft profiles retained from WOT optimisationFixed Combustion assumed– Does not predict worsening of combustion due to RGF
– Fuel consumption likely to be slightly higher than predicted here
Combustion stability limit estimated from CO2 dilution resultsCam timing map generated at each operating point
19MAHLE Powertrain Ltd., 14-October-2008 © MAHLE
Fuel Consumption Optimisation – 2000rpm 2bar
Fixed timing baseline Inlet only phasing
Exhaust only phasing
Fuel Consumption Optimisation 2000rpm 2bar
Cam timing map generated at each operating point
70345345
5050
Exhaust only phasing Dual equal phasing Dual independent phasing
Locus of dual equal cam phasing Dual independent timing window
BSFC [g/kWh]
p g pBSFC contoursRGF contours, with maximum limit
F]
50
60
345345
355355
365365
370370
360360350350
35353030
40404545
[g ] RGF [%] RGF limit
EVC
[°AT
DC
N
30
40
395395
385385 375375
390390
380380
20201919
16161414
2525
BSFCReductionin BSFC IVO EVC
(g/kWh) (%)Standard baseline 392 7 2 5
10
20
405405 385385
4004001212
1111
Standard baseline 392.7 - 2 5Inlet only 380.9 3 33 5Exhaust only 381.3 2.9 2 43Dual independent 362.2 7.8 33 43
0
IVO [°ATDCNF]-40 -30 -20 -10 0 10 20 30 40 50
20MAHLE Powertrain Ltd., 14-October-2008 © MAHLE
Pumping MEP and Manifold PressurePumping MEP and Manifold Pressure
BSFC shows strong dependence on PMEP (area B)Inlet Manifold Pressure (MAP) does not explain PMEP minima at IVC of ~25 to 35°Inlet Manifold Pressure (MAP) does not explain PMEP minima at IVC of ~25 to 35°For retarded IVO timing, cylinder pressure much lower than MAP, increasing PMEP
2626 Fi d ti i b li70
345345
355355
365365
370370
360360350350
2222
24242626
26262828
3232
3636
3030
Fixed timing baseline Inlet only phasing Exhaust only phasing Dual equal phasing Dual independent phasing
Locus of dual equal cam phasing Dual independent timing window
BSFC [g/kWh] PMEP [kPa]
F]
50
60350350
360360
370370
365365
355355
3453457575
757570707070
6565
6060
5555
5050
BSFC [g/kWh] MAP [kPa]
395395
385385 375375
400400
390390
380380
34343838
4242
4040
EVC
[°AT
DC
N
20
30
40
380380
390390
400400
375375385385
395395
5050
4545
-40 -30 -20 -10 0 10 20 30 40 50
405405 385385
3636 38384040
0
10
20
-40 -30 -20 -10 0 10 20 30 40 50
385385405405 4040
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IVO [°ATDCNF]40 30 20 10 0 10 20 30 40 50
IVO [°ATDCNF]40 30 20 10 0 10 20 30 40 50
BSFC Sensitivity to Combustion - 2000rpm 2barBSFC Sensitivity to Combustion 2000rpm 2bar
Presented BSFC cam timing maps have assumed constant combustionExpected that in reality the burn duration will increase with increasing RGFExpected that in reality the burn duration will increase with increasing RGFBSFC shown above against combustion duration and timing shown– Anticipated operating point degrades BSFC by around 1.3%
– Predicted BSFC improvement reduces to 6.5% at 2000rpm, 2 bar
nt
BSFC [g/kWh] Minimum BSFC with varying burn duation [%]
Default combustion data
% b
urne
d po
in
15
20
360 365
380
Default combustion data Anticipated operating point
atio
n of
50
%
0
5
10 360 365370
395390385380
375
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Loca 0
10 to 90 % Mass fraction burned duration20 25 30 35 40 45 50
395
Cam Timing Selection and Phaser ConsiderationsCam Timing Selection and Phaser Considerations
Cam timing map shows optimum WOT and part load requirements
60q
Cam envelopes overlaid– Dual layer 60° phasers
– Front and Rear 60° phasers 30
40
50
TDC
NF)
Front and Rear 60 phasers
Over 100° phasing angle required for inlet cam between part load and low speed WOT– Phaser not yet available
10
20
EV
C (°
AT
WOTP/LPhaser not yet available
– Likely to be transient response issue for vehicle performance and feel
Default Timing
-10
0
-70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60IVO (°ATDCNF)
/Zero Overlap at TDCDual Layer Phaser LimtFront & Rear Phasers Limit
– Parked position when phaser control not possible or for phaser failure
– Must allow adequate combustion stability at idle
23MAHLE Powertrain Ltd., 14-October-2008 © MAHLE
– 0° overlap can be achieved in this example using CamInCam end stop
CamInCam® Engine TestingCamInCam Engine Testing
Fitted with manually configured C I C
Peak torque increased by 7%Peak power increased by 16% Cam-In-CamPeak power increased by 16%Peak power speed increased by 1000rpm– Extends useful speed range of engine
– Can increase top gear ratio to give same top speed with better highway economy
Maximum Torque +7%
P 16%Power +16%
Average Torque (1500-6000rpm) +8%
Max Power Speed +1000rpm
24MAHLE Powertrain Ltd., 14-October-2008 © MAHLE
CamInCam Part Load Test Results – 2000rpmCamInCam Part Load Test Results 2000rpm
Standard Deviation of NIMEP [Bar]
BSFC [g/kWh] Fixed timing baseline Inlet only phasing Exhaust only phasing
Dual equal phasing
DN
F]
40
45
502000rpm 2Bar
370400400
395395 390407 376
1500 2 62B
70345345
350350
5050
Dual equal phasing Dual independent phasing
Locus of dual equal cam phasing Dual independent timing window
BSFC [g/kWh] RGF [%]
(TO
R) [
°ATD
25
30
35
40
0.125
150
0.080
375
380
38038
538
5
379 375
367 364
CN
F]
40
50
60 355355
365365
370370
360360350350
3535
2525
3030
40404545
[ ] RGF limit
Valv
e C
lose
10
15
20
25
3
0.150
0.100
0.060
0.040
5
380 377
379 375LowestBSFC
EVC
[°AT
DC
20
30
40
395395
385385 375375
400400
390390
380380
20201919
16161414
1212
Exha
sut V
5
0
5
10 0.0400.0385
392
IncreasingOverlap
RetardingOverlap
0
10
20
405405 385385
12121111
25MAHLE Powertrain Ltd., 14-October-2008 © MAHLE
-53000rpm 5BarIVO [°ATDCNF]
-40 -30 -20 -10 0 10 20 30 40 50
p ( ) [ ] p ( ) [ ]
Inlet Valve Open (TOR) [°ATDNF]-25 -20 -15 -10 -5 0 5 10 15 20 25 30 35 40
Vehicle SimulationVehicle Simulation
Data from the WOT and part load optimisations combined into a simple vehicle modelUse of variable valve timing over the fixed timing baseline gives:Use of variable valve timing over the fixed timing baseline gives:– 0-62 mph reduced by 1sec
– Vmax increased by 3mph
% f C– 4.7% fuel consumption reduction over the combine NEDC
D t 0 62 h 0 1000 V U b E t b C bi dData source 0-62 mph 0-1000m Vmax Urban Extra-urban Combined(s) (s) (mph) (mpg) (mpg) (mpg)
Published 14 36 96 39.8 58.9 50.4Baseline model 14.2 35.9 95.8 40.8 58.5 50.4Baseline model 14.2 35.9 95.8 40.8 58.5 50.4CamInCam model 13.3 34.9 99.2 43.2 60.9 52.9
26MAHLE Powertrain Ltd., 14-October-2008 © MAHLE
ConclusionsConclusions
A correlated simulation model has been used to select cam profiles and estimate improvements to a SOHC engine made possible by VVT with a CamInCam® systemp g p y y– Peak power increase – up to 7%
– Part load fuel consumption reduction – up to 8%Engine tested with CamInCam® hardware fittedEngine tested with CamInCam hardware fitted– Peak power increase – 16%
– Peak power speed increased by 1000 rev/min
Part load fuel consumption reduction up to 8%– Part load fuel consumption reduction – up to 8%Good agreement between calculated and measured benefits of CamInCam® systemNEDC combined fuel consumption reduction estimated - up to 4.7% with improved acceleration and Vmax performanceacceleration and Vmax performance
27MAHLE Powertrain Ltd., 14-October-2008 © MAHLE