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Dual VCP Optimization at WOT & part loads for a
Gasoline engine
2013 Indian GT-Suite Conference
1Copyright © 2013 Mahindra & Mahindra Ltd. All rights reserved.
Yashaswi R
Padmavathi R
Saravanan Muthiah
Mahindra & Mahindra Ltd.
2013 Indian GT-Suite Conference
23th Sep 2013
Introduction� Variable Cam Phasing (VCP) or Variable Valve Timing (VVT) enables control
of timing of valve events� Valve opening/closing time, over lap duration, dynamic compression
ratio, internal EGR can be controlled. Efficiency of the engine can be increased.
� Cam phasing also has a downside.
� The biggest downside is a substantial increase in the amount of testing
required for optimization.
� Moving the optimization process to a virtual engine model saves a lot of
2
� Moving the optimization process to a virtual engine model saves a lot of development time & cost. Also, it gives us valuable insight into the engine's
performance well in advance.
Mahindra & Mahindra - Dual VCP Optimization at WOT & part loads for a Gasoline engine
100 200 300 400 500 600 700
Impact of Variable Cam Phasing
� An optimized cam phasing gives an improvement in efficiency & BSFC.
� In a gasoline engine throttling leads to pumping losses which if reduced will
lead to efficiency improvements.
� The engine needs high volumetric efficiency for good full load performance
3
� But part load performance needs lesser volumetric efficiency in order to
reduce throttling pumping losses
� With cam phasing, the valve timings can be optimized so as to reduce volumetric efficiency which reduces pumping losses in turn improving BSFC
Mahindra & Mahindra - Dual VCP Optimization at WOT & part loads for a Gasoline engine
Pumping losses
� Comparison of P-V curves
4
� Increase in residual gases, which decreses volumetric efficiency� Less throttling is required with lesser volumetric efficiency hence
pumping losses are reduced.
Mahindra & Mahindra - Dual VCP Optimization at WOT & part loads for a Gasoline engine
T h r o t t l i n g – N O V C P T h r o t t l i n g – I V C P o n l y T h r o t t l i n g – I V C P & E V C P
IMEP 720= 2.9 bar IMEP 720= 2.9 bar IMEP 720= 2.9 bar
IMEP360=3.55 bar IMEP360=3.5 bar IMEP360=3.35 bar
PMEP= -0.65 bar PMEP= -0.6 bar PMEP= -0.44 bar
Residual gas= 9% Residual gas = 20% Residual gas = 20%
Methodology
ENGINE MODELING @ WOT•Engine modeling for WOT
•Validation of performance @ WOT
ENGINE MODELING FOR PTP•Modeling engine for PTP with test parameters
•Validation of performance @ PTP
OPTIMIZATION OF DVCP @ PTP
• Optimization throughout engine operating map
• Limiting residual gas % & re-optimization for trade-offs
• Selection of operating points for PTP
Selection of DVCP operating points
5Mahindra & Mahindra - Dual VCP Optimization at WOT & part loads for a Gasoline engine
RESIDUAL GAS ESTIMATION•Building a simple gas exchange model
•Correlation between Simulation & test
•Estimating RG limit for Combustion stability
OPTIMIZATION FOR DVCP @ WOT•Optimization for WOT
•Selecting the VCP operating points for WOT
points
• Selection of timing lock position & VCP ranges
• FTP vs PTP trade-off
Results & Analysis
• BSFC Difference Map
• Effect of improvement in NEDC Drive cycle
Engine Modeling
� Engine intake & exhaust layouts are modeled
as per geometry� All Pipe wall temperatures are variable (temp-
solver)
� Combustion is modeled by Wiebe model
parameterized from test data� Combustion is assumed constant w.r.t VCP
6Mahindra & Mahindra - Dual VCP Optimization at WOT & part loads for a Gasoline engine
� Combustion is assumed constant w.r.t VCPpositions.
� Throttle is controlled by a PID (targeting torque)
� Friction is varied w.r.t. load according to CF
model
� Engine operating points are optimized for
knock limitations, exhaust gas temperaturelimitations, min. BSFC.
Correlation with Test data
Torq
ue
4
3
-05-4
-4
- 1 0
5
7
6
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1
4
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6
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3
1 0
5
2 9
8
4
5
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4
1
-2
-1
0
1
-2
-9
-6
-2 9
-1 4
1
1
-0
-2
-2
-2
-1
-3
-4
-4
-1 0
-9
-3 2
-2 7
1
1
-1
-2
-2
-2
-1
-2
-3
-4
-8
-8
-2 7
-2 2
0
-0
-1
-1
-2
-2
-2
-2
-2
-3
-3
-2
-1 6
-2
0
-0
-0
-1
-1
-2
-2
-2
-2
-3
-2
-2
-1 4
-2
1
1
1
0
-1
-2
-2
-1
-1
-2
-2
-2
-1 2
-3
1
1
2
2
0
-1
-1
-0
-0
-1
-1
-3
-1 0
-7
2
1
1
2
2
1
-0
0
0
-0
-0
-1
-7
-3
2
1
1
1
1
1
1
0
0
-0
-1
-1
-4
-1
0
0
0
-0
-0
-0
0
0
-0
-1
-4
-5
-4
-5
0
0
0
-0
-0
-0
0
1
1
1
-0
-3
1
4
-1
0
1
1
0
1
2
3
1
0
1
3
5
7
1
1
2
2
2
2
1
2
1
1
0
1
2
2
-0
-0
0
0
1
2
1
1
0
0
-0
-1
-1
-2
-2
-4
-4
-3
-2
-1
-1
-2
-2
-2
-2
-2
-1
-0
3
1
1
2
-0
1
2
2
1
1
1
0
1
2
4
4
5
4
2
3
5
5
4
4
4
4
3
3
2
2
2
2
2
2
3
3
2
2
3
3
6
1 0
Torq
ue
3
3
130
-2
-10
5
7
7
8
8
2
3
4
4
6
5
10
14
16
15
2
3
4
3
-0
-2
-0
1
2
-1
-8
-13
-13
-12
2
2
1
-1
-1
-1
-0
1
0
-3
-9
-11
-10
-9
1
1
0
-1
-1
-1
-0
-0
-1
-3
-5
-6
-6
-5
1
1
0
-0
-1
-1
-1
-0
-1
-2
-2
-2
-2
-3
1
1
1
0
-1
-1
-1
-1
-1
-1
-1
-1
-1
-2
1
2
2
1
-0
-1
-1
-0
-0
-0
-1
-1
-2
-2
2
3
4
3
1
-0
-0
1
1
1
-0
-2
-2
-2
3
3
3
3
2
1
1
1
2
1
0
-1
-2
-2
3
2
2
1
1
2
2
1
1
1
1
0
-0
-1
2
1
1
1
0
1
1
1
0
0
1
1
0
-0
1
1
1
1
1
1
2
2
1
0
0
0
0
1
1
2
2
2
2
2
2
3
2
1
0
1
3
2
1
1
1
2
2
2
2
2
2
2
1
1
2
2
1
1
1
1
1
1
1
1
1
1
1
1
1
1
2
1
1
2
2
2
1
1
1
1
1
1
1
1
3
2
2
2
2
3
3
3
3
2
2
2
2
2
3
3
3
3
3
3
4
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4
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4
3
4
4
3
3
3
4
4
4
4
3
3
3
3
3BSFC %difference map Air flow %difference map
7
� An engine with IVCP was tested. � Simulation correlation for BSFC & air flow rates is shown here.
Mahindra & Mahindra - Dual VCP Optimization at WOT & part loads for a Gasoline engine
E n g in e S p e e d
9
5
9
1
2
1
7
2
0
1 4
1 1
6
-0
-4
-1
-1
1
2
0
2
4
6
-2
2
-1
0
1
-3
-1
1
5
-1
1
-1
1
0
-4
-2
-0
3
-2
1
-1
1
-1
-5
-3
-1
2
-2
1
-1
1
-1
-4
-3
-1
2
-1
1
-1
1
-0
-1 5
-1 3
-9
-4
1
1
1
2
0
-1 8
-1 5
-1 1
-5
2
1
1
2
1
-1 9
-1 7
-1 4
-1 0
3
2
2
2
2
-2 4
-1 9
-1 3
-3
2
1
2
1
1
-1 5
-1 3
-9
-3
3
2
3
1
0
-1 6
-1 2
-7
1
3
2
4
1
-0
-1 0
-8
-3
3
4
2
3
1
1
-1 0
-6
-1
6
4
2
2
1
1
2 2
1 9
7
8
2
2
2
0
1
2 0
1 7
8
9
2
2
3
2
2
2 3
2 0
1 0
9
-0
4
2
3
4
1 0
1 0
6
9
-1
3
2
3
2
Eng ine Speed
6
5
8
1
2
4
2
4
9
11
9
5
0
-2
0
2
1
2
8
8
7
4
2
2
1
1
2
6
7
6
4
3
2
1
1
2
7
6
4
3
1
1
1
1
1
6
4
3
2
1
1
1
1
1
3
2
2
2
2
2
2
1
1
1
-1
-0
1
2
3
3
3
2
2
1
1
1
2
3
3
3
3
5
3
2
3
3
3
3
3
2
7
5
3
3
3
3
2
2
2
3
4
4
4
3
4
3
2
1
4
5
5
4
4
5
5
3
0
9
7
6
5
5
4
3
2
1
11
8
6
5
4
3
2
2
2
10
8
6
4
4
3
3
2
2
10
8
7
5
5
4
3
3
3
9
8
7
6
5
4
4
4
4
9
7
7
6
5
5
4
4
4
Residual Gas Estimation & limits
� A simple gas-exchange single cylinder engine is modeled
� Engine speed, intake pressures, exhaust pressures, intake
temperatures, cylinder pressures & AF ratio is given as input
from testbed data
� Airflow rate is correlated within 2% & output residual gas
content is considered.
8
content is considered.
� At low loads, it is observed that ~20% residual gas content isthe limit for combustion stability
Mahindra & Mahindra - Dual VCP Optimization at WOT & part loads for a Gasoline engine
DVCP Optimization at WOT
� At WOT, intake & exhaust VCP are optimized for maximum volumetric efficiency & torque.
� An improvement in torque is seen at low engine speeds & small improvement is seen at high engine speeds.
� Maximum of 5% improvement is seen & an average improvement of 1%
6%Improvement in WOT Torque
9Mahindra & Mahindra - Dual VCP Optimization at WOT & part loads for a Gasoline engine
0%
1%
2%
3%
4%
5%
6%
1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 6000Engine Speed (rpm)
Improvement in WOT Torque
DVCP Optimization at Part loads (2000rpm – 2bar)
� The optimization plot for 2000rpm-2bar point is shown here
� Min. BSFC = 363g/kWh� IVCP = 350
� EVCP = 400
� Residual gas limit = 20%
Positio
n
60
70
80
2828
28
3232
32
3535
35
39
39
39
365
365350
360
10
� Higher residual gas % leads to lower
throttling & hence better BSFC
� This trend is clearly reflected in the plot attached.o Higher residual gas has better BSFC
Mahindra & Mahindra - Dual VCP Optimization at WOT & part loads for a Gasoline engine
Exh
au
st
VC
P
20
30
40
50
Intake VCP Position
0 5 10 15 20 25 30 35 40 45 50
2020
20 1818
18
2121
21
2525
25
28
1515
15
355
365
365375375
375
360
370 370
370
380
380380
380
Optimized VCP points� The optimum points for both
Full load and Part load are
shown here� The cam phaser range being
limited (600), we have toselect an optimum trade off
range� Thus, lock/reference positions
for valve timings are selected.40
50
60
70
Exh
au
st
VC
P p
osit
ion
(d
eg
)
DVCP operating pointsOptimum DVCP pointsCam phaser limitsFinal DVCP points
11
for valve timings are selected.
� Also, it is observed that
retarded IVO & EVC (retardedoverlap) in part loads reduces
pumping losses substantially
Mahindra & Mahindra - Dual VCP Optimization at WOT & part loads for a Gasoline engine
0
10
20
30
-50 -40 -30 -20 -10 0 10 20 30 40 50
Exh
au
st
VC
P p
osit
ion
(d
eg
)
Intake VCP position (deg)
BSFC Difference Map
� The % difference of BSFC isshown here
� We can see that the benefitbecause of EVCP is very lessat WOT & increases withdecreasing load
-0
-0
0-0-0
-0
0
0
3
2
2
1
0
0
1
1
2
3
3
3
2
1
1
0
-0
-0
-1
-2
2
2
2
1
1
1
0
-0
-1
-1
1
1
1
1
1
0
0
0
-0
-0
1
1
1
1
0
0
0
0
-0
-0
1
1
0
0
0
0
-0
-0
-0
0
0
0
0
0
0
-0
-0
-0
-0
0
0
0
0
0
0
-0
-0
-0
-0
0
0
0
0
0
-0
-0
0
-0
-0
-0
0
0
0
0
-0
-0
0
-0
-0
-0
1
1
1
0
0
0
0
-0
-0
-0
1
1
1
1
0
0
0
0
-0
-0
1
1
1
1
0
0
0
0
0
-0
0
0
0
0
0
0
0
0
0
-0
0
0
0
0
0
0
0
0
0
-0
0
0
0
0
0
0
0
0
0
-0
0
0
0
0
0
-0
-0
-0
0
0
-0
-0
-0
-0
-1
-1
-1
-0
0
0
-0
-1
-1
-1
-1
-1
-1
-0
-0
10BSFC Difference Map (IVCP BSFC – DVCP BSFC)%
12Mahindra & Mahindra - Dual VCP Optimization at WOT & part loads for a Gasoline engine
decreasing loado This is explained by increasing
improvement in throttling /
pumping losses withdecreasing loads
o Average improvement of 2% is
observed.
Torq
ue
Engine Speed
2
2
3
4
4
5
6
7
8
9
1
7
4
3
3
3
3
3
3
4
5
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8
5
5
4
3
3
3
3
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3
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4
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2
2
3
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3
3
4
4
3
3
3
3
3
2
2
1
4
4
4
3
3
3
3
2
2
2
2
1
1
1
5
4
4
4
3
2
2
2
1
1
1
1
1
1
5
5
5
4
4
3
2
1
1
1
1
1
0
0
6
5
5
5
4
3
1
1
1
1
1
0
0
0
5
5
5
5
4
3
1
1
1
1
0
0
0
0
5
5
5
5
4
3
1
1
1
1
1
1
1
0
4
4
5
5
5
3
2
1
1
1
1
1
1
1
3
4
5
6
5
4
2
1
1
1
1
1
1
1
3
3
4
5
5
4
2
1
1
1
1
1
1
1
2
3
4
5
4
3
2
1
1
1
1
1
1
0
6
6
4
4
4
3
1
0
0
0
0
0
0
0
5
5
4
4
3
2
1
-0
-0
-0
-0
0
0
0
5
5
3
3
3
2
0
-0
-0
-0
-0
0
0
0
4
4
3
3
3
2
1
0
0
0
0
0
0
-0
10
10
2
3
3
2
1
0
0
0
0
-0
-0
-0
-0
-0
0-0-0
-0
0
0
3
2
2
1
0
0
1
1
2
3
3
3
2
1
1
0
-0
-0
-1
-2
2
2
2
1
1
1
0
-0
-1
-1
1
1
1
1
1
0
0
0
-0
-0
1
1
1
1
0
0
0
0
-0
-0
1
1
0
0
0
0
-0
-0
-0
0
0
0
0
0
0
-0
-0
-0
-0
0
0
0
0
0
0
-0
-0
-0
-0
0
0
0
0
0
-0
-0
0
-0
-0
-0
0
0
0
0
-0
-0
0
-0
-0
-0
1
1
1
0
0
0
0
-0
-0
-0
1
1
1
1
0
0
0
0
-0
-0
1
1
1
1
0
0
0
0
0
-0
0
0
0
0
0
0
0
0
0
-0
0
0
0
0
0
0
0
0
0
-0
0
0
0
0
0
0
0
0
0
-0
0
0
0
0
0
-0
-0
-0
0
0
-0
-0
-0
-0
-1
-1
-1
-0
0
0
-0
-1
-1
-1
-1
-1
-1
-0
-0
10NEDC Cycle operating points on BSFC Difference Map
Improvement in Cycle FE
� Both engine BSFC maps when made to follow the NEDC cycle
showed an FE improvement of
1.7%� Operating points of the cycle are
plotted on the adjacent map
13
Torq
ue
Engine Speed
2
2
3
4
4
5
6
7
8
9
1
7
4
3
3
3
3
3
3
4
5
6
8
5
5
4
3
3
3
3
3
3
3
4
4
4
4
4
4
3
2
2
3
3
3
3
4
4
3
3
3
3
3
2
2
1
4
4
4
3
3
3
3
2
2
2
2
1
1
1
5
4
4
4
3
2
2
2
1
1
1
1
1
1
5
5
5
4
4
3
2
1
1
1
1
1
0
0
6
5
5
5
4
3
1
1
1
1
1
0
0
0
5
5
5
5
4
3
1
1
1
1
0
0
0
0
5
5
5
5
4
3
1
1
1
1
1
1
1
0
4
4
5
5
5
3
2
1
1
1
1
1
1
1
3
4
5
6
5
4
2
1
1
1
1
1
1
1
3
3
4
5
5
4
2
1
1
1
1
1
1
1
2
3
4
5
4
3
2
1
1
1
1
1
1
0
6
6
4
4
4
3
1
0
0
0
0
0
0
0
5
5
4
4
3
2
1
-0
-0
-0
-0
0
0
0
5
5
3
3
3
2
0
-0
-0
-0
-0
0
0
0
4
4
3
3
3
2
1
0
0
0
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Mahindra & Mahindra - Dual VCP Optimization at WOT & part loads for a Gasoline engine
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Summary
� This simulation activity demonstrates the optimization procedure for Variable Cam Phasing
� A good correlation of simulation vs test data is shown in FTP & PTP� An average improvement of 1% is shown in the FTP due to addition of
EVCP.� An improvement of 1.7% is shown in NEDC cycle fuel economy due to
addition of EVCP.
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addition of EVCP.� Although improvement in WOT performance is not much, improvement
in part load consumption is significant.� Effect on BSFC because of reduction in pumping losses because of
residual gases & volumetric efficiency is analysed
� Further work in this area would include Continuous Variable Lift & Timing (CVVT) optimization
Mahindra & Mahindra - Dual VCP Optimization at WOT & part loads for a Gasoline engine
