Low Carbon Vehicle Technology Project
Benchmarking and Teardown Activities
Undertaken on
Nissan Leaf and Chevrolet Volt
Johnathan Breddy, Tata Motors European Technical Centre (TMETC) plc
Agenda
• Benchmarking and teardown overview
• NVH challenges of alternative powertrains
Nathan Gabbott, TMETC
• Thermal benchmarking
David Bridge, MIRA
Car Selection
UK-specification Nissan Leaf
US-specification Chevrolet Volt
Timeline
Leaf 1 Delivery
Benchmarking
2 Delivery
Benchmarking
Teardown
Volt 1 Delivery
Benchmarking
Vehicle energy efficiency evaluation
2 Delivery
Benchmarking
Teardown
2011
Jun
Jul
Aug
Sep
u
u
u
u
Oct
Nov
Dec
2012
Jan
Feb
Benchmarking Activities
• Subjective Assessments
•
•
•
•
•
Aerodynamics
Braking and vehicle stability
Parasitic losses
Discharge behaviour
Energy efficiency
• Thermal
• NVH
Subjective Assessments
Subjective Assessments – Leaf
(Zytek)
Energy Efficiency – Leaf
(S Robinson JLR)
Energy Consumption by Vehicle State
(over 2 cumulative NEDCs)
2800
2400
2000
1600
1200
800
400
Energy Consumed / Wh
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
Whole Cycle
Urban
Extra-urban
Time
Distance
Time
Distance
Time
Distance
%
%
%
%
%
%
Accel
27
29
24
28
30
33
Decel
3
3
5
5
1
1
Cruise
43
68
35
67
58
66
Idle
27
0
36
0
11
0
0
Acceleration
Deceleration
Cruise
Idle
Vehicle State
Energy Consumed
Extra-Urban NEDC
Energy Consumed
Urban NEDC
180
Energy / Wh
200
160
140
120
150
Speed / kph
250
100
80
100
60
40
50
20
0
0
100
200
Time / s
300
0
400
1200
200
180
Cold Extra-Urban (780 < t <= 1180)
1000
160
Hot Extra-Urban (1960 < t <= 2360)
Scheduled Speed
140
800
Speed / kph
200
Cold Urban 1 (0 < t <= 390)
Cold Urban 2 (390 < t <= 780)
Hot Urban 1 (1180 < t <= 1570)
Hot Urban 2 (1570 < t <= 1960)
Scheduled Speed
Energy / Wh
300
120
600
100
80
400
60
40
200
0
0
100
200
Time / s
300
20
0
400
Energy Efficiency – Volt
(Integral Powertrain)
Braking Assessment – Volt
(MIRA)
Aerodynamics – Leaf Anti-Drag Lips
Aerodynamics – Under body panels
Teardown
• Completed at JLR Gaydon facility
• Primary objectives
> Permit viewing of EV and hybrid components in situ
> Liberate key components for teardown
Teardown - Nissan Leaf
Teardown - Chevrolet Volt
Teardown - Nissan Leaf Motor
Summary
•
•
•
•
Partners able to subjectively evaluate two new to market cars
In depth evaluations completed in a broad range of activities
Teardown enabled component level benchmarking
Cars available post project to support partners and University based tuition
and research
NVH Challenges of Alternative Powertrains
Nathan Gabbott
Principal NVH Engineer
Tata Motors European Technical Centre
NVH Challenges of Alternative Powertrains
Comparison of NVH characteristics of Electric and IC
Engine driven vehicles
Specific Challenges in Electric Vehicles
Integration refinement of an APU into the vehicle
Comparison of NVH characteristics of
Electric and IC Engine driven vehicles
EV vehicles bring many new challenges to the NVH engineer:
•
•
•
•
Reduced low frequency noise
Increased high frequency noise
Reduced load dependency
Increased road and wind noise sensitivity
However advantages can be found
• Reduced overall levels for improved passenger comfort
Comparison of NVH characteristics of
Electric and IC Engine driven vehicles
Nissan Leaf exhibits strong whine orders from
transmission spur gears
60
2000
1800
2000
1800
1600
50
50
1600
1400
800
30
600
1200
1000
800
30
600
400
20
200
10
10
40
60
80
100
km/h
120
Nissan Leaf
160
40
1000
800
30
600
400
20
200
0
Hz
40
dB(A)
1000
50
1400
1200
Hz
40
dB(A)
1200
60
1800
1600
1400
Hz
60
dB(A)
2000
Interior Noise
Wide Open Throttle
400
20
200
0
10
10
40
60
80
100
km/h
120
160
Chevrolet Volt
0
10
10
40
60
80
100
120
160
km/h
IC Competitor
Strong lower order content found in the IC engine is absent in the EV drives, reducing
overall level at the cost of a less balanced overall sound quality
Comparison of NVH characteristics of
Electric and IC Engine driven vehicles
• Both the Leaf and Volt exhibit noise from the power switching
electronics between 8 and 12kHz
• These switching frequencies present a new challenge in the
development of body sealing and trim packs due to their high
frequency
10
10
15000
14000
14000
14000
13400
13400
13400
13000
13000
13000
12400
12400
12400
12000
12000
12000
11400
11400
11400
11000
11000
11000
10400
10000
0
10000
9400
9400
9400
9000
9000
9000
8400
8400
8400
8000
8000
8000
7400
7400
7400
7000
7000
7000
6400
6400
6400
6000
6000
6000
5600
5600
5000
-10
10
40
60
80
100
km/h
120
Nissan Leaf
160
10
10400
Hz
0
Hz
10000
dB(A)
14400
dB(A)
14400
10400
Hz
15000
14400
0
dB(A)
15000
Interior Noise
Wide Open Throttle
5600
5000
-10
10
40
60
80
100
km/h
120
160
Chevrolet Volt
5000
-10
10
40
60
80
100
km/h
120
IC Competitor
160
Comparison of NVH characteristics of
Electric and IC Engine driven vehicles
Interior Noise
80
Nissan Leaf
Chevrolet Volt
IC Competitor
3rd Gear
70
Pa
dB(A)
Full Load
50% Throttle
0% Throttle
60
50
40
50
60
70
80
km/h
90
100
110
120
Neither the Leaf or the Volt show significant load dependency, this leads to a
disconnected feeling from the vehicle.
Comparison of NVH characteristics of
Electric and IC Engine driven vehicles
Masking Noise
80
78
76
74
72
Nissan Leaf
70
Chevrolet Volt
68
IC Competitor
66
64
62
60
Road Noise 50km/h
Road Noise 80km/h
Wind Noise 100km/h
Wind Noise 140km/h
The Volt and Leaf have similar road and wind noise to traditional vehicles
NVH Challenges of Alternative Powertrains
Comparison of NVH characteristics of Electric and IC
Engine driven vehicles
Specific Challenges in Electric Vehicles
Integration refinement of an APU into the vehicle
Specific NVH Challenges
EV vehicles have a number of specific issues that require attention, for example:
• Auxiliary Devices
• Vacuum pumps for brake assist
• Battery contactor noise at key on/off
• Pedestrian Awareness
• Nissan Leaf exterior sound source
• Chevrolet Volt Active Warning
Specific NVH Challenges
The Volt has a strong multi order characteristic
from the vacuum pump
Vacuum Pump Off
Vacuum Pump Noise
Vacuum Pump Running
Specific NVH Challenges
• The Nissan Leaf has significant noise from the battery
contactors at key on
• Nissan have created key on effects for the vehicle to help
minimise the disturbance from these noises
Key On Effects Off
Contactor Noise
Key On Effect 1 On
Specific NVH Challenges
• The Nissan Leaf includes an exterior sound source system to
improve safety for pedestrian, particularly the blind and partially
sighted
• The majority of the additional energy is added between 200 and
1000Hz with a swept tone up to 2300Hz
Exterior Sound Source Off
Pedestrian
Awareness
Exterior Sound Source On
Specific NVH Challenges
Pedestrian
Awareness
• The Volt does not have an ‘always
on’ exterior sound source fitted
• However an additional warning
mechanism is included - when the
headlight main beam is flashed
the vehicle horn is cycled rapidly
to provide a less intimidating
warning than the main horn
• This warning is effective whilst
being less aggressive to road users
not isolated from the horn by a
vehicle body
NVH Challenges of Alternative Powertrains
Comparison of NVH characteristics of Electric and IC
Engine driven vehicles
Specific Challenges in Electric Vehicles
Integration refinement of an APU into the vehicle
Integration refinement of an APU
into the vehicle
Powertrain Layout of the Chevrolet Volt
Planetary Gearset
ICE
Generator
Ring
Carrier
Traction
Motor
Sun
Intermediate
shaft
Diff
W
H
E
E
L
Integration refinement of an APU
into the vehicle
• The plot below shows how APU speed in range extended mode is a function of power
demand
• The APU appears to be run at or near full load in all conditions with the speed being
altered according to the power demand
• This causes an odd subjective feel during over run conditions, with the APU labouring
whilst the vehicle slows down
5000
APU Speed vs. Road Speed
4000
rpm
3000
100% Throttle
50% Throttle
0% Throttle
(Run Down)
2000
1000
0
0
10
20
30
40
50
km/h
60
70
80
90
100
Integration refinement of an APU
into the vehicle
• The start up of the APU in the Volt is very well managed, imperceptible in normal driving
conditions
• The use of the second motor/generator unit allows the IC engine to be spun up to operating
speed before it is fired, eliminating the kick usually experienced in IC only vehicles
• A similar strategy has been employed on shut down
40
35
APU Start Up
Road Speed
APU rpm
PT Vertical Vibration
Drivers Seat Rail Vertical Vibration
20
1800
30
1600
25
1400
1200
km/h
m/s2
20
10
15
1000
800
0
10
600
400
-10
5
200
-20
0
3
4
5
6
7
8
s
9
10
11
12
0
rpm
30
2000
Thermal Benchmarking of the
Nissan Leaf and Chevrolet Volt
David Bridge – MIRA Ltd
Tests Conducted
• Benchmarking covered
> Body Leakage
> Installed Airflows
> HMI
> Subjective Appraisals
> Climatic Wind Tunnel Tests
CWT Testing
• Power performance
> WOT throttle tests
• Cooling system related
> Gradient climbs
> City drive cycles
> Vmax
• HVAC related
> AC system performance
> Heater system performance
> Screen (defrost) clearing
LC Vehicle Testing Challenges
• Electric AC compressors & PTC heaters
• Independent cooling circuits
• Battery regeneration post test
• Battery temperature vs test time
• Heater performance test (1500rpm)
• Pre-conditioning
• PWM pumps and fans
• Auto vs ‘manual’ HVAC settings
• Amount of instrumentation (Volt)
Volt Coolant Circuits
Volt Coolant Circuits
WOT Test
Leaf vs Volt: Force at WOT
7000
Leaf
Dyno Limit
6000
Volt - Battery Only
Volt - Battery and Engine
Dyno Force - N
5000
4000
Engine On
3000
2000
1000
0
0
20
40
60
Speed - mph
80
100
120
WOT Test
Leaf vs Volt: Developed Power at WOT
120
Engine On
100
Dyno Power - kW
80
60
40
Leaf
Volt - Battery Only
20
Volt - Battery and Engine
0
0
20
40
60
Speed - mph
80
100
120
Body Leakage
Body Leakage
Leaf vs Volt Cabin Pressure Drop Characteristics
80
Leaf
70
Volt
Body Leakage
Leaf: 43.6 cm2
Volt: 29.0 cm2
60
Air Flow - l/s
50
40
30
20
10
0
0
20
40
60
80
100
Pressure Drop - Pa
120
140
160
180
Installed Flows: Face Vents
Leaf vs Volt Face Vent Characteristics
120
Leaf
Volt
100
Air Flow - l/s
80
60
40
20
0
0
20
40
60
Blower Setting (%)
80
100
120
Installed Flows: Floor Vents
Leaf vs Volt Floor (Hot) Vent Characteristics
120
Leaf
Volt
100
Air Flow - l/s
80
60
40
20
0
0
20
40
60
Blower Setting (%)
80
100
120
Installed Flows: Defrost Vents
Leaf vs Volt Defrost (Hot) Vent Characteristics
120
Leaf
Volt
100
Air Flow - l/s
80
60
40
20
0
0
20
40
60
Blower Setting (%)
80
100
120
HMI - Leaf
HMI - Volt
CWT Testing
• 45°C AC Pull Down
• 45°C Mumbai city drive
• 45°C Vmax and idle
• 49, 38, 25, -5°C EUCD drive cycles
• 45 & 25°C max acceleration cycles
• GL40 – 12% Gradient at 40kph (30°C) - GG
• GL100 – 7% at 100kph – (38°C) – DD
• GL60 – 8% at 60 kph (38°C)
• -20°C heater warm-up
• -8°C screen defrost
• WOT tests
CWT Testing
AC Pull-Down
• Vehicle soaked to 45°C
• Volt plugged in overnight but charger failed after 16miles
• Solar load at 1000W/m2 for 4 hours
• 60 kph 40 minutes
• 80 kph 30 minutes
• Static 20 minutes
• HVAC
> Full fans
> Full cold
> Face mode
> Recirculation
AC Pull-Down
Av Interior Temperatures - 45°C AC Pull-Down (Volt vs Leaf)
Temperature - °C
80
70
Average Interior (GM Volt)
60
Average Interior (Nissan Leaf)
50
40
30
20
10
0
0
20
40
60
Time - Minutes
80
100
AC Pull-Down
Av Interior Temperatures - 45°C AC Pull-Down (Volt vs Leaf)
80
4000
Average Interior (GM Volt)
Average Interior (Nissan Leaf)
Engine Speed
Temperature - °C
60
3500
3000
50
2500
40
2000
30
1500
20
1000
10
500
0
0
0
20
40
60
Time - Minutes
80
100
Engine Speed - rpm
70
AC Pull-Down
Av Face Vent Outlet Temperatures - 45°C AC Pull-Down (Volt vs Leaf)
Temperature - °C
80
70
Average Face Vents (GM Volt)
60
Average Face Vents (Nissan Leaf)
50
40
30
20
10
0
0
20
40
60
Time - Minutes
80
100
Heater Warm-Up
• Vehicle soaked to -20°C
• Volt plugged in overnight
• 50 kph 60 minutes
• 100 kph 30 minutes
• Static 20 minutes
• HVAC
> Full fans
> Full hot
> Foot vents
> Fresh air
Heater Warm-Up
Average Interior - -20°C Heater Warm-Up (Volt vs Leaf)
50
40
Temperature - °C
30
20
10
0
Average Interior (GM Volt)
-10
Average Interior (Nissan Leaf)
-20
0
10
20
30
40
50
60
70
Time - Minutes
80
90
100
110
120
130
Heater Warm-Up
Floor Outlet Temperatures - -20°C Heater Warm-Up (Volt vs Leaf)
70
60
50
Temperature - °C
40
30
20
LHS Floor Outlet (GM Volt)
10
RHS Floor Outlet (GM Volt)
LHS Floor Outlet (Nissan Leaf)
0
RHS Floor Outlet (Nissan Leaf)
-10
-20
0
10
20
30
40
50
60
70
Time - Minutes
80
90
100
110
120
130
Heater Warm-Up
Floor Outlet Temperatures - -20°C Heater Warm-Up (Volt vs Leaf)
70
3500
60
3000
50
2500
2000
30
20
1500
10
1000
LHS Floor Outlet (GM Volt)
RHS Floor Outlet (GM Volt)
0
LHS Floor Outlet (Nissan Leaf)
500
RHS Floor Outlet (Nissan Leaf)
-10
Engine Speed
-20
0
0
10
20
30
40
50
60
70
Time - Minutes
80
90
100
110
120
130
Speed - rpm
Temperature - °C
40
Conclusions
• Testing of EV and HEV type vehicles offers unique
challenges
• Both vehicles communicate to user impact of HVAC
choice on energy use
• Close attention to sealing of body and FEM on Volt
• Leaf delivers more installed airflows
• AC performance similar
• Cabin warm-up for Leaf is very poor
• Cabin warm-up for Volt much better (temp) but
depends on engine switching and is subjectively poor