benchmarking and teardown activities undertaken on nissan leaf
TRANSCRIPT
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
US-specification Chevrolet Volt
UK-specification Nissan Leaf
Timeline
2011 2012Jun Jul Aug Sep Oct Nov Dec Jan Feb
Leaf 1 Delivery u
Benchmarking2 Delivery u
BenchmarkingTeardown
Volt 1 Delivery u
BenchmarkingVehicle energy efficiency evaluation
2 Delivery u
BenchmarkingTeardown
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)
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Acceleration Deceleration Cruise Idle
Vehicle State
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En
erg
yC
on
su
me
d/W
h
Whole Cycle Urban Extra-urban
Time
%
Distance
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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
Energy ConsumedUrban NEDC
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erg
y/W
h
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eed
/kp
h
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 ConsumedExtra-Urban NEDC
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rgy
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ee
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Cold Extra-Urban (780 < t <= 1180)
Hot Extra-Urban (1960 < t <= 2360)
Scheduled Speed
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 ICEngine 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
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Nissan Leaf exhibits strong whine orders fromtransmission spur gears
Comparison of NVH characteristics of
Electric and IC Engine driven vehicles
Strong lower order content found in the IC engine is absent in the EV drives, reducingoverall level at the cost of a less balanced overall sound quality
Interior NoiseWide Open Throttle
Nissan Leaf IC CompetitorChevrolet Volt
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• Both the Leaf and Volt exhibit noise from the power switchingelectronics between 8 and 12kHz
• These switching frequencies present a new challenge in thedevelopment of body sealing and trim packs due to their highfrequency
Comparison of NVH characteristics of
Electric and IC Engine driven vehicles
Interior NoiseWide Open Throttle
Nissan Leaf IC CompetitorChevrolet Volt
Comparison of NVH characteristics of
Electric and IC Engine driven vehicles
Neither the Leaf or the Volt show significant load dependency, this leads to adisconnected feeling from the vehicle.
Interior Noise
Nissan LeafChevrolet VoltIC Competitor3rd Gear
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km/h
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dB
(A)
Pa Full Load
50% Throttle0% Throttle
Comparison of NVH characteristics of
Electric and IC Engine driven vehicles
The Volt and Leaf have similar road and wind noise to traditional vehicles
Masking Noise
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Road Noise 50km/h Road Noise 80km/h Wind Noise 100km/h Wind Noise 140km/h
Nissan Leaf
Chevrolet Volt
IC Competitor
NVH Challenges of Alternative Powertrains
Comparison of NVH characteristics of Electric and ICEngine 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
The Volt has a strong multi order characteristicfrom the vacuum pump
Vacuum Pump Noise
Vacuum Pump RunningVacuum Pump Off
Specific NVH Challenges
• The Nissan Leaf has significant noise from the batterycontactors at key on
• Nissan have created key on effects for the vehicle to helpminimise the disturbance from these noises
Contactor Noise
Key On Effect 1 OnKey On Effects Off
Specific NVH Challenges
• The Nissan Leaf includes an exterior sound source system toimprove safety for pedestrian, particularly the blind and partiallysighted
• The majority of the additional energy is added between 200 and1000Hz with a swept tone up to 2300Hz
PedestrianAwareness
Exterior Sound Source OnExterior Sound Source Off
Specific NVH Challenges
• The Volt does not have an ‘alwayson’ exterior sound source fitted
• However an additional warningmechanism is included - when theheadlight main beam is flashedthe vehicle horn is cycled rapidlyto provide a less intimidatingwarning than the main horn
• This warning is effective whilstbeing less aggressive to road usersnot isolated from the horn by avehicle body
PedestrianAwareness
Specific NVH Challenges
NVH Challenges of Alternative Powertrains
Comparison of NVH characteristics of Electric and ICEngine driven vehicles
Specific Challenges in Electric Vehicles
Integration refinement of an APU into the vehicle
Integration refinement of an APU
into the vehicle
ICE Generator Ring
Sun
CarrierIntermediate
shaft
WHEEL
Diff
TractionMotor
Planetary Gearset
Powertrain Layout of the Chevrolet Volt
0 10010 20 30 40 50 60 70 80 90
km/h
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rpm
• The plot below shows how APU speed in range extended mode is a function of powerdemand
• The APU appears to be run at or near full load in all conditions with the speed beingaltered according to the power demand
• This causes an odd subjective feel during over run conditions, with the APU labouringwhilst the vehicle slows down
APU Speed vs. Road Speed
Integration refinement of an APU
into the vehicle
100% Throttle50% Throttle0% Throttle(Run Down)
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s
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• The start up of the APU in the Volt is very well managed, imperceptible in normal drivingconditions
• The use of the second motor/generator unit allows the IC engine to be spun up to operatingspeed before it is fired, eliminating the kick usually experienced in IC only vehicles
• A similar strategy has been employed on shut down
APU Start Up
Integration refinement of an APU
into the vehicle
Road SpeedAPU rpmPT Vertical VibrationDrivers Seat Rail Vertical Vibration
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
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Dyn
oFo
rce
-N
Speed - mph
Leaf vs Volt: Force at WOT
Leaf
Volt - Battery Only
Volt - Battery and Engine
Engine On
Dyno Limit
WOT Test
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Dyn
oP
ow
er
-kW
Speed - mph
Leaf vs Volt: Developed Power at WOT
Leaf
Volt - Battery Only
Volt - Battery and Engine
Engine On
Body Leakage
Body Leakage
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Air
Flo
w-
l/s
Pressure Drop - Pa
Leaf vs Volt Cabin Pressure Drop Characteristics
Leaf
Volt
Body LeakageLeaf: 43.6 cm2
Volt: 29.0 cm2
Installed Flows: Face Vents
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Air
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Leaf vs Volt Face Vent Characteristics
Leaf
Volt
Installed Flows: Floor Vents
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Air
Flo
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Leaf vs Volt Floor (Hot) Vent Characteristics
Leaf
Volt
Installed Flows: Defrost Vents
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Air
Flo
w-
l/s
Blower Setting (%)
Leaf vs Volt Defrost (Hot) Vent Characteristics
Leaf
Volt
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
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Tem
pe
ratu
re-
°C
Time - Minutes
Av Interior Temperatures - 45°C AC Pull-Down (Volt vs Leaf)
Average Interior (GM Volt)
Average Interior (Nissan Leaf)
AC Pull-Down
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Engi
ne
Spe
ed
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m
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pe
ratu
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Time - Minutes
Av Interior Temperatures - 45°C AC Pull-Down (Volt vs Leaf)
Average Interior (GM Volt)
Average Interior (Nissan Leaf)
Engine Speed
AC Pull-Down
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0 20 40 60 80 100
Tem
pe
ratu
re-
°C
Time - Minutes
Av Face Vent Outlet Temperatures - 45°C AC Pull-Down (Volt vs Leaf)
Average Face Vents (GM Volt)
Average Face Vents (Nissan Leaf)
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
-20
-10
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50
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Tem
pe
ratu
re-
°C
Time - Minutes
Average Interior - -20°C Heater Warm-Up (Volt vs Leaf)
Average Interior (GM Volt)
Average Interior (Nissan Leaf)
Heater Warm-Up
-20
-10
0
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50
60
70
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Tem
pe
ratu
re-
°C
Time - Minutes
Floor Outlet Temperatures - -20°C Heater Warm-Up (Volt vs Leaf)
LHS Floor Outlet (GM Volt)
RHS Floor Outlet (GM Volt)
LHS Floor Outlet (Nissan Leaf)
RHS Floor Outlet (Nissan Leaf)
Heater Warm-Up
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3500
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-10
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Spe
ed
-rp
m
Tem
pe
ratu
re-
°C
Time - Minutes
Floor Outlet Temperatures - -20°C Heater Warm-Up (Volt vs Leaf)
LHS Floor Outlet (GM Volt)
RHS Floor Outlet (GM Volt)
LHS Floor Outlet (Nissan Leaf)
RHS Floor Outlet (Nissan Leaf)
Engine Speed
Conclusions
• Testing of EV and HEV type vehicles offers uniquechallenges
• Both vehicles communicate to user impact of HVACchoice 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) butdepends on engine switching and is subjectively poor