Powertrain Powertrain MatchingMatching
John BucknellJohn Bucknell
DaimlerChrysler DaimlerChrysler
Powertrain Systems EngineeringPowertrain Systems Engineering
September 30, 2006September 30, 2006
What is Powertrain What is Powertrain Matching?Matching?
Selecting the right engine and gearing Selecting the right engine and gearing for a given applicationfor a given application Not just performance, but giving the driver Not just performance, but giving the driver
the expected response to pedal inputsthe expected response to pedal inputs In automotive applications delves In automotive applications delves
deeper into transmission shift deeper into transmission shift schedules as fuel economy is heavily schedules as fuel economy is heavily impactedimpacted
A little side storyA little side storytoto
get you in the right mindset get you in the right mindset
which illustrates the difference which illustrates the difference between between
motorheads and everyone elsemotorheads and everyone else
The Story of The Story of PowerPower
and the Power Paradigmand the Power Paradigm(the early life of Electronic Throttle Control at Chrysler)(the early life of Electronic Throttle Control at Chrysler)
The BeginningThe Beginning
Driver pushes on Pedal to move vehicleDriver pushes on Pedal to move vehicle Pedal formerly known as Gas Pedal, and before Pedal formerly known as Gas Pedal, and before
that, Accelerator Pedalthat, Accelerator Pedal
PedalDriver
Driver Intent Relates to Pedal Driver Intent Relates to Pedal PositionPosition
Pedal Position
Foot off Pedal
Floored
Slow down
Maintain speed
Speed up a little
Speed up a lot
Dri
ver
Inte
nt
Driver IntentDriver Intent
Driver Intent is essentially Driver Intent is essentially acceleration rate (+ or -)acceleration rate (+ or -)
Since pedal position is related to Since pedal position is related to driver intent, pedal position is related driver intent, pedal position is related to desired vehicle acceleration.to desired vehicle acceleration.
Acceleration Relates to Pedal Acceleration Relates to Pedal PositionPosition
Pedal Position
Foot off Pedal
Floored
Veh
icle
Acc
eler
atio
n
Vehicle AccelerationVehicle Acceleration
Newton’s First Law:Newton’s First Law:
F=maF=ma Vehicle mass is constantVehicle mass is constant (ignoring (ignoring
fuel usage, washer solvent spray, and any fuel usage, washer solvent spray, and any fluid leaks)fluid leaks)
So, Force is proportional to So, Force is proportional to accelerationacceleration
Force Relates to Pedal PositionForce Relates to Pedal Position
Pedal Position
Foot off Pedal
Floored
For
ce A
pplie
d to
Veh
icle
Where Does the Force Come Where Does the Force Come From?From?
Engine produces some torque, at a Engine produces some torque, at a speedspeed::
Transmission:Transmission:
Ignoring Losses, of CourseIgnoring Losses, of Course
engineengine,T
trans
enginetrans
transenginetrans
n
nTT
Where Does the Force Come Where Does the Force Come From?From?
AxleAxle::
Ignoring Losses, of CourseIgnoring Losses, of Course
axletrans
engine
axle
transaxle
axletransengineaxletransaxle
nnn
nnTnTT
Where Does the Force Come Where Does the Force Come From?From?
TireTire::
Ignoring Losses, of CourseIgnoring Losses, of Course
Interesting, but not the end of the Story.Interesting, but not the end of the Story.
2
erTireDiamet
2
erTireDiamet
2
erTireDiamet
axlevehicle
axletransengineaxlevehicle
V
nnTTF
Where Does the Force Come Where Does the Force Come From?From?
Note:Note:
axletransengine
axletransengine TTT
Where Does the Force Come Where Does the Force Come From?From?
Power- the rate at which work is done:Power- the rate at which work is done: Power is Force times Velocity (linear)Power is Force times Velocity (linear)
Power is Torque times Rotational Speed Power is Torque times Rotational Speed (rotary)(rotary)
VF
VelocityForcePower
T
SpeedRotationalTorquePower
Where Does the Force Come Where Does the Force Come From?From?
Engine produces powerEngine produces power::
engineengineengine TP
Where Does the Force Come Where Does the Force Come From?From?
Transmission:Transmission:
Ignoring Losses, of CourseIgnoring Losses, of Course
enginetrans
engineengine
trans
enginetransengine
transtranstrans
PP
T
nnT
TP
Where Does the Force Come Where Does the Force Come From?From?
Axle:Axle:
Ignoring Losses, of CourseIgnoring Losses, of Course
enginetransaxle
transtrans
axle
transaxletrans
axleaxleaxle
PPP
T
nnT
TP
Where Does the Force Come Where Does the Force Come From?From?
Tire:Tire:
Ignoring Losses, of CourseIgnoring Losses, of Course
enginetransaxlevehicle
axleaxle
axleaxle
vehiclevehiclevehicle
PPPP
T
T
VFP
2
erTireDiamet
2
erTireDiamet
Where Does the Force Come Where Does the Force Come From?From?
Power is conserved:Power is conserved:
POWER IS ABSOLUTEPOWER IS ABSOLUTE
Torque is relative (depends on Torque is relative (depends on gear ratio)gear ratio)
Ignoring Losses, of CourseIgnoring Losses, of Course
vehicleaxletransengine PPPP
Where Does the Force Come Where Does the Force Come From?From?
The force comes from engine power:The force comes from engine power:
At a given vehicle velocity, force, and At a given vehicle velocity, force, and therefore acceleration, depends on therefore acceleration, depends on power produced by the enginepower produced by the engine
vehicle
enginevehicle
V
PF
Force Relates to Pedal PositionForce Relates to Pedal Position
Pedal Position
Foot off Pedal
Floored
For
ce A
pplie
d to
Veh
icle
Engine Power Relates to Pedal Engine Power Relates to Pedal PositionPosition
Pedal Position
Foot off Pedal
Floored
Eng
ine
Pow
er
025
5075
1000
25
50
75
100
-40
-30
-20
-10
0
10
20
30
40
50
60
70
80
90
100
Po
we
r D
em
an
de
d (
% o
f m
ax
po
we
r)
Vehicle Speed (% of max speed)
Pedal Position (%)
Engine Power Relates to Pedal Engine Power Relates to Pedal PositionPosition
Constant S
peed
Accele
ration
Decele
ration
Implications of the Power Implications of the Power ParadigmParadigm
Powertrain ControlPowertrain Control Vehicle PerformanceVehicle Performance Engine Performance Optimization Engine Performance Optimization
CriteriaCriteria
Powertrain ControlPowertrain Control Should provide the power level Should provide the power level
demanded by the driver as efficiently as demanded by the driver as efficiently as possiblepossible Efficiency could be based on:Efficiency could be based on:
minimum fuel consumptionminimum fuel consumption minimum emissionsminimum emissions best NVHbest NVH some combination of these or other some combination of these or other
considerationsconsiderations Should use the best combination of:Should use the best combination of:
engine speed (gear ratio)engine speed (gear ratio)throttle position (ETC)throttle position (ETC)
spark advancespark advancefuel flow ratefuel flow rateEGR rateEGR rate
cylinder deactivationcylinder deactivation
variable valve timingvariable valve timingactive manifoldactive manifoldexternal charge external charge motion devicesmotion devices
Powertrain Control ExamplePowertrain Control Example
Example: minimize fuel Example: minimize fuel consumption at a driver consumption at a driver commanded power levelcommanded power level pedal position indicates driver wants pedal position indicates driver wants
100 hp delivered (based on power 100 hp delivered (based on power required vs. pedal position and required vs. pedal position and vehicle speed)vehicle speed)
need to find engine speed and MAP need to find engine speed and MAP (throttle position) for best fuel (throttle position) for best fuel consumptionconsumption
assume Electronic Throttle Controlassume Electronic Throttle Control
Specific Fuel Consumption vs. Speed & Specific Fuel Consumption vs. Speed & MAPMAP
01000
20003000
40005000
6000
Engine Speed (rpm)
2030
4050
6070
8090
100
MAP (kPa)
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
BS
FC
(lb
/hp
- hr)
0.41
0.45
0.50
0.55
0.60
0.60
0.65
0.70
Engine Power vs. Speed & MAPEngine Power vs. Speed & MAP
0
1000
2000
3000
4000
5000
6000
Engine Speed (rpm)
20
30
40
50
60
70
80
90
100
MAP (kPa)
0
50
100
150
200
250
300
350
Po
we
r (b
hp
)
10.00
10.00
10.00
25.00
25.00
50.00
75.00
100.00
150.00
200.00
250.00
300.00
Specific Fuel Consumption vs. Speed & Specific Fuel Consumption vs. Speed & MAPMAP
0 1000 2000 3000 4000 5000 6000
Engine Speed (rpm)
20
30
40
50
60
70
80
90
100
MA
P (
kPa
)
0.41
0.45
0.50
0.55
0.60
0.60
0.650.70
Engine Power vs. Speed & MAPEngine Power vs. Speed & MAP
0 1000 2000 3000 4000 5000 6000
Engine Speed (rpm)
20
30
40
50
60
70
80
90
100
MA
P (
kPa
)
10.00
10.00 10.00
25.00
25.00
50.00
75.00
100.00
150.00
200.00
250.00
300.00
BSFC vs. Speed & MAP with Constant BSFC vs. Speed & MAP with Constant Power LinesPower Lines
0 1000 2000 3000 4000 5000 6000
Engine Speed (rpm)
20
30
40
50
60
70
80
90
100
MA
P (
kPa
)
0.41
0.45
0.50
0.55
0.60
0.60
0.650.70
10.00
10.00 10.00
25.00
25.00
50.00
75.00
100.00
150.00
200.00
250.00
300.00
0 1000 2000 3000 4000 5000 6000
Engine Speed (rpm)
20
30
40
50
60
70
80
90
100
MA
P (
kPa
)
Powertrain Control ExamplePowertrain Control Example
Any combination of MAP and rpm Any combination of MAP and rpm along the 100 hp line will satisfy the along the 100 hp line will satisfy the driver’s power requirementdriver’s power requirement
Low rpm and high MAP gives best Low rpm and high MAP gives best BSFCBSFC
Ideally, efficient CVT sets engine Ideally, efficient CVT sets engine speed (1900 rpm, set MAP to 90 kPa)speed (1900 rpm, set MAP to 90 kPa)
Conventional transmissions with Conventional transmissions with discreet gear ratios must pick gear discreet gear ratios must pick gear ratio for combination of rpm and MAP ratio for combination of rpm and MAP for lowest BSFC at a vehicle speedfor lowest BSFC at a vehicle speed
Vehicle PerformanceVehicle Performance Best possible vehicle acceleration if Best possible vehicle acceleration if
engine runs at peak power (not at peak engine runs at peak power (not at peak torque)torque) requires efficient CVT to change requires efficient CVT to change
transmission ratio vs. vehicle speed to transmission ratio vs. vehicle speed to maintain peak power engine speedmaintain peak power engine speed
Transmission that allows the engine to Transmission that allows the engine to provide the highest average power over provide the highest average power over an acceleration event will give best an acceleration event will give best vehicle accelerationvehicle acceleration more transmission gears improves vehicle more transmission gears improves vehicle
acceleration by keeping engine speed in acceleration by keeping engine speed in range that makes more powerrange that makes more power
Simulated Vehicle Performance with Simulated Vehicle Performance with Different TransmissionsDifferent Transmissions
0
20
40
60
80
100
120
140
160
0 10 20 30 40 50 60Time (s)
Ve
hic
le S
pe
ed
(m
ph
)
100% Efficient CVT
90% Efficient CVT
4 Speed Automatic
Engine Performance Optimization Engine Performance Optimization CriteriaCriteria
Typically engine program goals are a Typically engine program goals are a peak torque value and a peak power peak torque value and a peak power valuevalue
Assuming different sets of engine Assuming different sets of engine hardware could meet the program hardware could meet the program goals, only one set of hardware will goals, only one set of hardware will perform the best in a vehicleperform the best in a vehicle
The best performing vehicle will have The best performing vehicle will have the highest average power delivered the highest average power delivered to the wheels during an acceleration to the wheels during an acceleration event, which is dependent on event, which is dependent on transmission capabilitytransmission capability
Engine Optimization Example: Engine Optimization Example: Which Engine Performs Better in a Which Engine Performs Better in a
Vehicle?Vehicle?
0
50
100
150
200
250
300
350
400
450
1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 6000
Engine Speed (rpm)
To
rqu
e (
lb-f
t), P
ow
er
(bh
p)
engine A
engine B
engine A engine BPeak Torque (lb-ft) 400 400
Average Torque (1200-5600rpm) (lb-ft) 362 351Peak Power (bhp) 350 350
Average Power (1200-5600rpm) (bhp) 234 231
Engine Optimization Example: Engine Optimization Example: Which Engine Performs Better in a Which Engine Performs Better in a
Vehicle?Vehicle?
200
220
240
260
280
300
320
340
360
1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 6000
Engine Speed (rpm)
Av
era
ge
Po
we
r fr
om
x r
pm
to
56
00
rp
m (
bh
p)
engine A
engine B
Engine Optimization ExampleEngine Optimization Example Engine A & Engine B both meet Engine A & Engine B both meet
program objectivesprogram objectives Which one is better?Which one is better?
It depends on the transmissionIt depends on the transmission Engine B will perform better if Engine B will perform better if
transmission keeps engine speed above transmission keeps engine speed above 3200 rpm during an acceleration event3200 rpm during an acceleration event
This is true for any of the typical vehicle This is true for any of the typical vehicle performance metrics:performance metrics:
5 sec. Distance5 sec. Distance 0-60 time0-60 time 1/4 mile time1/4 mile time
SummarySummary The Story of PowerThe Story of Power
Pedal Position relates to driver demanded Pedal Position relates to driver demanded power outputpower output
The Power ParadigmThe Power Paradigm
Power is AbsolutePower is Absolute Powertrain (engine/transmission) Powertrain (engine/transmission)
matching is crucial to maximize matching is crucial to maximize vehicle performancevehicle performance
Closing RemarksClosing Remarks Powertrain Matching makes best use Powertrain Matching makes best use
of your engine potentialof your engine potential Torque & Power shaping can give Torque & Power shaping can give
optimal performance for a given set of optimal performance for a given set of gearinggearing
Optimal gearing can make your car Optimal gearing can make your car faster for no changes in engine faster for no changes in engine performanceperformance
Q & AQ & A