Powertrain Matching John Bucknell DaimlerChrysler Powertrain Systems Engineering September 30, 2006

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


AxleAxle::


axletrans

engine

axle

transaxle

axletransengineaxletransaxle

nnn

nnTnTT


TireTire::


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


Note:Note:

axletransengine

axletransengine TTT


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


Engine produces powerEngine produces power::

engineengineengine TP


Transmission:Transmission:


enginetrans

engineengine

trans

enginetransengine

transtranstrans

PP

T

nnT

TP


Axle:Axle:


enginetransaxle

transtrans

axle

transaxletrans

axleaxleaxle

PPP

T

nnT

TP


Tire:Tire:


enginetransaxlevehicle

axleaxle

axleaxle

vehiclevehiclevehicle

PPPP

T

T

VFP

2

erTireDiamet

2

erTireDiamet


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)


vehicleaxletransengine PPPP


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

Documents

Powertrain Matching John Bucknell DaimlerChrysler Powertrain Systems Engineering September 30, 2006