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

What is Powertrain Matching? Selecting the right engine and gearing for a given application Selecting the right engine and gearing for a given application Not just performance, but giving the driver the expected response to pedal inputs Not just performance, but giving the driver the expected response to pedal inputs In automotive applications delves deeper into transmission shift schedules as fuel economy is heavily impacted In automotive applications delves deeper into transmission shift schedules as fuel economy is heavily impacted

A little side story to get you in the right mindset which illustrates the difference between motorheads and everyone else

The Story of Power and the Power Paradigm (the early life of Electronic Throttle Control at Chrysler)

The Beginning Driver pushes on Pedal to move vehicle Driver pushes on Pedal to move vehicle Pedal formerly known as Gas Pedal, and before that, Accelerator Pedal Pedal formerly known as Gas Pedal, and before that, Accelerator Pedal PedalDriver

Driver Intent Relates to Pedal Position Pedal Position Foot off Pedal Floored Slow down Maintain speed Speed up a little Speed up a lot Driver Intent

Driver Intent is essentially acceleration rate (+ or -) Driver Intent is essentially acceleration rate (+ or -) Since pedal position is related to driver intent, pedal position is related to desired vehicle acceleration. Since pedal position is related to driver intent, pedal position is related to desired vehicle acceleration.

Acceleration Relates to Pedal Position Pedal Position Foot off Pedal Floored Vehicle Acceleration

Newton’s First Law: Newton’s First Law:F=ma Vehicle mass is constant (ignoring fuel usage, washer solvent spray, and any fluid leaks) Vehicle mass is constant (ignoring fuel usage, washer solvent spray, and any fluid leaks) So, Force is proportional to acceleration So, Force is proportional to acceleration

Force Relates to Pedal Position Pedal Position Foot off Pedal Floored Force Applied to Vehicle

Where Does the Force Come From? Engine produces some torque, at a speed : Engine produces some torque, at a speed : Transmission: Transmission: Ignoring Losses, of Course

Where Does the Force Come From? Axle : Axle : Ignoring Losses, of Course

Where Does the Force Come From? Tire : Tire : Ignoring Losses, of Course Interesting, but not the end of the Story.

Where Does the Force Come From? Note: Note:

Where Does the Force Come 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 (rotary) Power is Torque times Rotational Speed (rotary)

Where Does the Force Come From? Engine produces power : Engine produces power :

Where Does the Force Come From? Transmission: Transmission: Ignoring Losses, of Course

Where Does the Force Come From? Axle: Axle: Ignoring Losses, of Course

Where Does the Force Come From? Tire: Tire: Ignoring Losses, of Course

Where Does the Force Come From? Power is conserved: Power is conserved: POWER IS ABSOLUTE Torque is relative (depends on gear ratio) Torque is relative (depends on gear ratio) Ignoring Losses, of Course

Where Does the Force Come From? The force comes from engine power: The force comes from engine power: At a given vehicle velocity, force, and therefore acceleration, depends on power produced by the engine At a given vehicle velocity, force, and therefore acceleration, depends on power produced by the engine

Force Relates to Pedal Position Pedal Position Foot off Pedal Floored Force Applied to Vehicle

Engine Power Relates to Pedal Position Pedal Position Foot off Pedal Floored Engine Power

Engine Power Relates to Pedal Position Constant Speed Acceleration Deceleration

Implications of the Power Paradigm Powertrain Control Powertrain Control Vehicle Performance Vehicle Performance Engine Performance Optimization Criteria Engine Performance Optimization Criteria

Powertrain Control Should provide the power level demanded by the driver as efficiently as possible Should provide the power level demanded by the driver as efficiently as possible Efficiency could be based on: Efficiency could be based on: minimum fuel consumption minimum fuel consumption minimum emissions minimum emissions best NVH best NVH some combination of these or other considerations some combination of these or other considerations 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 advance spark advance fuel flow rate fuel flow rate EGR rate EGR rate cylinder deactivation cylinder deactivation variable valve timing variable valve timing active manifold active manifold external charge motion devices external charge motion devices

Powertrain Control Example Example: minimize fuel consumption at a driver commanded power level Example: minimize fuel consumption at a driver commanded power level pedal position indicates driver wants 100 hp delivered (based on power required vs. pedal position and vehicle speed) pedal position indicates driver wants 100 hp delivered (based on power required vs. pedal position and vehicle speed) need to find engine speed and MAP (throttle position) for best fuel consumption need to find engine speed and MAP (throttle position) for best fuel consumption assume Electronic Throttle Control assume Electronic Throttle Control

Specific Fuel Consumption vs. Speed & MAP

Engine Power vs. Speed & MAP

Specific Fuel Consumption vs. Speed & MAP

Engine Power vs. Speed & MAP

BSFC vs. Speed & MAP with Constant Power Lines

Powertrain Control Example Any combination of MAP and rpm along the 100 hp line will satisfy the driver’s power requirement Any combination of MAP and rpm along the 100 hp line will satisfy the driver’s power requirement Low rpm and high MAP gives best BSFC Low rpm and high MAP gives best BSFC Ideally, efficient CVT sets engine speed (1900 rpm, set MAP to 90 kPa) Ideally, efficient CVT sets engine speed (1900 rpm, set MAP to 90 kPa) Conventional transmissions with discreet gear ratios must pick gear ratio for combination of rpm and MAP for lowest BSFC at a vehicle speed Conventional transmissions with discreet gear ratios must pick gear ratio for combination of rpm and MAP for lowest BSFC at a vehicle speed

Vehicle Performance Best possible vehicle acceleration if engine runs at peak power (not at peak torque) Best possible vehicle acceleration if engine runs at peak power (not at peak torque) requires efficient CVT to change transmission ratio vs. vehicle speed to maintain peak power engine speed requires efficient CVT to change transmission ratio vs. vehicle speed to maintain peak power engine speed Transmission that allows the engine to provide the highest average power over an acceleration event will give best vehicle acceleration Transmission that allows the engine to provide the highest average power over an acceleration event will give best vehicle acceleration more transmission gears improves vehicle acceleration by keeping engine speed in range that makes more power more transmission gears improves vehicle acceleration by keeping engine speed in range that makes more power

Simulated Vehicle Performance with Different Transmissions

Engine Performance Optimization Criteria Typically engine program goals are a peak torque value and a peak power value Typically engine program goals are a peak torque value and a peak power value Assuming different sets of engine hardware could meet the program goals, only one set of hardware will perform the best in a vehicle Assuming different sets of engine hardware could meet the program goals, only one set of hardware will perform the best in a vehicle The best performing vehicle will have the highest average power delivered to the wheels during an acceleration event, which is dependent on transmission capability The best performing vehicle will have the highest average power delivered to the wheels during an acceleration event, which is dependent on transmission capability

Engine Optimization Example: Which Engine Performs Better in a Vehicle?

Engine Optimization Example Engine A & Engine B both meet program objectives Engine A & Engine B both meet program objectives Which one is better? Which one is better? It depends on the transmission It depends on the transmission Engine B will perform better if transmission keeps engine speed above 3200 rpm during an acceleration event Engine B will perform better if transmission keeps engine speed above 3200 rpm during an acceleration event This is true for any of the typical vehicle performance metrics: This is true for any of the typical vehicle performance metrics: 5 sec. Distance 5 sec. Distance 0-60 time 0-60 time 1/4 mile time 1/4 mile time

Summary The Story of Power The Story of Power Pedal Position relates to driver demanded power output Pedal Position relates to driver demanded power output The Power Paradigm The Power Paradigm Power is Absolute Powertrain (engine/transmission) matching is crucial to maximize vehicle performance Powertrain (engine/transmission) matching is crucial to maximize vehicle performance

Closing Remarks Powertrain Matching makes best use of your engine potential Powertrain Matching makes best use of your engine potential Torque & Power shaping can give optimal performance for a given set of gearing Torque & Power shaping can give optimal performance for a given set of gearing Optimal gearing can make your car faster for no changes in engine performance Optimal gearing can make your car faster for no changes in engine performance

Q & A