understanding valve spring science and selection, for ... · pdf fileunderstanding valve...

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Understanding Valve Spring

Science

and Selection, for Optimization,

Performance, and Longevity

Presenter:

Jason YoudPAC Racing Springs

AETC Conference 2011

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• Spring Performance Affects

•Maximum Engine Speed

•Durability

•Horsepower

•Cost

Key Spring Life Factors Overview

3

• Spring Performance Key Factors

•Static Stress and Design

• Dynamic Stress and Design

• Other Finite Components

• It’s all in the details

Key Spring Life Factors Overview

4

Spring Design and Application

Processing

30%

Spring Design

25%

Dynamic Design

(System)

30%

Material

15%

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Spring Design Overview Application Performance

•Material Selection (Alloy)

• Processing Selection (Recipe)

• Spring Type: Single, Beehive, Dual, Dampers, Triple

• Wire Shape (Stress per Lb.)

• Stress Range Comparisons

• Fatigue Requirements or Performance Requirements

• System Design inputs (RPM, Valve Lift Profile, Mass, other)

•Higher Stress Typically equals better dynamic performance but reduces

life

Spring Life Design Factors (Static)

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Spring Design Factors for Stress/Life Management

•Increase Tensile Strength

• Alloy Selection

• Heat Treating

•Metal Improvement with Addition of Compressive Stress or reduction in Tensile Stress

• Shot Peening

• Stress Relieving

• Polishing (removes stress risers)

•Spring Design Considerations

• Wire Shape

• Space and Application Considerations

• Required Load (Dynamic Control)

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Material Tensile Strength V. Application

250

270

290

310

330

350

370

OEM LS (Street) Circle Track Drag Race

0

10

20

30

40

50

60

70

80

90

Tensile Strength

% of tensile

Typical ASTM

Fastener % UTS

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Spring Life (Fatigue and Load)

-

10,000,000

20,000,000

30,000,000

40,000,000

50,000,000

60,000,000

70,000,000

80,000,000

90,000,000

100,000,000

OEM LS (Street Replacement) Circle Track Drag Race

Cycles to failure

0

20

40

60

80

100

120

Load Loss (Lbs)

Life Expectancy

Load Loss

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Stress Range Comparisons

20%30%

40%

65%

0

50

100

150

200

250

300

350

OEM LS (Street Replacement) Circle Track Drag Race

Application Type

Stress Range (Factor)

0%

50%

100%

150%

200%

250%

Dynamic Amplification %

Static Stress Range

Dynamic Stress Range

Dynamic % increased

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• Dynamic Stress Range

• Impact Force (Surge)

• Load Loss Impact (maintain dynamic robustness)

• Cooling and Heat

• Interference

• Damping (designed or external)

- Rate Curve (progressive, dual, linear)

- Frictional Damping (ribbon damper, interference of stacked springs,

or external damper)

Spring Life Dynamic Stress Factors

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Spring Life Dynamic Factors

Dynamic Amplification % ( Stress Increase % over Static)

0

5

10

15

20

25

30

35

500 1500 2500 3500 4500 5500

Engine Speed (RPM)

Dynamic Amplification (%)

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Spring Life Dynamic Factors

Exhaust Spring Seat Load

100

125

150

175

200

225

250

275

300

325

350

375

400

425

0 120 240 360 480 600 720 840 960 1080 1200 1320 1440

Crank Angle (deg)

Spring Seat Load (lbs)

1000

1995

3005

4000

5003

6042

6154

6351

6575

6761

7025

7157

7360

7557

7780

Coil Clash (Surge)

Bind Height and

clearance critical for

Energy dissipation

(impact energy)

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•Heat And Friction Implications

•Increased likely hood of failures from poor oil additives. Use good

quality oil and monitor changes when switching brands.

•Consider balancing added friction and performance with failures and

life expectations. Oiling is a large factor in improving spring life.

(Nested Springs/Dampers)

•Use oil as a coolant for components not just used as frictional

modifier. The more captive the oil flow the more localized cooling is

attained. Oiling shedding off of surface.

•Temperature changes the modulus of materials, which changes

stiffness factors. Robustness testing should be conducted to ensure

heat soak performance.


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Dual LS Spring (Right Bank)

After 3 Hrs Steady Run Non-

Fired Engine

(no external heat or cooling)

***Note increased thermal

profile from inside spring

Notice heat at interference

point (ID of nested spring)

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Beehive LS Spring (Left

Bank)

After 3 Hrs Steady Run Non-

Fired Engine

(no external heat or cooling)

***Note reduction in heat

from inside spring

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Spring Life Analysis

Excessive wear from spring to Excessive wear from spring to

spring contact resulting in failure. spring contact resulting in failure.

Removal of shot peened surfaceRemoval of shot peened surface

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Spring Life Dynamic Performance

Effect of Temperature on Spring Open Load

-100

-80

-60

-40

-20

0

20

50 100 150 200 250 300 350 400

Temperature (Degrees F)

Load (lbs)

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Effect of Temperature on Rate

-60

-50

-40

-30

-20

-10

0

10

50 100 150 200 250 300 350 400

Temperature (Degrees F)

Rate (lbs/inch)

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Spring Rate Curve Types

0

150

300

450

600

750

900

1050

1200

1.000

1.050

1.100

1.150

1.200

1.250

1.300

1.350

1.400

1.450

1.500

1.550

1.600

1.650

1.700

1.750

1.800

1.850

1.900

1.950

2.000

2.050

2.100

2.150

2.200

Height (Displacement)

Spring Rate

Linear Rate

2 Rate

Progressive Rate

Spring installed Height

Spring Open Height

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• Controlling Spring Dynamics with Other Alternative components

•Spring Damping Solutions

•Ribbon Damper

•Creates Heat and interference but provides good frictional damping (Located in highest stress area in spring) Known to cause spring failures from wear.

•Steel Outside Damper

•Provides good interference but can be noisy and the feet break off in high stress applications.

•Plastic Damper with Adjustable bands

•Provides spring wear solutions and wrapping effect from plastic, allows for more captive oil

flow cooling. Tested to over 300 Million cycles used in current OEM applications.

•Plastic Damper with Hydraulic Effect (tuned ports)

•Extreme cases have broken retainers from hydraulic lock-up. Oil inlet critical.


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Spring Life Dynamic Control (Hysteresis)

How to Measure and Identify Damping or Interference

Hysteretic Loop - is the difference vs. the static applied

load (input) vs. the measured output or response (in this

case interference).

We use this method to gage interference and frictional

damping effects.

This method is also used in industry to determine system

rigidity and compliance.

Note****

This is essentially measuring the force in compression and

overlaying the force in re-bound.

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Example of Hysteresis Loop

1.000

1.200

1.400

1.600

1.800

2.000

2.200

0 50 100 150 200 250 300 350 400

Force

Measured Height

Spring Force

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Hystresis - Percent Difference of Load

-7%

-6%

-5%

-4%

-3%

-2%

-1%

0%

Single Cylindrical

Spring

Single Beehive

Dual Minimum

Interference

Triple B&C Tight

C&D Loose

Dual Tight but

moves

Triple B&C Tight

C&D Tight but

moves

Triple B&C Tight

C&D Tight

Dual Tight

Single Beehive with

1 Steel Ring OD

Plastic Damper

Dual with Steel

Damper between

Outer and Inner

Dual with 2 Steel

Ring OD Plastic

Damper

Dual_plastic

damper bewteen

outer and inner

Difference Load (%)

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Spring Life Dynamic Control Alternatives

Typical Steel OD damper Typical Steel Ribbon damper

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Oil Ports

(Exit)

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Tension Rings

(provide damping force)

Engine Oil >in<

through hydraulic

action-oil captive with

retainer.

Engine Oil >out< through

hydraulic action-sized for

volume-(hydraulic damping

and cooling needed)

Engine Oil >in<

through hydraulic

action-oil captive with

retainer.

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Thank You!

For Attending the 2012 AETC Conference

For More information please contact PAC Racing Springs www.RacingSprings.com

Special thanks to:

Kyle Kibbey

John Keteyian


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