Engine Friction Reduction Through Surface Finish and Coatings

A. Gangopadhyay, D.G. McWatt, R.J. Zdrodowski

Ford Research and Advanced Engineering Dearborn, MI

DEER Conference

October 19, 2012

Contents

• Introduction • System and Subsystem Description • Tribological Conditions • Valvetrain Friction Reduction • Piston Ring Friction Reduction • Summary

System and Subsystem Description

Valvetrain

Ring / Bore contact

Frictional Losses in Engine

Valvetrain19%

Main Bearings

18%

C.R Bearings14%

Accessories12%

Piston Skirt11%

Piston Rings26%

Fric

tion

Coe

ffic

ient

(Viscosity x Speed) / Load

Direct Acting Valvetrain

Piston Rings

Con Rod and Main Bearings

Stribeck Curve

Standard Bucket – 0.10 µm Ra Polished Bucket – 0.04 µm Ra

DLC-Coated Bucket – 0.04 µm Ra Phosphated Bucket – 1.7 µm Ra

Different Bucket Tappet Surfaces in Valvetrain

Cylinder head Torque Meter Flywheel Motor

Coolant line

Motored Friction Measurements

1 piece bucket

Friction Results Mn Phos 5 - 14% improvement

Polished & DLC 17- 25% improvement

Wear Data

Piston Ring / Cylinder Bore Friction • Factors affecting friction

– Piston Ring • Ring coating (Mo-NiCr, PVD,

DLC, nitrided) • Ring tension • Ring design (barrel faced, 2pc vs. 3

pc oil control ring)

– Cylinder bore • Bore finish • Bore coating to replace liners • Bore cylindricity • Honing patterns

Lab bench tests

Single cylinder tests

Engine tests

Testing Sequence

CrN Coating Nitrided layer

Mo-NiCr Coating DLC Coating

Different Piston Ring Coatings Evaluated

Friction Results

Bore Wear

Ring Wear

PVD CrN ring/ PTWA 4130 (Test #30)

0

4

8

12

16

20

0 0.3 0.6 0.9 1.2

Ring width (mm)B

arre

l edg

e (m

icro

ns) 0 hr

20 hr60 hr80 hr100 hr

PVD CrN Ring

NPR DLC-coated ring/ 4130 PTWA(Test #44)

0

4

8

12

16

20

0 0.3 0.6 0.9 1.2

Ring width (mm)

Bar

rel e

dge

(mic

rons

)0 hr20 hr40 hr100 hr

DLC Ring

Moly-filled ring/ CI liner(Test #20)

0

4

8

12

16

20

0 0.3 0.6 0.9 1.2Ring width (mm)

Bar

rel e

dge

(mic

rons

)

40 h60 h80 h100 h

Mo-NiCr Ring

Next Steps • Further opportunities exist with advanced

lubricant technologies • DOE awarded a grant to Ford to explore

polyalkylene glycol base lubricants for engine friction reduction

Summary – Polished buckets showed significant friction

reduction in valvetrain application – DLC coating on piston ring offered some

friction benefit under boundary lubrication condition

– Improved surface finish on piston rings also offered friction reduction

– Thin film coatings showed lower bore wear and coatings appeared to be quite durable

– Opportunities exist for friction reduction with advanced material technologies