1. Ethanol: the Need for pHe Controls in the New Millenium
Robert Halsall
General Motors R&D Center
June 21, 1999

2. Outline Acidic ethanol: Why controls are needed
Effects of ethanol quality on durability
High concentration blends
Ed10 blends (Gasohol)
Latest GM survey data: Congratulations to the ethanol industry on their progress
Summary & Conclusions

3. Acidic Ethanol Problem: why controls are needed
GM has found that acidic ethanol fuels can cause serious problems with engines, pumps, injectors and other components, regardless of manufacturer
Cause: trace amounts of sulfuric acid or sulfuric acid reaction products
Southwest Research also reported acidic ethanols wear out fuel pumps
Proposed sulfuric acid reactant product in ethanol as cause

4. GM Investigations of Effects of pHe on Durability
Ed85 Tests
Fuel pump bench tests
Fuel injector bench tests
Engine cylinder bore wear dynamometer tests
Cylinder bore bench tests
Vehicle tests
E10 Tests

5. Manufacturer #1 Fuel Pump Performance in Ed85
pHe=4
Pump RPM/10
Pump Pressure
Injection Pressure
Fuel Flow Rate

6. Manufacturer #2 Fuel Pump Performance in Ed85
pHe=4
Pump RPM/10
Injection Pressure
Pump Pressure
Fuel Flow Rate

7. Fuel Pump Performance in Ed85
pHe=6
Pump RPM/10
Pump Pressure
Injection Pressure
Fuel Flow Rate

8. Fuel Pump Performance in Ed85
pHe=7

9. Fuel Pump Performance in Ed85
pHe=10
Pump RPM/10
Pump Pressure
Injection Pressure
Fuel Flow Rate

10. Summary of pHe Effects on Fuel Pumps
Acidic fuels <6 pHe greatly shorten fuel pump life
Basic fuels (pHe 10) damage some plastics
Other effects??
Neutral fuel (pHe 7) maximizes fuel pump life

11. Effect of Neutralizing Ed85 Fuels with Sodium Hydroxide on Conductivity
1000
900
800
700
600
Conductivity
500
S/m
400
Sodium
Hydroxide Addition
300
200
100 2 4 6 8 10
pHe

12. Engine Cylinder Bore Wear Engine Dyno Tests
Designed experiment to look at various factors (oil, ring, A/F, injector, block hardness, fuel pHe)
GM standard durability test, high load, high speed using 2.2L engine
cylinder bore wear a problem with Ed85
excessive wear also seen in durability test vehicle

13. Effect of Ethanol pHe on Engine Durability at High Speed, High Load Engine Dyno Durability Test

14. Effect of pHe on Injector Durability in Ed85 Fuels

15. Manufacturer #1

16. Manufacturer #2 pHe= 3

17. Photographs of Typical Injector Wear at 7.1 and 5.9 pHe

18. Guide Wear at 7.1

19. Guide Wear at 5.9

20. Effect of pHe on Injector Durability in Gasohol (Ed10) Fuels

21. Manufacturer #1

22. Manufacturer #2

23. Summary of Effects of low pHe Ethanol on Injectors run in Alcohol Blends (Ed10 or Ed85)
Neutral blends (7.1 pHe)
Internal wear negligible
Acidic blends
Serious injector calibration shifts
Heavy corrosive wear of bearing, seat and valve surfaces
Wear increases with decreasing pHe
Breakpoint for high wear and calibration shifts between pHe 6 & 7 in Ed85
Breakpoint probably between 4 and 6 in Ed10

24. Distribution of Ethanol pHe GM Survey Data

25. Effect of DCI-11 on pHe of Fuel Ethanol (treat rate 90 mg/L-fuel)

26. Summary & Conclusions
Engine and fuel system component life is maximized in neutral alcohol blends
Slightly acidic Ed85 fuels (pHe 5.9) causes serious fuel injector damage
Very high pHe fuel (10) can damage some fuel system plastics and will increase corrosion rates substantially due to high conductivity
We propose adding a pHe standard to ASTM D4806 and D5798 to control ethanol blends to pHe 7 to 9
Improvements in pHe will likely benefit all vehicles and customers because effects extend to gasohol blends (Ed10s)

27. Backup slides

28. Crossplot of pHe and Acidity

29. Seat Wear at 7.1

30. Seat Wear at 5.9

31. Dependence of Engine Wear In 1997 FFV Field Vehicle Test Fleet on pHe