High Ethanol Fuel Endurance Advanced Engineering Project

1
High Ethanol Fuel Endurance Advanced Engineering
Project

• A study of the effects of running 15 ethanol
  concentration in current production 4-stroke
  engines and legacy 2-stroke engines.
• Prepared By
• Dave Hilbert

2
Overview

• This project is a cooperative effort to assess
  the feasibility of increasing the allowable
  ethanol concentration in gasoline above the
  current legal limit of 10 for use in marine
  engines.
• Objectives of this project
• Run 300 hours of wide-open throttle endurance on
  3 engine families and measure emissions at 0,
  150, and 300 hours.
• 9.9HP 4-stroke carbureted, 200HP 2.5L 2-stroke
  EFI (represents legacy product) and 300HP L6SC
  Verado engines were chosen.
• Two engines from each family
• Test engine operated on E15
• Control engine run on pure gasoline

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Test Engine Specifications
4
Results Summary

• Verado
• Initial E15 engine generated HCNOx emissions in
  excess of FEL when operated on E15 fuel.
• E15 engine failed exhaust valves. Metlab
  analysis showed excessive metal temperatures
  caused a reduction in fatigue strength.
• F9.9HP
• The E15 engine on E15 fuel showed high HC
  variability at the post-endurance emissions
  testing. It is believed that this engine was
  misfiring at idle due to the lean operation.
• The E15 engine showed evidence of hotter metal
  temperatures due to carbon deposits, etc.
• The E15 engine showed signs of gasket
  deterioration on the fuel pump.
• 200HP EFI 2.5L 2 Stroke
• E15 engine showed no difference in emission
  deterioration.
• E15 engine failed the rod bearing. Root cause is
  indeterminate due to the degree of damage.
• How does ethanol affect oil dispersion in two
  stroke engines?
• Other than the bearing failure, the end of test
  teardown and inspection did not show any
  significant difference between the 2 engines

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Results Summary-Continued

• 4.3L V6 ECT Mercruiser
• Two emissions tests were performed on a 4.3L
  catalyzed sterndrive engine to compare the E0
  fuel and the E15 fuel. No durability testing was
  completed on the 4.3L engine with E15 fuel.
• This testing was not part of the contract, but
  was performed due to the fact that the E15 test
  fuel and a catalyzed engine were readily
  available on the dyno. Also, it compliments the
  testing on a 4.3L carbureted engine done by Volvo
  Penta.
• EGT increased 20C and catalyst temperatures
  increased 32C at Mode 1 (WOT).
• Valvetrain durability and catalyst system
  deterioration concerns.
• Fuel consumption increased by 5 (mass-based
  fuel flow) in closed loop operation.
• Aside from HC and CO reductions at Mode 1 (open
  loop), the E15 fuel afforded no real benefit to
  reduced emissions overall.
• NOx increased at Mode 1, but not as much as HC
  decreased for a slight overall reduction.
• HC, NOx and CO in closed loop operation are
  essentially unchanged between the 2 fuels.
• Overall
• The CO emissions were lower on all engines with
  E15 fuel due to leaner running (as would be
  expected).
• Fuel analysis showed the E15 fuel that was used
  in testing was in line with expectations.

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Conclusions and Recommendations Summary

• Despite the limited scope of project several
  significant issues were discovered.
• Durability Failures
• Emissions Issues (elevated NOx, HC variability)
• Run Quality due to Lean Operation
• More testing is necessary to understand effects
  on
• Driveability- Ex. cold and hot start, transient
  accel/decel, boiloff, etc.
• Oil dispersion in 2 stroke engines
• Storage (phase separation, corrosion, etc.)
• Test program was a cursory look at the effects of
  E15.
• Sample size was insufficient to have statistical
  significance.
• WOT operation only-masks effects of true customer
  duty cycle

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Fuel Comparison
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Fuel Comparison
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F9.9HP 4-Stroke Emissions

• Variability on E15 Engine is a concern.
• E15 fuel-zero hour and EEE-E0 fuel 150 hour
  checks are likely due to run-to-run variability.
• E15 fuel-300 hour variability is due primarily
  from Mode 5 (idle) HC emissions.
• Trends on EEE-E0 fuel are consistent between the
  2 engines.

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F9.9HP 4-Stroke Emissions

• Both engines had a tendency to run leaner at
  Modes 4 and 5 with increasing endurance time.
• The combination of the inherent leaner operation
  and the E15 fuel was enough to cause
  misfires/poor combustion at idle.
• The misfires caused the HC emissions to increase
  and become highly variable.

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F9.9HP 4-Stroke Emissions

• The fact that the E15 fuel emissions tests show
  that HC emissions increase with leaner mixtures
  supports the misfire theory.
• The graph below shows HC vs. equivalence ratio at
  idle for every emissions test performed on engine
  0R352904, which is the E15 engine.
• All E15 fuel emissions tests are shown in red
• All EEE-E0 fuel emissions test are shown in blue

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F9.9HP 4-Stroke Teardown and Inspection

• More carbon deposits on intake valves of E15
  engine.

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F9.9HP 4-Stroke Teardown and Inspection

• More carbon deposits on intake port of E15 engine.

E15
E0
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F9.9HP 4-Stroke Teardown and Inspection

• More carbon deposits on piston undercrown and
  rods of E15 engine.

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F9.9HP 4-Stroke Teardown and Inspection

• The gasket showed signs of deterioration on the
  E15 engine compared with the E0 engine.
• The gasket on the E15 engine had a pronounced
  ridge formed in the area that hinges when the
  check valve is in operation
• The E15 gasket material in the area that seals
  the check valve also had signs of wear that were
  more advanced than the E0 gasket.

E15
E0
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F9.9HP 4-Stroke Teardown and Inspection

• Material transfer from gasket to diaphragm in
  mechanical fuel pump.

E15
E0

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Verado Testing

• Summary / Review
• Verado E15 Engine
• Initial emissions tests on E15 fuel generated
  HCNOx values in excess of the FEL set for this
  engine.
• Three-run average on E15 fuel HCNOx 25.6
  g/kw-hr
• FEL set to 22.0 g/kw-hr
• E15 engine failed the exhaust valves.
• High cycle fatigue due to elevated temperatures

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Verado E15 Valve Failure Investigation
Cylinder 3 Bottom Valve
Cylinder 3 Top Valve
Cylinder 6 Top Valve
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Verado E15 Valve Failure Investigation
Cylinder 3 Bottom Valve
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Verado E15 Valve Failure Investigation

• The failed valves were checked for hardness and
  the values were low.
• Valves from other E0 engines w/o failed valves
  were measured and the hardness values were within
  expected values.
• Brand new valves were also measured for
  comparison.

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Verado E15 Valve Failure Investigation

• The new valves that were hardness checked were
  then oven-aged for 24 hours and the hardness was
  checked again.
• A simple linear interpolation would indicate the
  E0 valve temperature was around 780C and the E15
  valve temperature was approx. 890C or higher.
• The measured change in exhaust gas temperature
  was only 25-30C.

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200HP EFI 2.5L Two-Stroke Testing

• There was more variability in HCNOx on the E0
  engine than any of the changes on the E15 engine.
• The trend of CO emissions change vs. endurance
  time was similar between the 2 engines.
• The rod bearing failure on the E15 engine
  prevented completing the testing.
• Due to the extensive damage, the cause of the
  bearing failure could not be definitively
  determined.
• Assembly error causing a step at the rod / cap
  interface?
• If so, why did it run 250 hours of WOT?
• What effects would the ethanol have on oil
  dispersion?

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200HP EFI 2.5L Two-Stroke Emissions
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200HP EFI E15 Engine-Bearing Failure

• Root cause of bearing failure is unknown.
• 283 total engine hours, 256 WOT endurance hours
• No rollers were recovered.

Remaining Pieces from Cyl 3 Rod Bearing Cage
Undamaged Bearing
Undamaged Rod Rod from Cyl 3
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Additional Testing-4.3L V6 ECT Fuel Comparison

• Increase in EGT of 20C, increase in catalyst
  temperature of 32C at Mode 1.
• No appreciable difference in emissions during
  closed loop operation.
• Changes in HC and CO at Mode 1 are expected due
  to lean operation.
• The increase in catalyst temperature at WOT will
  cause more rapid deterioration of the catalyst
  system leading to higher exhaust emissions over
  the lifetime of the engine.
• Increase in fuel consumption (mass basis) of 5
  in closed-loop operation.