VAlve and ignition timings of internal combustion engine
- 1. IGN TIMING
- 2. IGN TIMING “TIMING OF SPARK AT THE SPARK PLUG GAP IN RELATION TO THE PISTON Position” PISTON Position AT ANY Point IN TIME IS SEEN IN TERMS OF Degree OF CRANKSHAFT Revolution
- 3. TDC TDC BDC BDC POWER EXHAUST INTAKE COMPRSSION 360/ 0 DEG 180 DEG 90 DEG 270 DEG
- 5. TDC TDC BDC BDC 10 10 10 10 10 DEG ATDC 80 DEG BBDC 10 DEG BTDC 80 DEG ABDC
- 9. IGN TIMING • IDEAL SIT – SPARK AT COMPRESSION TDC • REAL SIT – ? TDC TDC BDC BDC POWER EXHAUST INTAKE COMPRSSION
- 10. IGN TIMING CONSIDERATOINS • TIME REQ TO BURN THE FUEL COMPLETELY • TIME REQ FOR EXHAUST GASES TO RAISE THE PRESSURE
- 11. IGN TIMING CONSIDERATIONS • HAVE SPARK AT AN INSTANT WHICH GIVES MORE TIME FOR – FUEL TO BURN – BURNT GASES TO RAISE THE PRESSURE TO THE MAX AS THE PISTON REACHES TDC MAX DOWNWARD PUSH TO PISTON
- 12. LATE SPARK • SPARK AT OR ATDC – INCOMPLETE FUEL BURNING – LESS BURNT GASES PRESSURE – REDUCED DOWNWARD PUSH – MORE POWER LOSSES
- 13. ADV SPARK • SPARK BTDC – MORE TIME FOR FUEL BURNING – MORE BURNT GASES PRESSURE – MORE DOWNWARD PUSH – MAX POWER OUTPUT
- 15. OPTIMIZATION • NIETHER TOO EARLY NOR TOO LATE • VERY EARLY SPARK CAUSES DETONATION
- 17. ENGINE SPEED AND IGN TIMING CONSIDERATION MORE SPEED – LESS TIME FOR FUEL TO BURN TIMING SHOULD GRADUALLY ADV WITH THE INC IN SPEED
- 18. VALVE TIMING
- 19. VALVE TIMIING • AT WHAT INSTANT SHOULD A VALVE OPEN? • FOR HOW LONG SHOULD IT REMAIN OPEN? • MAX POWER OUTPUT CAN BE ACHIEVED FROM AN ENGINE AT DIFFERENT SPEEDS BY DIFFERENT VALVE TIMINGS
- 20. CONSIDERATIONS • PISTON SPEED IS NOT UNIFORM DURING A COMPLETE REV – DEAD AT TOP/ BOTTOM (30 – 40 DEG) – FASTEST IN THE MIDDLE • THE DEAD PDS ARE UTILIZED IN DEV OF TIMING SEQ
- 22. TDC TDC BDC BDC INTAKE OPEN INTAKE CLOSE EXHAUST OPEN EXHAUST CLOSE INTAKE COMPRESSION POWER EXHAUST
- 23. BDC TDC 28 71 DURATION 279 DEG FOR INTAKE VALVE INTAKE COMPRSSION
- 24. BDC TDC 45 78 DURATION 303 DEG FOR EXHAUST VALVE EXHAUST POWER
- 25. 45 28 TDC INTAKE OPENS EXHAUST ALREADY OPEN EXHAUST CLOSES INTAKE REMAINS OPEN 73
- 26. AT UPPER TDC • OPENING INTAKE VALVE BEFORE EXHUAST VALVE IS CLOSED – MIXTURE IS SUCKED IN DUE TO VACCUM GEN BY THE EXHUST GASES THUS INC VOL EFFICENCY – INTAKE MIXTURE COMING IN ALSO SWEEPS THE EXHUAST GASES – OVERLAP TAKES PLACE DURING ONE OF THE DEAD PDS THUS CAUSES NO EXHAUST GASES TO BE PULLED BACK IN
- 27. SPEED, VALVE TIMING AND POWER • BY INC THE VALVE DURATION AND OVERLAP ENGINE CAN BE MADE TO PRODUCE MAX POWER AT HIGHER SPEEDS • HOWEVER THE SAME ENGINE WILL RUN POOR AT LOW SPEED DUE TO TENDENCY TO PULL THE EXHAUST GASES BACK IN