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Midterm Review

Understand the distinctions between 2-stroke and 4-stroke engine operations, focusing on piston port timing and valve timing. Learn how diesel engines offer higher thermal efficiency compared to gasoline engines. Explore the nuances of diesel and gasoline injection methods.

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Midterm Review

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  1. Midterm Review R. Bortignon

  2. Piston port timing VS 4 stroke valve timing 4 stroke engine piston port engine

  3. 2 Stroke Diesel Engines 1 Compression Power Exhaust Scavenging

  4. 2 Stroke Diesels VS 2 Stroke Gas Engines

  5. Diesel Engine Operation • diesel’s have higher thermal efficiency than gasoline engines • in a diesel, thermal efficiency goes up with increased engine load

  6. Main difference between diesel & gasoline injection?

  7. Gasoline Injection • maintains a nearly constant 14.7:1 air-fuel ratio • the volume of air & fuel is varied to change engine power output • during heavy engine loads (low manifold vacuum) more air/fuel is delivered to the cylinders • during light engine loads (higher manifold vacuum) less air/fuel is fed to the cylinders

  8. Reminders… • drop off completed mechanical labs in my box • fill in “engine info” sheet on the last engine you worked on • fuel must be drained out of fuel tanks • engine stand brackets need to be removed • Engine Assessment Guide due this week! • should be generic, not manufacturer specific • should be applicable to both 2 or 4 stroke • 1 assessment guide handed in per team of 2 • “Engines of Unknown Condition” activities • moving away from lab based activity to examining & evaluating engine condition • use your assessment guide on the engine • bringing your own engine in? Peter or I must see it at least twice – once when it comes in, once when it leaves • engine must run – you will use the machine as it was intended • Peter, James, Phil & I will keep daily notes on your progress

  9. Reminders… • 100 Hour Project • do NOT dump off parts in the auto shop or its parking compound • consult with me 1st for large items that need to be left in the shop • motorcycles, riding mowers should be pressure washed 1st • all fuel should be drained & dumped into the black barrel outside the shop labeled “Stale Gas” • you are welcome to dismantle, clean & examine/modify parts any time I am in the shop & you have free time

  10. Scrap Metal Bin • any & all scrap metals should be placed in here… • large pieces need to be cut up or properly stacked so volume is maximized • bin is NOT a garbage can!

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