Midterm ReviewMidterm Review

R. BortignonR. Bortignon

2

3

4

Piston port timing VS 4 stroke valve timingPiston port timing VS 4 stroke valve timing

4 stroke engine4 stroke engine

piston port enginepiston port engine

5

2 Stroke Diesel Engines2 Stroke Diesel Engines

Compression Power

Exhaust Scavenging

1

6

2 Stroke Diesels VS 2 Stroke Gas Engines2 Stroke Diesels VS 2 Stroke Gas Engines

7

Diesel Engine OperationDiesel Engine Operation

• diesel’s have higher thermal efficiency than gasoline enginesdiesel’s have higher thermal efficiency than gasoline engines• in a diesel, thermal efficiency goes up with increased engine load in a diesel, thermal efficiency goes up with increased engine load

8

Main difference between diesel & gasoline injection?Main difference between diesel & gasoline injection?

9

Gasoline InjectionGasoline Injection

• maintains a nearly constant 14.7:1 air-fuel ratiomaintains a nearly constant 14.7:1 air-fuel ratio

• the volume of air & fuel is varied to change engine power the volume of air & fuel is varied to change engine power outputoutput

• during heavy engine loads (low manifold vacuum) more during heavy engine loads (low manifold vacuum) more air/fuel is delivered to the cylindersair/fuel is delivered to the cylinders

• during light engine loads (higher manifold vacuum) less during light engine loads (higher manifold vacuum) less air/fuel is fed to the cylindersair/fuel is fed to the cylinders

10

Reminders…Reminders…

• drop off completed mechanical labs in my boxdrop off completed mechanical labs in my box

• fill in “engine info” sheet on the last engine you worked onfill in “engine info” sheet on the last engine you worked on

• fuel must be drained out of fuel tanksfuel must be drained out of fuel tanks

• engine stand brackets need to be removedengine stand brackets need to be removed

• Engine Assessment Guide due this week!Engine Assessment Guide due this week! should be generic, not manufacturer specificshould be generic, not manufacturer specific should be applicable to both 2 or 4 strokeshould be applicable to both 2 or 4 stroke 1 assessment guide handed in per team of 21 assessment guide handed in per team of 2

• ““Engines of Unknown Condition” activitiesEngines of Unknown Condition” activities moving away from lab based activity to examining & evaluating moving away from lab based activity to examining & evaluating

engine conditionengine condition use your assessment guide on the engineuse your assessment guide on the engine bringing your own engine in? Peter or I must see it at least twice – bringing your own engine in? Peter or I must see it at least twice –

once when it comes in, once when it leavesonce when it comes in, once when it leaves engine must run – you will use the machine as it was intendedengine must run – you will use the machine as it was intended Peter, James, Phil & I will keep daily notes on your progressPeter, James, Phil & I will keep daily notes on your progress

11

Reminders…Reminders…• 100 Hour Project100 Hour Project

do NOT dump off parts in the auto shop or its parking compounddo NOT dump off parts in the auto shop or its parking compound consult with me 1consult with me 1stst for large items that need to be left in the shop for large items that need to be left in the shop motorcycles, riding mowers should be pressure washed 1motorcycles, riding mowers should be pressure washed 1stst

all fuel should be drained & dumped into the black barrel outside all fuel should be drained & dumped into the black barrel outside the shop labeled “Stale Gas”the shop labeled “Stale Gas”

you are welcome to dismantle, clean & examine/modify parts any you are welcome to dismantle, clean & examine/modify parts any time I am in the shop & you have free time time I am in the shop & you have free time

12

Scrap Metal BinScrap Metal Bin

• any & all scrap metals should be placed in here…any & all scrap metals should be placed in here…

• large pieces need to be cut up or properly stacked so volume large pieces need to be cut up or properly stacked so volume is maximizedis maximized

• bin is NOT a garbage can!bin is NOT a garbage can!