Hw help!

[mitchigan]

Can anyone help me with my IC engines hw? Please? My prof is horrible, never there and always sends a guest lecturer.

http://www.egr.msu.edu/ares/ME444/assig ... ssign7.doc

[timot_one]

If I had time to do your homework for you, it would be a nice exercise.  I didn't even have time to read through all the questions.  You have the books and the teacher though.  All I have is Google and inexperience.  Is there a specific question that's giving you a hard time?

[mitchigan]

If I had time to do your homework for you, it would be a nice exercise.  I didn't even have time to read through all the questions.  You have the books and the teacher though.  All I have is Google and inexperience.  Is there a specific question that's giving you a hard time?

#14. I always assumed the OHC was superior to the in the block cam, i.e. les components, friction, etc. thats even what i have down in my notes. And Tim, no I dont have the prof nor the book, its like $200 used because its an 'SAE' book and the profs never there, never answers his email. i'm going to talk to our dean about this... I'm not the only kid in class thinking like this.

[ikethegreat]

Why take the class if you can't even bother buying the book for it?  How do you expect to learn?  Seems like you're holding yourself back.

[mitchigan]

The book doesnt help... its just ramblings on about charts and pv diagrams

[timot_one]

Seems like a shitty class.  I'd be pissed if I were you.  Education is not cheap.

[stirfriedferret]

2. engine knock is the result of detonation and pre-ignition is it's own thing. they're both both forms of abnormal detonation. detonation occurs after spark plug firing and occurs the same time as propogation/ or flame travel. pre-ignition can occur anytime, but usually during the compression stroke (due to a hot spot) causing increased pressures before the power stroke.

3. this is explaining the egr. introducing exhaust gasses means that it basically fills up the cylinder with gasses that can no longer be lit or ignited.  this effectively reduces the amount of air/fuel that can be put into the chamber, resulting in less heat (due to less air/fuel being ignited).  as for the amount of gas that can be put in, i dont remember. but when i used the snap on modis, we could get the egr to about 50% before it started to bog down at idle.  if you exceed the limit, the car will not run and may even stall.

4. forgot the equation for VE. it's in my car somewhere, but that's downstairs... and im lazy and tired.

5. volumetric efficiency pretty much tells you how well your car pumps air in and out. the higher the ve, the more efficient it is.

7. oversquare = bore is larger than stroke
undersquare = stroke is larger than bore (like hondas!)

9. long skinny runners are used for an increase in velocity in lower rpms, but act as resistance in higher rpms.
   short fat runners are used for more volume in higher rpms, but dont have much velocity in lower rpms (think of the accord vs the tsx im)

12. look above

13. overhead cam results in less parts flex, therefore actual duration is closer to advertised duration. less moving parts results in less friction as well.

14. im stumped. ask them why 1940s technology would be better than year 2000's technology.

ill try to answer the others.

[stirfriedferret]

15. early intake valve closing can act as a sort of egr, recycling in the exhaust gasses by not letting them all out or sucking them back in.
     late intake valve closing ? i dunno.

oh and the second part of #7., oversquare results in more torque while undersquared results in more hp. usually. but there are other factors in it, such as rod angularity and cam lift, etc.

[stirfriedferret]

second part of #15, variable valve timing allows the vehicle to take advantage of different conditions (fuel type, air flow, etc.) by adjusting timing.  it may advance the timing for more power if the fuel type and air flow permit it. it may also retard timing if conditions arent too good and if the vehicle starts knocking.

16., i think the first hemi was in a plane? as for design the cylinder head combustion chamber is a hemisphere aka a half circle. the intake and exhaust valves are exactly opposite sides of each other and the spark plug right in the middle. the idea was for the air to flow from one side of the combustion chamber to the exact opposite side which allows for greater air flow.  the hemi also has a sort of weird valve setup. theyre sort of twisted and face weird directions to allow for the use of larger valves.

[mitchigan]

Thanks guys for all the help. I was able to get that and another report done just as my kids woke up yesterday morning... wooo. Sucks that I had to cite that crap, most of it was general knowledge.

Solns if you were curious...

http://www.egr.msu.edu/ares/ME444/assignments/soln7.doc