Engine trivia II

[BUIZILLA]

OKAY, WE HAD FUN WITH THE LAST ONE, LET'S DO IT AGAIN!!

1) If a gas engine has 20* btdc of initial timing at idle, at what point in the combustion cycle does MAXIMUM cylinder PRESSURE occur?

A) at *ignition* of 20* btdc
B) TDC
C) 20* atdc
D) 20* bbdc

2) At what point in the combustion cycle does maximum piston speed occur on any given cylinder?

Bonus question:

Of the 4 valve *events* that occur in one 720* combustion cycle, which is the MOST important and why on a GASOLINE engine?

The same reward applies. Cutoff will be 12:00am March 4.

Email answers directly to be eligible for the prize.

Have fun !!

J

<small>[ March 01, 2003, 03:14 PM: Message edited by: BUIZILLA ]</small>

[Tony]

Whatever Jamie Root is gonna say. (Can you tell that my favorite engine related term is "turnkey"!)

[mattyboy]

1. a
2. c
3. b
4. d
5. yes
6. true

those are the answeres to any multiple choice true false test given in the northern hemisphere.

Matt
proud graduate of the Acme school of liberal arts and basket weaving

[BUIZILLA]

7 reply's so far...

:cool:

J

[Ranman]

Professor Plum
with the candlestick
in the bedroom

[BUIZILLA]

The winner is...

Jroot...by a mile...

Congrat's dude !!

His answers were&gt;
1) 20* ATDC
2) 70*-71* ATDC for the MOST common rod ratio, which is an EXACT reply I was looking for. I didn't state EXACTLY which engine to use as an example. He is DARN close..
3) Intake valve closing is the most important event, since that degree* number controls cylinder pressure, cranking compression and cylinder filling, for a given static volume.

Good job!

J

Roots, email me your POSTAL address for the certificate.

[boxy]

Damn engineers :D :D He may know his engines, but ask him how his plumbing is doing... :D

<small>[ March 04, 2003, 09:38 AM: Message edited by: boxy ]</small>

[BillG]

Congratulations to jroot. I have only one reservation, maximum piston speed always occurs at half the stroke length no matter what the rod ratio is. When the crank throw is at 90deg.to the center line of the cylinder. Maximum acceleration is at the top and bottom of the stroke just as the piston moves off of TDC and BDC. Just plain old Physics.
Bill G

[b.guggenmos]

I agree. Maximum piston speed has to be halfway between strokes because the piston comes to a complete stop at both ends. Also I am still having trouble with the wrist pin being last to get lubrication. Most engines squirt oil at the pin from the connecting rod cap or a drilled passage up the rod to the pin. As soon as you have oil pressure to the rod bearings you have oil going to the wrist pin by spray or pressure. My opinion is a rocker arm pivot or a valve stem if you really want to get picky is last for lubrication.. Thanks, Brian

<small>[ March 04, 2003, 07:53 PM: Message edited by: b.guggenmos ]</small>

[Rootsy]

Actually, the answer i gave is correct, you can be a geek like me :rolleyes: and do all of the oh so fun derivations and solutions if you wanna have hours of mindless fun...

the only reason i knew the answer is because i had to do my final design project on a crank-slider system for my Kinematics (dynamics taken to a higher level) course way back when. This is the ONLY class i ever received a 100% in besides PE courses...

my final project consisted partially of a 50 some odd page matlab (read that fortran) program and derivations which given user inputs solved and graphed in 1/2 degree increments all pin translations, velocities, accelerations and forces. therefore i remember it way too vividly... even after 6 years... frown

[Ralph Savarese]

Where are you getting what you say is the correct answers . Can you tell us were we can find these answers documented so that the differences of opinion can be clarified!
Ralph
Check out this automotive dictionary
www.motorera.com/dictionary/car-dic.htmph (http://www.motorera.com/dictionary/car-dic.htmph)

<small>[ March 04, 2003, 09:08 PM: Message edited by: Ralph Savarese ]</small>