Help - Can Figure Answer to Q.

[Miguel.]

Can anyone shed light on below answer;

Q. During a compression stroke in a four cycle engine. What describes best the position of piston and valves?

Ans 1. Piston rising to expel burnt gasses through exhaust valve
Ans 2. Inlet valve is open and sparking plug is parking to ignite air / fuel mixture
Ans 3. Piston falling and valve opens to pull in new air fuel mixture
Ans 4. Inlet and exhaust valves are used and piston is opening/gasing

Which of the above best describes??? :S

Many Thanks!

[Shunter]

Err, none of them really.

During the compression stroke, both valves are closed and the piston is rising to compress the mixture.

Ans 1. Piston rising to expel burnt gasses through exhaust valve
- This is the exhaust stroke, so it's not this one.
Ans 2. Inlet valve is open and sparking plug is parking to ignite air / fuel mixture
- This answer is garbage. If the plug is sparking to ignite the mixture the inlet valve should be shut.
Ans 3. Piston falling and valve opens to pull in new air fuel mixture
- This is the inlet stroke. Inlet valve should be open, exhaust shut.
Ans 4. Inlet and exhaust valves are used and piston is opening/gasing
- Whilst not correct, this is the least wrong answer. I presume it meant to say "valves are closed". The piston should be rising. Pistons don't open, and pistons don't gas.

[Mercenary Pilot]

I'm guessing that it's one of those "lost in translation" questions from a JAA state other than the UK. :ugh:

http://upload.wikimedia.org/wikipedia/commons/a/a6/4-Stroke-Engine.gif

1/ Induction (Suck)

2/ Compression (Squeeze)

3/ Power (Bang)

4/ Exhaust (Blow)

[acuba 290]

there is a lot of "lost in translation" questions home-made in UK also, a lot of them is HPL ;) :ugh:

[Mercenary Pilot]

Nah, that's called psychobabble or waffle. :uhoh:

;)