A spark plug fires before the gases in a cylinder are fully compressed. How will the engine be affected?

A. The gases will do less work to the piston because the gases cannot expand as much.
B. The engine will not get hot because the ratio of work to heat will increase.
C. There will be fewer pollutants as the fuel has more time to burn.
D. The engine will get better gas mileage as less fuel is burned during each cycle.

Question

A spark plug fires before the gases in a cylinder are fully compressed. How will the engine be affected?

 		A.	The gases will do less work to the piston because the gases cannot expand as much.
 		B.	The engine will not get hot because the ratio of work to heat will increase.
 		C.	There will be fewer pollutants as the fuel has more time to burn.
 		D.	The engine will get better gas mileage as less fuel is burned during each cycle.

vera_ewing · Answer

@JFraser Help please!

jfraser · Answer

the cylinder can only expand to a certain point, if the spark fires $before$ the cylinder has compressed to its maximum volume, the $change$ in volume won't be as large.... what happens to the work done if the $\Delta V$ is less than it should be?

vera_ewing · Answer

The engine will not get hot because the ratio of work to heat will increase.

jfraser · Answer

I dare you to touch any part of a car's engine after it's been on for a few hours and tell me it's not hot

vera_ewing · Answer

Oops, the gases will do less work to the piston because the gases cannot expand as much?

jfraser · Answer

the formula for work done by a gas is

$$ Work = P*\Delta V$$
if the $\Delta V$ is too small, the work done is less

vera_ewing · Answer

Okay, so the answer is A?

jfraser · Answer

it is

vera_ewing · Answer

Thanks so much! :)