When a piston moves within a Cylinder...it has 2 positions...the BDC and the TDC (bottm dead centre and top dead centre)...whatever amount of fuel can be accommodated in the cylinder between these two positions for later ignition, combustion and thrust production in one movement is normally measured in cubic centimeters (CC) so thats why a 1000 CC car is also called a 1 litre car at times and this CC is the amount of fuel displaced for one cycle thus this is also at times called DISPLACEMENT.
HP is short for horse power which is simply the unit of power...Power doesnt have a universally constant relationship with the CC of an engine though normally more CC means more power and vice versa. Despite having the same CC two engines could have different HP as explained by another poster and similarly having same HP two engines might have different CC.
The question about fuel efficiency of two engines one with more CC and less HP and one with less CC and more HP totally depends on the testing regime. The throttle applied , the terrain conditions and many other factors. If the type of driving done on both engines is exactly same in exactly same conditions...theoverall winner wud be the engine with less CC and more HP for almost all the cases. so 1000cc and 200 HP wud be more efficient.
