An instructor pilot entered SGJ's Class D airspace accidently after he became distracted when the aircraft's engine began making a strange noise and vibrating during a student's practice maneuver.

Narrative

I departed CRG as the Certified Flight Instructor (CFI) on a training flight with a student pilot. We departed the airport and proceeded southbound climbing to 4;500 FT MSL. Once at altitude we performed all of our air work and maneuvers then turned back to the north descending 1;000 FT MSL. Announcing our position on the common frequency for the training area; we then practiced ground reference maneuvers and were aware of SGJ Class D airspace and remained clear. During 'turns around a point' the engine began to produce an alarming noise and slight vibration; I quickly began to assess the situation; checking all engine gauges and the overall condition of the engine. Meanwhile; I lost my situational awareness; and slightly strayed into SGJ's airspace without contacting them prior to. Once I realized I had accidentally crossed into the airspace; I immediately turned away from the airport; climbed; and preceded direct to CRG. A combination of not being familiar with the area and airspace; the overall distractions that occur when training student pilots; becoming focused more on the noises coming from the engine; and a loss of situational awareness all played factors into me accidentally busting SGJ's airspace. I learned a very valuable lesson as did my student. Sometimes lessons are learned the hard way and I believe this experience has made me a better pilot and flight instructor.