A a safe altitude, set up slow flight and set up an climb at initial climb
speed / takeoff configuration.  Reduce power and *maintaining best glide
speed* make a 240 degree turn. (a 180 would only get you parallel to the
runway, not back on it)  Note the amount of altitude loss.  My bet is that it
will suprise you. Add a bit extra to allow for reaction time when you are not
planning for this to happen. Be prepared to land straight ahead or with only
minor deviations) if you loose an engine below this altitude when taking off.
  Coordinated turns at best rate! dont spin while trying to do this
experiment!

Nathan,

 

If one has a constant speed prop, pull it to coarse pitch if the engine is not generating any power but is still rotating.  Pitch for best glide (a dot on the AOA). Any turn should be shallow (just take a look at the AOA).  Oh, if the gear is down, forget the turn or try for instant retraction (hah!).

 

Yes, the altitude loss would surprise anyone.  My takeoff climb is not at Vx or Vy.  I like to ascend towards heaven at 135 KIAS and it will not take long to reach 700 feet AGL, the critical return altitude decision point where the gear and flaps have already been retracted. Otherwise, no more than 30 degrees left or right for the landing area scan.  I hate taking off from airports in a densely populated area.