The left outboard does appear to be larger than the rest in the above image but I'll say it is just a normal engine with its maintenance hatches opened.  Normally when you mount a new engine on a quad-engine test bed, it will be installed on one of the inboard mounts as this will induce less yawing moment if that engine flamed out.
			
			 
				 
 
		 
	



 
 
		

 
 
		
 
 
		
