Boy!  Have I ever missed something.  This was the question,  
	
		
			
			
				Can I convert a typical basement sewer drain (4 inch PVC)
			
		
 
	 
 No mention of a wye  except in the title  and not tied back to the  question.  
Milo saw a tie in and Bobsleder  answered back.  Now we're talking about vertical or horizontal wyes whit both ends of the pipes fixed.
I have a few  questions,
1-  What ever happened to the floor drain you were going to convert to a toilet?
2-  Milo came out about a wye.  What did he see that I missed?  
3-   What's with the wye?  Did you now decide to follow code and vent the toilet?  
Inquiring minds want to know!  Cheers,   Tom