What I can tell you is that the road is actually open and looks very good. It’s all the way through, even the last leg from Sainshand to Zamyn udd just opened 6 days ago.
Further, in this presentation on page 17 created by an official of the road development body of Mongolia, before the construction was finished, it is mentioned that the average travel time on the road used to be 12-15 hours and should be down to 5.5-6.5 hours.
Since the road was finished 6 days ago, I would be very surprised if you would find someone with live experience however…
Credit:stackoverflow.com‘