If you're talking on AMZ, then I think it's manual. I just set the price for pre-order, and usually leave it for launch day as well at the lower price so my mail list can get on board, then I just change the price in KDP.
I will add however that I've seen limited value in pre-orders on AMZ. I've got a few for my next book, so that's nice, but they don't count towards first day sales so the impact on ranking is minimal. If you launch at a lower price without pre-order and mail your list/advertize your launch, you are likely to get more of a bump in the rankings, new and noteworthy etc.
This is NOT the case on Kobo or iBooks. They apparently count all pre-orders towards first day sales, so it may be worth trying it on those vendors. The rub of course is it is harder to get pre-orders on those sites (for me anyway).
