After struggling with their Renault power unit last season, Toro Rosso technical director James Key hopes the team's change to Ferrari will bring better results.
Red Bull's sister Formula One team moved away from Renault at the end of 2015 in an attempt to boost their points return, switching back to Ferrari, who they had worked with for six years from 2007.
Max Verstappen and Carlos Sainz secured 67 points for Toro Rosso throughout last season, but 11 retirements between them cost them the chance of challenging Lotus and Force India in the constructors' championship.
Both drivers have been retained for 2016 and Key hopes their new engines can help them battle higher up the grid.
"Our predictions move around quite a bit as more information comes to light," Key told Autosport.
"One second is a massive step from one year to the next. You'd normally expect to have quite a bit less than that.
"If you transfer all the aero performance we've found, that will be a reasonable step.
"The engine is a good step, but we need to see on track first how everything is working and whether we are able to make the most of that.
"We'll have to see what the performance is, but if the best predictions are right then it could be as much as that [a second improvement]."