Toro Rosso expects the next two races in the Formula 1 season at Spa and Monza to cause "problems" for the team.
After spending the 2016 season using a year-old Ferrari engine, Toro Rosso joined up with sister team Red Bull in using Renault power for this season.
But with both teams believing the French manufacturer is still behind Mercedes and Ferrari, the high-speed Belgian and Italian Grands Prix are likely to be difficult.
While Red Bull believes it can be "reasonable" at Spa, Toro Rosso fears both races will be a struggle.
"Mid-fast and mid-slow corners are where our car is working quite well, where the engine is not the priority as it is in Canada, Austria, Baku or Silverstone," said team principal Franz Tost.
"I expect once we are in Singapore, America, hopefully also Japan we will be will be quite competitive.
"I expect problems in Spa and Monza because they have such long straights where you simply need the engine power and we all know that we are down there a little."
Tost added that he is happy with how Toro Rosso has progressed this year given that it does not have the resources to match the development rate of the top teams.
While the team's pace has fluctuated slightly over the course of the season, it ended the first part of the year before the summer break with a similar pace deficit to the front as it had when the season kicked off in Australia in March.
"We've upgraded the car, we made some progress, but we are also from this end budget limited," he said.
"We cannot come up like the top teams every race with a lot of upgrades because they have three or four times the money of us.
"We really have to calculate always what we do, how we do it, and so far, I must say we have done a reasonably good job."