Renault believe major changes to their car will take them closer to Ferrari at Sunday's San Marino Grand Prix.
Renault have made a solid start to the season
The team will be racing at Italy's Imola circuit with a more powerful engine and revised aerodynamics.
Renault's Spanish driver Fernando Alonso said: "I think we can be pretty optimistic going to Imola."
Sources suggest Renault's engines will have an extra 30bhp, leaving them 50 behind dominant world champions Ferrari and the BMW Williams team.
The French team overtook Williams for second place in the constructors' title race when both their cars scored points for the third straight race in Bahrain.
Only Ferrari, 29 points clear at the top, and Renault have scored with both cars at every race so far this season.
But Alonso said Renault had under-performed so far, apart from in Australia where he finished third behind the Ferraris.
"We haven't performed to our full potential so far, and to
be able to say that when the team is second in the championship is very positive," he said.
Alonso's Italian team-mate Jarno Trulli said he had noticed the improvements in testing.
"There is more power, better torque and overall [the engine] is more driveable," he said.
"We also have some chassis developments - it is harder for a driver to feel those small steps in aero performance but the stopwatch has confirmed the wind tunnel readings in testing. It is definitely a step forwards."
Renault's chassis technical director Bob Bell said the
manufacturer expected a sizeable performance boost at the first race of the European season.
"Both drivers felt the developments represented a good step forward in testing and we expect to see a combined improvement of around four tenths of a second per lap at this circuit," he said.
"We certainly hope that it will help us begin to close the
gap to Ferrari, although of course nobody is standing still and we cannot predict what steps forward our competitors might have made.
"But the new package will bring a consistent performance
boost throughout the weekend. If we qualify in a sensible
position on the grid, around the second or third row, podium positions are definitely within our reach."
Alonso and Trulli are level on 11 points in the drivers' championship.