Stefano Coletti put Rapax on top of a rain-hit first day of GP2 testing at Barcelona.
The Monegasque driver, who won twice for Trident in his 2011 campaign, took advantage of a drying afternoon track to set the overall best, a 1m29.868s, in the closing stages.
That was enough to edge out Felipe Nasr and 2012 Formula Renault 3.5 champion Robin Frijns, once again testing for Trident.
Frijns, who had been the first of the trio to break under the 1m30s barrier, was less than one tenth of a second back from Coletti.
James Calado finished fourth fastest overall for ART and also ended comfortably top of a wet morning session.
His best effort, while some 20s slower than the afternoon, still put him almost a second clear of a chasing pack led by Daniel de Jong and Simon Trummer.
Halfway through the morning Tom Dillmann had gone quickest for newcomer Russian Time, testing for the first time after acquiring iSport's GP2 entry.
The poor morning conditions led to three stoppages. Rio Haryanto clipped the Turn 2 barrier and Kevin Giovesi stopped at Turn 8 in the first hour of running, while simultaneous offs for Rodolfo Gonzalez and Ma Qing Hua brought the morning to a slightly premature close.
Morning session: Pos Driver Team Time Gap Laps 1. James Calado ART 1m50.928s 20 2. Daniel de Jong MP 1m51.858s + 0.930s 34 3. Simon Trummer Rapax 1m52.240s + 1.312s 27 4. Fabio Leimer Racing Engineering 1m52.316s + 1.388s 21 5. Julian Leal Racing Engineering 1m52.334s + 1.406s 24 6. Tom Dillmann Russian Time 1m52.355s + 1.427s 15 7. Daniel Abt ART 1m52.416s + 1.488s 19 8. Felipe Nasr Carlin 1m52.630s + 1.702s 19 9. Robin Frijns Trident 1m52.716s + 1.788s 15 10. Rene Binder Lazarus 1m53.097s + 2.169s 28 11. Stephane Richelmi DAMS 1m53.252s + 2.324s 25 12. Ma Qing Hua Caterham 1m53.307s + 2.379s 37 13. Johnny Cecotto Arden 1m53.383s + 2.455s 17 14. Rodolfo Gonzalez Trident 1m53.549s + 2.621s 20 15. Sergio Canamasas Caterham 1m53.613s + 2.685s 30 16. Jake Rosenzweig Addax 1m53.621s + 2.693s 33 17. Mitch Evans Arden 1m53.690s + 2.762s 28 18. Marcus Ericsson DAMS 1m53.822s + 2.894s 25 19. Adrian Quaife-Hobbs MP 1m53.957s + 3.029s 17 20. Conor Daly Hilmer 1m54.099s + 3.171s 28 21. Jolyon Palmer Carlin 1m54.641s + 3.713s 14 22. Luciano Bacheta Russian Time 1m54.948s + 4.020s 17 23. Pal Varhaug Hilmer 1m55.910s + 4.982s 20 24. Rio Haryanto Addax 1m57.604s + 6.676s 9 25. Stefano Coletti Rapax 2 26. Kevin Giovesi Lazarus 1 Afternoon session: Pos Driver Team Time Gap Laps 1. Stefano Coletti Rapax 1m29.868s 24 2. Felipe Nasr Carlin 1m29.926s + 0.058s 18 3. Robin Frijns Trident 1m29.951s + 0.083s 19 4. James Calado ART 1m30.239s + 0.371s 24 5. Johnny Cecotto Arden 1m30.323s + 0.455s 25 6. Fabio Leimer Racing Engineering 1m30.335s + 0.467s 16 7. Stephane Richelmi DAMS 1m30.350s + 0.482s 22 8. Daniel de Jong MP 1m30.487s + 0.619s 23 9. Jolyon Palmer Carlin 1m30.505s + 0.637s 23 10. Daniel Abt ART 1m30.522s + 0.654s 21 11. Kevin Giovesi Lazarus 1m30.551s + 0.683s 16 12. Mitch Evans Arden 1m30.781s + 0.913s 24 13. Simon Trummer Rapax 1m30.831s + 0.963s 29 14. Jake Rosenzweig Addax 1m31.027s + 1.159s 25 15. Sergio Canamasas Caterham 1m31.032s + 1.164s 21 16. Tom Dillmann Russian Time 1m31.035s + 1.167s 25 17. Adrian Quaife-Hobbs MP 1m31.075s + 1.207s 24 18. Marcus Ericsson DAMS 1m31.433s + 1.565s 22 19. Julian Leal Racing Engineering 1m31.520s + 1.652s 28 20. Rio Haryanto Addax 1m31.626s + 1.758s 23 21. Conor Daly Hilmer 1m32.141s + 2.273s 29 22. Rodolfo Gonzalez Trident 1m32.178s + 2.310s 23 23. Rene Binder Lazarus 1m32.586s + 2.718s 24 24. Luciano Bacheta Russian Time 1m32.712s + 2.844s 32 25. Ma Qing Hua Caterham 1m33.360s + 3.492s 26 26. Pal Varhaug Hilmer 1m34.357s + 4.489s 17