SHANGHAI, China - Red Bull Formula 1 driver Daniel Ricciardo has admitted he is "surprised" Lotus is still struggling with its Renault engine.Lotus driver Romain Grosjean slammed the situation as "not acceptable" after both himself and team mate Pastor Maldonado struggled to driver the E22 amid "power unit-related" issues.'SO MANY PROBLEMS'Ricciardo, however, said he is "surprised" to hear the extent of Lotus' ongoing troubles: "It's not very reassuring to see another Renault powered team encounter such difficulties. "We also had a few problems with the V6 turbo in the tests, but nothing too serious. While we can make further progress on reliability I am surprised that they (Lotus) is still facing so many problems." Renault's chief engineer Remi Taffin said: "While we know that the others are still ahead, we have made some good progress in the last two races."At the test in Bahrain we tested several new software modes that will see us closer to the limits of the power unit than before." Stay with Wheels24 for the 2014 China F1 GP weekend.