It is rumoured the new power unit boasts better performance than its 2016 predecessor, but it obviously struck consistent reliability trouble during Barcelona testing.
Red Bull team boss Horner said: “Renault has taken a big step forward with its 2017 power unit. Everything that was promised has been delivered.
“There are a few small reliability issues that need to be addressed now, but there are no deeper issues, just simple things,” he told the French magazine Auto Hebdo.
Horner’s comments indicate a much better current relationship between Red Bull and Renault, and the Red Bull chief credits that partly to his Renault counterpart Remi Taffin.
“Our relationship is going well,” Horner agrees.
“It seems that under Remi’s leadership, Renault has recovered the desire to return to the competitive position it had.”
Renault-powered Toro Rosso driver Daniil Kvyat is also expecting a good season with his French engine.
“Renault is known for its conservative beginnings, so they have to be given a little time because there has been a considerable improvement,” the Russian told Spain’s El Mundo Deportivo.