Red Bull lost over two months of development time due to poor correlation between its wind tunnel, CFD and the data it collected on-track, according to team boss Christian Horner.
Red Bull were expected to steal a march on rivals Mercedes and Ferrari as new aerodynamics rules were brought in for the 2017 season, however the team found themselves some way off the lead pace with its RB13.
The team have begun to turn things around gradually with its latest upgrade package, which Horner says is down to the fact their correlation was inaccurate during the pre-season and only recently have they got on top of the problem.
"I think coming into the season, we came in on the back foot really. Our tools weren't correlating with what we were seeing on the track," said Horner.
"I think predominantly it was the wind tunnel that was leading us a little bit astray. The size of the model, the size of the tyres, in the tunnel that we have, gave some spurious results.
"Previously they'd been very, very reliable in specific areas, [but] suddenly we had this divergence between track, tunnel and CFD."
Horner says that has an ongoing impact on development as the team has to play catch-up, whilst their rivals continue to develop their own cars.
"It probably cost us around two months, two-and-a-half months, in terms of where it put us back to," he said.
"Then, of course, you're working flat out to try and recoup all of that time, but it's not like all the other [teams] are standing still."
The Briton added that it wasn't until the return to Europe at the Spanish Grand Prix that they began to make positive progress.
"It took… really it was around the Melbourne time that we identified where the issue was," he explained. "It was really Barcelona by the time we started to see good progress."
