The team is targeting fifth place in the constructors' championship, finishing ahead of Mercedes.
Kalternborn told Autosport: "Before the season got underway we wanted to significantly improve our position in the World Championship.
"After our strong start to the season, many people were predicting the wheels would come off for us, so to speak, as the season progressed.
"The reality, though, is we're getting stronger all the time, and I'm anticipating that we'll continue to deliver good performances through the final third of the season."
The F1 season continues in Singapore on September 23.