Ross Brawn on Friday confirmed reports the struggling HRT team is renting one of the wind tunnels at Mercedes' Brackley headquarters.
Hispania boss Colin Kolles refused to comment, but Mercedes chief Brawn admitted HRT "is renting some time in the tunnel".
"We have two wind tunnels. Because of the FOTA constraint regulations we only use one of them for our own Formula One programme so the other one is let out to customers," he explained at Sepang.
After the Melbourne calamity, HRT's new F111 car finally got some laps on the board on Friday, despite some reliability issues.
"It's good news that Narain was under the 107 per cent," said Kolles, while Indian Karthikeyan's teammate Tonio Liuzzi was several tenths slower.