IDIOMS

flat chat

(Australia, idiomatic) At maximum capability, intensity, or speed.

Example:   We had the car going flat chat down the highway when the cops pulled us over.
1987, Tim Winton, That Eye, The Sky, page 110:
  If there was a radio we'd have it going flat-chat, boy.
1998, John Marsden, The Night is for Hunting, unnumbered page,
  I spun around yet again and took off flat chat.
2012, Chris Hammer, The River: A Journey Through the Murray-Darling Basin, page 166,
  I′m driving flat chat as I cross Green Gully, a nondescript depression in the wide flat plain of western New South Wales.