Trading FE for acceleration and a convincing bumper sticker
 

Seen the little Fiat 500 with the Lambo engine, and wondered if that could be topped?
You bet!

https://i.chzbgr.com/maxW500/7376528128/h296B10F0/

Think of the bumper stickers you could put on that:
"If you can read this, err..."
"My other car is well done"
etc.

The sad thing is - practical Brayton cycle engines are more efficient than gasoline or Diesel engines. This particular one, though, probably is being used solely for thrust instead of shaft work. Of course, dumping all that fuel to create the pretty flame is probably working against FE, too.

"No... It doesn't have a flux capacitor"