Fiery exhaust overrun has been spotted on cars throughout the spate of shakedowns and tests in recent weeks.
Once a common sight in Supercars, flames all but disappeared when the series switched to E85 fuel in 2009, the exception being licks of blue during night time running.
The return of flames visible in daylight with these new Gen3 cars, running brand new-spec V8 motors, was evident when the cars were first testing using the old-spec E85 fuel.
The bright orange flames then continued to be prominent at Wednesday's test at Sydney Motorsport Park, where the field switched to the new E75 biofuel.
The welcome return of the spectacle prompted questions up and down pitlane as to what brought the flames back, with a number of theories from team bosses and engine builders.
It appears the matter is a combination of factors, including valve overlap and mapping, the shorter exhaust and the move to a single throttle body, while the reduction in ethanol on the new fuel blend could be contributing to the deeper orange colour.
"I think it's a mapping thing," Team 18 team manager Bruin Beasley told Motorsport.com. "The fuel blend might affect it, but it's part of the overall engine package.
"It's good for spectators, isn't it? It will be part of the show again now. It makes the cars look great."
Erebus CEO Barry Ryan said the more modern design of the new motors was the likeliest suspect for unburnt fuel.
"I've been trying to think of a theory," he said. "It could be that the inlet is so much smaller – we've only got one inlet now and we used to have eight.
"Maybe the engine can't breathe and let the gasses out, whether it's exhaust or out the inlet. And that gives the explosion inside the engine, because the engine doesn't have the breathing capacity it used to have.
"That's one thing I've thought of. There's more fuel build up in the manifold rather than the airbox. And it's an orange flame, which is strange for ethanol.
"But it's cool."
