Super Formula will try and emulate the sound of a V8 engine in its next scheduled test for its development cars at Sugo next month.
The Japanese championship has been holding tests with its two development SF19 cars before or after each race weekend so far this year as it seeks to reduce its carbon footprint and improve the quality of the race.
This week's two-day test at Autopolis on Wednesday and Thursday marked the third such test with development drivers Koudai Tsukakoshi and Hiroaki Ishiura.
So far, the focus of the tests has been trialling tyres and carbon-neutral fuel made from more sustainable sources, as well as hemp-based bodywork, and experimenting with different downforce levels.
But on Saturday at Autopolis, the boss of Super Formula promoter JRP, Yoshihisa Ueno, revealed that an engine sound experiment will be held at the next test, scheduled for the two days after the Sugo event on June 19.
Super Formula has used two-litre turbocharged inline four-cylinder engines since the 2014 season, but Toyota and Honda both supplied V8 engines from 2006-13. Prior to that, the series' spec Mugen engine was also a V8.
The Sugo test will still use the standard inline four engines, but a new exhaust pipe layout has been developed by Toyota to try and emulate the sound of a V8.
This involves creating a separate exhaust pipe for the turbo wastegate, instead of the exhaust gases from the wastegate using the main exhaust pipe.
In theory, this will double the sound produced by each individual cylinder per revolution, simulating an extra four cylinders' worth of engine noise.
However, the technical director for Super Formula's next-gen test programme, Yoji Nagai, suggested that it is unlikely that such an innovation, even if successful, will be introduced as early as next season.
Ueno confirmed that spectators will be welcome to watch the test take place at Sugo on June 20-21.