The FIA has written to all Formula 1 teams reminding them of the rules surrounding the use of exhaust gasses directed at the rear wing.

Special engine modes have previously been developed by teams which see the engine continue to produce exhaust gasses even when the driver is off the throttle.

These gasses are directed at the rear wing, providing additional downforce.

Since 2014, the FIA introduced a number of regulations in an attempt to outlaw the practice, including limitations on the exhaust size and placement, and the use of engine modes for the purpose.

However, the new technical regulations introduced last year, which saw the rear wing height reduced, has allowed teams to again exploit the practice.

“We do not accept that engine modes specifically designed to increase the exhaust flow in corners are permissible,” wrote Nikolas Tombazis, head of single-seater technical matters.

“Such (not permissible) engine modes can be either specific to a compressor-turbine by-pass system, or to flow passing through the cylinders.

“To be permissible, such flows should be the result of settings that genuinely increase the performance or reliability of the power unit, and not contrived to increase the exhaust flow.”

Teams are permitted to locate the exhaust in an ‘advantageous’ location, provided its within the limitations set out by the rules.

“Regarding the tailpipe position in relation to the rear wing and bodywork, we accept any position within the stated limits of the regulations,” Tombazis wrote.

“It is the right of any competitor to design their car in such way to have the most advantageous installation for their car’s performance, provided this installation is indeed within the limits of the regulations.”

A further discussion on exhaust design is set to take place at the next Technical Working Group meeting with a view to eliminating the practice entirely for 2019.