|Photo Courtesy of Team Lotus|
The system is used to increase downforce by using hot exhaust gases as part of the aerodynamic flow under the car, into the rear diffuser. Using hot air this way increases the effect of the diffuser no matter the speed of the car. However when the throttle is closed, no fuel enters the system and the air entering the diffuser is cold. This reduces the downforce available on the way into a turn and means that the car is unbalanced until the driver can get on the throttle again.
The teams have been experimenting with different engine management mappings which allow them to retard the ignition significantly. This allows them to put lots of fuel through the engine when the driver lifts of the throttle. Because of the retarded ignition, the fuel doesn't create any power but does burn on its way out of the exhaust. This means there is still hot gas exiting the exhaust and powering the diffuser, without creating any drive to the wheels. As far as the driver is concerned everything stays as it was before, except with more downforce on the way into the corner and an odd engine noise on closed throttle.
Obviously this system expends a lot of fuel on not going anywhere and this could be one of the reasons the FIA would like to ban it. Burning fuel when the throttle is shut is hardly improving the green credentials of the sport. It seems though that they may have sent out the first warnings without working out how to police the change. For now the regulation change has been delayed until after the Canadian Grand Prix when the next Technical Working Group can discuss the matter.
Red Bull are believed to have the best system currently but all the front running teams have admitted that this would affect their performance. We can only speculate how much closer it would make the racing at the moment, although it will be interesting to see the effect if and when the rule change happens.