Heidfeld's R31-04 chassis written off in fire

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Lotus Renault's technical director James Allison explains a little bit more about the fire that required Nick Heidfeld to abandon the Hungarian GP. The car caught fire on the left hand side when exiting the pitlane after a lenghty pitstop.

Four days after the incident on Nick’s car, has the team identified the reason why it caught fire after the pitstop?
The fire around the left hand exhaust, located ahead of the sidepod entry on the Lotus Renault R31} was partially caused by a new engine mapping the team was running.

James Allison: "As with most accidents, several incidents combined to cause the fire that Nick suffered in Hungary. First of all, we ran a slightly different engine mapping strategy in qualifying, which produced hotter than normal exhausts. We believe that this elevated temperature and caused a preliminary crack in the exhaust pipe. We presume that the crack then propagated during the laps to the pitstop - this was not evident to us as we believe that the failure occurred upstream of the place where we have a temperature sensor."

"We believe that Nick then came in with a partially failed exhaust. This pitstop took longer than normal, the engine was left at high rpm for 6.3 sec, waiting for the tyre change to be completed. Under these conditions, a lot of excess fuel always ends up in the exhausts and their temperature rises at around 100°C/sec. This temperature rise was enough to finish off the partially failed pipe and to start a moderate fire under the bodywork."

Additionally, while the car stopped and after Nick jumped out of the cockpit, there was a minor explosion on the left hand side of the cockpit.

"This was caused by the air bottle which supplies the air valves in the engine. It has overheated in the fire and failed."

The incident was in fact such that the chassis cannot be repaired anymore, and that the entire carbon fibre tub needs to be written off.

"It has caused us to write off a chassis. We will take steps prior to the next race to reduce the likelihood of a further fire and to ensure that the air bottle cannot overheat. We are in touch with the FIA both to provide them with a full report of the incident and also to explain to them the actions we are taking to prevent a reoccurrence."

This effectively puts an early end to the career of chassis R31-04.