Nick Heidfeld’s Renault R31 chassis used at the Hungarian Grand Prix is a complete ‘write-off’ according to the team.
A cracked-exhaust, the result of a new engine map setting which caused intense heat build-up, combined with a prolonged pit-stop meant the fuel and heat build-up led to the fire.
Renault technical director James Allison explained the scenario which led to the dramatic retirement and explosion which injured a marshall.
“As with most accidents, several incidents combined to cause the fire that Nick suffered in Hungary,” said Allison. “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.”
Allison also revealed that the explosion, which many speculated to be the KERS batteries, was in fact caused by an air bottle.
“This was caused by the air bottle which supplies the air valves in the engine. It has overheated in the fire and failed,” he added.
With the chassis being written-off, Renault are keen to avoid a repeat of such an accident and, along with an FIA report, changes will be made to ensure it doesn’t happen again.
“The incident was highly undesirable, as 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.”
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