Heidfield explosion: why did it happen?

You will all remember during the Hungarian Grand Prix the mysterious explosion from the left side pod of Heidfields car, well the reason why has been announced.

(c) Octane Photographic

GP Update did a lengthy analysis of the incident, and here is a summary:

Renault's technical director James Allison revealed it was several accidents combined which caused the fire and subsequent explosion. He began by explaining that the team chose a different engine map for qualifying which produced hotter exhaust gas than normal. This higher temperature of exhaust gas caused a crack to develop on the exhaust pipe. This crack then increased in size as the race went on, until the pit stop.

The Renault Lotus GP team think that the exhaust was partially broken when Nick came into the pits, and the stop took longer than it was planned to go on for. Nick revved his engine for 6.3 seconds as the tyres went on. This was because the tyres took longer to be put on the car. This high revving of the engine at a standstill caused some fuel to go into the exhaust, which then caught fire with the higher temperatures due to the different engine map strategy. The higher temperatures caused the exhaust to break completely, and cause a fire underneath the bodywork of the car. 

The explosion later on was caused by a failed and overheating air canister which had overheated in the heat from the fire, and burst causing the explosion. The canister itself would be used to supply the engine's pneumatic valve system.

Overall the chassis is a right off leaving the team to do a lengthy rebuild for Belgium. Lucky they have 3 weeks to do it then, isn't it?