Mercedes: Downwashed-Exhaust Sidepod

After 13 races of the 2012 F1 season, Mercedes AMG have finally followed the trend of side exiting exhausts to blow the diffuser area. After low placed exhausts were banned for 2012, each of the top teams found methods to coerce the exhaust plume back down from the higher tailpipe. Notably Lotus and Mercedes did not follow this route, although at the Young driver test at Magny Cours, Mercedes were seen testing the McLaren style of sidepod.

The sidepod sports a bulge in its flank to both house the exhaust tailpipe and divert airflow down over the exhausts exit. This downwash effect will bend the exhaust plume down towards the edge of the diffuser, even at relatively low speed. This helps to both speed up airflow under the floor and to seal the diffuser from airflow entering from the sides, which increases low pressure below the floor for more downforce. As a compound benefit this means Mercedes can run a higher rear height for even greater downforce. On the subject of the downforce benefit Ross Brawn told “We think that’s quite significant in low speed traction,” he said. “The effect of the exhaust is more significant at lower speeds than higher speeds, and also brings you the balance perhaps you need for the rear tyre”.

The Mercedes W03 original sidepod and exhaust layout

The old exhaust sidepod solution featured exhausts mounted higher and more inboard, which blew over the centre of the engine cover.  This would have had a positive effect on rear downforce, but this would not have been of the same order as the gains from blowing the diffuser with the new set up.

In detail the Mercedes iteration is closer to Ferraris later evolution of their sidepod. the normally smooth curved sidepods, now sports a distinct bulge from its side. This bulge also features some cooling louvers, probably as much for general sidepod cooling as for cooling the area around the exhaust. We can see the Lower wishbone has additional heat insulations to protect the carbon fibre from the heat of the exhaust plume. The floor has also been marked with stripes of heat sensitive pain to tell what level of heat is reaching the floor. I understand that the gas loses temperatures rapidly as it passes downwards towards the floor and evidence from other cars with this exhaust set up, show little protection is required on the blown area of floor.
Aside from the obvious bodywork changes and the reshaping of the exhaust system, the Mercedes engine will most likely also had a slightly different engine mapping. Both to optimise its use for the revised exhaust shape and lengths and also to smooth exhaust flow between on and off the the throttle. Their task will have been made more difficult by the clarification made by the FIA after the German GP that engine torque maps must not differ by more than 2% from the early season ‘reference’ maps. How much of a handicap this will be is not clear, as other teams have also switched exhaust solution mid season without major issues.

The team have just the three days of the YDT to test the solution before making the call whether to air freight the parts to Singapore for the next GP. As Singapore has several slow corners the exhaust solution will be a benefit, if the team are able to race it.


3 thoughts on “Mercedes: Downwashed-Exhaust Sidepod

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