Red Bull: Exhaust Driven Diffuser

Red Bull surprised everyone with their revised car that appeared on the last day of testing.  As the car sported revised exhaust systems with a low exit that aims the exhausts over the diffuser.  While exhaust driven diffusers were popular in the nineties before periscope exhausts became the norm, to have the exhaust play over the top of the diffuser is a relative novelty.  However the Newey designed solution on the RB6 is a little more complicated than it first appeared.  In one shot we can see the upper deck of the diffuser features a window (Arrowed) to allow the exhaust gas to pass inside the diffuser, rather than solely over it.  With the aim that the high speed exhaust gas will drive more flow through the diffuser to increase downforce.

One criticism aimed at exhaust driven diffuser is their sensitivity to the throttle position and hence the speed of the flow through the exhaust and in turn the amount of downforce it adds to the diffuser.  This issue was mainly related to when the exhausts   were placed right on the kickline between the floor and diffuser, thus their effect on downforce was much more pronounced.  Placing the diffuser further up the diffuser reduced this sensitivity.  Newey knows a thing or two about blown diffusers, the McLarens retained diffuser exhausts exits all the way to the MP4-17, even then the switch to periscope exhausts was largely driven by other  engine packaging factors.  Even the still born MP4-18 aimed to have diffuser exiting exhausts.  The placement of the exhaust some way upstream of the diffuser exit should allow a better compromise between downforce and sensitivity.

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