Here is the other end of the duct where it terminates near the CV joint.
The 992 GT3 rear diffuser is much larger than the 991 part and has a more aggressive up turn at its end. This is probably where a lot of the downforce improvements come from. The 991 diffuser is minimalistic compared to this.
There are 3 vents in the diffuser that feed air to the exhaust particulate trap/cat area and the PDK transmission. Interestingly the 991.2 GT3 didn’t have any venting in the diffuser for the PDK at all. We sort of feel that these vents are sort of in a bad place when it comes to diffuser effectiveness but good for cooling.
The two side vents feed air over the particle traps and the cats. The GT3 actually has a particle trap just like a diesel. Apparently, Porsche found that direct-injected engines make particulates like a diesel. We assume that the car probably has some sort of regeneration cycle to clean the traps that makes a lot of heat, hence this metal-lined scoop.
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“Apparently, Porsche found that direct-injected engines make particulates like a diesel. We assume that the car probably has some sort of regeneration cycle to clean the traps that makes a lot of heat, hence this metal-lined scoop.”
Dfi engines do create fine particules. It’s mendatory in Europe now to have a GPF on all engines. The only difference is EU spec cars (for PORSCHE) have a differential pressure sensor, US cars do not.
The normal regen cycle on gasoline engines takes place when you’re coasting, it’s the only time where a gasoline engine has enough oxygen in the exhaust to burn the particules.
There is also a forced regen mode. I’m not sure but I think it uses secondary air injection to get oxygen in the exhaust. Porsche informs that it must be performed with a lot or airflow passing under the car because with the car stationnary, the red hot GPF could potentially damage the road it’s on (and everything around it).
I really like the diffuser to brake scoop design.
My theory on the move to SLA double wishbone front is that the Cayman was posing a serious track threat and they needed to further differentiate the cars with a significant suspension upgrade on the 911.
Also, they could finally put the real GT3 engine in the Cayman GT4 RS without actually eclipsing the 992 911 GT3.
Great article. Would have been great to get some more zoomed out overall photos of the underside to understand how much of the floor is flat bottomed. The number of aero details is staggering