In order to better manage transmission, exhaust and differential cooling air flows, I have added a baffle and some louvers. The exhaust baffle now separates the exhaust cooling air flow more completely from the air passing over the transmission. Here is the forward bay before adding the baffle, looking to the right:
and looking left:
Here is the view looking right, with the baffle installed:
and looking left:
The orange silicone strip is a close fit with the forward panel, and it prevents metal-on-metal contact when the forward panel flexes.
I was reluctant to install hot air outlets (i.e. louvers) in the undertray last year, because dumping low kinetic energy hot air under the car will reduce its effectiveness. At this point, I think that the undertray is effective enough that it can afford the loss, and experience has shown that I need to add some cooling. I still want to have the transmission/differential cooling air flow the full length of the undertray before exiting at the rear wheel wells and above the diffuser, but I decided to pull some of the very hot exhaust cooling air out with a series of 8 louvers that follow the path of the midpipe.
I was unable to find a commercially accessible louver that I liked, so I designed a die to press out what I had in mind. The elongation required to form the louvers is too much for hardened T6 grades of aluminum I have used in the forward and mid panels, so I made the louvers as separate removable items. As they are susceptible to damage, making them removable also makes that damage easy to fix by replacement.
The louvers are made from 0.063” annealed aluminum sheet. The blank is CNC drilled and slotted, with the finish shape engraved to make trimming easy. The blank below is an early trial with some cracks visible. Cracking was later eliminated by refining the die and the technique.
Once the blanks were trimmed and deburred, 10-32 Pem nuts were installed in each fastener hole to make the installation one-handed.
The associated cutout was made easy by creating a router template.
Installation is from the inside, as this eliminates an external lap joint to spoil the air flow.
Hot air spilling from the louvers will result in warmer air entering the differential NACA inlet than did prior to the louver installation. That isn’t really ideal, and if I have cause to rebuild my diffuser, I will consider moving that NACA inlet laterally to put it in cooler air. Before I worry about that though I will take some temperature measurements and do some flow visualization to see if this is actually a problem. The volume of air flowing under the car is so much greater than that flowing out of the louvers that dilution of the hot flow may make the issue insignificant.
Time for some testing.