Tearing Down Tesla Segment 7: HVAC Differences in the Tesla Model 3 & BMW i3

There’s a rather traditional design tradeoff for the IP HVAC ducts in the Tesla Model 3 and the BMW i3. Read on to learn more!

Background:

The BMW i3 uses blow-molded ducting, which can reduce material weight and cost by allowing for thinner walls on the duct, but often requires multiple pieces to create the path to route the air. The Tesla Model 3 uses a three-wall injection molded duct, which reduces material weight and cost by eliminating one side of the duct and using the instrument panel substrate for that wall. This design often integrates several pieces into one part and requires more design work and a rather large specialty assembly jig to weld the part to the instrument panel.

Second, the BMW i3 has rather traditional air vents. There are four vent assemblies (two on each side of the driver and passenger) and each vent consists of several small parts assembled to allow for manual control of the air side-to-side and up and down. The Tesla also attempts to reduce cost using a very novel approach to controlling airflow at the vents. Tesla uses a patented air vent design that uses two opposed air streams to control airflow allowing for the need of only two vent assemblies with fewer vent components, as less directional fins are required to focus the air. To further improve the design, they motorized the control (via a touchscreen) to add an additional level of functionality. With this design, they were able to reduce that cost of the components by making it fewer parts, but then put that cost back into the system by adding functionality.

It is interesting to note that Tesla is possibly able to adapt this specialty design with a more complex assembly jig because its vehicle production volume is significantly higher than the BMW i3, which allows those engineering and tooling costs to be distributed across more parts, allowing for bigger development budgets.