Engine off … venting off?

November 20, 2015 // By Thilo Haiss, W. L. Gore & Associates
Electric cars, hybrid cars, or cars with conventional combustion engines – in all of them, the electronics are exposed to constant pressure fluctuations. Yet driving is not the only activity that poses major challenges for electronics housings. Shutting off the engine in particular causes huge pressure spikes, putting considerable stress on the seals that are supposed to protect sensitive electronics from dirt and liquids.

When the vehicle is in operation, the wind cools the electronics that heat up in the engine compartment. However, if the car is sitting in traffic or at a traffic light, then this natural coolant disappears. As a result, the temperature under the hood quickly shoots up. This increase is even more serious when the car remains stationary for several hours. The heat from the engine rapidly drives up the temperature, which in turn produces pressure spikes in the electronics housings. Because these spikes equalize only very slowly without vents, enormous strain is put on the seals. This scenario happens at least twice a day in commuter cars; the recurring stress can weaken the seals over time, eventually allowing ingress of dirt particles and liquids into the housing’s interior. Ultimately, this can damage the sensitive electronics.

Commuter test: dangerous pressure spikes are par for the course

Gore’s vent specialists tested the temperature and pressure changes in two identical electronics housings installed under the hood. One electronics housing remained in its original condition (in other words, non-vented), while a GORE Automotive Vent was integrated into the other one. The test observed both electronics housings during a typical “commuter day” – starting at 4 p.m. with the drive home and concluding with the drive back to work the next morning (see graph).

Temperature and pressure spikes in non-vented housings …

While the driver was running afternoon errands, the wind caused by the car’s motion was able to cool off the engine sufficiently. Yet around 5:30 p.m., when the car was sitting in rush hour traffic, the temperature under the hood rose from roughly 15 °C to about 45 °C (yellow line). It didn’t drop until traffic started moving and the generated breeze began cooling the electronics again – and even then it fell only slightly. As soon as the car was back at home, with the engine turned off and no wind

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