This week I've been focusing on the brake system. In a gas powered car, the gas engine provides supplemental vacuum pressure that amplifies the force applied to the brake calipers when you step on the brakes. In the electric car, I need to replace the vacuum by an electric powered pump. Reading the Porsche 911 repair manual, the stock brake booster vacuum system provides 10 inHg vacuum pressure. The solution is a vacuum pump + reservoir + vacuum switch. The idea is to use the vacuum switch to turn on the pump whenever the vacuum pressure is below 10 inHg. The switch has built in hysteresis so it doesn't open and close a bunch of time right at the 10 inHg transition point. The reservoir adds capacity to the system so once the system is charged up, it will take multiple brake presses before the pump needs to kick in again. I have yet to find a vacuum switch with the correct temperature range for Minnesota, but I'm still looking. To make the brake system a little more interesting, I plan to add a gauge in the cockpit to keep me informed of the vacuum pressure. The parts are on order, I'm excited to get them hooked up. Here are the pictures.
Cool vacuum gauge