The 24 Hours of Lemons Forums → Lemons Tech → Engine Cut Off
Last car I "built" already had a cut-off switch installed but when we tested it, it one cut the battery, it wouldn't shut off the engine once running. So to fix it, I had a team mate sit in the car with it rev'd to about 3k and I started disconnecting wires until the car stopped. We then wired the switch to that.
I am guessing there is a better/more scientific way to do this.
What should I be connecting the cut-off switch to?
Trevor
The diagram that came with your killswitch is very useful. See this one:
https://www.pegasusautoracing.com/docum … =TECH00109
To kill the car safely:
- Battery should disconnect battery positive from the rest of the car
- Power to the ignition coil should be interrupted (no spark, no engine running)
- Power output from alternator should be connected to a large resistor to be bled off (otherwise, the voltage regulator could be damaged as current tries to ground itself upstream).
You could also google killswitch on this website. There are literally 457 hits about other people asking this very same question.
https://www.google.com/search?q=killswi … p;ie=UTF-8
I like this switch because it's so easy to do correctly.
https://www.pegasusautoracing.com/produ … RecID=1464
It's a 2 post, with extra terminals. Battery goes to one post, main power and alternator go to the other side. Then with the extra terminals you connect your main ignition wire (we use the wire that feeds 12V through the ignition switch) to one, and the other gets a jumper from main power and a large resistor to ground. When you flip the switch it disconnects the battery, but it also interrupts the ignition wire, and opens a main dump to ground that lets the alternator safely discharge as the engine winds down.
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