Help with basic voltage reducing circuit for auto

[Terry335]

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[Norlin]

am no expert here, but I'm guessing you could use an undervoltage sensing IC such as the MC34164P-3 https://pdf1.alldatasheet.com/datasheet-pdf/view/12086/ONSEMI/MC34164P-3.html
Have the normal power go through a transistor, when the voltage hits 3V, have current flow through the MC34164P-3 to the circuit as well as the base of the transistor to turn it off (perhaps a PNP with an inverter between it and the MC34164P). Between the MC34164P-3 and the circuit, have something that will make the voltage climb slower. Just my probably not so great idea, hope it helps stir up some better ideas.

 

[3v0]

Do you need to consider throttle position, rpm, and maybe time ?

I do not know, if you do not you need to find out.

 

[Hero999]

It could be done using a couple of op-amps and a voltage reference IC but it's a bit long-winded.

Use a subtractor to get 0-1.3V divide it by 1.083 using a potential divider, then add 1.9 using an adder.

 

[Norlin]

in this circuit, even though you're diverting away some of the current you're not changing the voltage at the point where the circuit splits.