Battery to trunk on Honda civic! Help!

you need to check how many amps the cars systems use if you want to put in a breaker.Quad L Handyman services

I just did that on my 1991 Sentra.  I used a Phoenix Gold 140amp breaker, and it has yet to pop.  As long as you don't live in a particularly cold climate, I think the 140amp will work fine for your car as well. Remember circuit breakers take 100-150% of it's rated capacity to trip.   It is there mainly to protect your car from a short on that long power wire.  It also is a nice, as it is an easy way to kill power to the car when working on it, instead of having to disconnect the battery.  IMO, the 4 gauge wire might be a little on the light side for you.  I used 1 gauge welding cable on mine, and have no voltage drop from the battery to the original connections in the engine compartment.  Just check to see what your voltage drop is, and that should give you a good indication of whether you need to upsize your wire or not.