Depending on the type of system (gaseous vs AFF), and the size of the system, you may have 2 or 3 nozzles in which to place within the car. Personally, I prefer
AFF, as gaseous does not do well in an open cockpit environment such as a Cobra.
For mine, I've placed one at the fuel cell, one on the firewall facing the top of the engine, and one over my shoulder to spray in towards the footwell area. The idea of having one is not to save the car, but to save yourself and perhaps your passenger. The fire suppression system gives you valuable extra time to get out of the car should you have a fire.
Bill S.