Halon sucks the oxygen out of the air and starves the fire.

 

Halon is a heavier than air gas, so it displaces the air. The issue would be if the fire is in an open area that will not contain the Halon, allowing it to "spill" out. The common areas like the engine area, cockpit should contain the gas just fine. I would try to wait to activate the bottle until slowed so the gas does not blow away. Also, make sure not to activate a bottle in an enclosed area -- a lady died a couple of years ago in the basement of the DTCC when she got locked in a server room and activated the halon fire system.

 

Halon's primary method is not displacement or denial of oxidizer like some gasses such as CO2 use. Halon molecules disrupt the chemical reactions that makes and sustains fire. It can do so in low concentrations. Even when there is enough fuel and oxidizer to sustain combustion Halon will cause the chemical reactions stop. A little goes a long way and will also get into dark corners and down conduits where a smother function foam might not. Each system has good and bad points. Server systems are over built and try to get 100% flood to push deep into the electronic equipment as quickly as posable. You do not need 100% flood to knock most car fires down enough to get out. That is the goal, to get out. Don't fire it while still moving if you can.

Red can Brake-Kleen does the same thing. Not only is it non flammable but I was told that it too disrupts combustion. I checked this out and sure enough it will knock a fire right out. Spray some on an air cleaner and the motor will shut right down or it will prevent it from starting. Nice little paddock trick perhaps?

 

Yes you getting out safely is the number one priority, but saving(as much as I can at least) my $___k "investment" is my second.

 

I have what may be a silly question...

If you have one system with nozzles covering the engine and driver/cockpit, and you activate the system because of an engine fire, the driver gets doused with the extinguishing agent unnecessarily.

Does anyone use two separate systems, one for the engine compartment and a separate one for the driver/cockpit? That way if you have an engine fire (not that uncommon with 944 variants) you can localize the mess the extinguishing agent will cause?

 

Simplicity trumps complexity.

In a fire situation (and I've had one in my 944) the last thing I want to be thinking about is which lever do I pull to avoid getting my driving suit wet.

The sequence should be Fire! Pull giant red freaking handle! Bail if possible. I want my lizard brain to be taking care of the situation, not my "higher inteligence" worrying about my dry cleaning bill.

Lizard brain likes it simple.

 

If you have to go past the brain stem you might have entered delay and dither land.

Gas based fire systems don't leave a residue. Halon is not the only gas based system.
Perhaps you could install two systems. A full size one that covers all with a centraly located pull and a smaller one for the motor only with a pull that is more out of the way. This way you don't have extra thinking to save you and the car but you can also chose to hit just the motor if you see smoke poring out from under the hood only. Choice but the save me part is still simple.

 

I like fireaid 2000 and or AFFF. These agents seem to have the best properties to stop a fire under the largest Number of conditions we face in a race car. I still use AFFF eventhough all agents like halon are easily available. Anyway here are some problems I have experienced or know about with AFFF systems:
1 unless you have an ESS system if you activate the system by accident you cannot do an easy recharge so your weekend is over
2 AFFF freezes it is right there in the MSDS. I have tried multiple ways to keep these bottles warm overnight w/o electricity including those chemical footwarmer packs. Success has been spotty and taking my system out and replacing it the next day is a pain.
3 AFFF is water based and water corrodes parts so things fail. Can the oulet fail? I do not know but once I had a Safecraft unit and it's guage stuck in the greenzone. I was puzzled to find the guage not move as it got hotter during the day. I depressurized the system to fins the guage frozen. The moral of the story is my tank could have lost pressure and then if the guage is stuck on green you get a false pressure and your are dead.
4 AFFF tanks have flop tubes in them. OMP a few years back had problems where they were temporarily not available in the USA. This was because of failed flop tube that prevented proper siphoning of the AFFF if you were upsidedown and on fire. How many failed tubes or old hardenend tubes are there on all makers systems? I don't think halon uses those but I am not sure.

Anyway there more things to think about.