The VHF thread over in the electronics section brought this back to the front of my mind, so I thought I'd throw the high level idea to the masses and see what everyone thought.
There have been a few threads on engine fires in the past, and the one common conclusion is that once it's alight, the fire is in an enclosed space that to get any extinguishing medium in would involve squirting the extinguisher output through a relatively tiny hole at the back of the cowl, meaning you would need to lean over the fire and "out the back"to put it out!
This got me thinking - some form of remote release system piped into the cowl. Any powder system would potentially suffer settlement, so that leaves gas. Now CO2 as we all know is a common fire extinguisher agent. It then struck me. Remember the 80s? Soda streams were the thing to have in your kitchen. Fizzy drinks at your fingertips! (This lead onto a possibly more practical disposable canister for MIG welders with a 1/8 BSP connector instead of some weird propriatory fitting, but the theory still holds.)
I had a wee internet trawl. 60L Soda stream refill cartridge in argos - £9.99, Most Weklding shops punting the MIG CO2 can for £12-15. Now, the volume under the cowl of any engine is not anywhere near 60L. You could have the cyl mounted under your seat with a lifejacket type trigger (or a simple valve for the welding cyl) and pipe it back to the engine to fill the cowl with CO2 and extinguish the fire.
The two biggest problems I could see would be emptying 60L of pressurised CO2 in a hurry is likely to form a fair lump of ice round the discharge, instantly blocking the hose (probably not an issue if there;s a perol fire 3" away from it!) and if the cyls were mounted under the seat, how much air would be fanning the flames until the hose was fully purged and only moving CO2...... (an easy enough calulation to do, but what would the real world consequences be?)
It did strike me that the hose / air issue could be solved by "pre charging" the hose, and capping the end witha lid that would blow of as soon as the pressure built up. That way you might not need to dump quite so much CO2 into the hose in such a hurry, possibly reducing the freezing nozzle problem a bit. Problem I could see with that would be the CO2 leaching out in the same way helium ballons empty themselves, so how often would you need to re-charge the hose? - There are medical "CO2 proof" hoses out there......
So, Ribnet massive, your thoughts?