Dawg, don't use the ABC powder fire extinguisher. You may extinguish the fire but the heat will bond the powder to the engine, so in the end you must replace the engine. I don't know how effective the CO2 gas is with big fires, or how many seconds before the extinguisher runs out. Anyway, the 2kg CO2 tank is very heavy and bulky.
Another extinguisher is a 2kg gas propellant called AF11E fire extinguisher. It's a liquid that when discharged turns into gas so leaves no residue. Search youtube for AF11E to see how it works. I bought my AF11E from Newstar Chemicals Sdn. Bhd.(yellowpages search it yourself) One thing they will advise you is the canister must be upright, or the nozzle will clog or get damaged. This is the same with ABC extinguishers. So I made a bracket to secure it to the same bolts for the strut bar in my boot.
Of course the best is a plumbed in fire extinguishing system from Sparco available from N1 Sunway. It would be RM2000+ but it will discharge in both your passenger cabin and the engine bay.