Originally Posted by
jakobsladderz
On the injector - I mounted it into the side of the intake tube so it runs across the back of the engine (parallel with the engine fins. I used a dremel to make a hole just big enough that the injector end slid in then used epoxy resin reinforced with carbon rovings to hold it in place. The fuel squirts against the opposite side of the intake tube. The end result is that with the injector fitted the assembly is not significantly longer than without the injector. I would have liked to be able to direct the fuel into the port but there's not enough space for that at this point in time. The epoxy/carbon is quite tough and so far at least is holding up perfectly.
When the engine shuts off after a run, the injector is fairly hot (it is getting the hot air from the engine blowing over it) and when the pump shuts off the fuel almost instantly vapourises in the injector, expanding out into the supply tube. On restart, it very quickly compresses back to liquid again so the pump pressure appears high enough to avoid vapour lock. With the fuel being that hot, and sprayed against the hot intake tube, Evaporation should be near complete by the time combustion takes place.
I think your injector does not get hot from the cooling air, because that air is not all that hot (highest I have ever been able to measure, was less than 15 deg over ambient in an engine with a cooling duct. In freely exposed engines, I never saw more than 5 degrees elevation), but from heat conduction through the header. I had to thermally isolate header and carb because of vapour lock, because the header gets awfully hot. Easily 60~70 deg C despite the cold air and the fuel rushing through it. Even then, I had issues with lack of proper evaporation with the normal spraybar, because of the fuel entering in a continuous stream. The intermittent supply from the solenoid forces the fuel to break up in much smaller droplets, and as far as I can tell, I have fairly complete evaporation. The tell tale is black oil from the exhaust. It is caused by the oil still containing dissolved fuel at the beginning of combustion. When the residue from the exhaust starts to clear, you have good evaporation.