How long does it take for fuel to pass through an injector line? That is, from the pump to the nozzle. Less than a second? The reason I ask is that there are electric line heaters used on WVO set ups and I am wondering how they could be effective if the fuel passes through the line in microseconds. How much heat could it absorb in that little time? Anyone have any insight?

Strange someone has not answered your question yet. Anyways the bulk of the fuel in the line does not travel through fast. What your pump basically does is raise the pressure verry high at the start of the line. That pressure wave travels extremely fast through the fuel. Raising all the fuel in the lines pressure. All the fuel in the line is raised in pressure as you cannot for practical purposes compress fluid. When the pressure exceeds the injector opening pressure the injector opens and provides fuel to the engine. As soon as the pressure drops the injector clamps off. You are introducing a very small amount of fuel into the line and a verry small amount of the fuel at the other end of the line is being released. So basically there is always a lot of fuel in those lines for long enough to benifit from a heater. Thats why air in the lines air is such a problerm for example as it will compress. That results in terminal pressures not being reached. Or less fuel being provided to the cylinder if any.