Temperature of the fuel affects both the power and fuel consumption of an automobile. Both fuel injectors and fuel pump are cooled by the passage of fuel through them and if the fuel itself is hot, cooling of injectors would be affected. Colder fuel also gives slightly more power (but a bit higher fuel consumption). Additionally more ignition advance can be used as compared to hotter fuel. If you are planning on using ethanol fuel, then this procedure is not recommeneded.
As we start the engine, its temperature rises. Gradually, the engine starts to warm up all accessories under the hood. This includes the fuel rail too. If the fuel rail is metallic (which is usually the case), the fuel will be heated too. Petrol or Gasoline has a much higher evaporation rate as compared to diesel and if there is a leak in the fuel vapour recovery system, fuel vapours would be lost. Also if the fuel tank cap is not tight enough, vapours would leak from the tank at a rate proportional to the temperature of the fuel. Additionally, if the fuel pump starts to lose pressure, then vapour lock can occur in the fuel system if fuel is hot. If the fuel rail is insulated, fuel can be kept at a lower temperature. Here is an image of Renault J7T (designed and manufactured by Francaise de Mécanique) engine's fuel rail with rail-holding bolts removed.
Note: Thermal insulation of the fuel rail was officially used by Renault for J7T-760 engine of Safrane car.
Heat is conducted in three modes, namely condution, convection and radiation. First lets tackle conduction, which in our case happens through metal to metal contact. This metal-to-metal contact can be avoided by using non-metallic washers or o-rings (high temperature capable) as shown below.
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In the image below, two non-metallic washers have been inserted in two places. Firstly between screw and fuel rail and secondly between fuel rail and intake manifold.
Fuel rail secured to intake manifold with non-metallic washers.
To tackle heat transfer through convection, we need to cover the fuel rail with some silicon or rubber or other (high temperate capable) hose of appropirate length. We would need to cut suitable sized holes in the hose to fit it over the fuel rail.
In the image below, cut-outs have been made in the rubber hose to allow injectors to pass through the hose.
Rubber hose installed over the fuel rail.
Finally, the hose can be secured with some hose clamps.
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