Something you may expect to be a straight forward and even boring is an area where a small mistake has a large impact. Performance and reliability is compromised when a poor selection is made. Everyone’s favourite topics will get a mention. Fuel choice, operating pressure, temperature, flexibility, durability and cost.
Let’s deal with nitrile rubber style first. This is the most common of the three. Typically being constructed of a premium inner layer made from NBR (Nitrile), a reinforcing spiral wrap and an outer cover. The nitrile inner layer does not readily break down when in constant contact with fuel and provides hydrocarbon permeation resistance. The textile spiral weave middle layer adds mechanical strength to withstand the operating pressures. The thicker outer cover is often made from CR (Neoprene) and provides temperature protection, abrasive resistance and reduces construction cost. Having good flexibility this hose is easy to use and allows for versatility of installation. Worm type EFI hose clamps or step less clamps and barb fittings are used for connecting hose to fitting.
For sizing EFI hose the inner diameter isused and expressed in imperial measurements and or mm. 3/8 hose is also called 9.5mm. Getting technical this hose is constructed to SAE30R9 and has an operating temperature range of -30 degrees C to +100 degrees C with burst pressure as high as 4 to 5 timers the operating pressure.
The one big thing to remember is this hose is not for use inside fuel tanks. It is not going to self-destruct but the outer layer will break down over time when in constant contact with fuel blocking fuel filters and injectors.
Dash (-) numbers are used to identify the sizes of braided hose. A -6 hose will use a -6 fitting. Not only is the correct dash size required but also the correct fitting type with braided nitrile and PTFE hose useing unique fittings. Generically called braided hose the real term is 100 series, 200 series and so on. The series number identifies the fittings required and the hose construction. 200 series is the hose guaranteed to be compatible with all modern fuels. Nitrile braided hose is 100 series.
Braided PTFE is light weight and easy to assemble. The achievable bend radius is less compared to the other braided hose and often additional hose fittings are required for neat installation. PTFE is compatible with all fuels and oils. With operating pressure of 1200+psi and burst pressure of 4000+psi for performance applications this is a very good choice. Teflon or PTFE is 200 series hose.
Ordinary fuel hose is only designed to resist fuel contact internally. In a submersible application the exterior of the fuel hose is in constant contact with fuel. There are two distinct players, rubber style including stainless steel brained and nylon.
The rubber style submersible hose is constructed to meet the requirements of SAE 30 R10. This style of in tank hose will have an external flouroelaster tube cover to retard aging, aramid fibre used for the spiral wrap and a nitrile inner. Operating pressure of 250psi and busrt pressure of 500psi make this hose suitable for EFI systems. Flexibility is limited when compared to non-submerible EFI hose.
Nylon hose for in tank use has already been covered and is a very good choice for in tank use.
Did you ever think about using the cheaper low pressure hose for return line on your EFI vehicle? Carburettor or return hose is very similar in construction to EFI hose just designed for lower pressure. Typically the operating pressure is <50psi. Being rated to less pressure make cost of production less that the higher pressures hoses.
Size of the fuel hose is the same as EFI and compatibility with the different fuel type is also hose specific. This hose is manufactured to comply with SAE30R7
Seamless aluminium hard line is a cost effective choice for high and low pressure fuel lines. Very clean installation possible with full length seamless line. Hard line maybe more time consuming to install as it requires the use of tube benders and cutters. Fitting wise compression and flare fittings are commonly used. Hard line has exceptional durability being the best of all fuel lines. Burst pressures are similar to other fuel lines being in the range of 780psi. Stainless steel hard line is also an option.
Static discharge should not be overlooked. Fuel hose needs to be able to discharge static build up that occurs due to the fuel flowing within the hose. As fuel flows at high velocity the friction caused by the fluid will generate static electricity. All high quality fuel hose will have a conductive chemical additive to allow the static electricity to discharge safety through the hose to the vehicle body.
That’s plenty of information to enable good decisions when selecting your fuel hose.