> Fuel Solenoid:  All you need to know about using Air Solenoid Valves as Fuel Solenoids!

Fuel Solenoid - DIY Self Build Nitrous Systems

A pair of identical standard AIR solenoids. The FUEL one is stock.
The one with the Braided hose is modified for use with Nitrous Oxide
Gas. Otherwise they are both the same!

Required Parameters

You can use any locally available pneumatics valve if it fits the following specs:

• They must have a 1/8 inch (3mm) or bigger internal bore at the smallest place - the "seating" inside.

• They must be simple two port type open/closed valves.

• They must be 12v DC

• They must be 1/8th inch BSP inlet and outlet threads.

• They must be VERY reliable at 140/150 psi for engine safety.

• They must not leak!

• They must have sealing materials and gaskets that are not effected by Petroleum based fuels, alcohols, ands all fuel additives

Some Details...

Here is the piston that the electro (12V) magnet "lifts" up against the working pressure when you activate the Solenoid's). This is the reverse way round compared to a household tap "washer and seat" arrangement. The top one has been modified to work with Nitrous Oxide at high pressures. But the bottom one is from a standard air solenoid as purchased. This works just fine for fuel as it is!

The seat material and the valves "gasket" rubber seal, have been tested in a mixture of pump fuel, aviation fuel, race fuel (C16), octane boosters (mixed) methanol, ethanol, diesel, paraffin, nitro methane, nitro benzene, propylene oxide.

Over a period of 3 months of "soak" tests, in a jar, the seat material (some kind of rubber possibly NBR not sure) did not swell, soften, harden, change colour or change any of its properties as far as I could tell! This is important!  If it fails you could kill an engine... Nitrous without fuel spells disaster.

Interestingly an old NOS (Nitrous Oxide Systems manufactured) fuel solenoid from 1985 fails this test with the rubber "swelled" up and expanded. This when operated then does not lift far enough off the seat to allow full fuel flow!  Now you know why I sort out my own stuff...

If your solenoids are not the same make as mine, I suggest you mix all these items together and seal the piston in a bottle or jar with them inside for an extended period and try it!  See what happens to the materials... If it blocks the seat up, swells so the valve does not open properly or whatever your engine may be melted!  Be extremely cautious... I may have just been lucky.

Here is a stock Solenoid valve as I used to use. It is a simple 140PSI air solenoid valve with a 3mm or 1/8th inch seat cross section.  It only requires two fittings!  These are shown, one is a "tail" that allows a hose (fuel pipe) to connect to it. That's the thing that at the bottom left! The other fitting is shown below.

This fitting is plastic. The best ones to use are plated brass or plain brass, or stainless steel if you can find them easily. Chromed ones and anodised ones are available too at a price! But use the ones with nuts and olives!  The one shown is "push lock" - for simple prototyping great! But these are really only suitable for testing. After a few months at extremes of temperature under a car bonnet, they age, and the pipes can fall out! This fitting (now also the jet holder) goes into the solenoids outlet. The other thing is the brass fuel control jet.

Actually its a 130 Weber carb jet (1.3mm) in this case. It needs to be drilled and tapped and recessed into the fitting rear face as below pictures show! This fitting is 1/8th BSP to 4mm O/D Nylon pipe.

Once its screwed in fully and "flush" it can be fitted to the solenoids outlet. Fuel solenoid is completed! Simple stuff... Ten minutes work.

*Technically the term NOS is incorrect as this refers to an specific company (called Nitrous Oxide Systems, in the US)