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> Nitrous Pipes & Fittings:  What you need for what, distribution blocks, jet holders, injectors, nozzles

John WilliamsonNitrous Pipes and Fittings etc

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Siphon Tube & Fittings for Bottle / Valve
Fits into the bottom of the valve INSIDE the bottle.

This needs to be from metal "car brake pipe" so any car maintenance outlet will be able to sell you some. Halfords for Example. Brass/copper stuff, or Steel pipe is fine. This stuff is 5mm Outside diameter (or 3/16 of an inch).

This pipe needs a fitting to connect it to the bottom of your bottle valve, and this will be a 5mm compression (to fit your pipe) to a male thread. The male thread needs to be whatever size is easiest to tap into the bottom of your chosen bottle valve. Or whatever thread it already has. Example, 5mm compression to male 1/8th BSP. or 3/16 BSP OR 1/4 BSP. Use your brain! Compressed air specialists on your local industrial estate keeps these fittings.

Bend and cut the pipe so it feeds from the bottom corner of the bottle with the valve outlet pointing down when the bottle is in the same position as it will be fitted into the car. Refit the valve. Depending on valve type it may use a rubber ring to seal, or chemical sealant, or PTFE tape. It does not have to be ridiculously tight! You only need to tighten it as you would a water pipe! Some people go completely mad here! If you have trouble undoing the valve from the bottle, use a large vice, or a pipe vice and a rubber car mat to grip it without scratching it

Plastic large bore siphon tubes, sometimes fitted as standard, can have massive internal volume compared to the nitrous pipe that feeds the solenoid, so it is unsuitable as it may take a long while to clear of nitrous gas - we want the Liquid!*

Braided Hose - from Bottle to Solenoid & End Fittings
This is the stuff that you can buy to replace your bike or cars rubber brake pipe. It is about 3.75mm internal bore. You can buy this off the roll, and fit the end fittings yourself very easily.

Once you see the fittings you can see how easy they are to fit. Just tighten it up all the way. These types of fittings can be taken apart and re-assembled if needed.

To cut it to length tightly wrap some insulation tape around it, and using a disc cutter, or if you are careful a junior hacksaw will cut it through.

The Pipe and fittings (Braided to 1/8th BSP) are available from tuning shops at a price, or cheaply from the sort of people that do pressure hoses for industry, along with bearings, etc.

Some Braided Pipe, with the Fittings already screwed on!
The two bits of rubber, are for abrasion protection of the Motorcycles frame, that this pipe was fitted to.

4MM Diameter Nylon Tubing
4.00 Millimetre diameter (O/D) Nylon pipe, is needed to go from the solenoids to the distribution blocks or manifolds if used or/and to the point of injection. This applies to both Nitrous and Fuel. Get plenty its cheap!

Be careful when buying, because there is many different internal bores. The 2.5 inside diameter is the most common and so we use this. In most cases it makes no difference, but on some low pressure systems, and with bikes on gravity feed the pipes bore is important. So for the sake of consistency I will only use the 2.5mm bore stuff. This stuff does not like the full bottle pressure much in full time use, but its also OK for refilling bottles etc. When in use under your bonnet, it never sees high pressures, because its used AFTER the control jets. And the end of the pipes are open to the engines inlet manifold. At a push and for sub 50 to 70 bhp systems it can be used between the Nitrous Cylinder and the Solenoid.

Fuel pipe connector for Fuel Solenoid
You will need to connect your fuel solenoid to the cars fuel system - OR - you will need to connect your fuel Solenoid to a separate pump/regulator for racing/big Nitrous systems.  Either way you need to connect it up! 

1. For low pressure, carbs at 3 psi to 10 psi - you need a 6MM T connector to connect to the existing fuel system with hose clamps. And a 6mm "Tail" with a 1/8th BSP thread to connect your fuel pipe to the Fuel Solenoid.

2. Race type setups with separate pump/regulator, will not need the T piece but will need the 6MM hose tail to 1/8th BSP (Solenoid) connector.

3. If at all possible on fuel injected Vehicles, it is far better to use a Braided Hose (same as the Nitrous line) to connect to the fuel system instead of any of the above.  This is because of the 3 bar (45psi) fuel pressure. Hoses with clamps are prone to coming apart, or leaking at these high pressures unless fitted by an expert! It is quite possible to tap into your fuel system (after the fuel pump, but BEFORE the regulator @ 3 bar) with a simple tee piece and some hose clamps. It is done regularly. But in my opinion its not a very safe practice. Any leaks or problems and a LOT of fuel will get sprayed about! Fires can kill, and if not destroy your car! Be warned. If in any doubt consult an expert. Much better to use a short bit of Braided hose with whatever fitting(s) are required to connect up to your cars fuel system, if you can. A little thought, and a hole drilled and tapped, maybe in the banjo bolt on your fuel filter, or a T added before the fuel rail will do the job professionally. Don't use tubing that is not reinforced, or that may melt easily in the event of contact with hot engine parts.

A 6mm (or 1/4 inch hose to 1/8th BSP fitting to connect
your fuel pipe to your solenoids etc


Injectors or Foggers or Nozzles
Before we get carried away here, I have to say that there is more bullshit talked about Direct Port, Plates, Foggers etc than all the rest of the misinformation out there put together.

I have dyno tested loads of cars/bikes with all kinds of systems... And some with both. The only thing I can say for sure is that "AS LONG AS IT GETS IN THERE SOMEHOW, AND ATOMISES THE FUEL PROPERLY, IT WORKS GREAT!" I can't measure or find any difference between different Nozzles/Plates/Foggers, multipoint or single point injection at all!  And I have tried on all kinds of vehicles, so don't worry about it. (For NOS and other clone, addicts then there may be some differences simply because they are jetted at the wrong place... But I digress!)

Now I got that off my chest, lets see what we actually do need:

1. However you do it, it must atomise the fuel well, and reach all cylinders in roughly even proportions! You don't want to feed everything into a single port runner (Extreme example!) or one cylinder will make tons more power than the rest!

2. It must be as close to the motor as reasonably possible to prevent fuel dropping out of the "fog" before it reaches the engine. (This is amazingly non critical actually, because you only use Nitrous at FULL THROTTLE, and there's big airflow!) But Keep it in mind...

3. It preferably wants to be injected right under the carb in the Plenum area, or if fuel injected, right after the throttle body PROVIDED that this is close to the engine! If its not, then inject at the last part of the tube before it enters the plenum area, so that all cylinders get the same amount..

4. If you use separate throttle bodies, or more than one carb, then you are going to need TWO or more "Foggers/Nozzles"

5. On any engine with a common plenum area or air intake use only ONE injector. Even with 12 cylinders each one "breathes" in at a separate time. This ensures more even mixture distribution than separate "direct port" systems. Because the stuff is already mixed! And each cylinder will only ever be able to get a share of the same Nitrous/Fuel/Air mixture. With direct port systems, variations of pipe length, internal pipe work restrictions, temperatures, jet sizes etc will ensure that you NEVER get even power / mixture distribution!

6. On engines where you have no choice but to use Direct port, don't stress! Its not a problem. At least on properly designed systems with equal length low thermal mass nylon pipes and jetted at the solenoid.

You actually don't need a Nozzle or Fogger at all... Just a couple of simple fittings aimed so that the Nitrous atomises the fuel properly. But if you want one, then see below!

OR simply arrange the following situation using simple cheap fittings, and some drills and taps. This is often actually easier... Works just the same.

This shows a bikes port. The same principle applies anywhere though. The blue pipe is the nitrous - The black pipe shows the fuel getting atomised and swept towards the engine.

This works just as well. Keep the two streams close together though! The gas from the blue pipe will still atomise the fuel and carry it into the motor. The closer together the nitrous and the fuel streams are the better.

Or if space is tight, like this is also OK. 

Distribution Blocks for Multi-port Setups
On most bikes (not turbo) and some cars Multi-port setups (direct port fogger nozzle) cannot be avoided. In this case you will need some king of distribution block for the Fuel, and nitrous solenoid, so as to feed 2, 4, or more nozzles.

These can be bought from the same compressed air specialists as the pipe, solenoids, and other fittings cheaply as you need them.


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


Web design & contents, Nitrous / fuel Jet Sizing, technical information, pictures, charts are all 1987 and on. Any theft will be pursued vigorously..




















































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