Build your own (Do it yourself!) Nitrous Oxide (N
20) Injection Systems! newer info here!

All content and info burgerman 1985

20 Westlands Ave, Grimsby, NE Lincolnshire, DN34 4SP, UK. Email Me only AFTER you read the whole page!


(This is the complete "nitrous system" comprising of a CO2 Fire extinguisher bottle polished up, a couple of plumbers "threaded reducers"
and an 1/8th inch "ball" 1/4 turn valve, length of stainless steel braided "brake" hose, modified air solenoid to work at 1000 psi plus,
flexible nylon tube and fittings to feed the gas to the engine, with home made "injector" all shown above.
Not shown is the fuel solenoid/pipes/injector...)


Other pages...
How to set fuel mixture/graphs
Frequently asked questions - simple
Frequently asked questions - technical
Much more than you need to know about fuel!



 >>>go to <<<
(Because this page is old!)



Have a car or bike, and want to understand nitrous systems better?
Want build your own Nitrous kit/system from scratch?
Then read on, it's easy!


Many years ago when I wanted to drag race my old (new!!!) road bike, a Suzuki GSX1150 EF,  at weekend 1/4 mile events, I needed a Nitrous Oxide Injection System... The only way to get any real power from an otherwise stock motor - reliably.

I considered an N.O.S. or "NOS" system
("Nitrous Oxide Systems" - A US based company that most of the rest shamelessly copied complete with warts and all - or simply re-badged)  as used by almost everyone that drag raced bikes or cars back then.

This was the cheapest option, but my inexperience with Nitrous Systems at that time meant that I really needed someone with the knowledge and setup experience to guarantee me some instant success!

Now worldwide there are very few manufacturers of nitrous systems, and there was even fewer then! But it just so happened that a guy in the next town builds automotive Nitrous Systems (He was in Doncaster, in the UK) called Trevor Langfield, at TMC Automotive, or HighPower Nitrous Systems. His enthusiasm was infectious and I bought one of his very early systems and fitted it to my road/drag bike to try out and learn from... I also bought a second-hand NOS system, to examine...

This HighPower kit gave 25bhp extra as it came (Soon upped to 40bhp extra with a jet change) and worked reliably most of the time!

HighPower's latest modern Nitrous Systems are second to none and available off the shelf and are very well finished and reliable. These systems make the build quality and design of all the other ready built systems or "kits" look sick. He also builds state of the art shift systems, ignition systems, boost retard and progressive Nitrous controllers (that 'pulse' special solenoids called pulsoids) etc. Unfortunately all at a price! Obviously the best gear costs, if you cannot build it yourself!

Anyway to get back to the plot...

After messing about with Nitrous on my bike for a while and getting to understand the required parameters, and what made it work, how safe it was and much more, I decided that if I wanted full control, and to be able to fit systems to all my subsequent bikes and cars, as well as multi stage setups etc; then I needed to be able to build my own systems at home.

This makes it much easier to maintain, control, as you don't need to rely on others for every nut bolt and washer...
nd obviously it's much cheaper overall - With the added MAJOR benefit of really understanding what was happening. And I like to learn, and experiment, I have a brain like a sponge! And a sadly melted lawnmower! Anyway...



What it looks like! Minus fuel pump, etc

A typical home built Nitrous System, waiting to go on a vehicle...

One of the other advantages for me, was that I had around this time also designed an Automotive Dynamometer System. A super accurate commercial system, and able to accurately see even tiny differences in power such as when you turn on the lights during a run!

Actually I sold a software, electronics, (with optional machined up drum) package that I sold all over the world, and I obviously had my own (mobile) Computerised Dynamometer or Dyno, to test everything on too... This was an extremely useful tool to be able to play with - Don't you just love good tools! Below...

My Computerised Mobile Dynamometer, that was
used to test and check out these nitrous systems!

No hair...

So I worked out a way to build a cheap easy and safe, reliable Nitrous Injection System that I could build with limited equipment, and readily available components - mostly using off the shelf stuff from any compressed air or pneumatics specialists. Every industrial estate has at least one of these places!

Lots of these "home built" Nitrous Injection Systems (Not Nitrous "kits" as each was individual - depending on the vehicle and it's requirements) were built by me for friends, drag race cars and road-going cars and bikes alike, as well as a few boats and even a light aircraft! Many other people have now also built their own, since, due to this page! So far all have worked as intended and safely and reliably.

I don't sell these systems any longer, or parts, so please don't ask me! However all the info you will need to produce your own systems is here if you can get your head around it! And a great many have done so already.

I also had a home built Nitrous Injected V8 Rover powered Ford Sierra (was 1.6L) car... Below! This had a 70, then later 140bhp shot, and it is hidden! For more details on this car go here

Home built Nitrous V8 Ford Sierra super clean engine bay!

How Nitrous Works

To generate more power, you need to add extra fuel, and extra oxygen (or rather Nitrous Oxide in this case, which amounts to the same thing) to burn this fuel.

The System operates as all nitrous systems do, as follows:

1. The bottle (above CO2 tank) which has around 750psi of vapour pressure normally on an average miserable cool day day here in the UK, feeds liquid Nitrous Oxide (via an upside down bottle or a 'siphon' tube inside it) to the electronic on/off valve or "nitrous solenoid" valve. This is operated in an on off fashion to switch the flow on and off, electrically, via a switch, or micro switch on the throttle. It should only work at full (WOT) condition. After the solenoid and a flow control jet it enters the inlet manifold.

2. Fuel from the existing, if big enough, or a new fuel supply pump (or even gravity on some bikes) is fed to the second electronic solenoid valve. This is wired to operate when the Nitrous valve opens. So both fuel and nitrous are switched on and off together! The fuel also leaves this solenoid, and enters the inlet manifold via a flow control jet..

These 2 solenoids are both wired together, so they will always open and close together. The pipes are fitted into the engine in such a way that the Nitrous Oxide hits the stream of fuel entering the engine and finely atomizes it into droplets. This is important as you don't want un-atomized liquid fuel flowing through the motor for lots of reasons, the most important of which is that the stuff will not burn as it is in big droplets and gets spat out of the tailpipe! 

The extra power comes from the extra charge in the cylinders, of oxygen and fuel. The extra Oxygen comes from the breakdown of the Nitrous Oxide gas compound, into Nitrogen and Oxygen due to cylinder temperatures and additionally from the powerful charge cooling effect that the liquid Nitrous oxide has on the incoming charge as it turns to a gas from a liquid. It does this inside the inlet tract, as it "boils" from liquid into gas as it emerges from the injection point.

This point may be a single point say at the throttle body on fuel injected cars, or directly into the inlet ports on most bikes, but the effect is the same. In all cases the charge is cooled, extra fuel is added, and atomized.

This additional Oxygen and fuel in each intake cycle increases cylinder pressures (and temperatures), and therefore engine torque and power, quite drastically!

An example of how much difference a more "normal" shot of nitrous gives!

(We need a break from school...)

But first an idea of what is possible...

A friend - Gary Atkinson, added a system that I built for him, a slightly mental 140bhp extra! on a single stage, to a stock Suzuki GSXR1100 motor in a competition drag bike chassis. His 1/4 mile times and speeds went from 11.23 secs @ 119mph to an astonishing 9.10 secs @ 156 mph, with only a stronger clutch springs and 6 degrees retarded ignition than stock. It threw all the oil out into a now bigger catch can on every run. I suspect it needed a little less advance and this would have cured it. Unfortunately it was too long to fit on my dyno so I have no ridiculous power curves to show you. It certainly sounded extremely angry! I don't suggest you go for as much extra as this on a stock engine, but it just shows how safe a small 40bhp dose extra really is on these engines. Gary's bike ran all season like this without a problem. Other than annoying all the other competitors who spent thousands on "conventional engine tuning" in the accepted sense. It simply is not really necessary, other than to fit stronger transmission parts in extreme cases with really big increases.

OK... A more "normal" 50bhp increase on a stock bike engine.

Below is a normal power curve(s) with, and without N20 from my own otherwise completely stock road going Suzuki GSXR1100 WP (Derestricted) with stock quiet exhaust system and everything. Bottle was hidden. This will give you an idea of how much of a 'hit' that it's relatively small 50bhp extra really gives you! It's plenty...

The BLUE line is with the N20, GREEN line without, all at 400 miles old!!! (I never had mechanical sympathy!) The Nitrous button was pushed as the revs hit 7400 rpm on this run, on the dyno, actually it said 7500 on the bikes tachometer. From 137 BHP stock, up to 190 BHP at the rear wheel for the price a few beers! Now that's cheap performance. This engine had never even had a spark plug out so far. It was brand new! (Obviously, an open free flowing exhaust, and cooler plugs would see well over 200BHP as the stock exhaust is obviously restrictive at 190BHP.)

The "perfect" fuel mixture is slightly rich for engine safety reasons, and as can be seen on graph, it is set up a little richer than optimum on purpose. There is more to be had even with this nitrous jet, but why try.

Look at the curves. The nitrous gets to the engine faster than the fuel does so if set up a touch rich the power rises and then settles back a fraction as the fuel flow stabilises and the curve is then a little uneven, instead of exactly the same shape as the stock curve but simply higher up the page as it should be with a smaller fuel jet.

I did actually try this (smaller fuel jet) and the bike made only 5bhp more, without a safety cushion of excess fuel. Click the graph to see what happened with a much bigger fuel jet making it richer still. All of this was with stock ignition timing and exhaust system etc, in fact it was not even run in although it probably is by now!

Click here or on this graph to see another graph of rich mixture and to find out how to set up Nitrous/Fuel mixture ratio!

Click to see a richer run as well as these two

The torque curves below, (same stock water cooled GSXR1100WP with and without Nitrous) show the rather drastic "sudden go" effect much more clearly!  Whilst this looks good on the graph its extremely sudden on the road... You may want to start with 25bhp extra!

Torque is directly comparable to acceleration, it is actually a measure of acceleration "directly" or "actual thrust at the back wheel" on the dynos roller, so this is exactly what you would actually 'feel' through your backside as you hit that button... Remember this is only a relatively small shot on a stock quiet standard bike, compared to what my old 1100 EF Suzuki had (GS1100 if you are an American). That had two stages of Nitrous so you got one on the throttle, and the second one on a button! That was very lively!


Torque is up by 50 percent at the rpm that the vertical blue line shows 7798rpm, which on the road is all rather sudden! The front end comes up in most gears, which I just love! (I am power crazed OK?) If the button is pushed at a lower rpm, engine damage is more likely or possible, due to the enormous torque that would be produced as the nitrous oxide tries to make + 50bhp extra completely regardless of the engine revs!  Great if you fancy driving over the crankshaft... Notice that the torque increase, which is proportional to the pressure in the cylinders, is greater at lower revs, just imagine how high the torque increase would be at say 4000 rpm!

The reason...

Imagine a string chopping machine the "string" (your Nitrous & fuel mix) goes in at constant rate or speed because it is regulated only by a fixed jet. And because the bottle pressure and fuel pressures and flow rates are constant, and not RPM dependent.  If the string chopper (your engine) is going at high speed it chops off lots of little bits. (so your engine is safe - small bites!) If your string chopper slows down it takes bigger bites at a time! So the torque increase and cylinder pressure climb as the revs are reduced.

If you relate this to a bike or car engine taking a huge dose of nitrous and fuel (because the revs are too low) then the cylinder pressures are enormous. This means greater torque increases as rpm's drop. See torque graph.

Its also the reason why you don't want to hit the Nitrous button at low rpm in top gear... This would be OK in low gears (like off the line at the drag strip) as the revs jump up sky high, tyre lets go a little and you bugger off at high speed!

Try and draw an imaginary nitrous line on the torque graph back to say 3000 rpm and you will get the idea!

Anyone wanting a copy of this dyno software with these and other runs included can get it from here, because I build dyno systems as well! Or rather I provide the software and electronics and you build the rest.. Get software

OK then, some build your own details!

The Bottle
For bikes, you will need a 2.25 lb alloy CO
2 (Carbon Dioxide) fire extinguisher bottle as shown in picture further up the page - these are painted black normally, or more recently red. MAKE SURE you only use this type, no other type of extinguisher is suitable or safe as they will explode at this pressure!!! It must be safe at 3 times the working pressure of up to 1100 psi, so must be tested to 3,300 psi! All C02 extinguishers are, and this is clearly stamped on the cylinder. The one shown at the top of the page was polished by me. In my lathe. Hard work but what the hell...

Cars will need one of these as well, but the bigger the better! 10 or 15lb ones are excellent! Check out your local fire extinguisher suppliers in the yellow pages. Personally I used to use thrown out ones, that had failed the periodical pressure test inspections...

There was a skip at the back of a local fire extinguisher factory unit that had loads in every night... (But I am not advising you to do this!) For information only - They always "pass" pressure testing next time around as the test takes the initial 'stretch' out! (which is what they test for)  I don't advise you to use these failed bottles unless you are as daft as I am!

I used to buy 15 alloy 10 or 15 lb ones at a time for about 5 each, scrap value, or if for normal customers then obviously brand new ones. If steel bottles don't worry you (they look untidy, heavy etc) then the rear of any bar/pub should have a collection of CO2 bottles laying about! (Don't  just take them - ask first! And I was told to say that!) Also these are great for storage of extra gas, as you can refill your motorcycle one many times from one of these - or use one in your car boot. And have half a dozen spare full ones...

Or go to a place such as this if you are loaded with cash! There are actually many CO2 bottle (tank?) suppliers, normally to the home brew boys! Here is the first one I found on the net for tanks etc... New and Alloy! And with a suitable valves...


Bottle Valve
Some bottles come with a suitable valve already, some don't. Welding supply places, fire extinguisher suppliers, brewerie and home brew suppliers can all supply new CO
2  valves (picture at top to see details) if you persuade them! They also supply the special CO2 thread adapter or tail that gets you down to a female 1/8 BSP tapered or parallel thread (no.12 in pic). (You would need one to fit a regulator for example to use for electric welding purposes) - This CO2 thread is also found on the "horn" part of a CO2 fire extinguisher! That's where all mine came from as seen in the picture screwed to the valve. This fitting gets you to a standard BSP pipe thread. (1/8th BSP.) So you can connect up with any 1/8th fittings, like brake pipe, or air fittings in nylon.

The difficult bit here is trying to explain to the staff of these places what exactly you need - they find it much easier to say they haven't got one! They are often part of another bit of equipment like the regulator... You don't need a regulator though as you will want to feed liquid Nitrous at full bottle pressure to your engine. And you cannot regulate a liquefied gas as it just boils off and regains its normal pressure again... Depending on how you position your bottle you may need to fit a siphon tube to take liquid from the bottom of the bottle. 5mm or 3/16th  copper brake pipes as used for car brakes is ideal and suitable compression fittings are available to grab the pipe, but you will need to drill and tap the bottle valve bottom face to take the fitting. Or put the valve at the bottom - upside down.

These guys also sell all the CO2 valves, and CO2 thread to 1/8th bsp adapters that you will need in case you are too lazy to find one locally...  You DO NOT want a regulator though!!! Scroll down...


Pipe from N2O Bottle to Nitrous to Solenoid
This is best in 'Goodridge' , 'Earls', or any stainless braided hose type tubing and fittings as would be used for a brake system. Both the Nitrous Solenoid Valve, and the Co2 valve are 1/8th BSP taper threads so these fittings are readily available from the places that sell stainless braided brake hose as used on bikes and race cars etc..

On cars you can also use 5mm or 3/16 inch solid copper or steel brake pipe if you want to, from the bottle to the solenoid, as its cheaper and works fine.

If cost or availability is a real problem, then similar fittings can be obtained from airline / industrial hydraulics and pneumatics suppliers, and can supply 4mm OD blue nylon pipe for this (no.4 in picture) and it can "safely" (not according to specs but it does!) stand the pressure if nut and olive (compression) fittings are used. Also available are push lock fittings, and these are un-suitable for use before the solenoid, but may be used after the solenoid valve - because little static pressure exists here.. In all cases use 4mm OD tube only. If fitting in a car, with a big power output required then use 5mm or 3/16th solid brake pipe tubing to connect bottle to solenoid. Make very sure of no swarf or debris remains at all! This is the main cause of solenoids leaking or jets blocking.

Fit no filter, or a sintered metal filter at the solenoid inlet only. If you must... Best not to have one as the pressure drop across it during use causes the liquid nitrous to boil and foam, making jetting less reliable/accurate/consistent. The quantity of Nitrous Oxide delivered will depend on a Jet fitted into the output or engine side of the solenoid valve - described later on.


Pipe from fuel tank to fuel Solenoid Valve - Fuel supply side...
The fuel supply that feeds the second (fuel) Solenoid valve can be provided in a number of ways.
1. On a gravity supplied motorcycle, simply fit a tee piece into the supply pipe from the tank to the carbs, and run a normal 1/4" to 3/8" bore rubber tube to the fuel supply solenoid valve, to a 1/8" BSP to 1/4" Hose connector, with normal hose clips. In this instance gravity feed / normal inlet manifold or port low pressure is more than enough to provide the flow of fuel required for small power increases up to about 45BHP extra.

2. On a pumped system or a car using carbs, for small power increases simply tap into the fuel supply pipe to the carb.

3. On a higher pressure system such as a car fuel injection system connect to the fuel rail/fuel line to injectors/fuel filter or anywhere that the normal 3bar pressure side of the fuel system. Then use a normal fuel pressure regulator to lower the supply that you need for the nitrous system enrichment fuel to between 3 and 10 psi  depending on what you will require later. Or you could use a smaller fuel jet at full 3 bar fuel pressure. I prefer the lower pressure and a regulator personally, as it seems a tiny jet could block up more easily. You would not want that to happen, believe me!

4. Turbo systems must use a compensated 3 port type regulator and a high pressure pump if the fuel is added after the turbo. More details below about this.

In order to inject the correct amount of extra fuel, to match the constant nitrous flow, you must make sure that the extra fuel always stays the same amount of pressure above the manifold "boost" pressure. The existing injection system already does this, as it too will use a "compensated regulator" to maintain the correct 3 bar of pressure to your injectors. Provided it is set up as most fuel injected turbo cars are.
A standard regulator, like a "filter-king" or "Morosso" one, is just a simple pressure regulator. You put any (higher) pressure in and it emerges at the pressure you have chosen regardless of flow (up to a point!).  If your pressure is say 10 psi (or 3 to 5 for most simple road going carb systems then this works fine without a turbo. With a turbo you will get zero fuel flow as the boost approaches the outlets set 10 psi set pressure. So the top of the regulator has a pipe that connects to the inlet plenum so as to make the regulator's diaphragm see the inlet manifold pressure instead of the atmospheric pressure. (they normally just have a small drilled hole). Now the fuel pressure rises and falls with the manifold pressure, maintaining the correct flow. These are called rising rate, or three port regulators.

If an intercooler is fitted always add nitrous and fuel AFTER this point! or it will fill with fuel!

Basically all you need to do in all cases is ensure that a good uninterrupted fuel supply exists, above inlet manifold or injection point pressure. The actual volume of fuel will be controlled by a small jet fitted into the engine side of the fuel solenoid, described elsewhere on this page.

Controlling the fuel and nitrous flow
The on / off control is taken care of electrically, as both solenoids will be automatically 'off' unless an electricity supply is turned on. On a bike this can be the horn or starter button, or a small micro switch on the throttle so as to activate only at WOT (wide open throttle) conditions. An arming switch on the dash, or anywhere accessible is also required.

Actual power increase provided depends on the amount of Nitrous Oxide gas/fuel delivered to the motor, and this will be a fixed constant amount regardless of engine rpm. The amount of Nitrous Oxide delivered depends on the size of the 'jet' fitted into the Nitrous Solenoid outlet. This jet is fitted into the back of the 1/4" BSP to 4mm OD nylon fitting required to connect the 4mm OD blue nylon pipe to the Solenoid Valve. The best jets to use are 'Weber' carburetor jets available from many places. These are like cheese head screws, with a 5mm metric thread and a hole down the middle! (So if you can drill a hole down a screw you can make your own! as I do now. Actually M5 short stainless cap headed (Allen heads) are ideal jets once drilled. In all cases these jets like Japanese Mikuni jets are all in Millimeters ID, or bore. So a 125 main jet on a bike is 1.25mm bore.


These cheap plastic 1/8th BSP to 4mm nylon tube push and lock fittings are also available in brass or plated brass and with nuts and olives for greater security, but these work just fine. These screw into the outlet of the two fuel and nitrous solenoids, and one is drilled and tapped to accept the nitrous flow control jet  - Actually a Weber carburetor main jet from the local ford dealership.



Now the fun bit..  Nitrous can give as much extra power as you want, with the limiting factor being detonation or physical strength of gearbox or whichever bit breaks first! THIS IS THE ONLY REAL DANGER! TEMPTATION! (Don't ask me how I know this! - Clue, I am very greedy!)

Most healthy modern engines can cope with a 25 to 40% increase easily. So an average Japanese bike that makes 120 bhp at the back wheel will (should!) take a 40BHP increase easily, (and usually, much, much more!) Lean mixtures and over advanced ignitions are what does the damage. So retard the ignition by a good few degrees to begin with, and make very sure your nitrous system is set over rich to start with. The CORRECT timing and the one that gives the best power will be more retarded than stock settings because you have more everything in the combustion chamber! This means effectively higher compression. This also means that less initial advance will be needed as the oxygen rich, more densely packed cylinder also burns much faster. The faster pressure rise means a more retarded ignition will be needed, to prevent detonation, prevent unnecessarily high cylinder pressures, and prevent detonation that kills engines! Do not ignore this bit! Also use smaller plug gaps, colder plugs, and higher octane fuel all to prevent the possibility of detonation. Just in case!

Ok Sizes.... How much power will a given jet give? 

Well that depends on, engine type and efficiency, bottle temperature and pressure, how over rich your system is amongst other variables.

But generally the following formula applies: (Except with turbos, where the power increase is usually higher than expected!)

Learn this bit! (Formula)

 Jet size in Millimeters x itself x 70 = power increase  (under ideal conditions.)

So in the case of a 120 Weber carb main jet (or rather any 1.2mm drilling or 1.2mm jet) we get: 1.2 x 1.2  = 1.44 x 70 = 100.8 BHP extra. This formula works for all jet sizes as a general guide because the area of the jet is what matters as long as the pressure remains the same.

But since you are all lazy, I worked a few out for you! Buy a cheap small drill set! Tiny M5 Alloy anodised Allen screws make excellent jets! (If you cannot buy the Weber ones locally. Remember a "jet" is simply a screw with a small hole in it, that's all!)

Nitrous Jet Size

0.25mm = 4.30 bhp
0.30mm = 6.30 bhp
0.35mm = 8.75 bhp
0.40mm = 11.20 bhp
0.45mm = 14.17 bhp
0.50mm =

17.50 bhp

0.55mm = 21.17 bhp
0.60mm = 25.20 bhp *
0.65mm = 29.57 bhp
0.70mm = 34.30 bhp
0.75mm = 39.37 bhp **
0.80mm = 44.80 bhp ***
0.90mm = 56.00 bhp
1.00mm = 70.00 bhp
1.10mm = 84.70 bhp
1.20mm = 100.8 bhp
1.30mm = 118.00 bhp
1.40mm = 137.20 bhp ****
1.50mm = 157.00 bhp
1.60mm = 179.20 bhp
1.70mm = 202.30 bhp
1.80mm = 226.80 bhp
1.90mm = 252.70 bhp
2.00mm = 280.00 bhp
* A starting point with a 1.50mm fuel jet with gravity feed on bikes!
** Suggested starting point for gravity fed bikes with a 1.9 mm fuel jet.
*** If 4mm o/d nylon pipe is used from solenoid to fuel nozzle with a 2.1 to 2.2mm internal bore (as it normally is)  no jet should be needed here at all as the pipe forms the fuel line restriction on a gravity fed system  Mixture should be about right. BUT CHECK IT!

Above this level of power increase, gravity supply will not be enough. This works well up to a .8mm nitrous jet, provided that the bikes fuel tank is above the motor (some are not!) If the tank is not above the motor, or more power than this is needed, then a fuel pump of some kind will be needed, as it will with all cars. Fortunately, many modern bikes and all cars already have one. If it has sufficient extra capacity this can be used just by "teeing" into it before the carbs or fuel injection system. If not, or you are unsure best fit an extra one! A lack of fuel is a really bad plan, and it will ruin your day...

**** This needs no jet. This is the (maximum) size of the orifice drilled in the modified solenoids seat. So no jet is needed. You may be modifying different solenoids, or be using larger ones already, so bigger jet sizes are also included. If you want more than 140bhp extra then more than 1 solenoid would be needed if you use the same ones as I did.

With a pumped fuel system, the roughly correct amount of fuel for this hypothetical 1mm 70 brake extra nitrous jet would be around a pint delivered to the engine in 75 to 80 seconds. On a low pump pressure into a normally aspirated motor. So a trip to the pub for a pint glass will be in order... This is only a ROUGH guide!!! A starting point.

So for twice this, say 140bhp, you would start with a pint of fuel delivered in half that time. 40 Secs.

So for 35bhp you would be looking for a pint of fuel delivered in around 160 Secs.

A quick (APPROX!!!) guide for the lazy! Remember that this will be about right for most, but every car/bike and system is different slightly. And the more you add, the richer and more retarded you need to go.

Nitrous Jet Size mm

Estimated HorsePower Increase

A Pint of fuel (Petroleum)
 delivered in

0.30mm 6.3 bhp 14 min 0 secs
0.40mm 11.2 bhp 8 mins 24 secs
0.50mm 17.5 bhp 5 mins 20 secs
0.60mm 25.2 bhp 3 mins 43 secs
0.80mm 44.8 bhp 2 mins 10 secs
0.90mm 56.7 bhp 1 min 73 secs
1.00mm 70 bhp 1 min 20 secs
1.10mm 84 bhp 1 min 13 secs
1.20mm 100.8 bhp 56 secs
1.30mm 118 bhp 48 secs
1.40mm 137.2 bhp 40 secs

Now you can see that its easy to work out how much fuel you will need for any given nitrous jet size. But remember that this is a safe/rich guide only on most non turbo motors. Weather you get this fuel volume delivered by low pressure by a big fuel jet, or by using a very small jet and tapping into the fuel rail on a modern fuel injection car (3 bar) makes no difference!

The fuel flow is controlled via a similar jet in the same position in the fuel solenoid. At 10 psi regulated fuel pressure the correct fuel jet is about the same size as the nitrous jet used - but every installation is different. Mixture setting : Read this carefully (follow link!)

Pipework from Solenoid to Engine
Inlet manifold or cylinder head or carb rubbers must be tapped M5 to allow the fuel and nitrous injection points to be added. Fittings with a nut and olive or push lock fittings can be used, available for industrial airline or hydraulic system use. These fit the ends of your 4mm OD nylon pipes and have an M5 male thread. The Nitrous ones must be fitted in such a way as to atomize the fuel and carry it into the engine. This may require a little thought before you drill any holes!! It may be possible to use just one nitrous and one fuel injector for the whole motor or a pair of each, if fuel injected or turbocharged, depending on layout and throttle bodies etc. Bikes will normally need to have one Nitrous and one fuel injector per cylinder, unless turbo-ed.

A single injection point usually gives better distribution, as flow is constant and each cylinder inducts at different times. No jets are needed at the injection point only the ones fitted at the solenoids are required. If more than 1 point of injection is used then a distribution block or several tee joints will be needed. All pipes going to the injectors must be the same length.

Inline X2 X3 and X4 plastic push lock fittings are available for the 4mm plastic / nylon tube and these are ideal, but several tees are also ok - see pic! All compressed air/pneumatics dealers keep these kinds of fittings for industry.


Why jet it at the solenoids???

Lots of people keep asking why it is jetted at the solenoids rather that at the point of injection (as all US based commercial systems are). HighPower Nitrous systems are also jetted at the solenoids as they understand why this is superior, and did this first, well before me. I just looked and saw all the advantages.

Basically as follows:

Fuel? Firstly there is no air or anything in the fuel line before the solenoid so it does not atomise at all here the jet just controls the flow. It does this equally well if at the point of injection, or at the solenoid outlet under constant flow conditions. If there is any air in the lines (after the solenoid) due to the pulsing from the motor as different cylinders induct at different times, (and there always will be) - then the fuel cannot reach the motor until it has pushed all this air through the small fuel jet at the inlet manifold end (nozzle?) on US style systems, which increases the time it takes to for it to arrive at the motor. This means it can go lean for an instant when you hit the button - starting destructive detonation off nicely! If jetted at the solenoid valve outlet instead then the correct flow of fuel starts straight away as there is no restrictive jet at the end of the line that you have to first push all the air through.

Nitrous? If you are trying to get reliability and consistency then the nitrous too must be jetted at the solenoid as here it is metering liquid Nitrous Oxide direct from the bottle. It is still liquid as the solenoid is supplied by a larger pipe than its rated flow and it is cool, not attached to the hot engine. If the metering flow jet is installed here then you are measuring a known quantity and density of Nitrous..

If you fit these metering jets near the (sometimes hot) motor then the pipe work after the solenoid is long and warm due to the engines heat,  the Nitrous (no longer sat as a liquid at the correct pressure to keep it liquid in the bottle) is sat in a long open ended pipe. So it starts to expand and foam, so you are now metering what? A liquid? Or Gas? Or a mixture of both! In reality in unknown and varying proportions that depend on temperatures and length of the pipe work etc. Then eventually the pipe is cooled so the liquid flows all the way to the jet and you get to meter a much more dense liquid so it runs leaner later on... So it is far more accurate to meter it at the solenoids outlet where it is still a liquid.

Fitting the metering jets at the "end of the line" will obviously work, as all the US based NOS / Nitrous Express etc; systems show, but it is not as good a solution.

Also, if you decide to use a Nitrous controller that pulses the solenoids to control the power, with the jet fitted directly to the solenoid the amount of nitrous you get is proportional to the length of the pulse width. So 50 percent open time will give half the nitrous flow..
If the jetting is at the inlet port, then the size of the solenoids seat is the limiting factor - not the jet, as the pipe work becomes a nitrous reservoir that the solenoid just keeps topping up..

E.g. a solenoid rated at 150bhp maximum flow would flow around 75bhp of Nitrous at a 50% pulse width. If the jet on the end of this pipe is a 25bhp jet for e.g., then the solenoid just keeps topping up the reservoir, (the pipe work) so you would get about 20bhp at a 50 percent setting! This is not too serious unless you consider that the fuel is not compressible so it will be giving a true 50 percent... Melted pistons anyone??


Solenoids - Modifying and Buying Details..
The Solenoid valves that I use are available from the same type of industrial compressed air / hydraulic suppliers as the other fittings and nylon tubing. They are quite common in factories. They have an inlet at one end and an outlet at the other so are axial rather than the NOS type. This is neither an advantage or a disadvantage as I see it.

The solenoids that I use, are very simple pneumatics (compressed air) industrial ones. They are available in different makes, materials and styles but are rated at only 140psi. This is fine and can be used unmodified for Petroleum, Methanol etc, but MUST be modified to work at much higher pressures of Nitrous Oxide. For this reason, to work with 12V dc automotive systems, a stock 12V is fine for fuel, but a 6V dc one must be obtained for Nitrous use. A 12V one will work but only up to around 70bhp extra, where a 6V one will allow a larger seat area to be used and is completely reliable even on 12V supply (because cold liquid Nitrous Oxide flows through it and cools it) so can go up to 140 brake horsepower extra. A 12V and 6Volt electromagnet is shown here, both fit the same actual valve body.

These solenoids came from a small factory unit in Grimsby in the UK called M&H Pneumatics, call them on +44 (0)1472 241370 and fax on same codes but 346402. They are not on the net...  Update! They are now!

( Although these people may be able to help even with a ready to go solution! At a price.
Or maybe here )

Similar ones are made by many manufacturers around the world, and I have seen a few that could also be easily modified. Nitrous ready ones can also be bought, according to a recent email, contents here.

The fuel and the nitrous are both "jetted" to control the amount of power increase given. The jets are in the form of a simple carb type jet, in this case a weber carb jet, and these are fitted into the rear part of the pipe fitting that screws into the outlet of the fuel and nitrous solenoids. All three shown serve the exact same purpose. All are drilled and tapped to take a "control jet" and are standard easily obtained fittings. The all plastic one is cheapest and cannot corrode, and has low thermal mass but the brass one is safer as it uses nuts and olives to hold the nylon pipe rather than simple push/lock fittings. All accept 4mm nylon tube, and are male 1/8th BSP thread, to fit the outlets of the solenoid valves.
This is a weber carburettor jet (1mm bore or 100 jet size, so limits the nitrous flow to 70bhp). The rear of the plastic fitting is drilled and tapped M5 thread and countersunk to allow the jet to fit flush.
Half unscrewed...
Completely unscrewed! This "jet" can be a brass M5 grub screw, or M4 Alloy Allen headed set screw, or whatever, but drilled to form a jet. Small drill sets are much cheaper than buying bucketfuls of ready made jets!
The fitting here is about to be fitted to a standard solenoid for the enrichment fuel. This is jetted in exactly the same as the nitrous one. In the outlet.
1/8th BSP 1/4 inch "tail" for the petrol pipe goes in the end inlet end of the fuel solenoid..
The internal "bore" of a stock solenoid is 1/8th inch, or 3mm - you can see this by looking down the end of the valve.
Here is the same view of my modified one, with smaller new seat fitted.
Here is a modified one (similar view of unmodified one 9 pictures above!) to make it work at up to 1100psi, and with liquid Nitrous Oxide) It has to have a much smaller seat area. The old one needs to be drilled out, and a much more accurate and much smaller one machining up, and soft soldering in place. The plunger or piston on a stock one also has to be modified. The stock rubber type material is fine for fuel, or air, but will not work with nitrous! Check out the small nylon or PTFE black "Bic Biro" pen ends! there are two spare ones in the picture. Compare this to the photograph 9 places above, and also the new smaller seat area... (The ENLARGED bit!)
Another picture of the new seat.
Also detail of the modified Piston/plunger. The one with a "blob" sticking out is the modified one. PTFE works just as well, if no suitable pens can be found!
This is the other end of the piston. The modified one has had to have about 3mm machined off the end to give the correct (1.5 times the bore of the new seat) lift.
Ready to fit, tested at 1100 psi down to 10 volts, and works reliably and never leaks. If it will not open, then your seat area is too large or the area of the "seat rim" is too wide. The pressure will then hold it closed even when you apply power.
A simple nitrous injector/or nozzle. It has no jet. That lives at the solenoid outlet, this simply has to direct the flow in such a way as it collects and atomises the fuel as shown in the diagram. The nitrous must atomize the extra fuel well. The shiny bit is just a bit if brass tube from a local model shop, with a small 2mm hole drilled in the side, and the end soldered up. The plastic fitting has a M5 thread tapped in the bottom, and a 5mm grub screw screwed into it. This was drilled to accept the brass tube, and was all soldered together and tinned to make it silver at the same time.
Ok, for a clearer idea here is a fake inlet port or throttle body I made earlier! See the small hole in the side of the brass tube? it simply directs the nitrous down the port towards the engine. The fuel is added in front of it, so the nitrous collects it and atomises it. These fittings are a bit big, but I made them just for the photograph, for clarity. In reality I use various different methods to achieve the same result, and in any case small M5 fittings.  Often two small fittings can be fitted angled together slightly to achieve the same effect without any brass tube...
Pair of solenoids ready to fit to my V8 Sierra car. This was to begin with, so only 70 BHP extra. This meant a 1mm Nitrous Jet fitted into the fitting where the blue pipe is, and a 1.3mm jet fitted into the outlet of the fitting where the black pipe goes in the fuel solenoid valve. This was at 4 to 5psi of fuel pressure that also feeds the twin SU carburettors. The fuel solenoid was simply teed into the supply pipe. The nitrous solenoid obviously connects to the bottle in the back! (In this case with braided brake pipe.) Both of the 4mm pipes seen here are teed off (split two ways) to go to each one of the two carbs. In this installation the carbs were tapped and drilled in the bottom of each "mounting flange" so nothing could be seen! The solenoids were mounted near the cars fuse box and were not noticeable... It really IS this simple!

A typical example for a bike motor drawn but same principles apply to any engine!



They are available in all normal AC voltages, and also in 24v dc, 12v dc, and 6v dc. Although these may need to be ordered. 

For our purposes we will need one completely standard 12v valve (above), to use as our fuel solenoid, and one 6v dc one that will be modified internally to work with up to1,100 psi (rated at 150 psi only as stock) These valves have a 3mm or 1/8" inch internal bore or flow, and a brass seating with a neoprene sealing 'washer' for want of a better description, and 1/8th BSP threaded female connections for inlet and and outlet. They work the other way around to a conventional household tap, in that the pressure in the bottle actually holds the valve shut and the 12v or 6v magnet has to lift against the pressure to open the valve. This is why we choose to use a 6v magnetic coil instead of 12v as it draws twice as much current when used on a 12v system as it should, and produces twice the 'lifting' force to help try to lift the washer/plunger off the seating against the 5x normal working pressure. This closing pressure that the magnetic coil and plunger works against depends on the pressure in the bottle, and the area of the seat that the valve covers. 

Our fuel flow solenoid is the stock 12v dc valve as it comes. The sealing material is safe with all alcohol and gasolines and octane boosters and can flow plenty of fuel for our purposes. So just leave this one well alone!

Our Nitrous solenoid will be exactly the same kind of valve (but with some internal modification) but with the 6v dc 'electro-magnet' instead of the usual 12v one. We must however replace the soft 'rubber valve seal' that fits over the seating, with soft nylon, or PTFE bar machined to fit (or amazingly, a BIC biro blue plastic end cap works and fits great! without any machining and if you buy a box of pens you have loads of spares!) . 

This is very fiddly work..., but must be done as the stock rubber material absorbs liquid nitrous, which turns to gas rapidly when the valve is opened blowing little bits out of it. After a few dozen operations it will leak...

Once you have done all of this and connected it to a 800 psi Nitrous bottle, you may expect it to work when you add 12v dc to the terminals..... It won't open however, as the pressure of the gas holding the plunger down is simply too great for the magnet. This is because the valve has a full 3mm seat ID (1/8th inch) which is far too big! The solution is to drill this out and replace it with a new brass seat that can be a screw / soldered / push fit into the place where the old one was removed. This sounds complicated but in reality is dead simple. The new bore needs to be 1.4mm maximum (giving a maximum of 139bhp extra) with a very narrow seat area - similar in shape to the one you drilled out. If the seat area is too wide the valve will hiss when you connect up and try it, but not open fully. This is due to the gas rushing between the seat and the washer causing a low pressure area, stopping it lifting any further.

Some bloke with a name beginning with a B (long time since I was at school now) discovered this while blowing between two apples apparently... Why the hell would he do this? Beats me.

(Update... he was called Daniel Bernoulli! apparently!!)

Finally make sure that the 'lift' on this plunger is about 1.5x the bore of the new seat you fitted (1.40 x 1.5 = 2.1mm total lift)


Pulsed controllers...

I did try all this of course.
But, I decided that it was not worth the extra complication and expense on a simple cheap basic system, at least not for my purposes....
It works OK, but its easier just to use two stages or even three ...

Stage one say 40bhp (A single nitrous system)
Stage two say 80bhp (Another single pair of solenoids but jetted for twice the power)
Stage three open both the above pairs together...

First one on the throttle micro-switch, second bigger on the starter button, which cuts off the first stage. Third one (both stages) on the horn! You just need a couple of relays and some careful wiring. The arming switch disables both the starter and the horn of course, and changes the buttons over.

All into the same eight injectors, just tee together just after the solenoids. 3 stages from 2 pairs of solenoids...

But when I did try it (Pulsed controller circuit to vary power) I used 555 timer chip, solid state relays, variable frequency (to see what worked best - seems to make little difference actually) and variable pulse width to control power. The only bit thats not proportional is that at "around" 85 percent (depends on jet size, valve orifice area, volume in between) "on" you get almost full flow because the small space between the solenoid valve seat, and the jet acts as a reservoir... (This is also the reason that NOS style systems with the jets at the injectors are crap when pulsed!!!) The fuel is not compressible so it doesn't do this. So... it gets richer from 85 percent onwards which reduces power a little from this point upwards.

This effect is worse the smaller the jet size of course. In extreme cases a 25 bhp boost can be obtained with only a 30 percent on duty cycle! (NOS kit tested with big old solenoid and braided hose)


Useful web based suppliers, or at least a starting point...

These solenoids came from a small factory unit in Grimsby in the UK called M&H Pneumatics, call them on +44 (0)1472 241370 and fax on same codes but 346402. or 

Although these people may be able to help even with a ready to go solution! See this email here.

There are many CO2 bottle (tank?) suppliers, normally to the home brew boys! here is the first one I found on the net for tanks etc... New and Alloy!

They also sell all the CO2 valves, and CO2 thread to 1/8th bsp adapters etc in case you are too lazy to find one locally... 


Email me in detail if you are stuck! ONLY if the answer is not on this page!!!

Remember I don't sell nitrous systems or parts - I cannot be bothered any longer!

Me at the drag strip, with lots of nitrous!

This was a scrutineers nightmare,  200bhp+  at the rear wheel, (with 2 stages or 2 nitrous systems) bomber jacket, lace up shoes, jeans, no gloves, visor up...  don't do it!!!   (Don't do as I do, do as I say!)

This was a stock motor, with 5 degree (at the crank) advanced exhaust cam, colder plugs, stronger clutch springs, longer Spondon Engineering swinging arm, 6 inch wide back wheel with 180 or 190 tyre on back, Yamaha EXUP front wheel tyre and brakes, 2 big fuel pumps - one for the motor and one to feed both nitrous systems, ignition kill gear shift, and a stainless eagle race 4 into 1 exhaust with no internals, two nitrous systems. One operates at full throttle, off the line (+40bhp) The other as soon as the tyre can take it, in 2nd gear onwards operated by the starter button! (Another +60bhp)...

This is (was) also my road bike. It was eventually fitted with a big draw through Rayjay turbo too! Unfortunately it was destroyed in a fire in my workshop. Along with loads of my skin. The garage actually blew up, due to me not having a fuel tap. I removed the turbo carb to re-jet it and plugged the fuel line with a screwdriver. (No tap, for flow reasons) I left the building for an hour, and a full tank of Avgas/petrol had spilled on the floor as the screwdriver/plug had fell out. I stepped back in and instinctively flicked on the strip lights switch, realised I could smell lots of fuel and looked down. There was a thick fog of fuel vapour about 2 feet deep! And I was splashing about in liquid fuel on the floor. I immediately realised the danger just as the central heating boiler came on on its time switch. This also lived in the garage! BOOM! Loads of more booms later, (welding gear/nitrous bottles, lots of 5 gallon drums of Avgas etc) no garage left, doors, windows, roof all blown off walls/base cracked and tools and bike mostly melted. I only just made it out, because the side door was blown away, as it would not open! Landed in hospital for a few months!  Life's fun at times. Still, moving on...

Email If there is anything that I have missed. There can't be much since there is at least 40 people so far who have built successful systems for themselves and others from the info on this page. These include turbo diesels, (which are a little different to do) and bikes cars and boats.

Download a VERY useful small free program that runs on your desktop that converts almost any unit to any other to help with converting metric to imperial etc. Download Convert.exe.


Disclaimer - READ - Before you start on this project!

Most of this stuff is pretty simple and safe to do if you take care and think what you are doing.  However as most people have no common sense, and in some cases are a little simple I have to add this small note...

Some people simply do not have the experience, or the intelligence to do a job like this no matter what help I try to give them.  There is already enough info on here to build and understand DIY Nitrous injection successfully if you are bright enough. I am not ever going to add a "shopping list" of parts, as many keep asking for, because if you need one you simply don't understand enough yet and should not be attempting it... 

I am not responsible for anything at all, this means both engines, and/or the safety of others or yourself, YOU ARE!  Let me repeat this. Whatever happens it's your own fault!  All the info on here is basically my experience and simple physics and has been found through trial and error to be correct and entirely safe for engines and people!  But it may not be!  Solenoids and pipes are modified to work at higher than rated pressures, and with different substances. So on your own head be it!  You are doing your own development work! High pressures, and liquefied gasses can be dangerous. If you don't accept this and are not entirely confident in what you are doing, then stop now! I am not responsible for errors, misprints typos or anything at all OK?

On the other hand if you are methodical, test things properly, and understand what you are doing properly, then there should be no reason why you cannot achieve the same success as countless others have, and so far as far as I know nobody has yet damaged a motor, (except me on purpose when testing!) or themselves or anyone else. But it is possible so take care.


Visit my personal website for movies, pics (of my nurse!) My Nitrous injected V8 Rover powered Ford Sierra (was a 1.6 litre 4 cylinder car!), miniature gas turbines, tuned wheelchairs (no joke!) and loads more!


(All contents and pictures and information on this page is mine!)
1987 1995/6 and onwards!

Do not steal it!



Or go to my home pages,

Or my home build Dyno systems (no longer trading but interesting) stuff

Or for my gas turbines stuff old now...


Goodbye, and have fun! And don't blame me if it all goes pear shaped!