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> Why we jet at solenoids:  Its better to fit the Nitrous control jets at the solenoid outlet!

Why its always better to fit the flow control Jets into the Nitrous and Fuel Solenoid outlets rather than like all the Cloned US systems do, at the Fogger>>>

I get around half a dozen emails about this every week for about 10 years! So this time I posted my reply here so I can just send a link! And then I opened a forum (again)...

> Hey John,
> My name is Mark Shearin. I am in the US, in North Carolina. I am
> planning to use N2O on a bike I have.
> It is a single Cylinder, four stroke 762cc Yamaha. I am using it racing
> through a mud pit which is 80 meters long
> with mud and water a meter deep. I am a race car fabricator by trade.
> Although, I am uncertain on any Nitrous
> fundamentals. I am not one who runs out and buys a kit to bolt on, when
> I feel I can make it myself.


> The bike Single Carb, single cylinder, 105mm stroke, 88 mm bore
> I am open for any advise you may have.

My best advice is to read all of my site. My writing skills are crap but the info is all here!

> I have heard many rumours as to different fuels to burn. Even extra fuel
> tanks with a different fuel to burn with Nitrous.

Its all about octane. Detonation is the thing that stops power increase with any boosted, nitrous, turbo, supercharged system. If you use C14 or C16 race fuel its pretty detonation proof. (within limits!) So you can run daft compression, lots of turbo boost or loads of nitrous!

With nitrous you can also have a separate tank just for your enrichment fuel. It could even be methanol if you want real protection. Its very anti detonation! But you will need 2.2 times as much.

> I have read your website twice and do have a much better understanding
> of most of it. I do not really understand the
> difference between having the jets at the solenoid and having them at
> the the (fogger). It makes more sense to me to have
> them at the solenoid, why do we Americans do it the other way?

Because in the beginning one guy did it that way presumably and everyone else copied or "cloned" the systems. Its wrong for a massive number of reasons but its too ingrained to get rid of - at least in the US.


OK. more technical but will keep short because I'm off to the pub!

This is VERY important stuff that 99 percent of companies and racers simply don't get.

The Nitrous (that we want to use and meter with simple jets or orifices) is liquid. Its supposed to be at least. You cannot set the mixture accurately or correctly and keep it consistent day to day or run to run if its not. 

 It wants to be a gas. It tries to be a gas and "gas off" bubble and foam at any excuse it has.

Three things cause this. Heat, friction, and pressure changes. So say a warm metal pipe or fitting that has a change of cross section manages all three of these at once. So now your pure liquid Nitrous is all shook up like a bottle of Coca Cola after travelling through hot metal pipes and fittings to the control jets in the foggers or plate... Now you are metering a foamy mass of unknown density Gaseous/liquid nitrous. At best its guesswork, and will change with time and temperature.

With this in mind its best to use very low thermal mass tubing (like small bore nylon not huge braided hoses). From bottle to solenoid, and from solenoid valve to engine.. Or in fact anywhere before the metering Jet or jets.

Worse it will change density DURING a run as the nitrous cools the pipe work or fitting as it gasses off by the very thing that's causing it. E.G. a wider area (like a filter!) or a braided hose fitting will cause a diffuse area so a pressure drop. More so if metal and warmer than the Nitrous. What happens? It boils and expands!

It gets more dense as it flows and cools and eventually if you are lucky you may get about 80 percent density compared to an ideal pure liquid Nitrous.

Starting at the beginning...

a) Use small 4mm nylon pipe (2mm bore or 2.5) from bottle to solenoid without any filter. Keep it short and away from anything warm.  Make sure all fittings valve and solenoid have the same internal cross section as best as you can. This alone writes off most US based systems because they use the "bigger is best" "Hi-Flow" Mentality! Shot in foot at the first stage no less... The JET in the end of the system is the only real restriction! And once you turn it all to gas/foam it can only flow a small unknown variable amount...

If you use large bore pipe (like NOS etc) from the bottle to the solenoid which is metal and high thermal mass, then we get problem 1 above. Filter? As above. Large valve, or cross section changes? As above...

The nitrous turns to vapour or foaming low density nitrous in the pipes on the way or whilst sat in the pipe. This is why Compounded by internal cross section changes, filters and being metal temperature variations too along its length and from day to day. And even during a run.

b) fit a single Nitrous Control Jet at the outlet to the solenoid. many reasons. But reason one is that the solenoid is receiving liquid nitrous almost immediately. if you don't get a) wrong! Also there is then no need for a purge solenoid like NOS etc) due to small pipe volume and very low thermal mass. Now the jet in the solenoid outlet can only and will only meter LIQUID nitrous. This means total consistency, hot cold or indifferent. And after this point it does not matter what happens as its already been correctly metered.  After the solenoid the Nitrous will expand and become less dense. Especially if metal pipes, and larger bore than the seat in the solenoid is used. (Are you listening NOS NX and the rest?) If jetted at the fogger it would then be metering a boiling expanded mixture that varies between cylinders as well as with temperature!

You can use braided or metal but its less good and its less consistent again - physics dictates this no matter how much better braided looks!

That single jet at the cool solenoid outlet is metering liquid nitrous in a cool place. Before the hot engine bay. So you get a known amount of nitrous that is very consistent every time and and from the moment you hit the button to the end of the run. 

If jetted at the fogger (like in the image at the top of the page) the nice liquid nitrous exits the tiny orifice in the solenoid and blasts away down a pipe that's bigger than the solenoid bore. It expands because the end of that pipe is effectively open (apart from a jet) as it does so.

it finds a hot pipe and fogger in the engine bay. (or maybe a cold one and that's the problem... Consistency) and it gasses off yet more.

And on a 4 or 8 cylinder all these pipes are different temperatures and each has a different density of nitrous. Each jet then starts metering a thin foamy mass of nitrous liquid and nitrous vapour. And differently on each cylinder.  As time goes on the expanding gas cools the pipes and different cylinders get a more dense mix of liquid and gaseous nitrous.

Eventually the cooling effect will mean all liquid nitrous will be getting metered. But you are never quite sure when. And this isn't consistent on a daily basis. Or even one run after another.

And its worse with fuel. The fuel in the pipe runs or is sucked out while not using the Nitrous system.

When you hit the button the fuel has to push all the air out of the way through the jet before it can get into the engine.  This takes a certain time depending on pipe volume and jetting.  Lets hope these pipes are not also hot enough to cause the fuel to boil or create a vapour bubble... If it was metered at the solenoid outlet none of this is an issue.  And they had better be the same length too!

Meanwhile the nitrous may or may not have arrived in a dense enough form to need the fuel. We cant know if its being metered at the hot end of line in the engine bay. If it has, then you get a weak mixture for an instant and either detonation (which continues after the fuel does get there) or a flashback and fire.

It could also be that cool pipe or engine meant the nitrous for once arrived as a liquid and beat the fuel! Bang!  They do this regularly. Go to a drag meet and you will see that happen a couple of times. They accept it as "normal" behaviour!

Plus maybe they arrived at a "good" mixture and in reality they were metering a 50/50 vapour liquid (oversized pipe work/filters/high thermal mass etc) and it was running great. What happens on the next run after the nitrous has chilled the lines through use and now it 100 percent dense liquid? Melted bits.


If you have a solenoid on a pulsed system (nitrous controller) then it pulses the solenoids to control power.

At say 50 percent pulse they expect to get half the fuel and half the gas.
Now with fuel which isn't compressible that works.
With nitrous you may get 90 percent instead (or any larger figure) because the pipe to the small jet in the fogger is a big reservoir! The solenoid keeps topping it up since it flows more than the jet.  So as you reduce power the system gets weaker and weaker fuel mixtures...

Melted bits, flash backs, nitrous explosions on the start line, etc etc. Seen it all and your "home built" system wont do any of that since its much better designed.

Hope that helps!



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