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
> 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
> 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
> 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
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
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.
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
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
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
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
- physics dictates this no matter how much better braided
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
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
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
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!