Stuff you MUST understand if use any make or build your own Nitrous Kit!
Important Information for building Nitrous
page is heavy going but you really need to know it!
The scary bit of any home built
or designed Nitrous System is testing it for the first time!
This page is therefore ESSENTIAL reading. Before you
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 additional
The Nitrous system
operates as all nitrous systems do, as follows:
which has around
750psi of vapour pressure normally
on an average miserable cool day day here in the UK, (depends only on
feeds liquid nitrous oxide (via an upside down bottle or
tube inside of it) to the electronic on/off
valve or "Nitrous Solenoid"
This is operated in an on / off
fashion to switch the flow of Nitrous Oxide on and off,
electrically, via a switch, or micro switch on the throttle.
It should only work at full throttle (WOT) condition.
the Solenoid valve and a flow control jet situated at the exit of the Solenoid
valve it enters the inlet manifold via some 4mm Nylon tubing and one or two
fittings.. We now have a means of switching a flow of Nitrous Oxide Liquid on
and off blasting into the inlet manifold! If you do not understand this section please read it again!
At the same time:
from the existing fuel pump,
if big enough, or
a new fuel supply pump entirely if you prefer! (or even
gravity on some bikes) is fed to a second electronic Solenoid
This is very similar to the one we
fitted to control the Nitrous Flow. Only it allows fuel
instead, to flow when energised. This is wired to operate when
the Nitrous valve opens. Both the Nitrous, and the Fuel
solenoid are connected together, electrically. So both fuel
and nitrous are switched on and off together! The fuel
also leaves this fuel Solenoid when energised, via a small
control jet. It also flows via some 4mm Nylon pipe into
the inlet manifold. This gives the Nitrous Oxide some
fuel to burn!
Inside the manifold, the flow of nitrous is
arranged so that it hits the flow of fuel and finely atomises
it. The Atomised fuel, and cold semi liquid/gaseous boiling
nitrous are carried into the engines cylinders with the normal
airflow in the port to the cylinder.
2 Solenoids are both wired together,
they will always open and close
together as one. 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
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. Additional power and a deal of "anti
detonation" comes from 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 state.
It does this partly 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,
additional Oxygen and fuel in each intake
cycle increases cylinder pressures (and
temperatures), and therefore engine
torque and power, quite drastically!
As we will see below.
First an idea of what is
- Gary Atkinson, added a system that
I built for him, for a laugh at the drag strip. He didn't care
about his engine at all so we started a bit "high" on the boost
levels... A slightly mental 140bhp extra on a single stage
just to begin with, fitted to a standard Suzuki GSXR1100 N
motor in a "competition drag bike" chassis (which means
long, low, big fat slick etc)
His 1/4 mile times
and speeds went from 11.23 secs @ 119mph (expected) to an
astonishing 9.10 secs @ 156 mph, with only stronger
springs and a 6 degrees retarded ignition from standard engine! threw most of the oil
out the breather (into a now much bigger catch can!) on every run. I suspect it
needed a little less ignition advance still and this would
have cured it - AND made it even faster.
was just too long to fit on my Dyno
(Dynamometer) so I have got no ridiculous power curves to show
you. It was making a VERY strong 260BHP+ judging by its
performance on the drag strip. With ENORMOUS torque levels. It certainly sounded
extremely angry! I don't suggest
you go for as much extra power as this on a stock engine, but
it just shows just how safe a a small "40bhp+ dose" extra
really is on these particular Suzuki engines. 140 bhp extra from about 3000 revs
(where it normally has about 30bhp) is a 450 % boost at these revs! And over 100
percent at 9500rpm...
Gary's bike ran all season like this
without any problems. Other than annoying all the other
competitors who spent thousands on "conventional engine
tuning" in the accepted sense. It simply is
necessary, other than to fit stronger transmission parts in
extreme cases with really big power increases. And on
some engines maybe some stronger "forged" type pistons.
OK... now a more "normal"
increase on a completely stock bike engine (Mine).
Below is a normal
power curve(s) with,
and without N20 from my own
otherwise completely standard road going Suzuki
GSXR1100 WP (Factory power restriction "plates" removed) with
its 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 l 50 bhp extra really gives
you! It's plenty...
line is with the N20,
line without, all at 400 miles old!!!
(I never had any mechanical sympathy!) The
Nitrous button was pushed as the
revs hit 7400 rpm on this particular dyno
run. Power is up from 137 BHP
standard figure, up to 190 BHP
at the rear wheel for
the price a few beers!
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 it well over
200BHP mark as the stock exhaust system is obviously
restrictive at 190BHP. Remember this was stock timing, stock
fuel mixture setup 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 by leaning
the mixture off a touch. But why try, when the last few BHP
mean huge temperature rises, and greater peak pressures and possible detonation problems.
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 as can be seen on the initial hit at 7400 rpm and
then settles back a fraction as the fuel
flow arrives and 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. This shows me its a
fraction rich without even plugging the Gas analyser in. This
is how it SHOULD be on a safe set up road
I did actually
try a smaller fuel jet just out of interest
and the bike made only 5bhp more,
without a safety cushion of the excess fuel. Simply not worth
the risk. 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
and to find out how to set up Nitrous / Fuel mixture ratio!
The torque curves
below, (same GSXR1100WP with and without
Nitrous operated) show the rather drastic
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! (Sudden means it feels like someone just hit your
bike up the back with a Cricket Bat) You get longer arms and the front wheel
comes up even in 3rd gear by mistake.
Torque is directly comparable to acceleration,
it is actually a measure of acceleration
"directly" or "actual thrust at the back wheel" on the
dynamometers 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! This does not
compare to what my old 1100 EFE 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 one was
Torque is up by
50+ percent at the push of a button - at the rpm that the vertical blue line shows
7798rpm, which on the road is all rather sudden! The front end
comes up very fast 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 at least possible) due to the enormous
torque that would be produced as the Nitrous Oxide tries to
make its + 50BHP extra completely regardless of the
engines revs! Great if you fancy driving over the
crankshaft... Notice that the torque
increase, which is directly proportional to the pressure in
the cylinders, is greater at lower revs, just look at the
graph, and try to mentally draw the line back in your mind.
Imagine how high the torque increase would be at say 4000 rpm!
Imagine a string chopping machine
"string" (your Nitrous & fuel mix) goes in at constant rate or
speed because it is regulated only by a fixed jet, and
constant pressure. Like a hose pipe! The Nitrous Flow
and extra fuel flow is 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 its turning really slowly, its like setting a bomb off in
the cylinder! Because its got a HUGE dose of Nitrous/Fuel in
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. Or if its easier Nitrous has much more drastic effects
and MORE effect at lower RPM's. So it makes cars ACCELERATE
much harder! And you do not need much...
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, so no problem - But in top in town
it can't do this, so you could damage your engine if you try
it? Depends on the Amount...
Try and draw an imaginary nitrous
line on the torque graph back to say 2000 rpm and you will get
a copy of this (My own) 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..
nitrous/fuel mixture on power
This Dyno print
out shows the same two curves as before, but now in different
colours, and with a third additional dyno run added - green
line... This was the Fuel rich curve, caused by going up
a size in the Nitrous systems Fuel jet.
blue power curve shows the stock bike without the nitrous
system in operation.
2. The red curve shows the same bike with the nitrous
system set up with the correct or very slightly rich nitrous
and fuel ratio. The extra 'richness' prevents detonation, and
danger of burning the motor internals.
3. The green
curve shows the same bike with the nitrous system set up
fuel rich, to show the effect on the power curve, The system
was operated earlier this time during the run at 6400rpm,
and the richer mixture lowers the peak power produced, and
gives a 'wiggly' looking curve. It ran cleanly as far as you could tell however
misfires or anything. Power was still 180bhp peak and set up this rich it would be very safe to use on a daily
basis on the road with no danger ever of any engine damage. If
the bottle is cold in winter for example, a similar thing
happens anyway as the pressure is lower in the bottle, but
this time the rich mixture is caused by less Nitrous, rather
than too much fuel so even less power would be produced too.
Click graph to enlarge!
would set the Nitrous system up to be like the red curve
(just a little too rich) on a hot day so that it will be
very safe on any other day even if not completely optimal. At least if you
care about your engine.
throttle 'plug chop' on Nitrous, will also give a good idea
if you have the mixture correct, if no dynamometer is
available. Just run flat out through 3rd, 4th, 5th gear and
then release the Nitrous button hit the 'kill' switch and
disengage the clutch and coast or brake to a halt without
letting the motor turn over. Simultaneously...
pull out all the plugs, and look carefully at the outside
ring first - not the electrodes. It should be a nice dark
tan colour with some slight traces of black or spots of soot on it. No
traces of soot or black means that there is no un-oxidized
(excess) fuel present which means not enough fuel for
Nitrous is like oxygen, if you have too much of
it with no fuel to burn, it will burn your valves and
pistons instead which is not good! Too much fuel will give
less or even no power increase or even misfiring but it will not
damage your engine. The correct amount is somewhere in
Rough Guide to mixture setting - Nitrous
/ Enrichment fuel ratio - WITHOUT a handy Dyno and before you try a plug chop!
I suggest you try this only with systems jetted at the
solenoids not with US style Systems, because they are a bit
unpredictable to put it mildly...
sure you have both fuel, and Nitrous firing out of the
solenoids, or from the pipes that feed the injector's
(Disconnect first to test for flow!)
DO NOT allow
any Nitrous/fuel to be fired into a stopped engine ever!
The stuff sits there just waiting for something to ignite it
inside the intake system.
When you switch on, or when you crank the engine it will
explode! This often just makes a huge and scary bang, but it
CAN wreck your intake system, and cause fire or injury.
If you even
suspect a solenoid has been fired by mistake, or has leaked
into your engine, then you MUST remove the HT coil lead, or
disconnect the power to your ignition system and then turn
the engine over on the starter to clear it out! Now
reconnect and start normally.
Now the scary bit...
Run your engine at about 1/3 of maximum allowable
neutral. (Example 9000 redline? Test at 3000 RPM's...) Hold
throttle very still and do not move it...
Now operate N20
system, and the engines RPM's should rise rapidly, and then
after a second or so should drop back to around 2/3 max rpm
(say 5 to 7 thousand RPM in this case, and sound a little
uneven and a bit spluttery at the exhaust. It may be
misfiring and coughing a bit! But obviously rich with
traces of black smoke maybe visible at the exhaust. If it
does exactly this then you can go and try it out now on the
If the revs
rise then fall back and it runs too slow and/or it stops
completely, it's far too rich!
If the revs rise sky high and stay there! It's too lean, Add
fuel! (Bigger fuel jet) Don't go try it out...
If however it
sounds metallic, harsh, or strange, stop! and send me an
If it sounds like "big end" or "cranky" (ask an older
mechanic!) then it may be in need of a few degrees of retard
on the ignition. Or could be a bit lean for some reason. Or
Make sure you
try this test because it almost guarantees success first
time! Then see below few lines and try again!
If you are
using gravity feed on a motorcycle for e.g. without a fuel
pump, then the bit of 4mm O/D tubing from the solenoid to
the engine/distribution block effectively is your fuel jet.
Non need be fitted at the fuel solenoid valve. This will
provide the correct fuelling for about 40 to 50 bhp extra.
So fit a 40bhp nitrous jet to the nitrous solenoid and away
you should go! but also do the above test first!
If using a
fuel pump and regulator, then set the regulator at 3, to 10
psi as required. At 10 psi the correct fuel jet will be
approx the same size as the nitrous jet used, whatever size
this is.. At 5 psi you would need a jet about 1.3x bigger.
At 3 psi try a jet about 1.5 times bigger to begin with. Or
look at my jetting
Then try the test at the beginning of this section to check
you were right!
My real business was building
Here is one ready to test...
I started building
them to investigate Nitrous Systems initially as there was only really the
Dynojet Dyno available for bikes in those days.
Problem was that the
DynoJet Dynamometer was a bit clunky software wise and its drum was (and still
is) too light. So as usual I built my own better one.. Same with everything I
do. But the development cost was a bit high so I started selling them...
This one actually belongs to Andy at Quill Race Exhausts and was one of my first
customers for dynamometer systems many many years ago. About 1994 or earlier.
Love the floor!
the term NOS is incorrect as this refers to an specific
company (called Nitrous Oxide Systems, in the US)