Basically the electrical side of
Nitrous Injection Systems is very simple! All you need to do
is connect quality cables that will not corrode or fail, to
both the Nitrous Solenoid and the Fuel Solenoid. They must
be wired in parallel so that they both operate together. You
want the fuel and Nitrous Solenoids to work as one!
They need an Arming Switch fitted
inside the car somewhere then is easily reached while
driving. This does NOT operate the system, but simply allows
the power to be switched on ready for when the Throttle
operated Micro-Switch or whatever you use, does!
The Throttle operated switch will
operate the Nitrous System only when
a) It is "Armed"
b) It has the
Bottle
Valve turned on! If this is off, it is just the
same as an empty Nitrous Bottle. You will get the extra
enrichment fuel, but no Nitrous! So it will go slower!
If you need to ask how to actually
connect up a circuit this simple then I suggest you buy a
system it will be safer!
Pulsed Power
Controllers - And bad Jet positioning on US based Nitrous
Systems
A cars fuel injection works like
this. You have a fixed fuel pressure controlled by the
regulator.
This pressure is sat behind some fuel injectors. The
injector is very like a nitrous solenoid in the way that it
operates. A square wave (12vDC) signal opens it for a short
time period (short pulse) for low flow rates like idle, and
long (say 90 percent) of the cycle for say full power
motorway driving. This is known as PWM or Pulse Width
Modulation.
The same technique can
control the flow of fuel extremely accurately with a fuel
solenoid that we will be using with our nitrous system. And
to a degree the same applies to the flow of nitrous.
Unless you are using an
American type system! These are jetted at the very end of
the nitrous delivery pipes, the worst possible place!
If
the flow control jet is located DIRECTLY after the
piston/seal/seat in the solenoid valve as mine, HighPower,
Akamotos are then flow control is almost directly
proportional to the pulse width length. So a 50 percent duty
cycle will actually give 50 percent of the expected Nitrous
Oxide. As will the fuel. Because we are metering Liquid
Nitrous Oxide here with no time to change state or turn to a
gas.
If you fit the Nitrous Flow
Control jet at the end of the pipe from the Solenoid as in a
"NOS Fogger" type (or other cloned US systems like Holley,
Nitrous Express, etc) then you have effectively got a big
reservoir in between the Solenoid (which has a larger
internal cross section than the control jets) and the actual
jet!
What then happens is this. At 100
percent you get the correct amount of fuel and Nitrous
delivered. But at say 50 percent pulse width, what should be
half power is not!
You actually get far more than
this because the bore of the Solenoid is much larger than
the jet on the end of the pipe, so the solenoid just keeps
"topping up" the pipe! The pipe acts as a resovoire. This
effect is VERY pronounced when using small jets and/or a
large solenoid.
Worse, because the fuel is NOT
compressible this stays at 50 percent delivery rate. Meaning
that it runs leaner and leaner as the power level is
reduced! Bye Bye pistons...
This is one of the MAIN reasons
for using a more modern European developed system
Remember even on a big US race
car, a pulse width controller "start" at low power (weak!)
and this begins the heat, pre-ignition, detonation, so when
the 100 percent power is used further down the track the
detonation which is easy to start but hard to stop will kill
your engine...
So, you want to
build your OWN Nitrous pulse controller?
A guy called Simon Holland who
already has done sent me his circuit diagrams and
information to post here. He is using a DIY Nitrous
System with this controller successfully. Some other
members of my Forum are also building and using this.
Here is a copy of his email:
John
As promised some time ago in return for sending me the
circuit diagram, here are some pictures and notes I have got
together when building my controller. It took about two
evenings to build and debug the circuit and so far has done
three passes up the strip and not fallen to bits yet!
I printed the diagram at work using an expensive CAD thing
but have scanned it and saved it as a bitmap so others might
find it easier to open. It is possible to download able
graphics manager for a free 30 day period if people want to
have a better circuit diagram to work from.
His
instructions and how it works below!!!
A bit beyond me I think...
The MOSFET is
what decides how much power the circuit will drive. The one
selected (IRFZ34N) will drive a maximum of 26A if used with
a suitable heat-sink. I mounted the FET to the side of the
aluminium box and with no extra heat-sink it seems to cope
OK driving both the fuel and nitrous solenoids (I am using
Nitrous Works solenoids) If your chosen solenoids are going
to draw close to or exceed 26A it may be necessary to
substitute this with a more substantial FET. I would not
recommend using a separate FET for fuel and nitrous
solenoids as if the fuel FET fails then you will be left
with a dangerously over lean condition.
The prices and
RS stock numbers shown were correct when I built my circuit
but they are subject to change without notice. Check before
placing your order.
Due to minimum
order quantities you may have to order more than you need
(resistors for example come in lots of 10) but the price is
not affected much and you will have some bits left over for
your next project!
Some hints
from CBTS (Another guy on my forum who I think designed this
circuit and who supplied the circuit diagram)
To set up , measure frequency at the lm393
pin 2 , adjust pot for 20Hz.
activate throttle switch , wait till pulsing is at max ,
then use the 'full on cal ' to set the output so it just
turns completely on.
Then set start ,build and max to approx positions required ,
range of start is about 10-40% , max is about 50-100% ,
build time is 0.1 to 5 seconds over pot range.
The frequency can be adjusted if required and if the
solenoids will respond , the higher -the smoother the
delivery , but the less of a progressive range will be
achieved. The lower will give a wider progressive range ,
but a more 'jerky' power delivery.
if you try and pulse too fast , if a little
too fast - the solenoid will not start opening until 50-60%
or so , if much too fast - the coil will 'buzz' , get hot
and the solenoid will not open at all.
If testing this make sure you have full pressure on the
valves as with no pressure any solenoid will able to pulse
much faster!
I had some
problems with the build up time, CBTS's answer was:
look on the
positive terninal of the 47Uf capacitor. With throttle off
check the voltage and see if it changes with the start level
pot . set it to around 1v . then activate throttle - see if
it starts to rise to 6-7V.
If the start voltage is 6-7V the BC337 is permently on or
something is wrong around the start pot , if the voltage is
low but doesn't rise, then either the BC337 is not turning
on , or something is wrong around the build pot and
associated BC557.
If the voltage rises OK , the problem is around the max
level pot.
Cable colours used for
potentiometers
Yellow wires to
VR3 Start up Power level
Blue wires to
VR2 Running Frequency
White wires to
VR1 Build up time
Green Wires to
VR4 Maximum power Level
Disclaimer:
This circuit worked for my application. It was tested on a
closed race circuit. It is the individual’s responsibility
to ensure the suitability of this circuit for use in their
own application. Remember to check your circuit thoroughly
before connecting your solenoids and again with solenoids
before running your engine. Solenoids are best tested with
pressure on them. The author can-not be held responsible in
anyway for any damage or injury caused in using any
information supplied or inferred in this or any related
document.
IE Don’t blame
me if it all goes horribly wrong, people should start to
accept responsibility for their own actions!
OK so this box could be prettier! But hey, its
experimental!
It works OK! Some
comments from the Forum:
I built this circuit
today.
Gave up on my own design...
Worked first time exactly as described with the adjustments.
All fitted, pick up a full 10lb bottle of N2O tomorrow.
Fingers crossed.
Thanks everyone.
Andy.
Yes its cbts's circuit i
have built.
works fine
Excellent work mate :-]
I've built the same circuit and it seems to work well. Just have to
test it under pressure to set it up now!
