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I've put this page together to explain some of the ins and outs of run=
ning
nitrous oxide on your f-body. Hopefully, these will be useful for those
considering a nitrous installation, or just wanting to know what it's all
about. There are many differing opinions on the "right"
installation, or "right" philosophy, and I'm starting this page
with my own knowledge and opinions. Please feel free to email me if you disagree with some=
thing
I've said, I'll try to add your position to the page. How it works
Nitrous Oxide (N2O, I'll call it "nitrous" here) =
is a
non-flammable gas that's used for our purposes as a carrier for oxygen. M=
ixed
with the right proportions of fuel, and fed into the intake, it provides
additional combustible material into the cylinders, hence more power. The=
re
are many ways to get the nitrous and fuel into the motor, and I'll descri=
be
common ones as we go along. The Real Basics
The nitrous is compressed to high pressure (900-1100psi) in a tank, in
liquid form. From the tank (typically fastened down tightly in your trunk=
), a
hose runs up to the engine bay. From there, an electrically controlled (l=
ike,
by a button you push) valve called a solenoid is used to release the nitr=
ous
into the motor when you request it. At the same time, a fuel line in a
"wet system," is controlled by another solenoid, and releases f=
uel
into the motor. This provides the basic mechanism for the nitrous system.=
Wet versus Dry
I'm sure you've heard the terms "wet kit" and "dry
kit." Actually, let me start with a rant on the "kit" part=
. A
kit is a bunch of nitrous components packaged together by any of the usual
vendors, and sold as one item. Typically, these are completely devoid of
safety devices, so that they can be sold at a cheap price. This is where =
the
"$600 nitrous kit" idea comes from. While these are fine for
getting lots of the basic parts, they are horrible from a safety perspect=
ive,
and can easily damage your motor. Get the appropriate safety devices and =
add
them to your kit, if you go that way. I'll be calling a complete setup a
"system" here. On to the wet and dry discussion. A "wet system" is a nitrous
system which mixes nitrous and fuel, and feeds it (in a "fog") =
into
the intake. A "dry system" only feeds nitrous into the intake, =
and
tricks the existing fuel system to add the fuel. In an LS1 car, this is d=
one
via the MAF sensing the colder intake temperature as nitrous is fed throu=
gh
it. In an LT1 car, a dry system typically adds adds<=
/span>
about 50 psi of pressure to the vacuum =
nipple
of the stock fuel pressure regulator, increasing the fuel pressure to abo=
ut
90 psi, and driving more fuel through (hopefu=
lly
upgraded) fuel injectors via the muscle of the add-on fuel pump. Either wet or dry system can be made to work, of course, so how do you
decide which to use? Here's a chart f some pro's and con's with each to h=
elp
you decide:
Delivery Mechanisms
As I mentioned, there are several ways to feed the nitrous and fuel in=
to
your motor. Here are brief descriptions of them. Throttle Body Plate
|
![](3D"NewtoNitrous_files/image001.gif")
![](3D"NewtoNitrous_files/image002.jpg")
This is a 1/2" thick plate that's
mounted between your throttle body and intake manifold. Both nitrous and =
fuel
lines are connected to it (so it's a wet setup) and the plate combines th=
em
and sprays them into the intake.![](3D"NewtoNitrous_files/image003.jpg" "3D\"NOS")
A noz=
zle can
support either a single line for nitrous, or a pair of lines for nitrous =
and
fuel, and sprays them in a fine mist into the intake.![](3D"NewtoNitrous_files/image004.jpg")
The ultimate setup, a port is tapped =
and
threaded specifically for each cylinder, running eight nitrous and eight =
fuel
lines to spray directly into the cylinders. This setup is typically used
above about 250hp, to allow accurate tuning for each cylinder. At left is=
the
|
Fuel pump fails |
A failed pump wil=
l lose
pressure immediately, causing an extreme lean condition |
|
Fuel injector fai=
lure or
lockup |
Using stock fuel
injectors with a dry nitrous kit can cause the injectors to lock up and=
not
flow fuel |
|
Solenoid failure<=
/span> |
A failed fuel or =
nitrous
solenoid can cause serious damage |
Ignition RPM limiter
On a stock LT1 or LS1 computer, the rev limiter is implemented by cutt=
ing
the signal to the fuel injectors so the cylinders have no combustion. If
you're running a dry system, which depends on the fuel injectors to provi=
de
compensating fuel for the nitrous, losing fuel this way is the ultimate
disaster. An aftermarket ignition will typically implement the rev limit =
by
cutting off spark rather than fuel, which is a much safer implementation =
of
the rev limit. Typically, you'd get your stock PCM programmed to set the =
rev
limit up higher than you'll ever expect to go (like 7000RPM), and use the
setting on the aftermarket ignition as your actual rev limit.
Window Switch
This electrical device provides an open or closed circuit based on the
engine being between two RPM values (hence "window") that you
chose, so that you'll only flow nitrous in this range. Why would you do t=
hat?
Well, for two very different reasons.
At low RPM, think about what's going on: you're spraying nitrous into =
the
intake at a constant flow. That is, the nitrous bottle and solenoids have=
no
idea what RPM you're at, and they're just pushing it into the intake at a
constant volume. Inside the engine, though, the nitrous and fuel combinat=
ion
is being sucked into the cylinders during every stroke. The net result is
that at low RPM, you're getting far more of the mixture into the cylinder=
s.
At 3000 RPM, for example, you're getting twice the amount as at 6000 RPM.=
So,
you can imagine that running nitrous at, say 1000 RPM, is far more stress=
ful
on the motor as at 3000 RPM, and typically causes a "nitrous
backfire" - meaning that the nitrous/fuel combination can explode in=
the
intake manifold (rather than the cylinders) - a bad thing. So that's why =
you
don't want the system triggered at low RPM.
At high RPM, the situation is easier to explain. Given the discussion =
of
the rev limit above, you may just want the nitrous system to cut off befo=
re
hitting that rev limit. If you've got a stock LT1 or LS1 ignition, you
certainly want a window switch. If your rev limit is implemented by an
aftermarket ignition, it's perfectly safe for the motor to run nitrous during the rev limit. It's not particularly =
easy
though, on your transmission or clutch to have all that power during the
shift, which may be a reason to keep the window switch set a bit before y=
ou
shift.
Fuel Pressure Safety Switch (FPSS)
This is a device that's plumbed into the fuel system, and provides an =
open
or closed circuit based on availability of fuel pressure. It can be used =
in
the triggering circuit to make sure the system isn't on when you've got a
fuel problem. Typically, you only use it to switch off the nitrous soleno=
id;
turning off the fuel solenoid as well can start a cycle of switching the
solenoids on and off while the pressure raises and drops in the fuel syst=
em
when you're switching the solenoid on and off. Let the pressure build up =
in
the fuel lines when you open that solenoid, and when it's high enough, the
nitrous solenoid will open. The switch can be used whether you've got a w=
et
or a dry system. You can adjust the pressure at which it triggers by usin=
g an
allen wrench on the back of the switch (loose=
n the
screw lowers the pressure threshold).
You want to set the pressure on the FPSS, such that if the pressure dr=
ops
about 10psi the nitrous system will shut off. On a wet LT1 system, this w=
ill
be around 33psi, and on a dry system I'd leave the switch just above stoc=
k,
say 45psi.
To set the threshold pressure, you've got a few options"
1.
Connect enough plumbing so that you can ha=
ve
the FPSS installed at the same time as a fuel pressure gauge. Turn the ke=
y on
to pressurize the fuel system, then turn it of=
f. As
the fuel pressure bleeds down, monitor the continuity across the FPSS
contacts (disconnect them from the rest of the nitrous system) and when t=
he
pressure reaches the level you're interested in, adjust the screw on the =
back
so it just balances back and forth between the continuity signal.
2.
You could use an air compressor, with the
appropriate fitting for the FPSS. Remove the FPSS from the car, and threa=
d it
onto the compressor. Set the compressor for the pressure of interest, and
measure continuity as above.
3.
If you can't do option=
#1
above because you don't have two available ports, first thread in the
pressure gauge, and cycle the key. Then time how long it takes for=
the
pressure to bleed down to the correct level. Then disconnect the pressure
gauge, install the FPSS, and do the process against the clock rather than=
the
pressure.
Timing Retard
A nitrous/fuel mixture increases the burn rate in the cylinder, and
typically adding a few degrees of timing retard is recommended for safety=
. A
rule of thumb is two degrees per 50hp of nitrous, but this will also redu=
ce
the power generated. When I tune my system, I monitor engine knock, and
retard the timing only enough to eliminate the knock, which is usually ab=
out
one degree per 50hp. At the track, under harder conditions (actually pull=
ing
the weight of the car, possibly higher outdoor temperatures, etc) I'll ad=
d a
degree of retard.
The LT4 Knock Module is a common modification to 4th generation f-bodi=
es.
This device dulls the sensitivity of the knock sensor readings, which all=
ows
the PCM to avoid seeing noises from headers, exhaust and loud valvetrain parts incorrectly as knock. The net resu=
lt is
that the overall timing of the engine is advanced a bit, and the PCM is a=
bit
less sensitive to all knock, whether real or false. Unfortunately, knock =
when
running nitrous has more of a chance of doing
damage, and it's not at all clear that using a LT4 KM while running nitro=
us
would be a good thing. Personally, since I tune my nitrous while watching
knock, and retard my timing as well, I do use the LT4 KM. Once again, tho=
ugh,
it's your call on all these safety issues.
High Octane Fuel
High octane gas (e.g. 100 or more, unleaded) will also slow the burn r=
ate
in the cylinder. This will provide another way, similar to retarding timi=
ng,
to avoid knock. I only use nitrous on a 50/50 mix of 92 octane pump gas a=
nd
100 octane racing gas. Make sure it's unleaded, of course, or you'll dest=
roy
your O2 sensors.
By the way, watch out for Octane Boost claims. Typical claims are
"8-10 points of octane boost for a tank of gas." You should be
aware that these "points" are tenths of a point of octan=
e as
you'd purchase at a gas station. So the above example will raise your oct=
ane
from 92 to 92.8 or 93, not 100-102 as you might think.
Don't assume that if high octane fuel helps on nitrous motors, that it=
'll
help your naturally aspirated motor too. A naturally aspirated motor is t=
uned
for a particular octane of gas; adding more doesn't help one bit. Save yo=
ur
money.
Nitrous Filter
A simple part, but essential in any nitrous system. This filter is add=
ed
in-line to your nitrous line, between the tank and the solenoid. Install =
it
as close to the solenoid end as is convenient. It will trap any small
particles that may come through the line, much like a fuel filter. A comm=
on
solenoid failure is due to some particle jamming it open.
Fuel Systems
Your fuel system is the most important part of the system. As I hope is
clear by now, the worst scenario in a nitrous system is a lean air/fuel
mixture. The solutions to a good fuel system depend on the type of nitrous
system you're using.
On a wet system, you simply need to ensure that your fuel system can
supply adequate fuel, at standard (~45psi at WOT) pressure. A stock f-body
fuel pump can usually supply enough fuel for around 450 total horsepower =
to
the motor; any more and you want to get a larger pump. Much more than 650=
hp
and you'll want larger fuel lines as well.
On a dry system, not only do you want adequate fuel like the wet syste=
m,
but on an LT1 setup the fuel is added by raising the fuel pressure, which
forces more gas through the injectors. In this scenario, it's typically
recommended that you replace the stock fuel injectors with better quality
(not higher rating, just better, like Bosch) injectors. These injectors a=
re
able to handle the increased fuel pressures necessary.
Spark Plugs
Generally you want to use copper spark plugs as opposed to the stock
platinum ones. You also want to reduce the gap from the stock 0.050"
down to 0.035"-0.040". I've received a couple notes on why
you use a smaller gap. "The reason you want a smaller gap is because=
of
ionization. If you change from the typical air (78%nitrogen, 21%
oxygen)/fuel ratio, a given gap requires more energy to ionize the mixtur=
e,
resulting in less energy in the spark, if you even get a spark. You could
also increase the coil voltage instead of decreasing the gap, but I think
using a smaller gap would be preferential since the spark time will be
smaller." and also this message: "The reason that you will close
the gap on your spark plugs is because when nitrous is added, it raises t=
he
cylinder pressure, much like a supercharger. Therefore "blowing"
the spark out. When you close the gap it cannot put out the spark as
easily."
Testing Solenoids
I mentioned failed fuel or nitrous solenoids doing damage. Some of the
issues here may be hard to cover with only other safety devices. I recomm=
end
you wire your solenoids with spade clips, so you can easily disconnect th=
em,
and test them on a regular basis. Simply disconnect them from the rest of=
the
wiring, then ground one side, and connect the other side to 12V, and list=
en
for the click-click to make sure they open and close. Some folks will also
use two nitrous solenoids, in-line, which will ensure that both would hav=
e to
fail before the flow would fail to stop. Of course you still need to test
this setup, to ensure one isn't stuck open.
Tuning
All of the kit systems will come with a couple tuning setups, labeled
"50-shot", "100-shot", etc. These are tuned to provide
50, 100, or other horsepower amounts, usually measured at the crank (i.e.,
measured on a chassis dyno you'll get a bit l=
ess).
I consider these a starting point, and certainly good for your first pass=
es
(hopefully you'll make these with the lowest power, until you tune the sy=
stem
up). Once you've got the system installed and functional, though, tuning =
it
is paramount, before running any serious power through it. I really recom=
mend
you do this tuning right away, even though the temptation will be strong =
to
just go out and enjoy the power. This is the time you're very likely to do
some serious damage to the motor, so it's important to get it set up righ=
t.
Getting Started
I'm not going to go through a bunch of details on tuning here, other t=
han
to mention some ideas. You've got a plumbing system to test, as well as an
electrical system. You'd like to test each component of both systems, to
verify that it's correctly doing it's job. I s=
uggest
doing most of this in your garage, with the nitrous and fuel lines removed
from the intake, and pointing (or held) into a rag. Keep in mind the nitr=
ous
line will give a good kick under pressure, so don't just leave it loose to
whip around. You can test your WOT switch easily enough, your window swit=
ch
(maybe set the window range at a lower rpm for the test, so you don't hav=
e to
rev up to your red line). To test your fuel pressure switch, you'll need =
to
verify it's got a closed circuit when the engine is running (showing adeq=
uate
pressure), but you'll also want to verify that it opens the circuit as fu=
el
pressure drops. There are a couple ways to do this. On my car, the fuel
pressure bleeds off at about 2psi per hour. So if I switch the engine off=
, I
can use an ohm meter to check continuity across the FPSS connections, and
within a couple hours it should switch off. You can also test the FPSS on=
an
air compressor, by generating the pressure you want for the FPSS, and
monitoring that it switches at the right point.
For the plumbing, you of course want to verify that there are no fuel or nitrous leaks in the system. You shou=
ld be
able to leave your nitrous bottle open for hours without losing bottle
pressure. On the fuel side, of course a fuel le=
ak may
be the most disastrous possibility, so check this first by pressur=
izing
the system (turn the key to "acc" but don't start the car) and =
feel
around all the fittings.
I haven't listed all possibilities, but hopefully given you an idea of
where to start testing. Once everything seems to check out, put in a set =
of
50hp jets, and move out on the street...
Jets
![](3D"NewtoNitrous_files/image005.jpg" "3D\"Nitrous")
All
nitrous systems use "jets" inserted in the fuel or nitrous line=
s to
limit the flow. These jets have openings of a specific size, measured in
thousandths of an inch. So a "35 jet" is a jet with a hole drilled 0.035" through it. Increasing a ni=
trous
jet size will make the system run more lean,
increasing the fuel jet size will make the system run more rich.
There's also a good web =
site
with a jet size calculator on it for a wet setup (where you're metering t=
he
fuel and nitrous yourself). It will give you jet sizes based on desired
horsepower, fuel and nitrous pressure. I recommend you use these as a tar=
get,
maybe start a bit richer than shown.
I don't have information here on the use of a jet to apply vacuum pres=
sure
to a fuel pressure regulator, as in the NOS 5176 kit. The use of jets for
this purpose, and calling them "fuel jets" is NOT related in any
way to the normal use of fuel jets in a wet system, and I'm not aware of
algorithms that would allow you to select these jets in combination with
nitrous jets, to create a certain amount of horsepower. Contact the nitro=
us
kit vendor for recommendations.
Scanner Tuning
A PCM scanner (Diacom, Autotap,
etc) is crucial to successful tuning of your nitrous system. I run most o=
f my
nitrous passes while logging with an Autotap,=
and
also use it at the dyno. You'll be monitoring=
the
oxygen sensor voltages, knock, etc, and adjusting the jets to provide the
best combination. Note, though, that the stock oxygen sensors are not
particularly good, and a wideband O2 sensor (say, at a dyno)
is much better to use if you have access to one. Typical O2 values should=
be
around 860-880mv (higher is richer) when running the motor normally aspir=
ated,
and I try to tune mine to 900-940 on nitrous. As mentioned above, you'll
adjust jet sizes up or down to enrich or lean out the mixture. You'll
probably see some knock during a shift, but
should see none otherwise. You can add timing retard to reduce knock.
Dyno Tuning
Doing your scanner tuning at a dyno provid=
es
another benefit, since you can see the power the engine is generating, wh=
ile
you tune the system. It also makes the whole tuning process easier than
racing up and down the track, swapping jets in the pits, waiting in lines,
etc.
How much can I run?
On a stock V8 LT1 or LS1 motor, 150hp appears to be the limit. 125hp is
probably a "safe" setup, assuming it's working well. A built,
forged motor can take quite a bit more, 200-250hp is probably reasonable,=
but
you'll be going to direct port if you want more power. On a six-cylinder
motor, 75-100hp seems to be the highest "safe" setup. Of course=
, I
use the term "safe" very loosely here, to mean that folks have =
run
this amount of nitrous for quite a while without blowing up their engines=
.
Miscellaneous Options
Purge
Most nitrous systems are build with a purge
feature. The purpose of a purge is to get liquid nitrous oxide up to the
front of the car, filling the hoses with nitrous
rather than air. To do this, another solenoid is used, but rather than
shooting the nitrous into the motor, it's usually shot up over the hood, =
so
you can purge until it creates a nice fog. It also looks real cool :). Of
course, no fuel is used during a purge.
Bottle Heater
It's virtually mandatory that you install your nitrous system with a
bottle heater, which is used to raise up the
temperature of the bottle, and therefore increase the pressure at which t=
he
nitrous is delivered. If you don't use one, your pressure will quickly dr=
op
and won't supply the volume of nitrous your vehicle was tuned for.
Remote Bottle Opener
Normally, your nitrous bottle should be kept closed, with no pressure =
in
the nitrous lines. But when you're lined up against that guy that just lo=
oks
a bit too fast, you'd hate to say "excuse me, do you mind if I hop o=
ut
and open my bottle in the trunk?". Easy solution, get a remote bottle
opener! Most vendors have such a device, which allows you to open the bot=
tle
electrically via a switch on your dash.
Collateral Damage
You can break tons of other parts on your car by running nitrous, or any other large power adder. Running sli=
cks at
the track will just accelerate the damage. Here are a few things to keep =
in
mind.
Clutch
The huge torque spike at low rpm's is particularly hard on clutches. I=
had
to buy a new clutch as soon as I made my first pass with nitrous on slick=
s.
Keep in mind, on a manual transmission car, yo=
u're
likely to need one too.
Rear End
Not unique to nitrous, but certainly a common failure on high horsepow=
er
cars, is the rear end. A 4th generation f-body, with a stock 10-bolt rear
end, is not going to last long on nitrous. Pla=
n for
an expensive (~$2,000) upgrade at some point.
Tires
With all the extra power, you'll have trouble hooking up with any
traction, especially on street tires. You'll probably have to use drag
radials at least, or slicks if you're adding any significant power.
Thanks
... to Larry Kash for corrections to this =
page
Note: Running nitrous oxide in your e=
ngine
can be very dangerous, and the above document is intended on helping you
understand generally how it's done. My recommendation is that you not do =
it
at all, unless you can afford a new motor if something goes wrong. In eit=
her
case, the information above is just my recommendations, and in no way is a
guarantee, or acceptance of any responsibility on my part.
I happen to use mostly NOS components in my nitrous system, and
consequently you'll see pictures and examples of NOS products on my pages=
. I
don't necessarily suggest that they are the best products, though.
Specifically, I'm not happy with the NOS solenoid
failure I had, and the customer service response. I would probably
recommend another vendor's solenoids, like NX.