Hi,
Please help me with this:

I don´t know and I never have a nitrous system, then I need to clarify some ideas before buy a kit.

What is better a drysystem or wet system for my practically unmodidified L98 engine ?
I supose that my only mod that I need to take out is the chip.

I understand the function of the dry system on my car but I don´t the wet.
Where will be localizated the nozzles and of what part takes more fuel ?
I refering to the nitrous express system that do not use a body throttle plate like the nos dry system.

Thanks and regards

 

http://www.b-body.net/Technical/Driveline/n2o.html

From: Matt Paul

Nitrous, squeeze, juice, or whatever you like to call it, nitrous oxide is definitely one of the more "exotic" (and somewhat mysterious) ways of increasing the output of your engine without breaking the bank. Since I've now had quite a few questions about my nitrous setup (and I promised JPK an article for the newsletter), I thought I'd put what information I have down in writing to share with everyone. I'm not claiming that all the information is 100% correct or complete, these are simply the facts, conjecture, rumors, hearsay, and possibly fiction (hopefully not) that I have gathered before and during my purchase, installation and tuning of my system.

First, a few reminders. You should make sure that your entire vehicle should be in good running condition before attempting to inject nitrous into it. Some marginal items (like worn rings, bad gaskets, transmission, gears, pumps, belts, etc.) that will hold under the stock (or slightly above) output may give out under the additional power delivered by nitrous. Remember that the GM engineers designed a safety margin (above the peak stock levels) in each system that went into your car, but you will be putting a large number of these systems under conditions that they never had in mind when designing it, so proceed at your own risk.

In addition, as with any performance modification that increases the output of your engine, you will need to increase the strength and/or durability of a number of other items on your car to handle to output of your motor. Some items that you need to consider (but by no means is this list complete) are the transmission, rear end, brakes, and tires.

Nitrous primer
To start out, here's a little background on how nitrous works. The major way to increase to output of any engine is to burn more oxygen & fuel during each combustion cycle. Since adding more fuel into the engine is an easily accomplished task (how many of us have seen a car blowing out black smoke because it's running too rich?); the big challenge is getting more oxygen into the engine (and then holding the whole thing together, but that's a whole other article!). Blowers, turbos, cam/head/rocker arm swaps, bore/stroke increases and nitrous all are different ways to accomplish this same goal.

Nitrous injection provides additional oxygen via 2 methods. The first (and lesser effect) is by cooling the intake charge. Since the nitrous is stored in the bottle in liquid form (and usually at about 1000 PSI), when it is released into the intake, it expands into a gas. For those of you who have a physics background, you'll know that this will cause the temperature to drop considerably, which will cause the density to rise. A typical nitrous system will drop the intake temp by about 60-80 degrees.

The second effect (and the greater) is by breaking down into plain old nitrogen and oxygen in the combustion chamber. When nitrous oxide is heated to 572 degrees Fahrenheit it breaks down and releases the oxygen into the mixture, allowing extra fuel to be burnt.

There is a third effect to nitrous injection, which although not directly performance related, is a benefit. The nitrogen released during the breakdown process helps to buffer (dampen) the increased cylinder pressures created, which leads to a more efficient burn of the oxygen/fuel mixture.

"Wet" vs. "Dry" systems
There are 2 basic types of "bolt-on" nitrous system for the LT1, "Wet" systems, which inject additional fuel externally to the conventional fuel delivery system (the stock fuel injectors), and "Dry" systems, which increase the amount of fuel injected by the stock fuel delivery system. Obviously, there are advantages and disadvantages to each.

Dry nitrous injection systems for the LT1 (I'll use the NOS 5176 kit as an example) use the stock fuel injectors to add additional fuel into the combustion chamber by increasing the in-line fuel pressure (to the neighborhood of 80 PSI or so). By raising the fuel pressure (and keeping the injector pulse width constant), additional fuel is delivered into the combustion chamber. The NOS kit does this by applying positive pressure to the fuel pressure regulator, which in turn increases the fuel pressure above the maximum stock levels.

This type of system has a few major advantages. First, it requires no plumbing for the additional fuel delivery. Second, fuel does not flow through the entire intake manifold (the LT1 intake wasn't designed to flow an air/fuel mixture, so thereby doesn't do a real good job). Lastly, as the nitrous pressure in the bottle fluctuates, the amount of fuel delivered will fluctuate in the same amount (since the system is using the nitrous pressure against the regulator to boost the fuel).

There are some disadvantages to this type of system. First, the stock GM injectors may lock up at the 80+ PSI fuel pressures that the system needs (although a set of Bosch/Ford SVO injectors will cure this). Second, the amount of nitrous delivered to each cylinder varies slightly (since it will not be consistently distributed in the intake manifold), while the amount of fuel is the same. Either one of these can cause the air/fuel mixture to a given cylinder to go on the lean side.

Wet nitrous systems inject both nitrous and fuel into the intake via a plate between the throttle body and intake manifold or via an injection nozzle (or nozzles) prior to the throttle body. The biggest advantage to this type of system is that the nitrous/fuel proportion delivered to each cylinder is consistent (although the amount delivered varies from cylinder to cylinder for the same reason that the amount of nitrous delivered varies with a dry system).

The disadvantages to this type of system are that since the LT1 manifold isn't designed to flow fuel, and the fuel may puddle in the intake manifold (although a good rev on the engine after shutting down the nitrous system will clear this). Second, the nitrous solenoid will have to be periodically rebuilt (the seals deteriorate slightly due to the exposure to the fuel vapors). Lastly, if the nitrous pressure fluctuates too high, it may cause the air/fuel mixture to lean out on some cylinders.

As you can see, the common disadvantage to each system is the lack of a consistent amount and/or ratio of nitrous/fuel to all cylinders. The "cure" to this is a direct plumbed nitrous injection system. These types of systems use individual nitrous/fuel injectors for each cylinder, but are mucho expensive! My personal choice was to go with a wet plate type system from Compucar. The cost of the base system is slightly cheaper that NOS's 5176 system (about $500.00 for the Compucar versus over $600.00 for the NOS), and I wouldn't have to spend another $200+ for a set of new injectors.

After deciding on your nitrous system of choice, there are a number of other items that need to be upgraded or at least checked out before you can "get it on".

Fuel delivery
One of the biggest reasons that an engine "goes south" when injecting nitrous, is that the air/fuel mixture goes too lean. The fuel delivery system on anything running nitrous (this applies to blowers, turbos, strokers and most other power enhancers as well) needs to be up to the task of delivering the extra fuel into the engine needed to make power.

For nitrous systems under 100 HP, the stock in-tank fuel pump is usually sufficient. Anything over that amount, and I'd recommend upgrading the fuel pump or adding an extra in-line pump to supplement the in-tank one, depending on the level of additional horsepower. You may not need it, but (and I'll say this a lot!) it's pretty cheap insurance compared to the price of a complete engine rebuild.

A clean fuel filter is another important item. Although I haven't heard of anyone yet that has blown up due to a bad filter, for about $10-15.00, it's too cheap of an item not to replace at regular intervals.

As the HP level goes beyond 150-200 HP, a number of fuel system changes will be needed. Changing to a larger fuel line, or adding an additional feed line will most likely be required, as well as increasing the fuel pickup area and pump flow.

Ignition
Following a close second in importance to the fuel system is the ignition system. Nitrous injected engines require a few changes from the stock setup to perform well, specifically the plug type and gap, as well as the ignition timing.

First, the stock LT1 plugs do not "sit well" with nitrous. The platinum type plugs that come in the LT1's tend to retain heat, and it is possible that they will cause detonation (knock) when used with nitrous. In addition, with the stock ignition, the plug gap should be closed to about .035", so that when the mixture ignites, it does not "blow out" the spark.

I'm not going to recommend a set of spark plugs (it's kind of like wine, everyone has there own tastes/preferences), just make sure they're not platinum, and that the gap is no more than .035" with the stock ignition. Depending on the level of additional nitrous horsepower (and how often you like to "squeeze") a plug that's 1 or 2 heat ranges colder may also be needed.

Reducing the timing advance is the other important factor when using nitrous. I've heard two reasons for this (and I can't confirm or deny either, yet), the first is to reduce the chance of knock, and the second is that the nitrous causes the mixture to burn more quickly, requiring less advance to get the most power. The general rule of thumb is to reduce advance about 1 to 1.5 degrees for every 50 HP of nitrous.

In addition, any form of timing advance over stock (such as with the Hypertech Power Programmer Plus or other after-market PCM programs) should not be used whatsoever.

There other items to consider upgrading if you're going to run nitrous are the stock ignition and coil. Although not absolutely necessary, creating more/longer/hotter spark may increase the "completeness" of the combustion in the cylinder chamber.

Installation
Now on to the real work. After you've decided on your system, and have your parts in hand, it's time to bolt it in. I'm going to try to give an example of a "wet" system installation, since that is what I'm most familiar with, but most of this will apply to a "dry" system as well.

First off is the bottle. A nitrous bottle consists of 4 parts: The bottle itself, the bottle valve, the "blow-off" pressure valve and the siphon tube. I think the bottle and valve are pretty self-explanatory, so I won't bore you with details of those.

The "blow-off" valve is a safety device (usually located directly opposite of the main connector fitting) which is designed to open if the pressure in the bottle exceeds a given PSI (about 1600-1800 PSI).

The siphon tube is simply a slightly curved tube that runs inside the bottle from the valve down to the bottom of the bottle. Its purpose is to make sure that liquid nitrous is picked up from the bottom of the bottle (instead of gaseous nitrous at the top). The tube is curved or angled down slightly, so that at the bottom of the bottle it is near the edge.

The mounting position of the bottle is very important for good performance. The bottle must be mounted so that the siphon tube will be submerged in the liquid nitrous (even under acceleration). The manufacturers provide brackets and a diagram/instructions as to what proper bottle mounting position is. Typically the bottle should be mounted parallel to the centerline (front to back) of the car, with the bottle tilted at about a 15 degree angle (valve end higher), and the fitting for the supply line pointing down.

After the bottle and bracket are mounted, the next task is to plumb the nitrous supply line from the rear (inside the trunk, in my case) to the engine compartment. Although the easiest way would be to run it through the passenger compartment, this is not very safe. If the nitrous line would rupture, the escaping nitrous can cause severe "frost burns" as it expands from a liquid to a gas. I ran mine through a hole I drilled out in the front of the trunk, through the left frame rail and came up into the engine compartment near the fuel lines.

A good safety device (although it is by no means required) is to add a 2nd nitrous solenoid in line with the primary solenoid (Nitrous solenoids are less that $100.00 each). This primary reason is that if a small piece of debris gets into the nitrous solenoid, it can cause the solenoid to stick open after the power to it is shut off. The second solenoid acts as a fail-safe to turn off the nitrous in case the primary solenoid sticks open.

For wet nitrous systems, a supply connection from the stock fuel system is required. Fortunately, this is fairly easy on the LT1's. It simply consists of relieving the fuel pressure in the system (I usually just let the car sit overnight), taking the stem out of the diagnostic schraeder valve at the back of the fuel rail, and attaching a 4-AN line to the valve.

I also added an auxiliary in-line fuel pump to my system (it attaches using the stock type connectors between the supply line and the fuel filter) to make sure I had enough fuel flow for the 150HP system I am running.

For "wet" systems, the nitrous/fuel is delivered by either a plate (that goes between the throttle body and intake manifold), or one or two "fogger" nozzles. The plate type systems typically have 2 "spray bars" that sit in the path of the airflow into the intake manifold. When the system is activated, a number of small holes in each bar spray a fog of nitrous and fuel in to the manifold.

"Fogger" nozzles perform the same function, but do it via a single nozzle (or duel nozzles) which spray the "fog" in front of the throttle body.

The system that I use is the plate type. On the LT1, these simply install between the throttle body and intake. Installing is supposed to be simply a matter of removing the stock bolts, pulling the throttle body out a little, slipping the plate & gaskets in, and re-installing the new bolts.

Unfortunately, (as with most everyone else who has a Compucar LT1 system that I`ve talked to) the thermostat housing on the waterpump needs to be relieved a little (I used a Dremel) to clear the assembly on the bottom of the front side of the throttle body.

Next comes routing/connecting the lines and solenoids. Most nitrous systems (that are designed for a specific engine) will come with instructions and parts to mount and install everything and can be installed fairly easily (although may not be the most "aesthetically pleasing" installations). If you choose to "improve" the look (or go for the "stealth" look and hide the whole sucker) you're going to have to be a little ingenious, and possibly engineer a couple of things. I had to make a couple of brackets, order some extra fittings, and change the length of a few of the braided lines that came with the kit (they were too long).

The biggest issue that I came across was finding a place to mount the solenoids (nitrous, fuel and purge) where they would be out of sight. I ended up mounting mine behind the intake manifold on the passenger's side by using a custom bracket and bolting it to the rearmost intake manifold stud. Believe me, there isn't a whole bunch of room back there, so it took a little persuading to get everything to fit. If you're still running the stock intake system, hiding the install is much easier, since "home plate" will cover almost anything you put on the intake manifold!

Hiding the rest of the lines and fittings was fairly easy, I covered all the lines with convoluted tubing, and painted all the fittings and filter black. The entire installation blends in really well with the rest of the engine compartment, and usually can't be found without a bit of hunting around!

When hooking up your lines and fittings, there are a few things to take note of. First, do not use Teflon tape. If you need to use a sealer, use a small amount of the paste type Teflon sealer on pipe thread fittings only (the AN fittings will seal VERY well without it). The reason for this is that small pieces of the Teflon tape can come detached and get caught in the solenoids. Second, be very careful when tightening down the fitting on the fuel rail connector, it can crack or snap off very easily if you try to over-tighten it.

Now, after all the plumbing and mechanical installation (or nightmares), it's time to hook up the electrical connections. Hooking up the solenoids is simple, connect one side to ground, and the other to a power feed through a switch, and that's it.

An absolute basic installation just consists of the 2 solenoids wired in parallel to a switch (from a "hot in run" power connection). With this type of install, just hit the switch, and VROOM!

I personally would NOT recommend installing your nitrous system this way. I'm pretty sure that these types of installations are why nitrous gets a bad rap, one accidental hit of the switch and BOOM, there goes your engine.

Personally, I recommend at least using 2 switches, the first is a standard toggle switch (which will "arm" the system), wired in series with a throttle switch (these can be bought from most speed shops, or NOS directly) which will activate the system only at full throttle. The solenoids should also be fuse protected. Typically, the fuel and nitrous solenoids will draw less than 15 amps, so you can use most in-line fuse holders found at auto parts stores (just make sure it's rating is at least 15 amps).

Finally, with everything wired up, you will need to verify that everything is working correctly before trying the system out. To test out the fuel solenoid, make sure the nitrous bottle is closed, arm the system, and with the engine at idle, force the throttle switch closed (NOT the throttle, just the switch). If the solenoid is working, and fuel is flowing, the engine should bog severely or even die out from the extra fuel.

Testing the nitrous solenoid is almost as easy. Since the nitrous solenoid is much heavier duty that the fuel solenoid, you should be able to hear a "tick" sound as it opens and closes. If you can't hear it, put your finger on it and try it again it. You should be able to feel the click (but make sure you don't hold on to it for too long, as it does heat up a bit without anything flowing through it!).

Tuning
After the installation is complete, and everything is working correctly, the next step is to try and "dial it in". Before attempting to get the nitrous system tuned, I strongly recommend getting the naturally aspirated air/fuel mixture (O2 readings) set to a safe, consistent level. I found that I needed to replace my EGR valve, add an adjustable fuel pressure regulator and fix an exhaust leak to get my O2 reading where I wanted them.

One of the primary items to running safely and consistently is keeping the bottle pressure at the correct level. Typically, most nitrous systems are designed to run with the bottle at approximately 1000PSI. If the pressure goes over this amount, the air/fuel ratio will become too lean, and bad things can happen. If the pressure is much under this, the air/fuel ratio will be too rich, and a loss of power will result.

To be safe, it is better to run slightly on the rich side. This way if the bottle pressure runs a little high, you won't toast something in your motor (due to detonation, or worse!). A good method for monitoring the air/fuel ratio is via the O2 sensors with an after-market diagnostic program like Diacom, Autotap, etc. I've also heard from a number of the professionals that they like to use exhaust gas temps to check for a lean condition (A lean air/fuel ratio will cause a hotter exhaust temp), but the O2 sensors are much more convenient for me.

I typically look for O2 readings of at least 900mV (although a number of the f-body people like to run them down into the 800's more), with (for me at least) 920-930 "on the bottle" being the target values (I try to run right at 900 mV off the bottle). This is slightly rich, but I like having a little to work with in case the bottle pressure goes high.

There are a few ways to tune in your target mixture ratio (and O2 readings) when using a "wet" nitrous system. You can adjust your nitrous and fuel jet sizes. If you're running rich, go to a smaller fuel jet (or a larger nitrous jet, but this will tend to increase the output of the system, and the strain on your engine). If you're running lean, you can go to either a smaller nitrous jet, or a larger fuel jet.

In addition, if you have an adjustable fuel pressure regulator, you can make some adjustment to the mixture with it as well. The only caveat is that any changes you make to get the mixture correct for the nitrous will affect you when you aren't using the system. You may end up running just right with the nitrous, and too rich or too lean without. The computer will compensate for this in a short time, but any time you disconnect the battery, the computer will have to re-learn the proper fuel trim values.

Additional Goodies
If you're like me (and most everyone else who starts down the "mod path"), you'll want to add some of the "extras" to your nitrous system. These are a few of the items that I've either added to mine, or at least looked at when I put my system together. This isn't a complete list, but it should give you an idea of some of the additional items you can get.

First, the safety related items. An RPM switch (like the ones sold by MSD) is extremely useful in preventing you from activating you system at too low (or high) of an RPM. These devices work as another "activation switch", and only turn on during a preset RPM level. This is helpful (mostly) at the low end, since the rule of thumb (at least as far as I've heard) is not to activate the system below 2500 RPMs or so.

Another good thing to have (if you don't already) is a soft touch rev limiter (MSD, Crane, Accell, Jacobs and others sell these as stand alone items or as part of their ignition systems). The stock LT1 PCM limits the maximum engine speed by cutting off fuel flow. Under normal conditions this will work, since there will not be enough fuel to combust in the cylinder. But when your nitrous is flowing, this will create an extremely lean condition, which can cause damage to your engine internals. A soft touch rev limiter works by cutting off spark to the cylinders in a specific order, which keeps the engine from revving any higher. Worst case, the unburned nitrous/air/fuel will ignite in the exhaust system (much better than toasting a piston or worse!).

Lastly, I would also recommend a fuel pressure safety switch. This is another "activation switch" that you (typically) wire in serial with your arming and other activation switches (RPM switch, throttle switch, etc.) which turns on above an adjustable fuel pressure setting. This type of switch will automatically deactivate your nitrous system if a problem occurs with your fuel system and the pressure suddenly drops off (it can do it much faster than most any human could possibly do), preventing a "lean" condition and possibly saving your engine once again. One thing to note though, for "wet" systems, there is a pressure drop when the fuel solenoid opens, as the fuel must fill up the supply line between the solenoid and the injector. This must be taken into account when installing the fuel supply/solenoid (use the shortest fuel line from the solenoid to injector as possible).

Now, for the "upgrades". One of the most useful (in my opinion) upgrades is to add a bottle warmer. Most nitrous systems are designed to run with a bottle pressure of about 1000 PSI (if the pressure is below this, the air/fuel ratio will run richer). This typically occurs at about 85 degrees Fahrenheit.

An electric bottle heater is basically a small warmer pad (kind of like the ones used for waterbeds) that is held against the outside of the bottle. Usually, the warmer kits come with some type of thermostat (or pressure transducer) to turn the warmer on and off as needed.

A bottle blanket will also help to keep whatever heat is in the bottle from escaping (or keep the hot air out if the temps are really warm).

Another useful upgrade (once again, in my opinion) is to add a purge valve to your system. A purge valve is simply another nitrous solenoid with a small tube coming out of it that is mounted close to the primary nitrous solenoid. It is attached to a "instant on/off" button, and when the button is pushed for « a second or so, it releases the trapped air and gaseous nitrous in the feed line from the bottle. With the supply line purged, when the primary nitrous solenoid opens, liquid nitrous flows immediately. This pretty much eliminates the "bog" felt sometimes when a nitrous system first engages.

One of my other favorite goodies is the progressive controller. As far as I'm concerned these things are the best thing since sliced bread.

What these do, is allow you to gradually bring your nitrous system "in", instead of turning it on all at once. This can be a huge help in getting traction off the line, since you can adjust the amount of nitrous that you inject off the line, and quickly "progress" to injecting your entire shot a little father down the quarter mile.

One last item (this is more of a convenience than anything else) is a remote bottle opener. This device is basically a large solenoid that attaches right to the bottle valve, and allows you to turn on and off the nitrous bottle remotely. It does not replace the main hand valve on the bottle, but works in addition to it.

I've also added some other custom electronics that I (with electronics training and guidance from my friend Eric Danstrom) designed and built. Most of these are just for convenience (and the "OH COOL" factor), but some do improve the reliability of the system by replacing mechanical items with solid-state electronics. Some of the additional things I've added are:

Adjustable electronic throttle switch
Solid state controls/drivers for:
Progressive controller
Purge valve
Bottle opener
Bottle warmer
Aux. fuel pump
Indicators LED's and automatic lamp test circuits for most of the nitrous system components.
I think that the general reputation of "nitrous is dangerous" is just plain false. It is easy to see where it has gotten that reputation, since it is so cheap (compared to other ways of making the same power) almost anyone can just bolt on a system and run it, whether they know what they're doing or not. My opinion is that if you are careful and have the appropriate safety devices, nitrous is as safe as other types of power adders (blowers, turbos, stroker motors, etc.). All of the "incidents" that I have heard of, could have been avoided if the proper precautions were followed and/or safety items installed.

One additional benefit that nitrous does give you is the ability to turn it off when you don't want to use it, saving stress and wear on your drivetrain.

The other general belief is that "nitrous is cheating". I'm not quite sure why, since almost all of the forms of "big" power adders that I know of (including nitrous) use the same method, more air/fuel into to combustion chamber. I kind of like to think this is mostly due to us "juice heads" getting the same (if not better) quarter mile times than the guys with the "big buck" mods for a whole bunch less money. But don't forget, you'll have to keep filling that bottle (and it does go quick). Nitrous is more of the "pay as you go" plan (or should that be "pay as you go REAL FAST plan") for those who don't want to lay out the dollars up front.





[Modified by silver & red CE, 9:32 PM 2/12/2002]

 

Ya, what he said!!!! Whew. Nice write up by the way.

 

Holy crap is that a detailed post. That has got to be the longest post I have ever seen. Nice job.

Someone archive this, this question is asked twice a month and this is the response they should see.


[Modified by Hammer, 10:59 PM 2/12/2002]

 

I didn't write it, my buddy, Matt Paul did. I helped on some of the electronics.

Eric