Put simply, an engine is an air pump. In theory, the more air you cram in and exhaust from the engine’s cylinders, the more power that particular engine is capable of producing. The use of external power adders has been around nearly as long as the internal combustion engine itself, and one of those power adders – the chemical called nitrous oxide – works differently than traditional super- or turbocharging. Advancements in technology over the last several years have pushed nitrous oxide usage back to the forefront of the sport.
We’ve assembled some of the experts in the business of making power with nitrous oxide for this article, including Steve Johnson of Induction Solutions, Monte Smith of NOS/Monte Smith Performance, and Garrett Magers of Nitrous Express to discuss a few of these advancements.
Improving The Base Powerplant
As if spraying huge loads of nitrous wasn’t enough, racers have turned to an old trick used by super- and turbocharged racers by adding water injection to their nitrous systems.
Cooling the piston top and the combustion chamber is the main improvement, and the end result is to remove heat from the combustion chamber and allows for the use of either more jet or more timing lead, depending on the end goal.
The manifold above has been plumbed by Nitrous Express to use both nitrous oxide and their water-meth system, and has all of the hardware hidden underneath.
“There are multiple aspects of the engine that have gotten better,” Johnson tells us. “Guys have learned that creating a camshaft with better exhaust events helps to get heat out of the engine. When we start putting big loads of nitrous into these engines, we make heat. And you have to get the heat out.”
Wider lobe separations and longer exhaust durations in camshaft design have helped immensely, which has widened the tuning window when it comes to setting up the nitrous systems.
As camshaft companies become more involved with serious engine builders, the research and development obtained through dyno sessions, track testing, and experimentation have freed up the nitrous system suppliers to be more spot-on with their supplied tuneups.
“I think we’re a whole lot smarter,” says Smith. “Nitrous oxide injection changes the efficiency at which the engine runs at such a drastic rate – everything burns quicker. Over the years we’ve learned how to modify the engine to make it more efficient and happy on the nitrous oxide.”
With dataloggers, we are able to see variables and diagnostics that were never available to us before. – Garrett Magers, Nitrous Express
“The camshafts have to be huge – you have to hang the valve open and keep it open to get the air through the engine. You also have to open the exhaust valve really early to blow the cylinder down and get the heat out,” he explains.
Take, for example, two 500 cubic inch engines that are virtually identical, save for camshaft opening and closing events. One may make the best power on the dyno at 40 degrees of spark lead to make the best power naturally-aspirated, and the second engine with the different camshaft may only want 34 or 35 degrees to make best power. Add nitrous, and it increases the efficiency.
Computer technology has also greatly improved the power production available from a nitrous-injected machine.
“Data-logging has come a long way in the last few years. We’re able to see variables and diagnostics that were never available to us before, which makes tuning a lot more accurate and in depth,” says Magers.
Just In Time
“Say you have an engine that you’re putting 700 horsepower worth of nitrous into an old-school naturally-aspirated engine; you might have to run that engine in the low single digits of timing to keep it happy. You change the camshaft design to something more modern, and you can run the same engine at 12 or 13 degrees with that much nitrous in it,” says Smith.
Too little timing advance will not hurt an engine, only the timeslip, while too much timing will hurt parts and turn pistons into ashtrays. Along the same lines, running lean will not hurt the engine.
“If there’s no fuel, there’s no fire and no heat. You can’t make fire with no fuel,” Smith says. “You only need enough spark lead in the engine to light the fire and get a complete burn. If you can do that at 30 degrees of timing lead, having 34 degrees in the engine and starting the fire earlier is not going to help you. Your only goal is to light the fire, burn it clean, and get it out of the cylinder.”
One way to test your timing strategy is to remove timing from the engine until the car slows down on the timeslip – that shows the minimum timing that can be run without hurting performance of the engine. Tuning this way keeps the engine from being on the ragged edge, and allows the racer more room to tune for the weather conditions at a different track on a different day.
Keep in mind that an engine that makes 1,000 horsepower naturally aspirated will lose power as the nitrous is activated, as the nitrous oxide displaces some of the air flowing through the engine. The 1,000 horsepower engine may be knocked down 100 horsepower, and every additional stage of nitrous displaces more and more air, so the base power of the engine goes down.
“You only have to look as far as Pro Mod to see this – if it was only a matter of getting more and more nitrous to go faster, guys would add kits to their 600-cube engines to go faster. Instead they’re going to 900-cube engines to make more power,” says Smith.
Improving Quench To Optimize Nitrous Use
One item that’s been on the radar for the past few years is loosening the quench in each cylinder to improve the performance of the mixture’s burn. That goes along with chamber softening, which involves machining out the center of the combustion chamber to a predetermined dimension.
If the engine is not set up properly, it can be very timing-sensitive, and the timing can be dialed back only so far before it becomes a point of no return where power does not improve.
“Loosening the quench dimension opens up the chambers and helps to prevent the engine from detonating, which gives the tuner some leeway in terms of the timing lead they can put into the engine,” says Johnson. “Lowering the static compression and using the correct camshaft can be the difference sometimes in three or four degrees of timing that could be added to the engine if it’s built properly.”
There’s no standard in terms of chamber softening angles; each cylinder head is different, in terms of chamber shape, valve angle, and chamber depth, all of which affect the ability to soften them up. For example, an LS cylinder head or small-block Ford head will typically have a very small chamber and flat valve angle, where the valve is very close to the deck of the head, so it’s more difficult to soften the chamber as there isn’t much meat to work with.
Your only goal is to light the fire, burn it clean, and get it out of the cylinder. – Monte Smith, NOS/Monte Smith Performance
There’s no standard dimension in terms of quench, but .060-inch is a minimum number to shoot for to improve performance. Some big-blocks will have much more than that.
“The heads you have to work with dictates what you’ll be able to get away with,” says Johnson.
The engine’s static compression ratio also comes into play when adding big loads of nitrous oxide. As there’s more than one way to skin a cat, compression ratio can be adjusted through gasket thickness, piston dimensions, chamber dimensions, whether the piston is down in the bore, and more.
Many builders are loosening up the quench dimension and then adding a dome to the piston to raise the compression ratio. The whole point is to slow the rate of combustion and burn the full load of fuel and nitrous, especially in a small-block engine with a small combustion chamber.
Plate Versus Fogger
A plate nitrous system needs to be designed so that when the intake valves open and the pulses are coming through the intake tract, the engine is ingesting the nitrous-fuel mixture evenly – this is critical to ensure performance and tuning capability.
On the other hand, a direct-port nitrous system has nozzles placed directly into the intake runner and shoots the nitrous stream directly into the cylinder. A direct port system can include both nitrous and fuel ports – or just nitrous, in the case of a “dry” nitrous system, which we’ll get to momentarily.
“If two things don’t limit you from using a direct port system, that’s what I recommend all the time. The two limitations are budget and specific class rules,” says Johnson. “On the other side of the coin, plate systems work well. Since we’ve evolved the tuneups, plates work a lot more efficiently than they used to.”
Smith agrees with the use of a direct-port system where possible. “You’re not dependent on the distribution of the intake manifold at all with a direct-port system. Some people mistakenly think that a plate sprays into each runner through the holes and that couldn’t be further from the truth. The plate’s job is to fill the plenum – it acts like a waiting room, since the intake is full of nitrous and fuel and air, when the intake valve opens, it draws what it needs from the waiting room.”
As the direct-port systems don’t displace any of the air in the intake manifold, they’re inherently more efficient.
Dry Nitrous Systems
Technology advancements are behind the exploding use of dry nitrous systems, where applicable. Dry systems rely upon the fuel injectors in an EFI system to provide all of the fuel enrichment right at the injector, instead of an older-style fogger nozzle that sprays nitrous through the fuel stream in an attempt to atomize the fuel and nitrous mixture.
“Dry systems can work great with aftermarket engine management systems that have the ability to add fuel enrichment when the nitrous is activated. As long as you have a good ECU, fine tuning the fuel can be easily accomplished through the laptop without ever putting a wrench on the nitrous system. It’s worth noting that we do not recommend dry systems for carbureted applications or for most applications with factory ECUs,” Magers explains.
“As long as a guy has a good ECU and is comfortable working with his laptop, a dry system is the way to go. The systems are less expensive and they’re easy to manage if the racer is using a standalone system,” says Johnson.
“If a guy isn’t comfortable with this I typically lead them to a wet nitrous system. It seems to be the younger racers that are computer-savvy that use dry nitrous systems, especially among the LS and Mustang crowds.”
The electronic fuel injection systems of today, like the Holley Dominator and others, permit the user to adjust in terms of pounds-per-hour of fuel enrichment in the fuel table; no extra pumps or regulators or other equipment is typically required as long as the fuel system can support the extra enrichment required by the nitrous system. This simplifies the process and allows for much greater control of the nitrous system and fuel enrichment. The use of wide-band oxygen sensors and exhaust gas temperature sensors make the tuning process easier as well.
Quick Video Rundown On The Dry Vs. Wet Difference
“If I can run it dry, I’m going to. It’s just better,” says Smith. “It’s all about atomization – we have to atomize the fuel, reduce the size of the droplet and make it small. With a wet system, it’s all about atomizing the fuel by shearing it with the nitrous bar or nozzle, but with a dry system the injector is already supplying a mist of fuel and the droplets are tiny. Fuel is already atomized very well in an EFI car, so then you’re only worried about the intake system flowing the air.”
When Smith plumbs a dry nitrous system, he places the fuel injector up high in the runner and the nitrous nozzle as low as possible. The reason for doing this is to prevent the engine from being rich at the hit. “We also have to run a fuel delay on EFI cars to prevent a hiccup when the transbrake is released,” he says.
There are also benefits to running a wet nitrous system in many applications, especially where the vehicle may be run on the street for extended periods of time.
“Since wet systems deliver their own enrichment fuel you do not need to run huge fuel injectors. Wet systems can be fueled from the same fuel system that feeds the engine or they can be fueled from a completely separate fuel system dedicated to the nitrous system,” says Magers.
“Using a dedicated fuel system for the nitrous system allows the engine to run on pump gas and the nitrous system to run off high octane race fuel which lessens the need for timing retard while spraying nitrous.”
Large Single Stage Versus Two or More
With the advent of progressive nitrous controllers, and as those controllers have become more precise with their control, many racers have gotten away from the concept of running more than one stage of the giggle gas.
Nitrous isn’t dead. A lot of guys are using it, and a lot of guys are competitive with it. – Steve Johnson, Induction Solutions
“The other side of the equation is for a racer in a class like Top Sportsman and Top Dragster, where they run two stages. They can qualify on two stages and then run on one. That way they can move around during qualifying.”
In terms of tuning the different types of systems, a single stage is much simpler for the end user. The major tuning with a single-stage system comes down to manipulating the timing and getting the chassis to work with the nitrous hit.
“One big single stage system is a lot less cluttered on the intake so it’s easier to work on and easier to tune than multiple small systems. Obviously, some racers can’t hook the full nitrous horsepower right out of the hole so it’s important to have a progressive controller to limit power during the first part of the run,” says Magers.
“Progressive controller technology has increased exponentially over the last few years. The fine tune ability allows nitrous users to run faster than ever before on big and small tire setups. Having a large single stage with a progressive controller simplifies tuning and cost for the end user. Only one set of jets to change, and only one fuel system to flow,” he says.
On the other hand, with multiple stages, each one has to be dialed in in terms of where it will activate on the track, multiple steps of timing retard depending on each stage, and other factors that make them more successful in the hands of an advanced user.
“With a single stage, especially on a radial, you have to hit the tire fairly hard early to set the tire and the chassis, but then you have to back the power off a bit to keep the car from blowing the tire off and keep the car stuck,” says Smith.
Power management is the biggest struggle when it comes to multiple stages of nitrous. More electronics are required to control a big single stage, whereas multiple smaller systems can be managed with timers. Class rules often play a part into the recommendation made by all three of our experts on the type of system suggested to the user.
Importance Of Flowing The System
In a nutshell, setting the system up for optimal performance involves ensuring that there’s even flow and distribution throughout the entire system. Ensuring that the nitrous flow and fuel flow are correct for the horsepower required from the package simplifies the process once the system is installed on the vehicle. It can be thought of as a dyno session for the nitrous system.
“As we flow a system, we have close jet dimensions to work from based on our previous experience. We establish the horsepower, which gives us the nitrous jet dimension, then calculate the nitrous to fuel ratio that we want. Once we have the jet spread and fuel pressure set up, we know the ratio of nitrous to fuel are very close. The only variable at that point becomes dialing in the timing,” says Johnson.
Not only is providing the best-performing system to the customer a goal for flowing the nitrous system, it’s also to ensure that there are no problems when the end-user goes to install the system on the car.
Video Of Flowing A System At Induction Solutions
“Sometimes when a guy goes to install his own system they don’t have the nozzles in the right place or at the right depth, and that’s when the system doesn’t do what it should do if it were correctly installed,” says Smith. “In my mind there’s no difference between blueprinting an engine and blueprinting a nitrous system. You can buy all of the best parts in the world, but if you don’t put it together correctly, it isn’t going to perform.”
“Flowing the entire system ensures that the nitrous system tune will be close on the first run and that the system works as anticipated,” says Magers. “Once we develop and flow a particular nitrous system part number, we lock down that recipe so our systems will achieve very consistent performance right out of the box without the customer having to pay hundreds of dollars to flow test each and every nitrous system.”
Theories abound about nitrous oxide performance and how to get the most from a system. While there’s more than we could possibly cover in this article (or an entire month’s worth of articles), we think the comment below sums up the continued development of the power adder.
“Nitrous isn’t dead. A lot of guys are using it, and a lot of guys are competitive with it. That being said, there’s a lot of progress being made on both the engine and nitrous system side. It’s a continued evolution,” Johnson explains.