MASSMATICS

An advanced nitrous oxide article written by and on loan to us from one of the best in the business. PDQmotorsports.com would like to thank the legendary Butch Schrier for sharing this information.

The Measurement of Pressure

I know for many, this data will be very rudimentary, but for those who have not seen any of this, I am sure it will help a little in understanding the basis for the collection of data to baseline an engines “desire” for air. In all of the experiments associated with nitrous flow the complete understanding of pressure is all important.

Many people have difficulty converting quickly from "pounds per square inch" to "inches of mercury", or from "ounces per square inch" to "inches of water" or "inches of Mercury". This often leads to confusion.

Pressure Equivalents

One pound/sq. inch = 2.04 inches of mercury
One pound/sq. inch = 27.72 inches of water
One pound/sq. inch = 16 oz./sq. inch
One inch of mercury = .491 lb./sq. inch
One inch of mercury = 13.6 inches of water
One inch of mercury = 7.866 oz./sq. inch
One ounce/sq. inch = 1.7325 inches of water

We use mercury when we want a very accurate measurement of pressures up to perhaps ten or fifteen pounds per square inch. One psi is equivalent to a little over two inches of mercury. It's not at all unusual to measure five or six psi using a mercury "U tube" and reading the pressure in terms of inches of mercury-as we do when measuring the air pressure from the turbocharger to the carburetor. For pressures less than one pound per square inch, some people use ounces per square inch. However, the usual practice in the USA is to use either a water manometer or mercury manometer because these can be read accurately and there is no danger of the instrument being "out of adjustment". Gauges require constant calibration to be completely reliable.

The one interesting thing we have to deal with in a nitrous injected engine is the displacement of both volume and pressure within the intake manifold during nitrous enable conditions. This is why intake manifold configuration is so important.

I have included a color print out of a data set that I offer as a way to better understand the relationship between the throttle plate and the pressure inside an intake manifold. While this data set is a little complicated, I have made notes on it in an effort to help make it a little easier to decipher. This data set was collected on one of the most accurate dyno facilities in the country. Many of you know that I started my business in 1984 as a manufacturers agency and it grew in to an engineering consultancy. This data set was a baseline study of the relationship between MAP (manifold pressure) signal, O2 signal, and TPS (throttle position) that I performed as I completed a catalyst recovery study for the American Petroleum Institute.

While it is not a nitrous charged engine, the relationship and the data set is very valid as a model of what is going on in the intake manifold when it comes to absolute pressure. The better we understand what lives inside that hunk of metal or plastic, the better we can be when we go to screw with that signal once we introduce nitrous oxide into it.

Massmatics lives in this study through a better understanding of signal interruption, atmospheric displacement, and data quantification management.

Formulas for Cubic-Feet-Per-Minute (CFM) Air Flow Requirements. Determining specific airflow requirement for any engine requires only the application of the following formulas:

Naturally Aspirated Engines (Carbureted)
CID x RPM . 1728 . 2 x .85 = CFM Required

The engine airflow requirement determined by this formula is at 85-percent of volumetric efficiency for four-cycle engines. For two-cycle engines double the cubic feet/minute valve.

1. Determine the cubic inch displacement of the engine from the identification plate or the user's manual. (If the displacement is known in cubic centimeters, convert to cubic inches by multiplying cubic centimeters by .06102. If in liters, convert to cubic inches by multiplying liters by 61.02.)

2. Multiply the figure by the RPM figure corresponding to the maximum engine speed at wide-open throttle. (Use the point at which the tachometer is redlined. If the engine is not equipped with a tachometer, refer to the user's manual supplied with the vehicle or engine.)

3. Divide this CIM (cubic inches per minute) by 1728 to obtain cubic feet per minute.

4. Divide the result by 2 for 4 stroke engines.

5. Multiply the figure you obtain by .85 for 85% volumetric efficiency.

6. This figure is the precise airflow requirement for the engine, accurate to one cubic foot/minute.

Example:

351 CID x 4000 RPM = 1,404,000 cubic inches per minute

1,404,000¸1728 = 812.5 CFM (2 stroke)

812.5 ¸ 2 = 406.25 CFM (4 stroke)

406.25 x .85 = 345 CFM (at 85% volumetric efficiency)

Fuel Injected Engines

Due to improved intake manifold design, use 100% of volumetric efficiency for fuel injected engines.

CID x RPM ¸1728 ¸2 = CFM required.

Example:

351 CID x 4000 RPM = 1,404,000 CIM

1,404,000 ¸ 1728 = 812.5 CFM (2 stroke)

812.5 ¸ 2 = 406.25 CFM (4 stroke)

406.25 = 406.25 CFM (at 100% volumetric efficiency)

Turbocharged Engines

CID x RPM ¸ 1728 ¸2 x % boost pressure + 1.00 = CFM Required

Normal air inlet pressure to the engine is 14.7 PSI (one atmosphere). Adding a turbocharger merely serves to increase the inlet pressure. For example, 6 PSI boost equates to 14.7 PSI plus 6 PSI, or a combined inlet pressure of 20.7 PSI (or 140% of one atmosphere) at sea level. Here is how this works starting with the above formula:

I. One atmosphere equals 14.7 PSI.

II. 6 PSI boost equals 40% of one atmosphere.

III. Thus you must multiply the normal CFM by 1.40 to establish the requirement for six pounds of boost pressure.

Example:

351 CID x 4000 RPM = 1404,000 CIM

1,404,000 ¸ 1728 = 812.5 CFM (2 stroke)

812.5 ¸ 2 = 406.25 CFM (4 stroke)

406.25 x 1.4 = 568.75 CFM (at 6 PSI boost)

AIR PROPERTIES

1. Weighs .076# per cubic foot @ 59° F and 29.92n HG pressure.

2. Weighs 3% less for each 1000' above sea level. a. Weighs approximately .042# per cubic foot @ 15,000' altitude.

3. Weighs 1% less for each 10° above 59° F. a. Weighs approximately .0714# per cubic foot @ 120° F.

4. 1 cubic foot of air contains .21 cubic feet of oxygen. (59°F, 29.92 HG) "

EFFECTS OF ALTITUDE ON POWER OF NATURALLY ASPIRATED ENGINE

1. Since weight (density) of air consumed determines available horsepower from a given engine:

a. Deduct 3% from rated horsepower for each 1000' above sea level.

2. 7# of air are required to produce 1 horsepower for 1 hour. A naturally aspirated engine can pump into its cylinders only a fixed volume of air regardless of its weight.

a. An engine that breathes 92,000 cubic feet of air per hour will take in 92,000 x .076# = 6,992# of air at sea level.

b. Since 7# produces 1 H.P. for 1 hour 6,992 . 7 = 999 H.P.

c. At 15,000 ft. altitude, air weighs only .042# per cubic foot, thus 92,000 x .042# = 3864# of air. 3,864 -. 7 = 552 H.P. @ 15,000' altitude, a difference of 447 horsepower.

3. 3%/1000' altitude power decrease does not take into account the effect of friction power loss.

EXAMPLE:

100 Brake (Shaft) H.P. @ Sea Level

+15 Friction H.P.

115 Indicated (Total) H.P. @ Sea Level

x .7 30% Decrease @ 10,000' Altitude

80.5 Indicated H.P. @ 10,000' Altitude

-15.0 Friction & Accessory H.P. or... 34.5% Less Brake H.P. @ 10,000' Altitude

AIR-TERMS AND MEASUREMENT

1. The condition of air is described by the terms:

a. Atmospheric pressure.

b. Absolute pressure.

c. Pressure differential.

d. Volume.

e. Weight and density.

f. Gauge pressure.

Atmospheric pressure

Atmospheric pressure is the absolute pressure above a perfect vacuum at any geographic location or temperature.

a. The atmospheric pressure at sea level is calculated to be 29.92" of mercury column or 14.7# per square inch at 59° Fahrenheit temperature.

b. Any change in altitude, temperature or movement of atmospheric air masses will change this figure, as shown on a barometer, which registers in inches of mercury column.

Absolute pressure

Absolute pressure is the actual pressure above a perfect vacuum, which is impractical to produce mechanically.

Pressure differential

Pressure differential is the difference between two pressures, generally with reference to atmospheric pressure as one of the two.

a. Intake manifold depression (vacuum) is actually a measurement in inches of mercury between atmospheric pressure and absolute pressure within the manifold as produced by controlling the air inlet with a throttle valve, and pumping air from the manifold into the cylinders, thereby reducing the pressure in the manifold.

b. Average absolute pressure obtainable inside the intake manifold of an unloaded engine is 9" of mercury, or about 41/2# per square inch above a perfect vacuum. Since the mean atmospheric pressure at sea level is 29.92n HG it follows: 29.92" atmospheric (absolute) - 9" = 20.92" manifold depression (vacuum).

Volume.

a. Volume is constant, being a measurement of space rather than a condition of air or gas.

b. Since an engine of given displacement pumps air into cylinders of a constant size, the volume of air and gas required to fill those cylinders is constant. When the carburetor throttle valve is closed causing a high manifold depression (vacuum), the pistons continue to draw the same volume of air and gas into the cylinders-only the weight and density of the charge are less. A supercharged engine also draws the same volume into the engine, with the weight and density of the charge being greater.

c. The only change in total volume entering the cylinders occurs when R.P.M. is changed. The same volume is drawn in per revolution, however there are more or less revolutions in the allotted time.

Weight and density of air.

a. Weight and density of air of a given volume, vary proportionally with pressure. An air receiver tank filled with air at atmospheric pressure will float on water, whereas the same tank of air pressurized to 1000 pounds contains a more dense mass of air, and the increased weight will cause it to sink.

b. While total weight of the charge drawn into a cylinder does not increase, the charge becomes more dense as the piston compresses it. Consequently the charge becomes heavier per cubic inch of volume when compressed.

c. Weight and density of the charge introduced into the cylinder on the intake stroke directly affect density upon compression. The more dense the mass is within practical limits, the more power will be produced when ignition occurs.

d. A higher compression ratio may be used at high altitude, as the mass drawn into the cylinder weighs less and may be compressed more to reach practical limits of density when ignited.

e. Gauge pressure may be absolute pressure as indicated by a barometer. It is generally a measurement above or below atmospheric pressure, as 100# gauge pressure on an air receiver tank.

Why is this stuff important? It is the basis of how we quantify an air fuel ratio with in the normally aspirated and non-normally aspirated engines. With a set nitrous to fuel ratio, we can to a certain degree develop a specific quantity of nitrous to introduce into an engine. All we need now is to know beyond a shadow of a doubt just how much a molecular weight of 44 means in pounds per hour gaseous or liquid nitrous oxide. Once we have that, the fuel side of the curve is easy.

Off the Diving Board We go…

Here is where things start getting interesting. I would like to start that journey with what I know as the functional understanding of the cause and effect challenges associated with the movement of nitrous oxide through a specific flow path. The challenges of moving a gas over liquid mix through a flow path that can extend over 20 feet and calibrate it's delivery into an engine is what I consider when starting a design assessment and targeted challenge of a nitrous oxide injection system.

One of the first experiments I performed at NOS was a delivery line creep study. In this study we drew on several data points in which to try and quantify what effect the flow path had on what I perceived as an extension of the totals storage capacity of the nitrous bottle. The first part of the study included the construction of our delivery line. We studied both –4 and –6 line sizes. In this case I wanted to try and define some of the original questions that I had that actually has lead me down this path. I wanted to know just exactly how we would loose flow in mass across the flow path leading to and including the solenoids. I had no idea that this would start this massmatics thing.

I can’t find the –6 data but I remember the –4 effects. At pressures of 950 psi, the –4 line would expand to a size of .307 when measured out of direct sunlight and at about 72 degrees F. This was important because as the area of the line increased, so did it’s effect on not only bottle pressure but the sweet nitrous storage capability of the flow path leading up to the solenoid. Start asking yourself all the “why do you purge, and how effective it is” questions right now.

The standard OD of a –4 Teflon hose is about .295”. So, hit it with 950 psi and it goes to .307”. I can’t find my calculator on my desk right now but you can do the math of the AREA differential between .295” and .307” and you can start to see what I mean. Do your area calculation for a 12” piece or segment of tube, multiply it by the length of your nitrous feed hose, and you can start to see what I am talking about here about the control of phase change, nitrous stagnation, and final nitrous to fuel ratio control.

The line shrinks to .301” during nitrous enable, which is pretty interesting when you want to try and manage the delivery of nitrous in a controlled manor. Now…that I am sure sounds a little redundant but as we started this particular study, it was out idea to not only map the pressure fluctuation during nitrous enable. But map the effects of pressure drop across the flow path in mass. Once we discovered that the flow path itself was out of control, my education concerning the way we are never really in control of nitrous delivery had started.

Ok…so now, the study. We assembled 20 feel of 4 foot pieces of nitrous delivery line. At each junction we would add a nitrous gauge so we could watch the pressures as we drove our nitrous flow path at 10-second intervals. The bottom line is that for every 4 feet of flow path feed line you experience about 25 psi of pressure differential. These tests were conducted with a 10# bottle that we maintained up to pressure with an NOS bottle heater. We wanted to use a 10# bottle specifically because of the quantity of 10# bottles in the marketplace but also the delivery line was vented directly to atmosphere to increase the pressure drop of the bottle to the maximum. If we installed a plate on the end of each junction (unless it was a cross bar or annular) the pressure drop would have been less. We saw some really cool results with this and this single study probably made me start to think or better yet anticipate some speculative hypotitist in which to move forward on some of my ideas that I still maintain today.

I am convinced that there is a cyclic phase change as the nitrous migrates through the feed line but the resolution of the experiment could not identify this phenomenon. I still think it happens and someday I will have the data acquisition sophistication to validate or dis-prove this opinion.

What the Hell is Sweet Nitrous?

I have always maintained the belief that you only have about 30 to 33% sweet nitrous in your bottle at a full fill condition. The 3% variance is accounted for by the atmospheric conditions that surround the bottle. This is why I am moving all of my very high consumption nitrous users into 15# bottles. As we walk through all of this stuff and you read some of the nitrous flow curves you will understand this better. Many of the old timers understand that the larger the bottle the more mile an hour a race car will run without fully understanding why….I am getting ahead of myself on this.

It is the visualization of the factor of equilibrium within any given point within the nitrous oxide injection flow path that requires the most study and initial consideration. You see, many people speculate as to how nitrous looks in storage and what it looks like while it is moving through the flow path on the way to the engine. With nitrous, the term equilibrium is an important visualization tool for doing just that. In fact equilibrium is what allows us to have "sweet" nitrous and un-useable nitrous in the bottle.

When I was working at West Virginia University, I had access to a lab stand that held propane in equilibrium. This stand had a glass in it so you could see the liquid propane with the high-pressure gas cap above it. I would hook this stand to my glass engine or to a Bunsen burner, and the propane would start to boil whenever we would draw it off. The reason for the boil off lies in the desire for the propane to try and reach a condition of equilibrium by generating gas from the liquid….this is called phase change. The same thing happens to nitrous oxide. The minute you start to draw nitrous from the bottle, it starts to boil to attempt to return to a state of “balance” between gas and liquid. This event inside the intake manifold I have labeled “atmospheric equilibrium. In the case of the nitrous storage bottle, the minute there is a pressure of less than 760 to 780 psi, all liquid flashes to a gas….and makes no power.

It is equilibrium that causes us to question our flow paths and in fact is the reason why I use the term “Atmospheric Equilibrium” to describe the action of nitrous oxide as it enters into the intake manifold. Again, to be redundant here….this term is to describe the condition of expansion within the intake cavity until the nitrous can no longer seek a “pressure balance” even in the less than atmospheric pressure conditions.

Equilibrium as it is defined in the dictionary is "balance between two opposite weights or forces". In case of a nitrous system application, (and for the sake of this conversation we will not be so consumed with the term opposite) we have many different situations in which we can seek balance between two different (what appear as different forces) "conditions".

These conditions can be found in the relationship between line length at a distribution block and a nozzle, the entrance and exit of a distribution block, the relationship between the pressure in the bottle and the pressure in the flow path, etc. In some cases, we could call this set of conditions "pressure differential" or "pressure drop". However, the study of the balance of a flow path differential (while a consideration) is secondary in our search for equality among pressures. In other words we will consider the dynamic association of pressure/flow over energy expended vs. the static quantification of the same conditions. I have included a chart that shows the relationship of line length to time in filling of a feed line.

There will be many of you out there that could say with a great degree of accuracy that no matter what you do, to seek equilibrium across components, pressure thresholds, etc. is impossible. As all fluids cross a "threshold" (component, pressure or flow control, jet, etc.) there is always a loss or drop of pressure/flow due to the energy cost to move across the component or control. To what the degree of cost in energy is and to the amount of energy cost is totally dependent on the amount of control and the degree of effect in the efficiency of the mechanism used as the control. This is where I apply what I call "orifice coefficients", which is my way of creating an efficiency quantification factor in percentage of the aforementioned cost or expenditure of energy.

So how does all of this equilibrium talk equate to better running vehicles or more power? When you start to lie out the design of your nitrous system, a good first step would be to consider equality of flow, and ease of flow throughout the system. If you are racing and you want to know what jetting pattern will be best, consider the balance between flow capability and how much nitrous and fuel your application will use/need.

I have talked to many racers that work very hard on being able to use more nitrous by utilizing large flow capability plates or nozzles. They always look toward installing ever-larger jet patterns to go faster when many times the efficiency of a flow path needs the work, not necessarily the individual components. To stabilize a jet pattern may not make you more power but by doing so you end up with much more jetting resolution therefore making better use of the combination you have.

I originally built my nitrous spider as an experimental fixture in which to build on and hopefully demonstrate my theories on balance. If I could do that I could go about designing into every system flow path junction a methodology that would fix the inherent compressibility problems of nitrous oxide as it approaches a pressure differential "condition". My spider is adjustable to and from un-balanced and balanced conditions. It was a very successful demonstration to the balance of nitrous flow. There is a fixture coming that will demonstrate the same balance issues and fixes with fuel…stay tuned on this one.

I was able to demonstrate the difference between excited nitrous oxide and un-excited nitrous oxide at atmospheric pressure. This was pretty simple when I got into it. I would take a 100 CC beaker full of nitrous oxide and offer this beaker to a multitude of atmospheric conditions which would vary from the parking lot and blacktop in direct sunlight, to sitting in front of an air conditioner at full blast. I could control the boil off to up to 15 minutes. While some considered this to be a pretty boring thing, it showed me a lot about what was going on at the mouth of the nozzle or the edge of the orifice in the spray bar…THINK ABOUT THIS!!!!

Why you ask is this so important? Well as I have probably said way too many times here, I need to model some very basic tendencies and traits of nitrous oxide and then through the modeling validate some of my perceptions of my desires and thoughts as they apply to nitrous itself. From this modeling, we can build plates, nozzles, and solenoids that can better move nitrous oxide in a way that we predetermine to be within a given tuning parameter of our choosing. The whole idea of my experimentation in the case of core traits is to anticipate questions we will stumble upon during the creation of the massmatical strain. What this will look like (the strain) I still have no idea. I have learned the hard way that many things that we may assume to be true are not even close when it comes to nitrous oxide. This is not to say that I have proven Sir Isaac Newton wrong and discovered a new physics…it is just that in the application of nitrous oxide to the automotive engine we run into situations that we just don’t have the complete picture to be as accurate as we would like to be. This stuff can be maddening to say the least.

I have said this many times and that it’s our job as designers, tuners, racers, and technicians to manipulate variables through a methodology of control. Simply put, if we want to make a jet change, any change we make must make a predictable change in the way we want it to change. We must have the flexibility of choice when it comes to calibration changes with a high degree of certainty as to the degree and resolution of said changes. Without predictability, we have chaos…non-linear control for the most part is no control at all.

Without jet or orifice resolution, we wouldn't have (nor would we need) numbers stamped into and very specific sizes of holes drilled in these things we call jets. However, many racers/tuners as they start out do not consider that any component within a fuel, oil, water, or nitrous oxide (fluid) flow path involved in the processing, manipulation, or movement of that particular fluid can and does require "calibration" or "quantification of effect". This quantification requires that we first understand the tendencies and traits of these fluids. In this case we are very safe in saying "water is easy, nitrous is hard"!

With what I perceive to be an ultimately dynamic fluid, control and manipulation strategies can get a little complicated (and potentially expensive too!!). In the specific case of an automotive nitrous oxide system, control methodologies could be considered to be solenoid internal orifices and pathways, jet orifices, line diameter, distribution block configuration and nozzle tip design to name a few. All of these examples are the very obvious examples of nitrous system components. Trust me when I say this, no matter what your power adder is or even each engine and powertrain component, all of the aforementioned parts and systems no matter what the fluid, face the same challenges when you have the ability to alter the calibration of a specific operational parameter.

The major reason for me to consider this type of modeling is that I am in the middle of development of some new plate and nozzle designs and it is difficult for me to know if I have hit or missed my targets without some solid research to back me up when I go into live testing of these designs. Without this nitrous sensitivity flexibility that I am dreaming about, we will just be doing the same old things and living with same old results.

Now do not take that last statement to say that I think all that we in the nitrous business have been screwed up to date. I couldn't be prouder of what this industry has done and continues to do. Every time a pro mod car makes a pass down the drag strip, or a local bracket racer eclipses his or her last standing personal best with the help of nitrous oxide, I couldn't be happier. What I am speaking of here is the forward movement of systemic technologies.

Okay, so lets ask a basic question. Can I try to use the different phases of nitrous to add more power or to stabilize the power output in the name of repeatability?

...As I sit here I don't know that answer ether, however I can say that I want to. One of the reasons I am looking so hard at phase change is that I want to figure out a way to "manage" or control the phase change in both rate (time) and what quantity (mass) of liquid nitrous I can end up with after I try to control it. I even as I write this to you wonder if I even need to worry about all of this crap...but hey...its a living. Seriously, there have been many pulls on the dyno that point at fundamental discrepancies when it comes to horsepower figures with no solid data to point at why the discrepancies exist. So for me to try and find the answers it was my feelings to return to a base-lining of core information on the nitrous itself.

The possibility that we now have the ability, or could have the ability to assess a level of "activation" of nitrous oxide offer us possibilities that are endless in application. In anticipation of success I have developed a sliding scale that will allow for nozzle and plate classifications along the lines of "passive" delivery and "aggressive" delivery. This scale of activity will help in assessing the quantity of liquid nitrous the plate or nozzle will present to the engine. Why you ask is this a breakthrough and what does it mean to me?

For example, you would be amazed at what happens with ultra aggressive orifices in atmospheric pressure testing. I can make ice at the tip of the nozzle causing a fluxating quantity of nitrous delivered into the test chamber. So, if we are too aggressive with a nozzle or plate in its delivery we can artificially create events that will hamper flow rates and accuracies instead of increasing the mass flow of nitrous. And by hyper accelerating the phase change of nitrous into the intake do we further confuse the carburetor(s) or radically alter the jet orifice relationship because we are nitrous deficient? Another way to consider the ultra aggressive nitrous introduction could lie in the high amount of pressure drop across the flow section of the intake manifold. While I wont visit that here, the idea of pressure ranges, boundary layers and pressure pulse thresholds all get pretty evident in the dissemination of cause and effect of pressure differentials.

The passive orifices deliver solid portions of (un-excited) liquid nitrous and therefore very little "effect events" (my term) hamper the flow into the chamber. The interesting part of this scenario is validated through the base modeling of excited and non-excited nitrous.

The amount of liquid in the un-excited nitrous introduced from the passive orifice is greater due to the lack of enhanced energy and subsequent decreased level of phase change across the orifice threshold associated with the excited nitrous. This begs us to ask, is this right? Do we need to keep high levels of liquid nitrous in the intake manifold, or are we fooling ourselves? That is a high dollar question for sure.

Of course these "effect events" vary with temperature and pressure. In fact, it is amazing to me that the phenomenon exists in such dramatic fashion and in lab conditions exist with some initially predictable results. Again, going back to the idea or premise that we have different degrees of excitement or installed energy into the nitrous becomes very evident when you dramatically increase the pressure and/or the orifice size of the nozzle, these are exciting premises for further testing.

Let me give you a bottom line example of how I would apply this kind of tuning flexibility. For some time now I have played with the ideas of pressure based tune-ups for nitrous oxide cars. Now I know what you are saying….and it is "well, all nitrous tune ups are pressure based because it is common knowledge that we need to make our runs in all nitrous oxide cars at 950 psi". AND...that is a very true statement because almost every jetting chart is calculated with nitrous pressures at 950 psi. But what if you could say with a high degree of confidence that you could now run nitrous pressures from 800 psi to 1150 psi and enjoy a greater amount of jet resolution? How could you do that? Lets face it, 800 psi is dangerously close to loosing equilibrium so that doesn't sound too good. 1150 psi has yet to yield reliable results (repeatability) even though I feel a lot of racers out there would like to raise the pressure quotient of their tune-ups. Maybe the answer (or key) would lie in the amount of liquid nitrous released into the engine and at what speed it phase changed completely into a gas? Think about it!!!

Well, I have for some time now wanted to know if the phase change of the nitrous from a state of equilibrium goes away the moment the nitrous charge crosses the orifice in the spray bar or at the tip of the nozzle? To this end those questions will remain unanswered due to several reasons most of which we will continue to review here at "The Purge". I can assure you phase change will consume the majority of my research hours for this year. Without that knowledge massmatics will not become a reality.

Jetting Map 101…

As you know massmatics is all about trying to redefine the role of determining the calibration requirements of a nitrous system no matter what its application. I cannot say how many times I have seen or chatted about jetting maps and what system requires what jetting. This for me has become my number one priority for this year as far as research goes. The amount of half truths, and mis-application of jet recommendations have brought this to the fore front of open issues for me, and all hours I have to devote to research is going to be directed towards a better understanding of what is needed to help all that run nitrous oxide.

I have made many friends in chat and on the bulletin boards and we discuss the issue of jetting patterns all of the time. It is at these times I remember the meetings at NOS when a guy named Mark Shaurette used to fight tooth and nail when it come to jetting charts and patterns. It was he that first brought to my attention that we in R&D needed to think about developing a better way to "do the math". Now more than ever I know he was right in his convictions. Thank you Mark, wherever you are.

In my humble opinion, this industry needs a more universal way to calculate jetting for both nitrous and fuel and I am working on just that better way. All that I have written about to date are pieces to the puzzle we need to move forward on this. From nozzle flow patterns to solenoid orifice diameters I learn more everyday that I think will help us move forward in the area of being better about understanding jet resolution.

One look at the chart that shows the flow shape of the different size jets will tell us that the flow capability is totally dependant on the relationship of the specific jet area to the symbiotic relationship that it shares with the solenoid and the delivery methodology. As I write this I must laugh while I wonder as I hope that I have not bitten off more that I can chew. Oh well...no guts, no glory, right?

Area over Distance over Time…

Well, lets talk about Area over Distance over Time. As we have talked about before in this dissertation, the whole idea behind “massmatics” is to develop a way to make closer nitrous calibration set-up (jet maps) when dealing with trackside variables and be relatively close without the benefits of knowing the exact flow rate of the nitrous solenoid. The questions that came early in this quest started me looking in the direction of flow path configuration. The quantification of flow path components led us down the path of area, distance, and time.

In the charts that I have provided one of the major axis was time and that understanding was fairly achedemic in my integration into massmatics. The area and distance relationship was not so easy. Yes, we can see the shape of the flow curves to comprehend the effects of distance but to try and turn these 3 entities into a fraction was most difficult. It has been such a challenge that as I look back over some of my nitrous design work, a lot more things make sense now than they did when I was in the middle of any given project.

The 2 entities that we are considering to marry in a ratio we call the nitrous to fuel ratio could not be more dissimilar that if we tried. The idea that each would become predicable enough for “us” to consider a linear way to calibrate the two in concert is very assumptive to say the least. From the dawn of man, we have lived our lives on assumptions…they are even more important than sex. Anyone who does not believe me just think about it….anyone reading this ever go a day without an assumption? I mean…everyone assumes the sun will rise in the east right?

At this time it troubles me to offer jetting advice to combinations that I have not worked with due to the fact that if I have not flowed the system? How am I qualified to give any jetting that is not grossly rich to keep from burning a potential customers stuff up when I (or any other nitrous tuner) has not worked with a particular combination? It is very difficult for me to do this for many reasons. The bottom line here is that I (as well as every other nitrous company) am very careful in the way I approach the jet map development for customer’s combinations.

I have a factor associated with the amount of nitrous flow in pounds per hour that I use when I set horsepower levels of a given jet when I flow their systems. This factor in my opinion is very close. It is a very important tool when it comes to associate mass flow nitrous horsepower levels. So….I thought I would try and associate this factor (as a mass calculation) to orifice size. In the grand scheme of things, this sounded like a great idea and in fact was looking like if I could do that here is the easiest way to do the kind of jet tuning at the track that I am looking for. Think about it, if you had a factor or multiplier by orifice size (in thousandths of an inch) to a horsepower level….that would be pretty cool.

So, if this had worked, we would say that for every .005” of an inch in jet orifice you would make 1 horsepower. So simply stated, a .070” jet on the nitrous side would be worth 140 hp. Now, there would be parts of this association that would need to be included like the amount of spray bar orifices etc., but you get the general idea. Unfortunately, I need to leave a couple of factors out here because they tie into much of the research that I am still doing but again, you all understand what I was thinking here.

The key side of this factor would then lie in a simple multiplier of the fuel number based on a sliding scale down in factor size as the horsepower number comes up….simple right?

Pretty simple I think. But alas, it has not been completely successful for a couple of reasons. The primary reason (without going into all of the machine variations of each jet) is the fact that the jet flow in mass as the jet orifice increases is a very non-linear curve. In fact it is grossly non-linear. Therefore the multiplier would change as the jet orifice would grow and could be affected by many different variables due to the unstable growth or change in each threshold of jets. These thresholds could be few or could be many, who knows for sure.

The success that I have had so far has to do with the development and establishment of a factor based on horsepower to set a relationship between the fuel and nitrous jet no matter what the flow rates of ether side of the system you are dealing with. This factoring has been a big help in understanding a good baseline in which to tune from and you do not need to quantify and flow rate of fuel or nitrous. I have currently 5 factors based on horsepower ranges and I am currently looking to increase the amount of factors to increase the accuracy through resolution of the ranges of horsepower. Not perfected…but looking good.

Another thing that I found out is that both droplets of liquid suspended in a gaseous substrate flies through that hole in the jet. As the amount (percentage fractionally) of liquid passes through the jet orifice, it blocks gas…so at the exit end of the jet, a phase change wave is predicted to exist (not proven yet) and therefore the true amount of total nitrous exiting a jet is not really known. If we don’t know that for sure, we don’t know the exact nitrous to fuel ratio.

I have been testing this program and have had some promising results. Some of you may ask why am I spending so much time on something so academic. Well, many through the last year have been disappointed with many of the jet maps from the manufacturers (including mine) of being too rich. Everyone knows why we work with very rich jet maps and that is to remain safe with generalized tune-ups. This is also help those that are new to nitrous oxide to be closer on making the jetting decisions when someone would not have the most experience.

The other success that I have enjoyed recently is in better communication between the delivery of the nitrous and fuel signals. This is where all of the Area over Distance over Time comes into play. Again, in developing a set of factors (you are all tired of that word factor right?) that works directly on improving the relationship of loading in the spray bars of both the nitrous and fuel from a relative timing standpoint.

Now what does all that mean?

A Lot About Fuel Pressure…

In “Area Over Distance Over Time”, lets take a look at just one quotient of the relationship of the three major fluids (atmosphere, nitrous oxide, and fuel) we look at when we consider the design and tuning of a nitrous injected engine. Lets talk a little about the fuel side of this triad.

Many people have recently asked me about a comment that I made about going to high pressure tune –ups with future nitrous systems. The meat of the comment was about my desire to run 100 to 200 psi fuel pressures with a non-solenoid type of delivery system. I also said that I felt that the nitrous industry might be ready to move forward in the raising of both the nitrous and fuel pressure standards. So….with that I thought we could discuss one of the fundamental philosophies of “brand X” when it comes to designing my plates and nozzles.

I think the idea of a very high-pressure fuel system in support of a nitrous system has come of age. I understand the low-pressure tune-ups, but I have not embraced them. I am very excited about the potential of what I would call very high-pressure tune-ups for the future. As of yet, I have not been able to find the time to model this theory yet but in time I will. I do differentiate a difference in my 4150 fuel pressure and Dominator carburetor fuel pressure settings largely because of spray bar area. Thank you Area/Distance/time work so far. This is one of the areas of massmatics that has proven to be working.

I have recently had a exploratory conversation concerning the use of high-pressure with a racer that then set up an experiment using 25 psi as a baseline in which to compare the difference in the typical 6 to 7 psi tune up and the 25 psi tune up. The results of the initial test were inconclusive in that we were not able to establish a trend. Is that to say that it will not work? Jury is still out.

This is not to say that ultra high-pressure fuel systems are not viable but from my point of view right now still need quite a bit of exploration. On the percentage of pressure drop issue, since “drop across a jet” pressure differentials are non-linear, even with the fact that the percentage of pressure drop would be the same between low and high pressures, the high pressure tune ups will always have a greater pressure drop quotient that the low pressure tune up.

This is because as the jet orifice increases the orifice coefficient changes and therefore the effect on “drop across the jet” will change the percentage of drop across the system in mass. One of the phenomenon’s that I saw early in my NOS career was what I now call jet resolution in that every orifice within the system effect the system in mass This systemic association of sub flow curves and pressure drops create an overall pressure drop effect of a given percentage.

There is always going to be pressure drop whenever you desire to move a fluid over any given flow path no matter what the fluid (molasses to nitrous oxide) and no matter what the configuration of the flow path (sewer lines to stainless steel tubing). The simple and shortest answer is that final feed “volume over pressure” is the only thing you need to worry about in the grand scheme of things. Yes I know head pressure, feed line area, pump capabilities, droop, etc. are all considerations but in the final analysis it is non-melted pistons and horsepower that we all care about most. The final feed rate and supply of fuel is “all-seeing” and “all knowing” here. In fact I am spending 9 times more engineering work on the fuel side than I am on the nitrous side right now.

Here is the simplest way that I try to view the pressure thing. Think about pressure as “energy”. So…with a given pressure we have a given energy associated with our system. Now…consider the mass of the fluid as “bulk” or “weight”. Think about the flow path, as a “journey” or “trip” ..and so here is the equation. It takes a certain amount of “energy” to move a certain “weight” over the length of a certain “journey”. When you set out on a hiking trip you assess your ability to carry (energy) what supplies (bulk or weight) you will require over the duration (journey) of the trip.

The weight of nitrous oxide compared to fuel is quite small or light compared to the bulk of fuel, and the delivery pressure of nitrous oxide is quite high compared to fuel pressures we are used to running.…so everything you can do to bring the movement of each (fuel and nitrous) to being the same (symbiotic) the better your combination will run….and be safer too!

So I guess the answer is that pressure drop across the high-pressure system even when dealing with the same percentage number would be driven higher due to non-linearallity. The high-pressure system would defiantly recover faster just because of a system that could produce that kind of pressure would have a fairly high volume capability as well (an assumption there…but a good one I think).

For me, I would like to run a NOS car just like we run fuel cars with adjustable fuel pressure stages that could at some point rely on what I will call ultra high fuel (and nitrous too…remember the 3000 psi thing?) pressures and delivery systems. More on this in the next 2 years…

Jet Resolution Or What’s In A Hole?

My core research has a lot to do with the traits of Nitrous Oxide as it is in two-phase flow conditions. My definition of core research in this case is knowledge gathering within static laboratory conditions and not necessarily associated with dyno cells and engine compartments. Instead, we will search for answers through experiments that model base tendencies (important term) and fluid mechanics of nitrous within constraints that simulate but not necessarily visually look like automotive application situations.

All nitrous companies have mathematical equations that they use to calculate jetting recommendations for customers. Again, massmathics must be flexible enough to account for any variation within the envelope of a given customers application. The major difference in massmatics as applied to each of these applications will be in its ability to account for system efficiencies, and fluid variables. The paradox lies in trying to be more accurate in defining just what the percentages are within the two-phase ratio. The question that no one can answer (at least I cant answer it) is just what is the ratio and furthermore can we manipulate that fraction to our benefit? The jury is still out on when we will have this “next step” quantification methodology finished but hopefully when we are done the accuracy of baselines will increase substantially. Plus, and here is what I want out of this is, can I increase the resolution of the flow curve. I will leave it up to you to think about how greater resolution would help you…especially with high horsepower stuff. I have a good idea of what the ratio or percentage is…but I am so not confident about this speculation that we will talk about this much later.

I am still working on the final quantification of a true nitrous flow curve. Initial research indicates that a true flow curve is a multiple format curve in that a nitrous flow curve has more than one section and therefore can be manipulated through specific component relationships. I want this because of several reasons but two of the major reasons lie in mass flow articulation and true flow quantification. These two attributes will both yield substantial gains in offering new products as well as drastically improving existing designs. For those of you that have had this conversation with me before please excuse my redundancy but when we get this one figured out…watch out. The curves that I have included in this package are the best that I can do with where I am at so far. The curves that I have included are my representations of my data sets. I am sorry that I cannot provide the “real” data sheets, but I need to keep what I am using to achieve these results quiet for a while. I know this will probably draw some complaints but I feel like this must stay quiet until we get closer on releasing our final opinion of what a true nitrous flow curve looks like…(and after we get a patent on how we achieved it…hehehe)

It is the component relationships that we will first try to understand and from that comprehension we will offer a new way in which to discuss the needs of a particular engine application and its nitrous “consumption capability”. Some of you might think this one will be easy but let me tell you, I seriously doubt we can get this one done by the end of this year. My point is that why do we associate an orifice with a horsepower setting and not a mixture/flow setting. In my opinion the reason why lies in two major points. One is that this is the way the industry has always done it. They don’t call nitrous oxide a power adder for nothing. The name alone indicates that this is a power adder so why not quantify the working of such an animal with the numeric values associated with the term “power”. At this point and to support why we just don’t remove all jets is due to mother natures atmospheric pressure limitations and the term stoichemetric ratio.

The second reason is somewhat of an outcome of the first and that is the idea of describing the flow rate of fuel and/or nitrous into an engine has to date no direct way of association of vehicular performance in the field. Again, thinking about it…how many times have you heard a carbureted racer say…”well, I just put 10 more cc’s into the engine per second with that jet change”…I am sure it will haul now! To say that you increased the flow of nitrous in lbs. per hour with a jet change is just unheard of. I can say that all of the times that you have made a jet or pill change in whatever intake system you have used at one time or another that is just what you have done. You have made adjustments in a fractional as cc’s, oz’s, lb’s, etc. Well… maybe not so unheard of later this year.

This brings us to what we know about a nitrous flow curve and the basic perception of the general consumers of nitrous. Now let me say BEFORE I go any further I am NOT saying that anyone that is in the nitrous business is stupid or that they do not know what they know. However I wish to look at the nitrous flow curve as a result of orifice relationships as they relate to mass proportions. “Mass” here is very important because (take this statement to the bank) there is a direct relationship between levels of flow efficiency to the ratio of solenoid orifice (flow rate) to plate or nozzle orifice (flow rate). Remember…Massmatics!

Why is this so important? It lies in the fact that to look at a nitrous flow curve properly you must look at it in (at least) 2 sections (again not giving the farm away). The first curve or section is what I call normalization of potential flow curve. The potential flow is the curve in time/flow in mass up to max flow in mass. The second section of the flow curve is what I call the nitrous consumption flow curve. These 2 curves are created as a result or the interaction between the max flow potential of the solenoid and the max flow potential of the jet/plate or jet/nozzle. And let us not forget engine consumption. And a few other things as well…

One major facet (read that BIG challenge) is to make all jet changes be as linear as possible with every orifice change that you make. This improvement will come from reducing the effect upon the nitrous consistency as possible. The trouble with this comes in the lack of accurate flow methodologies within the industry. Now do not take that last statement as me saying everybody that has ever flowed a nitrous system is wrong or isn’t doing it right. I am saying in the truest since of the word two-phase flow methodologies are expensive and to a high degree not accurate to a high degree of resolution. I would love to hear anyone’s stories about how and if they have ever flowed nitrous and quantified the two phases of nitrous oxide at the same time…outside of the processing and/or medical field.

Ok…I know enough is enough. If there is a general overall theme here it lies in concurrency and multiplicity. All of the future developments will come at a high price. Not only in flow benches and glassware but in pistons and ring lands too. In fact I am sure that many of you will read this stuff…deem it crap from the mind of a lunatic and press on. At times like this I can remember Bill Jenkins contemplating ring friction coefficients and push rod flex and Scott Shafiroff saying screw all of that and leave the starting line first. But then again….one mans lunacy is another mans brilliance.

Right now I am more confused than ever about wet flowing jets. I have spent many weeks in the dyno cell and have spent a lot of time trying to manipulate jetting maps to air fuel ratios, bsfc, and nitrous to fuel ratios. At NOS, we had a jet flow bench and all we saw was variations across all of the jets. This is to say that you could theoretically have 100 jets that had a .035 orifice in them and they could all flow differently. I also remember that when I taught at West Virginia University and worked in the Aero lab, we always saw different fluid data results from our computer modeling and the mathematical calcs we made. We could get them close…. but never aligned with each other.

The system that we all use now is the best that we have and until this industry comes up with a better way we need to stay with the way we flow things outside of the lab. This is also why I am out of the tune up game until I can get past my questions.

The question about ambient or atmospheric pressures is a valid one at this point. Lets all go back to what our advanced auto shop teacher tried to tell us about a vacuum gauge. It is a very simple pressure differential gauge. There is never anything inside of an intake manifold other than a factor of pressure LESS than atmospheric. At wide-open throttle, the pressure drop across the throttle plates is about 2 inches. So if atmospheric pressure is 29.92” (measured at 59 degrees and at sea level) manifold pressure at WOT is 27.92”, or 2 inches on you vacuum gauge. Take another look at the color copy that I included in this package for another look at the relationship between throttle plate and manifold pressure.

So, lets say that you have a nozzle that is put into a pressure differential chamber (an intake manifold) and you spray a liquid (key word there) into this chamber at atmospheric pressure. The only effect on the fluid would be the pressure on the backside of the fluid therefore a true 7-psi (if there is such a thing) could be calibrated. In other words, there is no demand of overcoming any pressure other than atmospheric placed on that column of liquid and thus the 7-psi is a constant. Why? Because it only has to overcome the forces of nature (atmospheric pressure) to spray into the chamber. If we were to look at a psia gauge it would read 7 psi + 29.92” + X (an unknown factor of resistance).

Now, what happens to that column of liquid at less than atmospheric pressures? If our goal is to keep a steady pressure then we need to now consider flow rate as well. The reason for this comes with the ability to flow a given mass in rate at a given pressure. To shorten this point, the pressure would go down from your starting 7 psi because the pressure would be less that atmospheric on the front side of your fluid. Your mass rate would be a constant at a much lower pressure measured because the resistance to the movement of your fluid would be less. Man….that sounds kinda convoluted but we can re write it later if you have more questions.

I have never measured exit pressures on nozzles or plates….yet. That is something that I would love to do but unfortunately it is sometime in the future. On the effects of nitrous pressure on fuel exit, there are a couple of factors. One is what I call the confluence point. This is the point in which the column of nitrous and the column of fuel first intersect. This point is not widely discussed because I think all that anyone has looked at is the atomization factor (mostly visually) of the 2 fluids. I can tell you that the mass of each fluid is dramatically different and with that difference the momentum, and the stored energy of each once accelerated is dramatic as well. I contend that we will advance designs of both plates and nozzles once we can better map the initial interaction of the fuel and nitrous.

Usually the narrower the spray angle, the higher the impact on performance you'll receive at a given distance and the further the trajectory. This is probably why nitrous engines respond so favorably to carburetor spacers. The droplet sizes generated by nozzles/plates are considered to be fine to coarse. As the liquid leaves the exit orifice, the droplets follow a trajectory influenced by the orifice shape and design. The result is a consistent spray angle and uniform droplet distribution. Droplet size and spray distribution are very predictable and not dependent upon a laminar flow. The "free passage" of nitrous flow cones are determined by the largest particle size that can pass through the orifice without getting stuck.

It is the nitrous droplet that is interesting when you start to consider the same relationship of surface area. When we cause the shrinkage of a nitrous droplet we increase the surface area of the nitrous droplets in mass therefore exposing more liquid nitrous surface area to internal engine atmosphere therefore accelerating the possible rate of phase change and release of the molecular bond between the nitrogen and the oxygen. This is one more way that we can possibly “tune” a nitrous oxide injection system to greater efficiency levels.

Imagine two droplets of the same size, one droplet you break up [atomize] into 1000 smaller droplets and the other you leave alone. If you measure the surface area of each "small droplet" and add them up, the result will be more than the total surface area of single large droplet. Simply put, the smaller the droplet size, the more surface area you'll have at a given flow rate. More surface area translates into more efficient heat transfer, surface contact and reaction with gas streams.

You see, the primary laws of physics don’t lend themselves to perfect compromises ever let alone “just kinda” compromising. For example, in the case of a nitrous plate, perfect distribution will many times get in the way of hitting horsepower targets, hitting your horsepower targets can produce a very unrealistic jetting map…you get my point here I am sure. So, by designing one plate shape/tube configuration to meet all of the needs of every manifold/engine/powertrain/vehicle. Etc, etc, etc….. is not possible (at least with current technology).

Compromises must be made in certain areas to insure the greatest coverage and applicability of the system. In this design exercise, consumer safety and overly rich calibrations would also be high on my list of considerations. Rich fuel calibrations are one more way that the nitrous industry tries to insure safe usage of a nitrous system once it is sold to those that not only live at sea level but at 10,000 altitude as well. In the case of my dyno testing, I was particularly interested in what I call final air/fuel ratios during testing. Watching the Horiba was much more important that looking at the spark plugs. Why? Well, when we looked at the final air/fuel ratio, we were not only considering the influence of the enabling of our nitrous system but how it interacted with carburetor signal and air/fuel ratio on a whole.

Some consider the over-jetting on the fuel side to be a point of contention for a nitrous system and many individuals can trim a jet package to be more efficient. This is a point that I would never argue. Many times I do not know which boxes go to Denver, and which go to Death Valley. So an over-rich mixture is a good thing. By the way….did you know that the United States is the country with both the Wettest and the Driest places on the earth? My nitrous systems will run great in both!!!

Reprinted and posted with the written consent/permission from Butch Schrier

Thank you Butch, and to all our customers, readers and visitors please be looking out for a new nitrous oxide book coming soon from Butch Schrier.

NOTICE ! NO PART OF THIS ARTICLE MAY BE REPRINTED WITHOUT THE EXPRESS WRITTEN CONSENT OR PERMISSION FROM BUTCH SCHRIER.