Are Your Electrical Systems Keeping Up With Your Race Car?
An Interview with Automated Racing Technologies
By Deborah-WFO, Bluebaugh Racing- October 2009
Why are the world’s fastest Nitrous Pro Mod Racers so fast? The bottom line is that a consistent race car using 100% of its potential wins races. The question is how do you make a race car more consistent and know that you are maximizing potential with so much going on? I met with Chris Patrick of Automated Racing Technologies to get some answers. Patrick is the inventor of theTotal Function Control (TFC-5) automated race car management system. The TFC-5 is a light weight digital processor that can give you total programmable control of all the electronics and electrical components in your race car at the touch of a screen. This system just may be one of Jim Halsey and Pat Stoken’s little secrets to success.
What we are really talking about here is the precision and speed of electricity applied in race car technology. Patrick’s digital system runs more than 23 times faster than conventional analog systems with out absorbing an abundance of electricity. There are three basic parameters the system addresses.
The primary function has to do with making a race car repeat exactly from run to run. Tuners set many functions in a race car to go on and off at certain times. This however is not happening with conventional analog systems, relays, and the abundance of wiring running up and down a car. These analog systems can have a fairly significant variance. They can also severely hinder all electrical operations because they spike voltage, build heat, and slow down. It would be impossible to get anywhere on time, if your clock moved forward or backward an unknown amount each day. It’s the same with a race car. If you can not depend on a system to turn a parameter on and off at exactly the same time each run, there is no way the tuner can ever know what is happening. It’s also impossible to be consistent. If the tuner can rest assure that all systems are working with precision accuracy, only then can a race car really be tuned to 100% of its potential.
The second function has to do with reducing the error rate of the driver. To simply fire up a race car and get to the starting line, there are many things the driver has to remember to do. Missing even one simple step can lose the race and in the worst case cause significant damage to the race car. The TFC-5 automates all of these processes. A small touch screen computer monitor is mounted in the car. All the driver has to do is touch the screen in a sequence that is as easy as ready, set, go. The digital processor does the rest by turning multiple systems on and off at the exact preset times and automatically sequences the process of steps. This allows the driver to concentrate on the most important task, which is driving the car. When the driver is able to be comfortable and assured that nothing has been forgotten, the outcome is a sharper driver. The system also allows an override, just in case the driver wants to make some last minute changes to the preset.
The last function is about durability. If you have ever searched for the break down in an electrical system, it can quickly turn into a frustrating nightmare. The reality is that our race cars currently have hundreds of feet of wire, relays, sensors, switches, and solenoids that are all subject to break down through heat, high voltage spikes, voltage variance, can be just plain slow or worse, intermittent. Even a variation in the voltage output of your battery can cause a problem with these analog systems. The TFC-5 digital system flows the electricity through your components and uses very low voltage to do it. This is in comparison to analog systems that absorb electricity and use high amounts of voltage. Once installed, the TFC-5 will eliminate massive amounts of heavy copper wiring installed in most cars along with any number of analog components. The result is a system that is more reliable and durable. In case you were wondering about the impact of acceleration and bumpy rides, the TFC-5 has survived the hardest accelerating Pro Nitrous cars in the world, it has been in crashes, and it is still working.
Interview with Chris Patrick of Automated Racing Technologies
Q: Tell me about Automated Racing Technologies. What do you have going on?
A: What we having going on right now in the world of Pro Mod nitrous drag racing and street car nitrous cars; We put together an electrical system of all digital state of the art components and put it out on the market. It’s come to be the World’s Fastest electrical system right now. We are pretty proud of that.
Q: This system has been tested in some pretty fast cars. Who’s running this system and who has helped you with the R& D in this process all along?
A: Most of the R&D was done in the Automated Racing Technologies 41 Willy’s nitrous Pro Mod driven and owned by me over the years. This year we put Jim Halsey’s new light weight Tim McAmis Camaro and Pat Stoken on to the Automated racing team. They have been doing a lot of R&D and research too. We have run some phenomenal times. Right now we hold the ADRL Pro Nitrous points lead, won three of the first five races with consistency, set mph hour records and reset it twice after.
Q: Now you mentioned consistency. How does your on board system help a racer be more consistent?
A: It’s a digital signal instead of analog. Digital signals don’t take any time to saturate coils or pull contacts. You do not have redundant wiring running back and forth in the car to do the same thing. You set a digital signal and it’s either on or off. We do this at really fast speeds as compared to saturating a coil which sometimes takes 15 to 17 hundreds. When you are only working with 4 seconds, 15 hundreds becomes a whole bunch
Q: You mentioned that the system moves at 14,000 frames per second. How does this differ from what we have now on the market?
A: There’s nothing even close. There’s nothing even in the realm of reality. Your ignition box works at about 600 frames per second. Our speeds can run up to 14,000 frames per second on certain things we do. We do it on the most critical things for example clutch switches and timers. We have a lot of emphasis put on the clutch switch and timers in the system to make sure they are as accurate and fast as possible
Q: What systems can this operate? What do you have this system hooked up to besides the clutch switch and timers?
A: Pretty much everything in the car; it becomes a management system. For years we have taken a delay box, an ignition box, or a data recorder and we have programmed them or wired them to do things they were really not supposed to do, but we made it work for us. Like we will make the ignition box send a signal to something to turn something else on. What we have done is build a system from the beginning that takes the ignition box, the data recorder, the other features you put in your car and we put them to one central control unit. The control unit is a third party in the car that controls all functions of the car rather than having one thing turn another thing on. The system actually knows where it’s supposed to be at any given time and where it’s supposed to go next. It becomes a quicker and more efficient system by knowing what it’s supposed to be doing.
Q: In laymen’s terms, this system is really moving all of the electronics at a much faster speed and a much more precise speed. So when you set something at a certain parameter, you can rest assure that where you placed the setting is where it’s coming on. It’s not late and it’s not early.
A: That’s correct; very much correct. There again when you’re only working with; most of this stuff we do on the east coast is only eighth of a mile. We have been 3.84 in Jim’s car. When you are working with 3 point 84 seconds to go 660 ft, every number on that ET counts, every number. If you can’t repeat every number during the whole 3.84 seconds of the many things that the car does while its going down the track, than you can’t possibly ever expect to win races unless you can repeat.Q: We are talking about hundredths even thousands of a second here making a fundamental difference in how fast the car goes
A: That’s correct
Q: If we have a car out here running 8 seconds, say more the average racer in the country; How much of a difference does that make to me in that 8 second run?
A: The tools are only as good as the people using them. I hate to say that but it’s the truth. What you have to do and what this tool does becomes something you can depend on. With analog signals, with older systems, digi-sets, and relays, you don’t know. One time it might come on 15 hundredths late or the next time it comes on 17 hundreds late. The clutch switches are the same way. If I set the clutch 20 from the bottom, one time it will come on 15 from the bottom and the next time it will come on 25 from the bottom. So you catch yourself always chasing something and you can’t figure out why it won’t do the same thing twice. Well it probably has nothing to do with the tuner whatsoever and has everything to do with the parts on the car. So what we try to do is make something as accurate as possible therefore the tuner can be assured that when he tells it to be on, it’s on. Therefore we take that old parameter out. As you start using the system, a level of consistency just automatically comes with it
Q: So whether you are a fast guy or a slow guy, this system is going to give you repeat-ability and tune-ability to get the maximum potential out of your car with what you are running no matter what it is?
A: That’s correct. What it does is there again, I don’t care if you’re running four seconds, six seconds, eight, ten, twelve. It does not matter; you have parts and pieces you spend good money on. It’s all the motor you have, it’s all the car you have, it’s all the transmission your have. If you utilize 100% of everything you have and utilize it in a way to where you know you are headed forward at all times, you will get the most out of what you have. You will find that you have much more than what you think you have. Too many times we use a thing that I call brute force trauma. If my car is not fast enough, I just go to Fulton or Sonnys and I buy a bigger motor. Well that’s not necessarily the case. You know there are so many of these in the Pro Mod world today. There so many of them that have more power than what they can ever utilize anyway. They are just not utilizing it to a finite science. I mean therefore you just think you need more motor and in all actuality there is a whole lot left there, you just have got to find it. You can find it with tune-ability.
Q: So what you are telling me is actually really exciting because I don’t have to dish all that money out of pocket for bigger, better, and greater. I just have to work on fine tuning what I have and this is really what this system is about. It is allowing me to use all of what I have. So I am not forking out 60, 70, 80 thousand dollars for a bigger motor and the latest greatest on the market.
A: That’s Correct. I am not saying that you’re going to turn the average street
Crash Science Tech: Closed Head Injury in Racing and the Physics of Force
By Deborah WFO, Bluebaugh Racing, July 2010
Man’s ability to accelerate his body faster than naturally possible has come with consequence of a number of unique injuries that are a result of the physics of force. The force required to cause closed head injury varies and depends on a number of factors; velocity meaning speed and direction, the multiplication of force itself, mass or weight, direction of impact, area affected and the properties of the human head. The human head and brain are particularly susceptible to acceleration, deceleration, and rotational forces all of which are amplified to very unnatural proportions in a race car. In this article, we take a look at two types of closed head injuries, Basilar skull fracture and diffuse axonal injury, and the laws of motion. Why in racing are driver’s more susceptible to closed head injuries? To answer this question one must understand just a little about anatomy and physiology, and applied physics.
A Basilar skull fracture is a break in the bone at the base of the skull and requires more force to cause than other types of skull fractures. By definition a Basilar skull fracture may occur anywhere along the base of the skull including the back and sides. To refer to the Basilar bone in the skull simply means the floor of the skull area that incases the brain. However particular to a frontal impact is fracture around what is called the foramen magnum in anatomical terms. It is the area of bone in the skull around the opening in which the spinal cord enters and turns into the brain stem. In cases of fracture, a circular fracture may be found in the skull bone rounding the spinal cord. In very extreme cases, internal decapitation can occur where the bone completely breaks and the skull becomes disconnected from the spinal cord. Oddly enough, people in rare cases have survived the worst where the skull and spinal cord have separated. It is not the skull fracture itself that causes death. The cause of death is rupture of major arteries secondary to the fracture resulting in the injured person bleeding to death almost instantly. It goes without saying that any variation of injuries may occur in this area having a number of severe consequences. It’s an injury that is now very preventable with the use of a head and neck restraint device. The concept of a head and neck restraint was adopted by the NHRA in 1996, following the loss of Top Fuel driver Blaine Johnson. It became mandatory for drag racing in 2004, after the loss of 2003 Top Fuel Rookie of the Year Darrell Russell who was killed during the Sears Craftsman Nationals in Madison, Illinois.
Basilar skull fracture does not kill in all cases and people have escaped with no permanent brain damage or injury. The condition can be mild enough that the fracture is missed in diagnostics. It is therefore important to understand the symptoms and warning signs that a fracture may have occurred. Left untreated, a Basilar skull fracture can lead to serious complications from infection due to Meningitis. When the fracture occurs an opening is created. Meningitis is inflammation of protective membranes covering the brain and spinal cord brought about by infection. Meningitis is treatable however can be life-threatening because of the inflammation's proximity to the brain and spinal cord, and is considered a medical emergency. Tell-tale signs of Basilar skull fracture according to available literature on the Internet may include; leaking cerebrospinal fluid from the nose and or ears, blood in the sinuses, bruising around both eyes which is dubbed as Raccoon Eyes, bruising behind one ear which is called a Battle Sign, abnormalities in vision, difficulty hearing, and difficulty smelling things. It is advisable in any crash in a race car to seek medical attention and forgo being a tough guy for the moment.
Diffuse axonal injury (DAI) was noted in the loss of Funny car driver Eric Medlen in 2007. DAI is a special traumatic lesion, which occurs most frequently in motor vehicle accidents again where the physics of force has played a part. This is a separate issue from the discussion of Basilar skull fracture. DAI is not preventable by a head and neck restraint. However the possibility of occurrence may be reduced by a properly fitted helmet and additional roll cage padding. Skull fracture may or may not be present. In the course of DAI injuries, the brain goes into a back and forth gliding motion pivoting around the upper brainstem. Brain damage is most severe along midline structures at the corpus callosum and brainstem where the shear forces are greatest. This phenomenon is produced by various angles of acceleration with prolonged rapid incidents of acceleration and deceleration. In short, it is a violent shaking of the brain inside the skull. The major cause of damage in DAI is the disruption of axons, the neural processes that allow one neuron to communicate with another. The basic result is a degeneration of the brain due to the trauma. It’s actually quite a bit more complicated as far as what occurs physiologically. Fifty percent of crash victims with DAI die within two weeks and 90% with severe DAI never regain consciousness. Those who do wake up often remain significantly impaired. The other possibility is a persistent vegetative state or severe disability until death. Scientists believe that DAI can occur with various severity and better prognosis for milder cases.
There are three basic laws of motion in physics to examine in understanding why closed head injuries occur. The first law has to do with inertia. The first law of motion states that an object at rest will remain at rest and an object in motion will remain in motion at a constant speed and direction unless or until outside forces act upon it. Physicists use the term inertia to describe the tendency of an object to resist a change in its motion. Speed and direction together is called velocity. Object here is defined as the mass and for purpose of racing the mass is the race car and the driver. When the car is accelerating down a race track, the force provided by the engine is creating the movement, less of course negative factors like friction, drag coefficient, and gravity. Let’s forget about force for a moment though in this law. Inertia alone is working to keep car, driver, and each of their parts moving at a continual sustained rate. The car is moving and the driver is moving in this forward motion together. This could happen endlessly in time without incident. The problem occurs when another force such as impact disrupts the current course of movement. When the car impacts something, the driver is for a brief time still moving forward until impact with the safety harness. In this impact, the pelvis is stopped first, then the torso. However with nothing more than a safety harness, the head is still in motion in accordance with the original inertia. It is for this simple reason that a head and neck restraint is so important. Without it, the neck itself is the restraint. When the head reaches the end of the capacity of the neck to serve as the restraint, it is still straining to move forward in accordance with this law. Basilar skull fracture is a case for the weakest link. It is right here in this straining motion that injury happens.
Let’s put force back into the equation now. According to the second law of motion the net force acting upon an object is a product of its mass multiplied by its acceleration (F=ma). In physics, force is measured in Newton’s, mass is measured in kilograms, and acceleration is measured in meters per second squared. One Newton can be compared to the force of .22kg or the size of a medium apple falling and hitting you on top of the head. While, you may have a bump or bruise, you will be no worse for the wear. Now imagine the impact of 50,801 Newton’s, 11,430 pounds, or 5165 apples falling on your head at the same time. This is the force generated by a 2500 pound car at 100 mph. The magnitude of the force is directly proportional to both mass and acceleration. Force now applied in a Basilar skull injury is working very hard to pull everything in the head and neck through the top of the skull in a high energy transfer as impact takes place. Something here has to give when enough force is applied. If the Basilar skull fracture does not occur, then the neck breaks and or severe stretching of the brain stem may result dependent on the amount of force. If a driver is experiencing an acceleration of ten times the force of gravity 10g, then the force on the body is F = (m)(10g) or ten times what would be normally experienced. A head and neck restraint system maintains the relative position of the head to the body, transferring the energy to the much stronger chest, torso, shoulder, and seat belts as the head is decelerated.
Acceleration and deceleration are a change in the velocity of a mass with respect to time and there are many possibilities. The exact nature of the acceleration produced depends on the relative directions of the original velocity and the force. A force acting in harmony going the same direction with a race car affects speed. For example, if we add a shot of nitrous to our engine, the car goes faster. A force acting at an angle to the velocity changes the direction of the velocity but not the speed. Changes in the direction of acceleration or deceleration that are rotational twisting forces further complicate the computation of the sum of forces brought to bear on the driver. If the head and brain are “torqued” in a rotational fashion it has a considerable influence on the outcome of the injury. The head does not merely decelerate in unidirectional fashion but is actually decelerating in the original direction and accelerating in a new direction. Multiple rapid occurring incidents of acceleration and deceleration in response to forces applied account for most axonal injuries as noted in DAI. It is short distance and time between incidents that result in the greatest injury. In the case of the angled impacts, deceleration distances and times are usually longer thus injury severity is less likely such as in the case of grazing the wall. Both the time and the distance over which changes in velocity occur influence outcome. For instance, the cushioning effect of helmets increases the distance of deceleration and therefore reduces the forces associated with these injuries. Helmets also increase the surface area across which the blow or force is absorbed. Following the loss of Medlen, the NHRA enacted a new safety requirement within the Funny Car division stating that roll bars within the car have to be padded again for the value of a cushioning effect. Medlen’s car was estimated to be generating 40,000 pounds (177,928 Newton’s) of force with each incident of acceleration and deceleration.
A force may also act in the opposite direction from the original velocity. In this case the speed of the mass is decreased. A decrease, still a type of acceleration is often referred to as a deceleration. The third law of motion states that when one object exerts a force on another, the second object exerts on the first, a force equal in magnitude but opposite in direction. For every action there is an equal and opposite reaction. Forces act in pairs. If a small compact car collides with a big truck, it might seem that the truck would produce a greater force, however this is not true. The collision of the car and truck produce an equal force upon each other. The truck fairs better due to its construction. Going back to the first law of motion however mass is the total mass of all parts meaning car and driver. When a speeding car crashes into a concrete wall, the sudden stop puts the body through a tremendous amount of strain in some cases more than 100 times the force of gravity. The severity of G-spike that can be fatal varies with the type of car and its built-in protection.
So what is the potential net force of your race car and potential for a closed head injury? Remember that both the mass and acceleration are proportional. A head and neck restraint system is only required in a faster car. For that matter, if the car is slow enough a helmet may not even be required. Is it however a false sense of safety that only speed kills? In the first law of motion an object traveling at any speed will remain at that same constant speed and direction with out incident until a force is applied. In the second law of motion, the net potential force is a proportional calculation of both mass and acceleration. The two cannot be separated out. Therefore speed alone is only a part and not the total equation. In the third law of motion, the magnitude of force is equal and opposite in that what ever force is imposed is returned. A 2500 pound race car at 100 mph has a net force of 50,801 Newton’s (11,430 pounds). However a 3500 pound race car at 75 mph has a greater net force of 53,339 Newton’s (11,991 pounds). A 2000 pound race car at 200 mph has a net force of 81,280 Newton’s (18,272 pounds) and a 3000 pound race car at 150 mph has a net force of 91,437 Newton’s (20,555 pounds). A heavier car going slower can have the same potential net force as a light car going faster and therefore just as much potential for injury is present.
Accidents happen in racing. There are things however that can be done to reduce the possibility of injury. Remember that the laws of motion are never on vacation. Make sure you have the proper safety equipment regardless, inspect it regularly, and keep it updated. Check the structural integrity of your race car before each race. Never forgo safety for a moment.
Understanding Weather Tuning Basics
By Deborah-WFO, November 2011
Changing weather can have a profound impact on your engine performance. Many top racers actually take advantage of weather readings as part of the engine tuning process. Your first look at weather may seem confusing with unending contradictions and possibilities to ponder. Tuning using the weather is not an exact science. First, the weather is always changing. What is useful is being able to predict a direction and need for change before you find yourself shelling out thousands of dollars for burnt and broken parts. Tuning using the weather may be used as a defensive strategy that protects your investment. The goal is to produce fast efficient runs down the race track with some degree of advanced certainty in how the engine will perform. Tuning with the weather will also help you understand how to take advantage of making the best possible power under a given condition. Once you learn to read the weather and predict changes needed in engine tuning, it will become second nature like anything else.
In order to fully apply tuning by the weather you must also have a working knowledge of your engines behavior. This comes from reading the spark plugs and knowing which cylinders are predominately lean or rich, and how the overall engine is using the air/fuel mixture. Defined below are the parts of the weather typically used in engine tuning for naturally aspirated and nitrous engine applications. Remember that the definitions are relative and directional. You will still have to estimate how much and what change is needed for your engine, which will only come with practice and observation over time.
Absolute Barometric Pressure is measured in inches of Mercury (in. Hg) and has to do with the atmospheric pressure conditions of a given location. Normal pressure gauges have a scale that sets the zero point for atmospheric pressure at 14.7 psi or 29.92 in Hg. (Barometer), which is gauge pressure. This is defined as the Standard Day Absolute Barometric Pressure at sea level and gives a point from which to measure. 14.7 psi is pounds per square inch of pressure exerted on an object by the air at sea level. So what we are really talking about is the pressure of air and how it impacts conditions in the engine as it changes.
Absolute Barometric Pressure is not the same as what is reported for an area on weather forecasts, which is a sea level corrected pressure. For this reason, it is important to measure the Absolute Barometric Pressure and all weather samples with a weather data instrument at your location for an exact reading. The Absolute Barometric Pressure will only encounter very minor fluctuations during a typical racing weekend. Once measured, the reading will remain fairly consistent varying by a few hundredths. So how does this factor play out in tuning the engine?
When the barometric pressure is higher there is more oxygen available for combustion in a given volume. Consequently the opposite is also true. For every thousand feet of elevation climbed, the barometric pressure is reduced by approximately one inch of mercury and there is less oxygen available for combustion in a given volume. Absolute Barometric Pressure also has an affect on cylinder pressure. The engine is subject to increases and decreases in compression ratio as the pressure of air changes. When the barometer reading is low, for example 24 in Hg, the air quality is both comparatively oxygen poor and the cylinder pressure in the engine is low. This creates a noticeable drop in power. Technically one could run less fuel to air ratio for low oxygen and more timing to increase cylinder pressure if Absolute Barometric Pressure was all the measure needed. It’s however only once piece of the equation for consideration.
Racers coming from sea level tracks are often surprised when their engine burns up coming to a higher altitude low Barometer track. This has to do with dry air conditions and high Density Altitude. High Density Altitude and extremely low water grains in the air (almost none) create a lean condition when combined in the equation that reverses the direction of timing and fuel. Because this lean condition is produced, a little fuel may need to be added and timing taken out. Ultimately the engine cannot make power in these conditions and the car will slow down. There is a bell curve exception rule somewhere around 5000 ft in the Density Altitude where fuel needs to be added despite the fact that most other weather conditions will indicate that less fuel is needed. Dry air is rather self explanatory. Even though the oxygen is relatively poor with a low Barometer, you are getting all of it with no water grains to offset any oxygen that is in the air that you may have been used to at a humid track. In this case, one needs to use caution in not taking too much fuel out. I will get to how timing fits in the discussion of water grains.
Temperature affects how tightly molecules of air are packed together. As air cools it releases energy, slows down, and the molecules become more condensed. The opposite is true in warmer weather where the molecules excite and begin to bounce off one another moving rapidly. Temperature rising and falling can be used to predict directional changes in the Density Altitude. A cooling temperature will produce a lower Density Altitude reading resulting in a need for more fuel because you are getting more air. If the engine was on lean edge in the day time, you might consider that you will need to add fuel to race later that evening if there is a significant drop in temperature. The night air will be more condensed. If the engine ran a lean mean pass at night in cool temperatures and performed well, it’s relatively safe to run in hotter temperatures the next day. The engine will be richest at the hottest point of the day with the same tune up because the air is least condensed at this point. In measuring the temperature and all weather conditions, it is important to at least implement a consistent practice and its best to measure a condition most similar to what the engine will actually intake.
Relative Humidity, Vapor Pressure, and Water Vapor- Relative Humidity is a value used to indicate how much water vapor is present in an air sample. It is a relative figure as relating the amount of water vapor present to the maximum amount that air could hold at a specific temperature. Air has the ability to hold more water vapor as temperature increases in theory. However, it is common to see this figure increase at night during a racing event. 50% Relative Humidity is 50% of the possible saturated water vapor content for air. This differs from Vapor Pressure and Water Vapor. Vapor Pressure is calculated from both temperature and Relative Humidity. The Vapor Pressure number indicates the portion of the available air pressure that is absolutely water vapor. Water vapor is expressed in grains and is basically the same as Vapor Pressure however expressed in a different measurement. Some racers use the Vapor Pressure readings, while it has been more common for most to use Water Vapor or grains of water as the reading. Water Vapor is grains of moisture per pound of dry air at Standard Day Density Altitude (14.7 psi or 29.92 in Hg, at 60 deg with 0% Humidity.
Water Vapor in Air (grains water vapor/lb dry air)
The power output of the engine depends on oxygen intake, so the engine output is increased or decreased as the equivalent "dry air" density increases or decreases, and produces more or less power as moisture displaces oxygen in more humid conditions.
Water Grains are an indicator of the margin of safety for our purposes as related in figuring the amount of fuel needed. The more water grains there are in the air, the greater the window for margin of a lean error. When water grains are low there is more oxygen in the air and fuel needs to be added with the opposite being true. With increased grains of water in the air, the air/ fuel ratio becomes richer as a result.
Low water grains also indicate a need to put less timing in the engine. In dry conditions, timing is taken out and with higher water grains you can put timing in the engine. Advanced timing in the engine increases cylinder pressure, can make more power, but also increases the chance for detonation. Advancing the timing will lean out the air/ fuel ratio of an engine and is something to consider in dry air. In advanced weather tuning, timing can be used to compensate for water grains at the track or as an adjustment for Density Altitude. Adjusting timing can be a first line of defense consideration before changing carburetor jets or the nitrous spread. This is where you can take the greatest advantage of individual cylinder timing. Timing knocked out of one or two cylinders that look a little lean or glazed according to the spark plug can allow you to fix the problem without having to take an action the affects the power of the whole engine. Too much timing will burn up an engine more quickly than an imbalance in the fuel.
Density Altitude is a value expressed in feet above or below sea level. It is a combined calculation that considers Absolute Barometric Pressure, temperature, and Relative Humidity. In simple terms, density is the mass of anything, including air, divided by the volume it occupies. Density altitudeis defined as the altitude at which a given air density is found in the Standard Atmosphere or Standard Day. It’s actually a height, which is not the same as the physical elevation of a location. For example if an elevation of approximately 6100 ft is equal to the pressure of the Standard Day at that elevation, and the temperature is roughly 100 degrees, the density would be the same as that found at about 10,000 feet. You cannot therefore simply depend on track elevation as a valid measure although track elevation will be an indicator of what you may expect to find. Density Altitude can swing dramatically during a racing weekend and some times even in-between rounds. You will hear people asking and discussing good or bad air at the race track. Typically this stems from looking at the Density Altitude reading. The lower the Density Altitude reading, the better the air is for making power. It is even possible for Density Altitude to fall below zero. Lower readings generally mean a need for more fuel with the opposite being true also less the exception rule stated above. For a given altitude, the Density Altitude changes with changes in Barometer, air temperature, and Humidity with each capable of impacting the reading. The Barometer and temperature both have a greater impact on Density Altitude than Humidity. Being that we already know that the barometer stays fairly stable during an average racing weekend, temperature then becomes the greatest predictor in the rising or falling direction of Density Altitude.
An increase in barometer or pressure increases air density, therefore decreasing density altitude
An increase in temperature decreases air density, therefore increasing density altitude
An increase in humidity decreases air density, and therefore increases density altitude
(Increased air density = decreased Density Altitude) = Increased need for fuel with the opposite being also true less the exception rule
Air Density Ratio (ADR) is another way of looking at the engines need for changes in fuel. The ratio is produced by dividing the calculated density of the air by the Standard Day Altitude Density. At the zero point, the ADR is equal to 1.00, which is 100% Standard Day. As the ADR goes up or down, the amount of fuel needed by the engine also goes up and down by that same percentage in order to maintain the same air/fuel ratio in the engine
In order to make power, the idea is to cram as much condensed air and fuel into the cylinder as possible. To keep the engine from burning up, the ratio of air and fuel must fall into a given middle ground window. If the engine is too rich or too lean problems will occur. Changing weather changes this ratio without a single thing ever being mechanically changed in the engines tuning. If you have wondered why at a particular race there seems to be a large number of cars sitting in the pits with a burnt piston, weather is the answer.