The plot below shows the cumulative number of cautions per mile since 2007. I’m using number of cautions per100 miles to 1) make up for races that were not run to completion; 2) compensate for green-white-checkered finishes; 3) compensate for tracks that have shortened races; and 4) compensated for changing order in which tracks are visited.
Cautions per 100 miles can be thought of as follows: If the cautions per 100 miles is 1.6, then the number of cautions for a 500 mile race would average (1.5*500/100) = 6.
The results are sort of interesting:
Things to notice:
1) All of the final values for cautions per 100 miles end up between 1.8 and 2.4, even though the values at the start of the year ranged from 1.4 to 3.1.
2) The data for the first 10 races changes wildly with each race. The data don’t start to converge toward their final values until at least 15 races into the season. I suspect that if you plotted a drivers’ standing in the points as a function of number of races, you would see the same behavior. Why? As the total number of miles run increases, the number of cautions in a race is increasingly small compared with the total number of miles run.
3) Despite the decreasing fluctuations, there are still quite a few noticeable jumps upward. When I saw them, I immediately thought: Ah – there’s Bristol. But closer inspection showed me wrong. The big troublemakers are Richmond and Martinsville, which together account for the largest number of upward jumps.
4) There seems to be a significant difference in caution rates from 2008/2009 to 2010/2011. Anyone want to venture guess as to what is responsible?
I honestly cannot help it – scientists are naturally skeptical. If you make an assertion, I will have to question you on what data you have that supports it. This is second nature to the people I work with, but I realize it is damned irritating to non-scientists (aka “normal”) people.
So when I started reading everywhere that “cautions were down 35%”, I had to go look into it. This is a preliminary post – more detailed analysis will follow as soon as I’ve read my students’ final projects and gotten comments back to them.
First, let’s talk statistics. Reliable statistics require large numbers. It drives me nuts when people extrapolate from the first few races of the year. You can’t claim much on the basis of five data points. Even the top quark required seven (if I remember right – they did get more after they announced they’d found it).
The stock market fluctuates up and down. Everyone except people who are thinking about retiring ignore the short-term fluctuations and focus on the long-term trends. What do the data say about cautions in NASCAR?
I picked five tracks to analyze in this first round: Martinsville, Texas, Talladega, New Hampshire and Atlanta. The first four represent a range of track types, while the last was chosen to see whether the cautions were “cookie cutter-like”. I first plotted the number of cautions as a function of year for all the tracks together. If cautions are decreasing, we should see a general trend downward. Here’s what I got:
Not much of a clear trend, huh? If anything, it looks like the overall trend (since 1950) is going up.
Thinking it might be unfair to use really old data, I decided to focus on 1997-2012. I plotted all five tracks on their own graph for just those years. I’m sorry for the color – those are the defaults on Origin. I will change them when I do a full post.
What do you think? I might buy a downward trend for Texas, but it’s hard to make that argument for the other tracks. Martinsville went from 18 in the last race of 2011 to 7 this year – that’s a 61% drop right there — but if you compare it to the Spring race (and an argument can be made for comparing Spring to Spring and Fall to Fall), that race had only 11 cautions. That’s a drop of 36.3%. there is a wide gap between those two figures.
Just for fun, I took the historical data for the three tracks with long records. Here they are:
As I said, I’ll follow this up with more extensive analysis, but I wanted to get the data out there ASAP.
One of those phrases you tend to pick up as a NASCAR fan without thinking is “cookie cutter track”. That’s the accusation commonly directed at the one-and-a-half mile tracks (like Texas Motor Speedway, which we’re visiting this week). The complaint is that these tracks are so identical that it’s almost not worth bothering to watch. But are they really identical?
My disclosure, before we start: I am a fan of short tracks. I like being able to see the whole race and I like watching drivers try to pass each other. So I started out with a bit of a bias toward the intermediate tracks — Atlanta, Charlotte, Chicagoland, Homestead, Kansas, Kentucky, Las Vegas and Texas — myself. But there is nothing a scientist likes more than sitting down with a pile of data and trying to make sense of it, so (armed with Google Maps, a load of data from racing-reference.info, and the Excel file in which I’ve collected track parameters), I dug in to see for myself how similar these tracks are. After a couple false starts, I decided to try to develop a taxonomy. Taxonomy is a Greek word meaning a ‘method of arrangement’. My 1.5-mile track taxonomy is shown below.
The Differences
We start at the top with 1.5-mile tracks and a missing hyphen. The first distinction is the track shape because not all ovals are equal. Homestead actually is oval shaped. The other tracks have one of two shapes: the D-shaped oval and the quad-oval. Atlanta, Charlotte and Texas fall in the latter category, with Chicagoland, Kansas, Kentucky and Las Vegas in the D-shaped oval Camp. The difference is evident in the figure below. The photo in the upper left is Kansas (our representative of the D-shaped oval) and in the lower right is Atlanta. The difference is subtle: the D-shaped oval is more of a triangle while the quad-oval has a double dogleg. I’ve driven at Texas and you can see two distinct angles in the wall as you approach them. The D-shaped oval looks like someone grabbed an oval in the middle of one of its long sides and pulled on it. The D-shaped oval is not specific to intermediate tracks. California, Michigan and Richmond are D-shaped ovals, too.
Within the D-Shaped oval category, no two tracks have the same corner banking. Kentucky is 14°, Kansas is 15°, and Chicagoland is 18°. Las Vegas is in a class of its own, as it has progressive banking that runs up to 20°. (Homestead also has progressive banking.) The quad-ovals all have the same corner banking (24°), so we can’t differentiate that class any further in this level. These three tracks really are very similar. To make any distinction, we have to look at things like the backstretch length. Charlotte and Texas have approximately the same backstretch length (~1350 ft), while Atlanta has an 1800 ft. backstretch. Although Charlotte and Texas have similar frontstretch lengths, they do differ by 300 feet, so if you were really looking for an excuse to put them in separate categories, that’s about the most obvious division.
The tracks definitely race differently. The pole speeds on these track vary from an average of 174.8 mph to 193.0 mph (values given are averages over the last four races run). Out of curiosity, I plotted the pole speeds for the tracks as a function of different variables and finally found the following relationship. Note that there is no data for Kentucky since the first Cup race was run just last year and starting order was determined by owner points. The pole speed definitely depends on corner banking, which makes perfect sense. Banking helps the cars turn by providing some of the required centripetal force. More banking means more speed given that the track length is constant.
There is still, however, a 4.2 mph difference on the three quad-oval tracks, which suggests that there are other factors to be considered beyond shape.
The track surface makes a huge difference in speed. Asphalt is a composite of aggregate (stones) and binder (bitumen). A host of variables such as the size distribution of the aggregate, the chemical makeup of the asphalt and the conditions under which the asphalt is laid down have a huge impact on the track’s grip and how it wears. The track is changed constantly by the weathering and no two tracks experience the same combination of factors. The diagram at left shows how the aggregate (grey) and asphalt (black) wear over time. More of the aggregate is exposed with time and sharp edges get worn down. The track also changes in response to temperature and, again, different tracks will change in different ways. Atlanta, for example, is known as a tire-eating track because its rough surface is very hard on rubber.
The same issue arises over the course of a single race. When you hear a driver or crew chief talk about “chasing the race track”, it means that the setup they had that worked so well at the start of the race didn’t work as well during the race. A track changes significantly over the course of a race: it heats up due to friction between tires and the track, plus it may heat or cool due to the way the Sun hits the track (or portions of the track) or even just because a race goes into evening and the overall temperature changes. Different weather means different racing.
In addition to the small-scale roughness discussed above, some tracks have unique, larger perturbations in the track surface. Texas has a major bump between Turns 1 and 2 that was caused by the track settling over the entrance to the infield. In 2007, they drilled a bunch of holes in the area and injected a structural urethane to try to fix the giant distraction. They made it better, but you have still heard drivers all week talking about “the bump”. This isn’t unique to Texas: Charlotte has a big bump entering Turn 1. Those bumps pose major challenges for setting up the suspension. The ideal position for the splitter is as close to the track as possible – but if there’s a big bump, you have to make sure that the splitter doesn’t hit the bump. There are also issues like seams and patches, where the texture or type of asphalt changes, that challenge drivers.
The Similarities
This is not to say that these tracks don’t share some similarities. They are all fairly wide (50-60 feet) compared to the smaller tracks. The most important similarity is less a function of the track and more a function of the car. The current version of the NASCAR stockcar is highly aerodependent on one-and-a-half-mile tracks. Aerodynamic forces go like the speed squared, so these high-speed tracks have three-to-four times more emphasis on aero than short tracks.
A car depends on air rushing over it to push its tires into the track. Turbulent air – like you find in the wake of a high-speed car – doesn’t provide as much downforce as laminar (straight-flowing) air. This is why drivers value “clean air”. If you’re the first car in line, you don’t have turbulent air from the car in front of you because there is no car in front of you. Another feature of 1.5-mile tracks is that, because it is larger, you don’t run up on lap traffic as much as you do at a short track, and there’s plenty of room for a lapped car to get out of the way. At these tracks, being out front gives you have a huge advantage. That leads to a car that can easily put quite a distance between itself and the rest of the field.
The ‘aeropush’ effect happens when you get too close to the car in front of you. The air coming off its rear end is turbulent and doesn’t give you as much downforce as laminar flow would provide. It’s like running over ice: the only thing you can do is slow down. The aero-push makes it really hard to pass because you have to get close to the car in front of you in order to pass it. If the cars weren’t so dependent on aerodynamic downforce, then losing a fraction of that downforce wouldn’t affect them a significantly.
The Conclusion
I’d say there are actually only three ‘cookie cutter’ tracks: Texas and Charlotte are identical twins that get their hair cut differently and refuse to wear identical clothing. Atlanta is a fraternal twin to Texas and Charlotte. Lumping the D-Shaped Ovals in with these tracks, however, is unfair. The issues that many race fans have with racing at these tracks requires changing the car rather than changing the track.
Atlanta is known as a really rough track that eats tires.
There’s been an awful lot of talk recently about changing the layout at various track to make racing more exciting. Bristol is the most-talked-about track, with Bruton Smith planning a $1M revamp of the track to take it back to the way it was before he changed it in 2007.
There are a number of factors that dictate how “exciting” racing is. For example, the track width and how many “grooves” there are make a big difference in how easy it is to pass cars without “helping” them out of your way with your front bumper. But last I looked, grip — the source of all speed — is dependent on the interaction of two things: the tire and the track. There’s a lot of talk about tracks, but not a lot of talk about tires.
Remember back a few years when tires were a topic of conversation every other week? Tony Stewart lighting into Goodyear for the tires at Atlanta in 2008? The Indy tire debacle that same year? The 2005 Charlotte ‘levigation’ when they “smoothed” the track using a diamond grinder? Tires aren’t much of a topic these days. Goodyear’s done an amazing job amidst a slew of re-paving projects from Talladega and Daytona to Bristol and Michigan.
But have they done too good a job? Some people have suggested that the tires stay in good shape for too long. It’s possible to go multiple fuel runs without taking tires at many tracks. If the tires wore faster, might that add an element to the racing that’s missing now by forcing crew chiefs to make tougher decisions about whether to take tires and drivers to take better care of their tires? Harder tires don’t wear as fast as softer tires – but softer tires are more likely to fail by being worn down rapidly. It’s a difficult balancing decision and the consequences for Goodyear if they’re not exactly right are significant in terms of how fans perceive the brand. Take a look at the opinions below and tell me what you think.
Straddling the fields of science and motorsports as I do, members of one community often email me articles about the other community. It’s interesting to see what ‘outsiders’ think is interesting about the other world. Last week, it was a series of articles about how NASCAR’s popularity is waning because kids are too busy playing video games.
Frank Deford (on NPR and in Sports Illustrated) declared America’s “Love affair with the car” over and done. He supports his assertion with interesting facts: For example, the more time kids spend in front of the computer, the longer they delay getting their drivers’ licenses. It is true that most Americans are more interested in the amenities and comfort (and mpg!) of a new car than they are the torque of the engine. Deford tells us that NASCAR’s recent $5M research project to find out why fan interest is declining showed that it’s our fault: Current NASCAR fans aren’t replicating themselves. Kids are more interested in screens than speed. According to Deford:
“There are no more gearheads growing up in America.”
“Nobody cool wants to look under the hood anymore.”
Let’s remember that Deford’s MO is taking things to their ironic extreme in order to get reactions out of people. This is the same person who said on NPR that Carl Edwards shouldn’t have been fined for his wayward oil can lid because the lid was still in the car and he thus didn’t have a weight advantage. There is some danger in commenting on things when you don’t understand the subtleties. This is why I don’t write blogs about Kardashians, dentistry or raising chickens.
Deford doesn’t say anything the motorsports community hasn’t already discussed. Increasing (or, in some cases, stopping decreases in) the number of people coming to races, watching them on TV and listening to them on the radio is hotly discussed by sanctioning bodies, fans and pundits.
The economy is an issue. Until we emerge from the current economic hard times, we have no way of knowing whether decreasing attendance and television ratings are part of the normal rise and fall of life or if people really are so irritated by the television coverage that they are staying away. The unspoken fear is “What if we are the dinosaurs, we’re headed toward extinction and we don’t even know it?”.
I don’t think we are – and I don’t agree with DeFord (or anyone else who says that the American public’s fascination with cars is over and done). I would argue first that the decreasing number of people at and watching events is a simple consequence of having so many options. Second, I believe that the automobile is in yet another one of its historic lull periods and will — in the near future — start to engage young people again.
“Fragmentization”
Decreasing numbers of eyeballs is consistent with the increasing fragmentization of life and it is not specific to motorsports. Other sports (like college basketball) are experiencing the same declines. We have so very many options for how to spend our time, plus the ability to customize information flow so that we never see anything we didn’t ask to see. Back when we had three networks and one television per house, you ended up watching TV shows that you wouldn’t have picked because it was someone else’s turn to choose. Today, it’s not unusual for four family members to be in four different rooms, each doing their own thing. The number of television watchers, for example, is (relatively) fixed. The more stations, the fewer eyes per station. This has nothing to do with motorsports and everything to do with the enormous number of options we can choose from.
The ramifications of this fragmentization are much more wide ranging than motorsports. When I read a hardcopy newspaper, I at least scan over most of the articles. When I read the same newspaper on the web, I look at a much narrower range of stories. It’s possible for us to customize our news and entertainment so that we never encounter news about other countries, political opinions we don’t agree with, or people we would never cross paths with in our daily lives. If you’re not already interested in motorsports, you are likely to never be exposed to it. All the more reason for motorsports to develop crossover projects that introduce them to new audiences.
The Evolving Automobile
Secondly, the automobile is in a chrysalis stage. We have developed and implemented just enough electronics to make cars totally opaque to the average person. When you open the hood of a late model car, you don’t see anything but parts covers. There’s nothing to be interested in.
This is going to change. As electronics become more advanced and more integrated into cars, I predict that those electronics will provide people will more and more information about their vehicles and how they work. That knowledge will make cars more interesting.
Witness how the visual storage/regeneration process display engages Prius owners. They like watching what their car is doing. They even run experiments – like changing how they drive to see if they can eek out another tenth of a mile per gallon. I look forward to buying a car that I can not only monitor, but tailor using my laptop. I’ll set it to run on four cylinders (OK, probably six) to optimize fuel mileage when I’m going to work. On the weekends, I’ll engage all eight cylinders, change the effective gearing, engage the stick shift and just enjoy driving along a deserted twisty mountain road.
I’m not worried about motorsports imminent demise. Most series realize that Americans value personality as much as (or more than) accomplishment. They put a lot of effort into making their drivers marketable and accessible. They’ve noticed the younger generation’s interest in gadgets and have introduced fantasy leagues, statistics sites, social communities, twitter, and supplementary on-line material designed to be used during a race. I’m not against that – I use most of them myself.
But here’s where my two worlds collide. We have graduate students who treat their lab equipment like black boxes – totally unaware of how it works and unable to fix it when it breaks. The fancy interfaces allow them to use something without understanding how it works — sort of like we do with our cars. We cannot escape the need to understand the mechanical. Until we have hovercrafts, most commercial ground vehicles will include gears, pistons, and axles – regardless of how much electronics you put in-between the mechanical and the user. Even if you have a tricorder, the human arm is still a lever and no computer is going to know how to splint that arm if it breaks. We cannot escape the importance of the mechanical, even in a highly electronic world.
When did we decide it is better to pander to people’s bad habits instead of encouraging them to develop better habits? Every week on NASCAR radio, someone suggests we shorten races to accommodate decreased attention spans. Shouldn’t we be concerned about the consequences of an entire generation that can’t concentrate for longer that 30 seconds, can’t process information in chunks longer 140 characters and can’t fix a broken door handle? As we sit around glued to our computer screens watching an ever-narrowing range of information we’ve pre-selected and tweeting random opinions, emerging economies like Brazil, China and India are developing ideas that solve energy and health problems — and selling them back to us.
Instead of mourning the demise of motorsports because today’s kids have short attention spans and no interest in mechanical skills, maybe getting kids interested in cars, trains, bikes and planes (heck – in lawnmowers) is a way to get them back to being interested in understanding the world around them.
Every week we hear at least one driver say that they are bringing back “the same car we raced at…”. This is a little misleading because — unlike Indy or ALMS racing — each shop builds multiple cars, each specialized for a specific track.
Let’s start by examining the anatomy of the stock car. I think of the car in three major components: The chassis, the body and the bolt-on parts.
The Chassis
The skeleton of the car is the chassis, a purpose-driven structure welded together from very strong round and square steel tubing. Shown at right, the structure consists of a front clip (to the left), a rear clip (where the fuel cell sits) and the roll cage (located in the center).
The plans were provided to teams via an AutoCAD file – which should give you some idea of how precise NASCAR expects the teams to be in implementing the chassis plan. Since the design was developed to optimize safety, teams aren’t allowed to modify the chassis at all.
How faithful teams were to the original blueprint is determined using coordinate-measuring machines (CMM). CMMs consist of a probe (which may be mechanical, optical or other) and a reading device that transmits data back to a computer that processes and stores the information. Mechanical CMM devices include the Romer and Faro arms, which are brand names of popular CMMs. These devices really do look like arms, with joints that mimic the elbow, wrist and fingers. Those joints allow motion along all three axes (up/down, left/right and back/forth), plus the ability to rotate about each of these axes. (Check out this interview with the inventor, Homer Eaton.) To measure something, the arm is touched to the car in specific spots. The probe transmits its three-dimensional coordinates to the computer. The pictures below shows a Faro arm.
NASCAR uses a Romer arm to certify the chassis (testing over 100 distinct points), and for measuring the body (as I’ll explain in a moment). One of the challenges using mechanical CMMs is that they have to be accurate over a very large volume. The NASCAR system measures over a 13′ x 20′ area defined by a set-up plate. To improve the measuring accuracy, 5/8″ diameter touchpoints are mounted in the plate every three feet. The placement of the touchpoints is verified during surface plate installation using laser triangulation. Before measuring the car, the CMM is touched to any three of the points to ensure that the probe uses the same origin every time and measurements are consistent from car to car.
Triangulation is also the basis for the CMM. The distance from the origin to the arm’s pointer is the unknown length of one leg in a triangle. If you know the length of one side and two angles of your triangle (which you do using your reference points on the plate), you can calculate the lengths of all sides and all angles.
After verifying the chassis, NASCAR attaches RFID (Radio Frequency IDentification) tags to strategic points. Those tags are scanned at the track to make sure that the chassis hasn’t been changed. For example, if a car was in an accident, these measurements tell the team whether the chassis has been even slightly bent or twisted. Very small changes can compromise safety, so accuracy is very important.
The Body
The roof, hood and decklid (a.k.a. trunk) are supplied by the manufacturer. The remainder of the body is fabricated by scratch from flat sheets of steel. The steel that makes up the body is surprisingly thin – in the the range of 25-30 thousandths of an inch thick. Most people who see a stock car up close are surprised at just how flimsy the metal is. (Ask Kevin Harvick and Carl Edwards how easy it is to accidentally dent the hood of a car during a fight discussion.) The only parts on the body that aren’t metal are the front and rear fascia, which are made from a carbon-fiber/Kevlar composite.
NASCAR uses Romer arms to measure body position and sheet metal thicknesses, as shown at right. We’re talking accuracy to the thousandths of inches level. Teams can take cars over to the R&D shop anytime to have them checked with the ‘official’ equipment, although most have one or more Romer arm systems in their own fabrication shops. It’s not a small investment: A Romer system costs about $60,000. That’s not including installing a surface plate, which has to have no more than a few thousandths of an inch variation in height across a distance of 12 x 20 feet.
It is impractical to bring a Romer arm and surface plate to the track. At the track, NASCAR uses a template structure – similar to the one shown here (from the Super Chevy website) to check that each car conforms to the rulebook. The template grid is not the most sensitive measuring device. I have watched inspectors tap the template to “make” it fit more than once. The template makes it easy to see gross violations, but racing these days comes down to thousandths of an inch and that is why the cars have to be brought back to the R&D center for measurement.
The video below shows the template grid system and the body. After the templates are lifted off, the body rises to reveal the chassis underneath. (In reality, of course, the body doesn’t just lift off the car – it’s attached with rivets and welds.) I think this demonstration (from the Hendrick museum and video courtesy of Santa Fe Productions) illustrates well the difference between the chassis and the body.
The “parts” as I call them are all the pieces that are bolted to the car: suspension component, transmission, engine, windows, etc. Because they aren’t welded to the car, these pieces can be changed during the course of a practice or even a race.
What Does “Same Car” Mean?
When a driver or a crew chief talk about ‘bringing back the same car’, they are almost always talking about the chassis. When you give “a car” a name, you’re naming the chassis, not the bodywork and certainly not the A-arms or the engine. When a car comes back to the shop after a race, the engine is removed, most (if not all) of the bolt-on parts are removed and more often than not, the body is removed. The engine is stripped down and entirely re-built before being used again. All of the bolt-on parts are inspected for wear and possible damage. In theory, the body could be left on and all the parts re-used.
It is rare, however, for a team to be satisfied with how a car ran — even if the car won the race. Teams are always looking for advantages, so there may be different bolt-on parts used for the next race, or the crew chief may want to modify the body slightly (within the rules, of course) to make it more aerodynamic. When a team talks about “a car”, they’re almost always talking about the chassis — which is changed only when it has been damaged.
Can You Bring Back “The Same Car”?
In their recent appeal, the 48 team claimed that the car that had been deemed illegal was the ‘same car they had used” for all plate races in 2011. How is that possible if so much changes from race to race? I guarantee you that there wasn’t one speedway car sitting in a corner in the Hendrick shop under a cover waiting to be brought back out for the next plate race.
The key is laser scanning.
Mechanical arms are really nifty pieces of technology; however, they measure specific points. The more complex a curve (or the more subtle its departure from the specification), the more points you have to measure. Laser scanning takes accuracy one step further.
We can make measurements similar to those made with a Romer arm using a laser. We know exactly how fast light travels (300 million miles meters every second), so measuring how long it takes for a beam of light to travel to and from a surface lets us calculate the distance from where the beam is emitted to the object.
A slightly more complex setup is used for 3D scanning. A laser stripe is projected on the car. If the surface onto which the line is projected is flat, the line will appear straight. A curved surface distorts the line, with the distortion proportional to the amount of curvature. A sensor looks at the line and back-calculates what surface shape would cause the observed line to appear as it does. Most of the big teams have their own laser scanning system and scan every car before and after it goes on track. Subtle differences in curvature could mean a few hundredths of a second improvement per lap. Everyone knows that the days of finding a half second per lap are over. A few hundredths can make a huge difference.
I suspect that the 48 team was able to produce laser scans of each of their speedway cars for the last year and show how the C-posts on those cars compared to the C-posts on the car that was deemed illegal. I can’t say anything about the decisions that were made on the basis of those measurements, but the routine laser scanning of cars provides a pretty solid documentation of everything about a car.
Putting Bristol “Back”
Cars aren’t the only thing laser scanners measure. Laser scanning is also used (in a slightly different form) to scan tracks. NASCAR.com’s Raceview and iRacing provide amazingly accurate pictures of the tracks. Those graphics are due to 3D laser scanning that allows them to measure every dip and every oil spot on a track. The video below shows how iRacing does it.
Bruton Smith definitely has access to very detailed measurements of the pre-2007 Bristol from a variety of sources. Does that mean he can put it “back” the way it was? If he can, does that mean racing will go back to the way it was?
No. Definitely not.
Our ability to measure accurately far exceeds our ability to replicate accurately. There is a huge human element, whether it be making a car or re-surfacing a track. Sure – you can replicate the track dimensions pretty accurately — but how do you duplicate exactly a concrete surface that has been weathered by decades of weather and use? Bruton hasn’t announced exactly what he’s going to change, but we’ll analyze it when he does.
It didn’t take long after Brad Kezelowski pulled out his cellphone during the 2-hour-long Daytona red flag for the conspiracy theorists to leap into action.
The argument goes like this: Cellphones should be banned from the car because a driver could use his specially prepared cellphone to a) change the Engine Control Unit (ECU) and/or b) transmit data from the car back to his crew chief during a race. We will not address the suggestions that the driver could use the cellphone to talk secretly to the crew chief during a race because anyone who has been in a race car or worn a helmet knows that’s just plain dopey.
Let’s differentiate between telemetry and electronics. The word telemetry comes from two Greek words: tele (meaning ‘at a distance’) and metre (meaning ‘to measure’). Telemetry technically means measuring something (like the speed or acceleration) remotely, but many people use the word to include the ability to send information from the crew to the car.
Let’s start with the assertion that is the easiest to disprove: you cannot control the ECU remotely. Some people seems to have problems distinguishing between electronics and telemetry. Just because something is electronic does not mean it can be communicated with remotely. I can start my 2010 Fusion from inside the house by pressing a button on its remote. My 1998 Ranger remote doesn’t even have such a button because the truck lacks the ability to receive instructions from a distance. An app that sends a signal to a car doesn’t do anything if the car isn’t able to receive and interpret the signal.
The McLaren ECU is built specifically to preclude the ability to change any engine parameter without plugging a computer into the system using wires. There simply is no way to change the ECU wirelessly. When NASCAR initiated the switch to EFI, they worked with McLaren from day 1 to develop a system that would minimize any possibility of “cheating”. If you want to keep someone from stealing something from your car, you can make sure you lock he doors. The sure way to make sure it doesn’t get stolen from your car is not to leave it in the car.
No major racing series allows teams to talk to the ECU remotely. Even F1, which used to allow it, realized that fans don’t want to watch engineers race absurdly expensive RC cars. NASCAR drivers are not controlling their ECUs with their cellphones.
The second argument is a little more subtle because we all know that data can be read from the car during a race. For the last 10 years, a company called SportVision has provided information to NASCAR’s television broadcasting partners using telemetry. This information includes the throttle position, brake, rpm, speed and position of each car. Prior to the introduction of EFI, SportVision got their throttle and rpm data from throttle position and shaft speed sensors in the car. This year, rpm and throttle data are acquired directly from the ECU (which, incidentally, provides much more accurate data than the sensors did).
The question of intercepting data isn’t new with EFI: The company has been required by NASCAR to keep all data they collect out of the hands of the race teams since the program began. SportVision encodes the data that is transmitted from each car. If you were able to intercept the data, it’s not like you could open up the data file in Word and see a line like “4500 rpm, 147.6 mph, 80% throttle”. It would be a series of ones and zeroes that would take some serious decoding in order to figure out what each piece of data was, much less what it meant. This makes it difficult for anyone besides SportVision to intercept and make sense of the data.
Let’s assume for a moment, however, that a team did figure out how to intercept and interpret the data (and incidentally, you wouldn’t need the equipment to be insider the car – you could do it from well outside the car). The SportVision folks told me that the sum total of all the data from the 43 cars competing in each race ends up being about 2 Gigabytes worth. To set a scale: One character is a byte and an average word is about 10 bytes. One page of an encyclopedia is 10,000 bytes or 10 kilobytes. The 2 Gigabytes of data collected during each race is 2 billion bytes, or 200,000 encyclopedia pages.
Each car provides about 46.5 million bytes of data, which corresponds to 4,650 encyclopedia pages worth of information each race. For an average three-and-a-half hour race, a single car transmits information at a rate of about 3700 bytes (a third of an encyclopedia page) every second. Handling this rate of data input and analyzing it in real time is nearly impossible. In the words of one of the SportVision engineers, “If you find someone who can get the data and analyze it in real time, I want to hire that person!” SportVision doesn’t even do real-time data analysis because of the huge amount of data coming in. Even if you were able to intercept and read the data, analyzing all that data and getting something useful out of it (something you could use to make the car better) would be a huge challenge.
For the sake of argument, let’s assume that a team WAS able to intercept, interpret and analyze the data from the car in real time during the race. What can they do with that information? If they want to change anything on the ECU, they have to take the car behind the wall. The time it takes to make the ECU change isn’t going to be offset by the performance advantage you might get from making the change. The teams get all of the data from the ECU after the race anyway, so there’s absolutely no advantage to capturing it during the race.
Let’s also think about the practical. If you had invested all this time and expense to develop the software and hardware necessary to intercept and transmit data from the car back to the pit box, don’t you think you’d tell the driver not to pull out his cellphone and make a show of carrying it in the car during a red flag in the most-highly-watched race of the year?
Here’s my biggest concern about cellphones in cars. If you are going 180 mph and you stop suddenly, anything not secured in the car becomes a projectile with an initial speed of 180 mph. Putting the phone in your firesuit pocket (yes, firesuits have pockets) is also not advisable: Do you really want a hard piece of metal and plastic trying to embed itself in your leg? Or elsewhere?
Conclusion: if you want to argue against cellphones in racecars, the best argument is the 180-mph projectile safety argument. The drivers are not controlling their cars with their cellphones, they’re not intercepting data and sending it to the crew chief with their cellphones and, even if they were, there isn’t anything useful the crew chief could do with that intercepted data. So let’s put that theory to bed for good and just enjoy some Bristol racing.
In my last post, I detailed how the relays in the ECU system allow the system to flip to a default engine map. This lets the team keep running, even when something fails, and it decreases the chances of the ECU doing something that blows up the engine. Here’s a short explanation of what exactly an ‘engine map’ is and what it does.
The race at Phoenix was the first non-restrictor-plate race. A number of drivers experienced engine-related problems, leading some media outlets to start blowing the “EFI problems” horns as loudly as possible. Mark Martin, the pole sitter, was an unfortunate casualties of a “flipped circuit breaker”. One of the most interesting exchanges to me was a series of tweets and a radio interview with Mark Martin’s Crew Chief Rodney Childers (@rchilders55) in which Childers repeatedly said it not “an EFI problem”, the radio commentators persisted in saying that it was.
Here’s his verbatim tweets (and if you’re not following him on twitter, please do!)
Man I hate that!! We had a breaker POP on our ECU for the fuel injection about half way. Which makes it switch to a safety fuel map.
It popped about half way.. it didn’t affect the performance. Just the Mpg, which made us have to pit. But we are really happy..
That made our mileage go from 4.2 to 3.8… And no way we could have made it. Good job to mark and all the Aarons guys though.
The EFI deal isn’t really the issue.. probably a wiring issue that we have to figure out. We had the same deal happen in practice.
Each car has a relay box, which acts sort of like Mission Control. I’ve said before that the ECU (Engine Control Unit) is the brain of the EFI system. The ECU collects information from a number of sensors located in different places on the car that measure things like humidity, pressure, temperature, and air-fuel ratio. The ECU makes decisions on what to do next based on the information it gets from the sensors, and it acts on those plans by sending messages to the rest of the car through the relay box.
What happens if one of the sensors stops working (or a wire breaks and the sensor, even though it works, can’t send information)? If the ECU believed the data it was being given, it would have a rather warped view of reality and could start telling the car to do all types of goofy things, including some that could actually damage the engine beyond repair.
The EFI system is smart – smart enough to know when it is getting suspicious data. Instead of acting on that data, a relay is triggered and the ECU changes over to an alternate engine map (what Childers called a ‘safety fuel map’). The alternate map isn’t optimized for performance – it’s purpose is to allow you to keep running, but your performance won’t be as good as you would have with the information from the sensor and the optimized engine maps. As an analogy: You eat more efficiently when your eyes are open. If someone blindfolded you, you could still eat, but it wouldn’t be as efficient (or clean) as with your eyes open. This relay system protects the engine from the actions of a confused ECU. You might not run as well, but you also might not destroy a whole engine.
The relays work on the basis of a voltage threshold. They’re like an electron bouncer. A relay has a maximum current or voltage it will tolerate. Bob Pockrass reports these relays have limits at 5V and 100 mA. If an electrical signal comes through with a higher voltage (or current, depending on the type of relay), the relay switches everything to an alternative circuit. Unlike the circuit breakers in a house (which are normally on/off, in contrast to these, which are circuit 1/circuit 2), it’s very difficult to re-set the relays. It’s not like there’s a switch that the driver or a crew member can reach down and flip back. When they flip, you’re pretty much stuck with them for the rest of the race.
Teams will be looking for anything that might cause the relay to flip. That could be a wire that vibrated loose, or an electrical spike (like, say, the spike you get when you turn a switch on or off perhaps…?) I understand some teams are switching to boxes without relays – but then you take a chance that something gets out of whack and you blow up your engine entirely. One of the real pains in the neck with a short or a transient spike is that they can be hard to reproduce. You can do the same thing 10 times and the problem may only happen one time out of those ten. Makes for some long nights for the engine shops.
Childers tweeted that the mileage dropped from 4.2 mpg to 3.8 mpg – that’s just about a 10% drop in efficiency. Phoenix is a one mile track, which means that the change in fuel mileage cost them nine laps per tank of fuel. When teams are scrapping for one-percent increases, a 10% decrease is just going to kill you.
Keep in mind that we’re in uncharted territory. NASCAR teams are subjecting these systems to environments they haven’t seen before. I expected a few problems like this at Phoenix and I expect a few more in Las Vegas. Teams will figure out how to make their system withstand the high-vibration/high-temperature world under the hood of a race car and drivers will gradually learn which of their techniques still work with the new system and which ones they’re going to have to change.
And if you’re wondering exactly what an engine map is, I’ve got a video going up on Friday to explain it.
Although there is a lot of science behind bump drafting, the act of bump drafting is an art. Even the experienced bump drafters are surprised by the touchiness of the cars this year.
Things to notice:
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