The NASCAR Vortex Theory

The NASCAR Vortex Theory says that cars racing around an oval track create a rotational disturbance that repels oncoming storms. Truth? Or Myth?

What’s a Vortex?

A vortex is a region in a fluid (and remember: air is a fluid) where the flow revolves around an axis line. A physicist or engineer represents a vortex with vectors, where the shorter vectors mean the fluid is moving faster. You’re looking at the vortex below from the top. The axis about which everything revolves is coming out of your screen.

A vector diagram of a vortex field

FACTOID: The plural of vortex is vortices OR vortexes. Either one is right.

Scientists use vortices to describe lot of things including

Vortices in Aerodynamics

Vortices are also important in aerodynamics: they create drag and lift — in planes and race cars.

A NASA image showing the vortex off the wing of an airplane

Vortices in Nature

But you see them pretty much everyday, too. For example, when you pull the plug in a drain and the water runs out…

A beautiful photo of water draining.

Or when you flush the toilet

A toilet flushing

You’ve probably heard that water drains in different directions in the Northern and Souther hemispheres; however, toilets use jets of water to flush, so the direction they flush depends on the toilet design, not the hemisphere. Similarly the shape of a sink and how you remove the plug can change the direction a sink drains. A definitive experiment was performed and the video is well worth watching.

The Vortex Effect is Real

Aerodynamics is critical to racing, but there’s one thing that’s even more critical to racing: weather.

The Coriolis effect is a force related to the rotation of the earth. The Earth is bigger at the equator than the poles. A spot on the equator moves at 1,040 mph, while a spot close to the axis of rotation moves 0.00005 mph.

If you stand at the Equator and launch a ball to someone in Kansas, the ball will land to her right: she’s moving slower than you are. This effect was first described in 1651 to explain why cannonballs fired a long distance missed their marks. My father used to tell me about his time at Fort Lewis learning to calculate trajectories using a slide rule to account for the Coriolis force in calculating munitions tracks.

Size and Speed

The equations for the Coriolis force are complicated, but here’s all you really need to know:

  • The bigger the distance, the bigger the Coriolis force.
  • The higher the speed, the larger the Coriolis force.

Jupiter has the fastest rotation in the solar system. One day on Jupiter is about 10 hours. The Coriolis force is so strong that it transforms north-south winds into east-west winds, with speeds of up to 380 miles per hour. This wind pattern creates belts of clouds and the boundaries between those belts are very active storm regions. The Great Red Spot is one of those storms.

The bands on Jupiter are shown. They're due to the Coriolis Force, as is the Great Red Sport

But we’re not racing on Jupiter. So what — relative to the planet Earth — can we consider “big” and “fast”.

Weather systems.

A NASA image of Hurricane Irene from 2011

Hurricane Irene was about 510 miles in diameter, with is about 1/3 the size of the U.S. The inner 140 miles were hurricane-force winds; the rest were ‘merely’ tropical-storm force. It did 14.2 billion dollars of damage.

In the Northern Hemisphere, hurricanes rotate clockwise. In the Southern Hemisphere, they rotate counter clockwise. Coriolis forces are responsible for hurricanes, tornadoes and cyclones, as well as everyday weather trends, like the trade winds.

The ‘Vortex Theory’ of the Coriolis Force is unquestionably real.

Is the NASCAR Vortex Theory Real?

So if the circling of the Earth can cause big-scale effects like tornadoes, then is it possible that the circulation of very fast cars about very big speedways might be able to cause similar effects and cause storms to veer away from the track?

Daytona International Speedway is the biggest of ‘big tracks’ and the speeds reach 200 mph. But that’s pretty much nothing compared to a tornado.

But what about a smaller storm?

According to the National Weather Service, your garden-variety storm is 15 miles in diameter and lasts an average of 30 minutes. Daytona’s effective diameter is about 0.8 miles. Even Daytona isn’t big enough to affect the weather. And if it can’t happen at Daytona, it won’t happen at Martinsville or Bristol, which are tinier and smaller.

But I’ve Seen It!

We all remember times in which it looked like it was going to rain, but then the race started and the race held off. If you collected systematic data, you’d find just as many cases of a race starting, then being called because of rain. (Like last weekend at Dover.) As Chad Myers, a CNN meteorologist with a background in motorsports broadcasting says:

“Considering how much rain we’ve had and how many races have been rained out, if this theory actually worked you’d never rain a race out. You can’t pick and choose when it works and when it doesn’t.”

Chad Myers via Turner Sports Interactive

Then Why Do They Keep Talking About The Vortex Theory?

A photo montage of DW creating a vortex at a track.

‘The Vortex Theory’ has become NASCAR’s version of the catch phrase, the same way ‘Dy-no-MITE!’ and “NaNu NaNu” became catch phrases in the 70s and 80s. People picked up on the phrase and so Darrell Waltrip kept using it.

A DW tweet about The Vortex Theory

Just like those catch phrases from the 70s drove my parents nuts, the Vortex Theory drives a number of NASCAR people nuts.

Jeff Gluck's tweet expressing frustration at the Vortex Theory

And just like we used those phrases even more once we realized it annoyed our parents…

Mike Joy's tweet trolling Gluck

I am sure that Mike Joy knows better. Larry McReynolds, with his interest in the weather, definitely does. So it’s mostly tongue-in-cheek; however, there are some downsides to pulling this out every time it rains.

The biggest downside is that there are some people who believe everything they hear. Just visit the r/NASCAR site for examples.

The second downside is that most people outside of NASCAR don’t realize it’s an inside joke. Combine that with their stereotypes of NASCAR fans and, as one fan complained on Reddit, “it makes us look like hillbilly rubes.”

Maybe we should let the concept leave with its originator.

So There’s No Such Thing as ‘The Vortex Theory”?

Actually, there is.

It’s also wrong.

Rene Descartes — the ‘Cogito Ergo Sum’ (I think, therefore I am) guy — came up with a theory about how the universe worked and called it “The Theory of Vortices”.

Descartes postulated that space was entirely filled with matter (in various states) whirling about the Sun like a vortex. You see, Descartes died in 1650. Little Isaac Newton was just seven years old and the theory of gravity was still thirty-seven years away from publication. Despite Newton’s convincing arguments, the French championed Descartes’ theory for nearly one hundred years after Newton showed it was impossible.

Is the Coriolis Force Why We Turn Left?

The Coriolis force makes things circulate oppositely in the Southern Hemisphere than the Northern Hemisphere, so someone always wants to ask if they race in the opposite direction in the Southern Hemisphere.


  • There are a lot of clockwise tracks (horse and car) in Europe.
  • About half the horse tracks in Germany are clockwise and half are counter clock-wise.
  • In Australia, horses race counterclockwise in the states of Victoria, South Australia, Tasmania and Western Australia, but clockwise in Queensland and New South Wales.
  • Formula One has historically raced on both clockwise and ‘anti-clockwise’, as they say in Europe, tracks.
  • In 2014, the Indy 500 ran counter clockwise and the Grand Prix of Indianapolis, at the road course, was clockwise.

So We Could Just Decide to Turn Right?

Although we turn left by tradition, most tracks are designed to run in a specific direction. The entrances for the emergency vehicles are directional, as shown below. The green arrow shows the correct direction. The orange area shows the wrong direction..

An overhead view of the Walt Disney World Track and the sharp end of the barrier at the emergency egress.

If you run the track backward, you have a much higher probability of running head on into the sharp end of the barrier (circles). Running a track backward resulted in the death of driving instructor Gary Terry at the Walt Disney World track in 2014 when his student lost control and they this barrier.

But there’s another reason for us to keep turning left: The driver’s seat is on the left and you are more likely to hit the outside wall than the inside. That means you hit the side of the car furthest from the driver, and the driver has an easier time getting out of the car because he’s not right up against the wall.

NASCAR: Caps, Limits and Level Playing Fields

Every sport faces it: One, or a few, teams pull ahead because they can spend more money than anyone else. Those teams and their fans are fine, but it means the league has failed to ensure a level playing field.

What is a Level Playing Field?

A level playing field is a lot like obscenity: People can’t describe it, but they know it when they see it. Especially when the field is tilted away from their driver.

In commerce, a level playing field is a concept about fairness, not that each player has an equal chance to succeed, but that they all play by the same set of rules.


Megacorporations subsume or kill off smaller companies, becoming so large that no one can compete with them. In business it leads to monopoly. In sports, it leads to disinterest, and disinterest can be fatal, especially in this day and age

A level playing field does not mean everyone has the same chance of winning. If we put every driver in the same car, some of them will run faster than the others. If we put one driver in different cars, his lap times will be different in the different cars.

A level playing field means that everyone has to follow the same rules. They all have to make the same number of laps, but they don’t have to run the same line. The bodies have similar downforce counts even though they’re not identical. That’s a level playing field.

Motorsports is more complicated than racing or horse racing because there are more moving parts. It’s not just about the best driver. It’s about the best match between driver and car and the ability to adjust to meet the particular conditions of that track on that day.

A level playing field in NASCAR has to consider the driver, everyone who builds, maintains, repairs or services the car and the car itself.

The Constraint: Money

As in the stick-and-ball sports, the level playing field is usually warped because of different amounts of money. NASCAR is far from the only series worrying about this.


Compare the 2018 budgets for F1 teams. I used an average 2018 exchange rate of $1.15 per Euro to convert the numbers given by Autobild.

F1 team budgets for 2018

The lowest-funded team in F1 spends about one-quarter what the highest ranking team does. F1’s ten teams cumulatively spend about $2.6 billion annually to compete. The cost to compete is going up, too.

Comparing 2013 vs. 2018 budgets for F1 teams.

A couple notes about this graph because they aren’t the same teams

  • Merdedes, who was the fourth largest spender in 2013, almost doubled their budget.
  • Force India went bankrupt in 2018 and had to be bailed out
  • Lotus, Caterham and Marussia are gone
  • Renault and Haas are new

The budgets are larger because the audience is larger. F1 races reach an audience of almost a half-billion people around the entire world.


The World Endurance Championship series started in 2012 and includes the legendary 24 Hours of Le Mans race. Four car classes race, but the LMP1 cars (LMP = Le Mans Prototype) are the acme of technological race car achievement.

The LMP1 car that Fernando Alonso tested recently in Bahrain

Audi and Porsche were reportedly spending $200 – $250 million each on their LMP1 programs. By the end of 2017, both had pulled out of the WEC in favor of competing in the Formula E Series. (To be fair, Dieselgate had some impact on Audi’s leaving.) Toyota has the only manufacturer team.

WEC has four classes and there are still privateer LMP1 teams, so it’s not like the class is dead — but it’s certainly lost a lot of luster.


The domination of three drivers in the early part of the season drew a lot of complaints from fans, as did the period of time when Jimmie Johnson won five championships in a row.

But NASCAR is focused not just on the current season: they’ve been concerned about the future of the sport. A level playing field can’t mean that everyone has equal opportunity to go bankrupt.

NASCAR instituted the Charter System in 2016 to help stabilize the sport. The charter system made NASCAR and the teams more equal partners, and gave some of the smaller teams a little more security going forward.

Forbe's numbers for the Net Worth of NASCAR teams

Some teams have fallen on hard times. In 2005, Roush put all five of its teams in The Chase and prompted NASCAR to put a limit on how many teams one company could run. This year, they’re down to two teams. Forbes’ numbers didn’t include Furniture Row, which closed last year.

But NASCAR racing is expensive. The BK Racing bankruptcy showed them spending about $20 million in 2016, which covered 82 race entries split over three cars. The best teams in NASCAR spend $20-$30 million per car. We’re also in a time where a lot more effort is needed to find sponsors because there are fewer sponsors willing to commit to an entire season of support.

Partial expenses for BK Racing, obtained for their bankruptcy filing

The Challenge

So… we want a level playing field and we don’t want to do it by making everyone spend more money. We want to protect the existing teams and owners, nurture new teams, and have great competition.

No problem, right?

It used to be that going faster meant spending money on better car parts. Now you’re spending it on better (and more expensive car parts), but also on engineers, wind tunnels, simulators, 3D printers, computerized milling machines, vehicle dynamics simulation programs, computer clusters…

Whereas NASCAR could once control costs with fairly simple rules, like “no exotic metals” and limited rear gear ratios, it’s a little harder when you’re talking about people and computers.

This All Started With Testing

The biggest challenge is that this is a giant game of whack-a-mole. Every rule has a consequence and sometimes the consequences are bigger than whatever the rule was meant to prevent.

NASCAR steadily cut on-track testing in an attempt to save teams money.

  • In 2003, teams had
    • 5 two-day and 4 one-day tests at Cup tracks of their choice
    • Unlimited testing at non-Cup tracks
  • In 2018, teams had
    • 4 two-day tests at Cup tracks chosen by NASCAR

These limits drove teams to develop other tools: driver simulators, software to model everything from suspension movement to engine combustion, seven-post rigs, wind tunnels and computational fluid dynamics. Teams that could spend more money on these elements got faster. Teams that couldn’t fell behind.

Is it feasible for NASCAR to control how teams use these tools?

Driving Simulators

I blogged earlier this month ago about the amazing driving simulators the manufacturers have developed. it doesn’t make sense for NASCAR to try to limit those

  • The manufacturers create and run them, so it’s not a team expense.
  • Manufacturers are increasingly using simulators for passenger car design and testing, so much of the technology can benefit their street-car programs
  • The simulators do generate data for engineers to analyze, but the time any one driver gets on the simulator isn’t huge.

Wind Tunnels and CFD

A graphic showing a computational fluid dynamics visualization

F1 realized the importance of aerodynamics in the 70’s and 80’s. Their teams initially used facilities at universities, many of which could only accept up to 40% scale models and worked at lower wind speeds.

In the 90’s, the bigger teams built their own wind tunnels that were specialized to F1 racing, ran at high speed, and could accommodate full-sized cars. F1 teams ran their tunnels 24/7, with one set of engineers running tests and another analyzing the data from those tests.

Teams also invested heavily in Computational Fluid Dynamics (CFD), a computer-intensive simulation technique that uses fundamental equations of physics to model how air interacts with objects. You can buy CFD programs, but you need specialized expertise to understand how to use them properly. Most commercial CFD packages aren’t optimized for racecars, so most race teams invest in developing their own, proprietary CFD packages, which they keep top secret.

NASCAR teams have pretty much done the same thing with CFD and wind tunnels, although they not every team has their own wind tunnel.

NASCAR teams primarily utilize two wind tunnels in the Charlotte area: Windshear and Aerodyn. Gene Haas opened Windshear, but it’s available to anyone willing to pay. Penske has a proprietary wind tunnel, but’s a 40-50% scale.

An hour in one of the two full-scale wind tunnels costs anywhere from $2000 to $3500 depending on which wind tunnel and what features you need. Aerodyn has enough business that they run two shifts: from 6 am to 3 pm and from 3:40 pm to 12:40 am. The hourly cost doesn’t include getting the car ready for and to the wind tunnel, or paying your engineers to run the test and analyze the results.

NASCAR teams have also invested in high-speed computer clusters, advanced graphics processing units and aerodynamics specialists to develop, run and maintain CFD programs.

Limiting Aerodynamic Research

F1 has restricted CFD and wind tunnel time. Wind tunnel research is limited to 60% scale models and speeds of 50 m/s (112 mph). Aerodynamics work is even banned during a designated two-week period in July/August.

F1 has limited the computing power that can be employed for CFD and require teams to submit fortnightly (that’s every two weeks) logs of CFD time, which is supplemented by periodic inspections. They implemented a formula that gives teams a little leeway in how they divide CFD and wind tunnel time; the two techniques together can only add up to some maximum amount.

The FIA has restricted wind tunnel and CFD time since 2009, but each limit they impose spurs teams to find new (and often more expensive) ways around the limits. One F1 team even worked with chip manufacturer AMD to develop a brand new type of computer processor that effectively doubled their CFD capacity.

Similarly, as wind tunnel time was reduced, teams put more effort into designing more advanced data acquisition tools that allowed them to get more data in less time. Some teams also put money into upgrading their wind tunnels, for example by creating rotating platforms that allowed them to run the car through a series of yaw angles.

Again: money and time.

And every time technology advances, the limits have to be revisited. They now have two sets of rules: one for teams that have the chips they’ve been using; and one for teams with the newer chips. Why don’t they just have one option? Because either teams would be forced to invest in old technology or teams would be forced to upgrade, which would cost money, which was the opposite of what they were trying to do.

If we look at it in terms of dollars per tenth of a second gained, the cost is going up, not down. This means that the teams with the highest budgets still have an advantage.

And how do you monitor the research and development of CFD programs? A good aerodynamicist is thinking about new ways to understand aerodynamics day and night. Nothing about these rules prevents teams from hiring consultants or a battalion of aerodynamicists. The same arguments apply to other types of simulation programs.

Honestly, this starts to sound way too much like the nuclear monitoring arguments during the Cold War.

Budget Caps

Instead of trying to dictate individual elements, what about just capping how much money a team can spend, analogous to the salary caps in stick-and-ball sports?

New series have a much easier time because they can build cost control into the series design. Formula E has a $3.5 million spending cap, and has mandated that the price of any racecar should not exceed 800,000 euros ($945,000). That’s a ready-to-race price with powertrain included — but it’s a mostly spec car at the moment. The plan is to gradually allow more customization, but they realized there was no way to start a new series and attract teams if the intial investment was huge

F1’s Struggles with a Budget Cap

F1 has been trying to implement a budget cap for quite some time to create a level playing field without having to get into the weeds of details. They have to overcome some problems NASCAR doesn’t, notably that the top teams have banded together to oppose cuts. They tried to create the equivalent of a RTA, but it splintered into two groups: the haves and the have-nots. In addition, the sanctioning body and the rights owner haven’t always been on the same page. Those issues are the primary reasons why they don’t have a cap already.

In 2010, F1 proposed a $60 million cost cap, which enticed three new teams to sign up to run. The cost cap failed and all three teams collapsed — one reason why the new proposals for a cost cap are being met with skepticism.

The current cap proposed by the sanctioning body (FIA) and the rights owner (Liberty Media) is $185 million in 2021, $160 million in 2022, and $135 million for $2023 – but that excludes

  • engine costs
  • top manager and driver salaries
  • marketing and hospitality expenses

Considering that the top teams are current spending upward of $500 million, we’re talking significant cuts. But Gene Haas says that the big teams have five people for every one his team has. Cutting their research and development efforts is the only way a new team will ever catch up.

An analysis of a previously proposed budget cap of $150 million said it could cut as many as 1,244 jobs — and that’s only counting the seven UK-based teams. Those jobs are 31.5% of the workforce.

Would It Work in NASCAR?

NASCAR took steps in 2018 to limit how many people teams could bring to the track, but they’ve never tried to mandate how many people a team employs at the shop. Hendrick Motorsports has over 500 employees: A cap comparable to that imposed by F1 might mean cutting 158 jobs.

NASCAR has the best cooperative relationship with the teams they’ve had in a long time. Even if everyone agrees a budget cap is a good idea, it’s not a simple thing to do.

Some teams exist strictly for racing, whereas others have allied businesses like engine companies and performance racing products. As precision machining becomes important, how do you weigh contributions from Haas CNC? Or Brad Keselowski’s new manufacturing concern? Henrick and RCR’s performance car parts divisions?

Enforcement is also a problem. NASCAR isn’t rolling in money, either, as evidenced by recent layoffs. (To be fair, they’ve also made a couple new, very good, engineering hires they haven’t trumpeted very loudly.)

But consider the costs of having to hire accountants to review each team’s budget and the costs to the teams of having to adopt accounting procedures that allow them to comply with the regulations. That’s especially onerous on the smaller teams, who are already at a disadvantage.

Creating a level playing field is complex problem with no simple answers, but the future of racing series may depend on it.

Brad Keselowski: The Smartest Driver in NASCAR

Brad Keselowski may not have an engineering degree or years and years of experience, but I’m ready to nominate him as the Smartest Driver in NASCAR. He is a man with a plan and it’s a really good plan.

He is building what has been called by industry leaders an “Anything Factory”.

NASCAR Career Planning

A NASCAR driver’s career is uncertain, especially as he gets older. Everyone wants the next hot driver and the current level of competition means that having a merely ‘good’ year can mean losing your ride. And there’s always the possibility that an accident could take you out for a few races, a season, or for good.

Even if you have a long and productive career, Cup drivers tend to retire these days in their early 40’s — and that age is going down. The average lifespan of the American male is 78.7 years.

That’s a lot of time to fill.

What’s After Retirement?

A lot drivers (Burton, McMurray, Gordon, Earnhardt, Jr., Rusty Wallace, both Waltrips, Bobby Labonte…) move into broadcasting, but the broadcast booths are getting pretty full. Even with the 24-hour news cycle, the argument can be made that we’ve got more race-car-driver analysis than we really need. Plus, the season is limited: the broadcast rights are split between PRN and MRN, between Fox and NBC. For many people, broadcasting is not a full-time job.

Some drivers (Dale Earnhardt, Jr., Tony Stewart) go into team ownership, or take on other roles with race teams (McMurray). Some go into slighty less-fast-paced businesses like car dealerships (Mark Martin, Rusty Wallace).

Brad Keselowski’s Path

Until recently Keselowski looked like he was ticking all those boxes. He appears frequently as a television analyst for XFINITY races. He’s made no secret of his interest in eventually becoming a Cup-level owner and, in 2007, started Brad Keselowski Racing.

Brad Keselowski Racing Shop with Sign and car out front
The BKR Racing shop “before” picture.

Focusing on the Camping World Truck Series, BKR ran part-time until 2011 and got their first win in 2012. Brad himself drove one of his own trucks to victory in 2014 at Bristol.

But in August of 2017, Keselowski announced the team would shut down.

He’s not the first driver to shut down a race team, and not even the first one to shut down a promising, successful team. Kevin Harvick did the same thing so he could focus on his own career and his family.

But here’s where Keselowski did something unique. He turned his 70,000 square foot race shop into a factory.

On January 24, 2019, Keselowski announced a new business: Keselowski Advanced Manufacturing (KAM), which had actually started in 2018. KAM started with 30 employees and expects to have 100 employees by the end of this year.


What does a NASCAR driver know about manufacturing? It turns out, plenty.

Keselowski’s grandfather spent WWII making drill bits for the military. Keselowski’s father and uncle had a race shop in Michigan where they built race cars, but also did production work for local racers and the “Big Three” car manufacturers. Brad saw firsthand how hard it is to make money racing. His family used manufacturing to fund their racing.

They couldn’t make a living from racing, so basically, they funded their love of racing through their abilities as craftsmen and fabricators.

Brad Keselowski, Inc.

He got his first look at the advanced tools of the time at Hendrik, where he saw his first CNC (Computer Numeric Control) machines. Then he landed at Penske, where having an IndyCar team in the same shop meant exposure to manufacturing techniques that weren’t common in NASCAR at the time (like carbon fiber), but are now migrating over.

But Isn’t Manufacturing Dying?

A lot of people who used to make their living in manufacturing don’t anymore. The share of Americans working in factories has fallen from a peak of 30% in 1950 to 8.5% in 2017. Some people want to bring back those jobs, but others — like Keselowski — want to be part of movement that is changing what manufacturing means

Additive vs. Subtractive Manufacturing

When I took shop class (in high school and then again as a graduate student in physics), I learned how to use lathes, drills presses, milling machines, band saws and such. In the main physics shop, they used CNC machines, laser cutters and EDMs.

The Michigan State University Department of Physics and Astronomy Machine Shop
The Machine Shop at the Department of Physics and Astronomy at my Alma Mater, Michigan State University. This is a new building. When I was there, it was a windowless cave in the basement.

Anything you made started with a block or sheet of material and you eliminated the materials you didn’t want. You made things in pieces, then soldered or welded them together. When you were done, you had your part, and a pile of turning, shavings or scraps on the floor. This is subtractive manufacturing.

Additive manufacturing says, instead of starting with a big block of stuff, let’s start with something smaller and build our part.

A pictorial explanation of subtractive manufacturing (top) and additive manufacturing (bottom).
A pictorial explanation of subtractive manufacturing (top) and additive manufacturing (bottom).
A quantum corral made of individual iron atoms
A quantum corral made from iron atoms.

At it’s most basic, this means building things atom by atom. For example, this is the quantum corral made by moving individual iron atoms one by one using a scanning tunneling microscope into the shape of a ring. It’s a corral because the waves you see are electrons being reflected back. And it’s been colored to make it pretty.

The IBM logo made using 35 xenon atoms.
35 Xenon atoms were used to make this exceptionally tiny advertisement for IBM — but it appeared in newspapers around the world.

And just so you know that science is just as sponsor-obsessed as NASCAR, the very first image made by moving individual Xenon atoms was made in 1999 and was a corporate advertisement.

You can also make things by assembling nanoparticles, which I used to make. The image below is from Brookhaven. Each one of the tiny cubes is 46 nanometers. To give you an idea, a human hair in 70,000 nanometers.

A nanoparticle superlattice.
The next step up from atoms and molecules are nanoparticles. Each tiny sphere is 46 nanometers, with is less than 1/1000 of the diameter of a human hair.

Additive manufacturing is the manufacturing of the future. Atomic-level is the manufacturing of the far future because, in addition to being cool, it is hellaciously slow. It took 22 hours to make the IBM logo. Methods have improved, but it would still take about 15 minutes to make three letters. Nanoparticle assembly, which is usually chemically directed, is also still pretty slow.

If you want to make, say, a race car, or an engine or even an engine mount, we’re talking about a pretty long time.

3D Printing

3D printing is a larger-scale additive manufacturing technique where, instead of moving atoms or nanoparticles, we’re moving larger bits of material. The technique has been around for awhile, initially for polymers, but later for metals. Today, 3D print with just about any type of material.

How It Works

You start by designing the part you want in a CAD (Computer Aided Design) program, then use special software that separates your part into thin slices.

A pictorial explanation of how you go from drawing to finished part.
A pictorial explanation of how you go from drawing to finished part.

The actual printing is done slice by slide, with each slide going on top of the previous one. The printer draws the first slice, depositing liquid that is hardened using lasers once it’s in place. Then the stage moves down and the next slice is deposited until you’ve drawn the entire part.

The video below illustrates how it works. You can burn off a whole afternoon watching videos like this on YouTube. I chose this one because it shows how detailed you can be and how much space there actually is in the structure.

The process is a little different for metal. You use the same process of building the structure slice by slice; however, you start by laying down a thin layer of metal powder. In one method, a laser writes the slice by melting together the metal powder that is to be part of the finished product. In another method, a binder material is written over the metal powder you want to keep. This process is repeated over and over, then the excess power is removed and the part is heat treated to remove the binder and sinter the remaining powder together.

Depending on the method, you may need to heat treat the part – to remove the binder and/or to relieve stresses in the part.

The technique below uses sandstone powder, but is a great example of how intricate a part you can make. The excess power you see them remove at the end is mixed in with other powder and used again.

Advantages of Additive Manufacturing

  • Speed:
    • Rapid prototyping: Can customize and tweak parts during development easily
    • Ability to make changes quickly. The idea of a ‘production run’ will eventually be a thing of the past.
  • Don’t need specialized tooling for each part
  • Can combine multiple parts into one
    • Eliminate welds and other joins, which are common failure points
    • Save the time shipping and assembling multiple parts
  • Much less waste, so it’s cheaper and better for the environment
  • Starting material is powder as opposed to bulk; you need less inventory and the powder is cheaper
  • You can use “exotic materials” because there is less waste.
  • Can make parts without solid insides, meaning the parts can be just as strong, but lighter.
  • Can make parts impossible to make with traditional manufacturing techniques.

The photo below is an example of how you can 3D print something that appears solid, but isn’t. Because of the internal structure, the parts are just as strong as if they were solid, but they are lighter. Now think about these not as curved cylinders, but as straight cylinders that might serve as pistons.

Disadvantages of Additive Manufacturing

  • Performance:
    • While you can get the same strength from 3D printed parts, the fact that they’re made in layers means that they tend to fail by layers (i.e. delamination). They also have a tendency to crack.
    • Because you’re starting with powders, incorporation of oxygen can be an issue
  • Speed
    • Most videos are time lapse because the process still takes a lot of time.
    • Pieces that require very tight external tolerances often need additional machining.
  • Size
    • We’re still limited as to how big the printers are. About a cubic foot is a realistic size for now.
  • Cost
    • 3D printing machines (and the support equipment necessary, like computers, drawing programs, etc.) aren’t cheap.

Hybrid Manufacturing

KAM is a hybrid manufacturing company, which means they use additive and subtractive manufacturing. The subtractive techniques are often used for parts requiring high precision exterior tolerances, or for polishing.

Uses of 3D Printed Parts

Many of the cool things people show on YouTube make it look like 3D printing is an expensive replacement for those wax mold-injector machines you used to find at zoos and museums, but 3D-printed parts are being used in mission-critical applications.

  • In 2014, Space X launched a Falcon-9 rocket with a 3D-printed main oxidizer valve in one of the nine Merlin engines. The valve had to work under high pressure, at cryogenic temperatures and a lot of vibration.
  • Just this month, the SpaceX vehicle that will eventually carry humans was launched with a combustion chamber fabricated in Inconel (an iron-nickel-cobalt alloy that survives extreme heat and pressure) by 3D printing.
  • NASA has also created 3D printed parts, such as rocket nozzles, in an effort to increase efficiency and reduce cost.
  • The GE Leap airplane engine uses a 3D-printed fuel nozzle that helps combust fuel more efficiently, which saves money every time the plane flies.
  • Boeing expects that switching to 3D printed parts will save $2-3 million dollars per 787 plane.

You’ll notice that these are applications that require performance in extreme environments and those are usually the first industries to adapt new techniques. But they’re also being used in more mundane, but no less important applications

In the medical realm, 3D-printed hip replacements are common.

The surface of these hip joints are purposely made to mimic the porous structure of real bone. You can even custom print repairs.

For some reason, this reminds me of a drywall patch.

Medical applications of 3D printing includes hearing aids, surgical tools and prosthetics.

That last one is very important: prosthetics usually weigh more than their corresponding natural limbs, which makes them harder to use. 3D printed prosthetics can be made lighter and in more natural shapes. (Or more unnatural, depending on what the wearer wants.

This picture shows a traditional prosthetic for a person with a below-the-knee amputation and the 3D-printed replacement on the right.
A traditional steel-rod-based prosthetic for a person with a below-the-knee amputation and the 3D-printed replacement on the right.

This is especially important for children with amputations. Prosthetics, even the simplest ones, are expensive. Because kids grow quickly, they either have to keep buying new prosthetics or they have to cope with a prosthetic that isn’t the right size.

3D Printing in Motorsports

F1 teams like Ferrari use 3D printing to make new micro-injectors for their engines that increase performance and increased fuel mileage.

F1 teams are also revisiting steel pistons, which fell out of favor because they’re heavy. Aluminum alloys are subject to deformation and breakage. But 3D printing allows you to make a piston that isn’t solid inside (using, perhaps, a honeycomb structure). This means you can you can lighten the part and still take advantage of steel’s properties.

McLaren has been using 3D printing and produced a rear wing in a week and half, which sound slow — but procuring the wing through traditional channels would have taken five weeks.

Nascar teams are just starting to explore the possibilities of 3D printing, although Penske was one of the first. Some teams are using 3D-printed parts in the car now, but mostly on the interior of the car like dashboard parts, electrical harnesses and mounts.

NASCAR, EFI and 3D Printing

Back in 2012, when NASCAR was switching over to EFI, they had a problem with a relay control box: it had two circuit breakers, but there were five circuits. This doesn’t sound like a demanding application, but it is: the box must be as light as possible, can’t be electrically conductive, had to stand up to heat, and had to be able to be changed on the fly. And had to be available quickly.

NASCAR Prototyping and Testing

The 3D printed electrical box from the EFI system
The 3D printed electrical box from the EFI system. Note the seven fuses.

DC Electronics had a body 3D-printed for the electronics from a proprietry composite material (polymer reinforced with glass fiber) that met all the requirements. Traditional

When developing the latest versions of the manufacturer car bodies, 3D-printed parts were used to modify the body shape during wind tunnel tests. Instead of testing a bunch of different bodies, the engineers can add and subtract parts in real time. That makes it easy for them to try new things and allows them to try more things as they’re trying to get aerodynamic parity for the three different bodies.

Penske and others are using 3D printing to make mirror housings, again taking advantage of the ability to custom-make a part that’s light and strong.

One surprising use of 3D printing is to make tools and jigs. When you’re dealing with custom-made parts that have to satisfy strict tolerances, you need all the help you can get. Jig and tools that allow the people in the shop to do even traditional machining better and faster.

Keselowski thinks that Toyota teams are way ahead of the pack at the moment.

3D Printing for the NASCAR Fan

And you can also buy 3D-printed fan gear, from track replicas

You can get Bubba in 3.5″ or 5″ and four different uniforms.

…to figurines.

In fact, the web page lists 8 different versions with two sizes and four different uniforms for Bubba Wallace. They can do that because they don’t have to make a large production run of any of the figurines. If they run out, they can make a few more. At some point, they’ll be made on-demand.

KAM’s Present and Future

Keselowski is a cheerleader for 3D printing, saying that the technology will “help improve fuel efficiency, be the technology that enables mankind to set foot on Mars, enable safer operations of nuclear power plants, and reduce gigantic amounts of manufacturing waste.”

That won’t happen immediately, and it will require other cutting-edge technologies as well. Keselowski isn’t just looking at car parts, but at medical, aerospace, energy, defense and eventually, he says, medicine.

Right now, KAM is working on some smaller-scale projects. For example, the company was asked to develop a heat-transfer piping component that had been made in three pieces that then must be assembled. The total process took four weeks.

KAM was able to make the component in a single piece with no connecting points and in less than two days.

So Keselowski Will Leave Racing When He Retires?

This is the great part. KAM is all part of his long-term plan to become a Cup owner at some point. He’s reportedly investing about $10 million of his own money in the company. He’s been watching how the business of NASCAR works and realized that this venture could pay for him to become an owner, the same way his father and uncle bankrolled their racing aspirations.

If I’m able to do what I want successfully, it will give me a pathway back to being an owner. One of the things I’ve learned from Roger Penske is the importance of having a successful core business outside of motorsports. If you have a successful business venture outside of motorsports, you can kind of roll with the ebbs and flows of the sport as an owner. That’s the position I want to be in, and that I’ll need to be in to be an owner who lasts in NASCAR.

Brad Keselowski, personal blog

I think this is a really brilliant plan. It’s looking toward the future while still providing solutions today. It gives him the opportunity to affect technological development in NASCAR while solving problems of national and global importance.

He’s also bringing jobs to North Carolina. They’re not traditional manufacturing jobs: they require facility with computers and complex equipment, chemical safety and a whole lot of other things we don’t traditionally associate with manufacturing. But they’re good jobs and they’re the jobs of the future.

If the National Science Foundation or the National Academy of Engineers is looking for a spokesperson, they should look here — especially given his long-standing concern about the lack of depth in America’s engineering pool.

Will You Be Able to Tell if NASCAR Cars are Slower in 2019?

When is the answer to better racing slower cars? It just might be for NASCAR.

Note: This post analyzes the change in speed due to the new rules package. Please don’t interpret it as my defending the rules change. I won’t be making up my mind on whether this package ‘works’ until after Phoenix at the the very earliest. I share some of the drivers’ worries that instead of a level playing field, we’re going to get random winners. But I’m going into it with an open mind and we’ll see.

Why Slower?

For years, NASCAR has battled ‘the passing problem’. Teams have made huge gains in aerodynamic downforce over the years. These gains don’t just affect peak speed: If you have more grip, you can corner faster. Higher corner entry speeds narrow the racing groove, which makes it difficult to pass. The theory is that decreasing corner entry speeds will widen the groove and allow for more passing.

Aerodynamic downforce (Fd) depends on speed (v) squared.

F_d \propto v^2

The squared is important:

  • If you double the speed, you get four times the downforce.
  • Conversely (and more relevant to our purposes), to reduce the downforce by a factor of 2, you only have to reduce the speed by a factor of the square root of two (which is 1.41)

The graph below compares the mechanical grip of the car (i.e. its weight) with its aerodynamic force. The weight doesn’t change with speed, but the aerodynamic downforce does. The faster you go, the larger the fraction of your downforce that is aerodynamic.

A graph comparing mechanical and aerodynamic grip.

NOTE: These numbers are for an earlier rules package, but they give you an idea of how significant aerodynamic grip is.

The easiest way to slow down a racecar is to decrease its engine power. That’s why NASCAR is using differently sized tapered spacers at different tracks in 2019.

A bar graph showing how the effective horsepower changes with various sized tapered spacers and restrictor plates

So Why Give the Cars More Downforce?

It seems counterintuitive that, at the same time they took away engine power, they increased the spoiler and splitter sizes. That’s because the situation is much more complex that simply total downforce. Different corners of the car experience different forces.

  • When turning left, the mechanical load shifts to the outer wheels and the inner wheels lose grip.
  • When accelerating, the rear wheels gain grip and the front wheels lose it.
  • When braking, the front wheels gain grip and the rear wheels lose grip.
  • The aerodynamic downforce depends on the attitude of the car, so when the car turns, brakes, or accelerates, the aerogrip of each wheel changes.
  • Proximity to another car (or a wall) near a car also changes the aerodynamic forces on the car.

Remember that the goal isn’t simply lowering speeds: It’s lowering corner entry speeds. You don’t need to slow the cars down everywhere. Also, you want the cars to have enough stability to be able to race close to each other. That’s the only way they can pass.

So NASCAR took away horsepower, but made a number of other aerodynamic tweaks. NASCAR took from the engine, but gave back a little of what they took on the body.

How Much Slower?

All some NASCAR fans heard was that they were dropping 200 hp and there was a hew and cry from some NASCAR fans that this rules package would Ruin. NASCAR. Forever.

In reality, the change in average lap speed at the affected tracks is likely to be in the 7- 12 mph range. Some people still think that’s a big deal.

But can you even tell whether a car is going 200 mph or 190 mph?

CAVEAT: Record books record average lap speeds. If you slow corner speeds, average lap speed will slow, but we don’t know how much slower the cars will be on the straightaway — if they are slower at all. Everything from here on out is dealing with average lap speed.

CAVEAT 2: As I’ve discussed before, the speeds reported are not measured. Lap times are measured and the average lap speed is calculated using the standard track length. That doesn’t account for different lines around the track. I’m using speed here because that’s what people complain about, but it would be the exact same analysis if I used lap times.

Speed vs. Time

One of the very first equations you learn in physics is the equation that relates average speed (v) to distance (x) and time (t):


The television broadcasters like to show this formula when talking about pit road speed and, much to my consternation, someone gets it wrong at least once every year. So watch for it and inundate them on twitter if they do it again this year.

It’s not like this is a difficult formula to remember. Speed is measured in miles per hour. To get a distance (in miles) from miles per hour, you have to multiply by time. Scientists call this dimensional analysis. Regular people call it common sense.

Our perception of speed is really our perception of the time it take an object to traverse a distance. Since the distance the racecars travel doesn’t change, what we’re really talking about is how we perceive time.

What is Time, Anyway?

There’s a philosophical answer to that question and a physics answer. Let’s go with the physics answer first.

The second was originally defined at 1/86,400 th of a mean solar day. (‘Mean’ meaning ‘average’, not ‘cruel’.) This was slightly less than robust, so in 1960, the world agreed that:

One second is the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom when the cesium atom is ata temperature of 0 Kelvin.

National Institutes of Standards and Technology

Believe it or not, that is actually much clearer than the first definition. But for us, it doesn’t really matter because what’s important here is how we perceive time, not the actual time.

Time vs. Time Perception

While the second is a very precisely defined quantity, your perception of it differs if you are getting married or sitting in the dentist’s chair. They may both last the same time, but it sure doesn’t seem like it. And there are people who devote their lives to trying to understand why this is.

The study of time perception requires psychology, linguistics and neuroscience. It considers time, not the objective way we measure it, but the way human beings experience it. And human beings’ experience of time is highly subjective.

  • People tend to remember relatively recent events happening further back in time then they actually happened; conversely, events from the far past are often remembered as being more recent.
  • Vierodt’s law says that shorter intervals tend to be overestimated while longer intervals tend to be underestimated.
  • How long you perceive a task to take depends on how motivated you are to do it and whether you are focused on doing the task or just having it done.
  • Your emotions and mental state can change how you perceive time.
    • People who are depressed tend to more accurately estimate the passage of time.
    • Fear tends to make time seem longer.
    • Even something like very loud or very high pitched noises can skew our perception of time. You will perceive a loud car as being faster than a quiet car

Hence my husband’s suggestion that all NASCAR really needs to do is add 10 deciBels to the engine so everyone would think the cars were faster.

The Data

The only numbers we have with the new rules package so far come from the late-January test at Las Vegas Motor Speedway. So let’s use LVMS as our test track and take a look at historical pole speeds. (Data from the good folks at, as always.)

The history of pole speeds as a function of time at Las Vegas Motor Speedway
The red square represents the 2018 fall race.

If we consider only data after the track was reconfigured in 2006, you can see that the pole speed increased almost 15 mph from 2008 (182.3 mph) to 2016 (196.3 mph). The most recent pole speed (fall 2018) was 188.1 mph. The pole speed that spring was 191.489 mph.

Now let’s look at the data from the January testing sessions. There were three test sessions and 50 total runs. These are the top speeds for each car from all three sessions.

A histogram of the top speeds for the January 2019 test at Las Vegas Motor Speedway

Of the 50 runs reported

  • 22 (44%) were between 177 mph and 178 mph.
  • Only 5 runs (10%) were above the median speed
  • This leaves 22 runs (44%) below the median range.
  • The highest speed in a team car was Jimmie Johnson on Thursday morning, at 178.885 mph.

OUTLIER EXCLUSION: Ross Chastain reached 183.16 mph on Thursday morning, but a) that was in the heavily instrumented Chevy Wheel Force car and b) No one else got anywhere near that speed during the entire test. I’m being conservative and going with Johnson’s speed.

That’s the Clock: What About Me?

What would you see if you were sitting in the stands at LVMS?

The front straightaway at Las Vegas is about 1800 feet. How long does it take to drive that distance?

The time it takes to go 1800 feet at different speeds from 178 to 188 mph.
  • If you drove at last year’s pole speed (188.1 mph), it would take 6.524 seconds to make it all the way from Turn 4 to Turn 1.
  • If you drove at the top speed in the testing session (178.885 mph), it would take you 6.861 seconds.

A difference in speed of 9.236 mph corresponds to a difference in time down the frontstretch of about a third of a second (337 milliseconds). The blink of an eye takes about 300-400 milliseconds.


The difference we’re talking about ‘slowing the cars down’ is

  • About a third of a second down the frontstretch
  • A little less than 2 seconds over a 1.5-mile lap
  • 8.9 minutes over the course of a 400-mile race.

Will I Notice That?

Yes — because you’ll be looking for it.

Unfortunately, we can’t do the experiment because you already know the cars will be slower. Your expectations impact what you see. To really test this, we’d need to have you at a track, have a driver make laps at two different speeds and ask you which one was faster and by how much. And we’d have to do it with maybe a thousand people to get a range of opinions.

It would be like when you visit the eye doctor and do the ‘Which is clearer: 1 or 2’ thing. When we’re close, I can’t tell much of a difference. I bet you’d see the same thing with the track experiment.

In general, people aren’t very good at estimating speeds. A 2016 study from the Centre for Accident Research and Road Safety (in Australia) found that drivers did a miserable job estimating how fast trains were coming when approaching railroad crossing.

When the train was 350 m (382 yards) away

  • Drivers estimated a train going 130 km/h (~81 mph) was only going 90 km/h (56 mph) — a 29% error in judgement.
  • That means the drivers thought they’d have 14 seconds before the train got there when, in reality, they only had 10 seconds.

The farther away the train was, the worse their speed estimates were. When the train was 1100 m (1200 yards) away and going 130 km/h (~82 mph), people estimated the train was only going 75 km/h (47 mph) – a 44% error in judgement.

The lesson here might be that if you think you just have time to scoot past a train crossing before the train gets there, you probably don’t.

A 2009 paper in the journal Vision Research found that people are also very bad at estimating the speed of a flying object, such as a ball. And there are plenty of studies that show that people have a really, really hard time interpreting the motion of accelerating objects, even if those objects are moving slowly.

The takeaway: If you’re one of those people who’s already convinced that the cars are going to be slower and it’s going to ruin your enjoyment of the sport, it’s very likely that this is exactly what is going to happen.

But Is Racing Really Just Speed?

I’d argue no. So would NASCAR, because the entire point of this speed-reduction exercise better racing at intermediate tracks.

I love the people who call into radio shows and say that NASCAR should just use a rules package that is fast and allows for close racing. Believe me, if that were possible, they’d already have done it. That’s what they’d like, too. But the laws of physics say otherwise. And the laws of physics always win.

If all you care about is how fast the cars go, you’d probably find drag racing more your, uh, speed. If you want fast stock cars, follow the folks setting land speed records — like Bob Keselowski, who shattered the all-time stock car speed record by 30 mph at the Bonneville Salt Flats last September by running 271.84 mph.

The best part of this story is that this Dodge Charger was driven in a 2010 Martinsville race, crashed, and repaired. The second-best part is the headlines: “Retired NASCAR Cup Racer Makes 271.89-MPH Pass, Smashes Class Record at Bonneville” and “1989 ARCA Champ Keselowski Sets Speed Records in Utah“. That’s Bob Keselowski on the left and, I think, Bobby Gerhart on the right, who was there to earn his license.

NASCAR fans have been complaining about lack of passing for years. NASCAR has made a number of attempts to address it given the constraints of time and money. I guarantee you that all of this is being taken into account as they design the Gen-7 car.

For me, watching two cars run fender to fender as one tries to pass the other is the best part of racing. It’s good at Bristol at 100 mph and it’s good at Texas at 200 mph. And if I get a choice between Texas at 200 mph with minimal passing and Texas at 190 mph with more passing, I’ll take the latter, thanks.

In summary, the world is not fair. No one’s figured out a way to get high speeds and passing with the current car. Sure, you could solve the problem by throwing money at it, but that’s not a possibility in the current climate. What you see is highly influenced by what you expect to see. So I encourage you to go into Atlanta with an open mind and fingers crossed.

Thanks to @dmcgrew, who figure out I’d transposed the digits in the calculation of time and had 6.681 instead of 6.861. I can’t blame this one on Excel. I messed up typing! Thank you, Drew!

The 2019 Rules Package: The Tapered Spacer

NASCAR announced the 2019 rules package last week. Reactions from fans ranged from wait-and-see to despair to a surprising amount of anger.

The 2019 package is similar to the package was tested at the 2018 All-Star Race, but different in some very important ways. It further specializes the standard set up for different types of tracks. The larger spoiler and splitter and the underbody changes will be required at all tracks. Other changes (the tapered spacers and the aeroducts) will be different at different tracks.

So how much is really changing?

Tapered Spacers Aren’t New

A 1.170″ tapered spacer was introduced in 2015, reducing engine horsepower from about 850 hp to 725 hp. (Note that teams did quickly find ways to increase the horsepower a little, despite the new rules.)

That same spacer that was introduced in 2015 remains one of two spacers that will be used in 2019.  You’ll also note that the spoiler goes back to its 2014 height and the driver-adjustable track bar that was introduced in 2015 is being taken away.

Which Rules at Which Race?

  • The Daytona 500 will be the only race that will use a restrictor plate.
  • A 1.170″ tapered spacer will be used at all tracks less than 1.33 miles and will (still) result in about 725 hp* overall engine power.
  • A 0.922″ tapered spacer will be used at all oval tracks 1.33 miles and above. which will decrease engine horsepower to about 550 hp*.
    • At five of those larger tracks (both Pocono races, Darlington, Atlanta and Homestead), the aero ducts won’t be used.
    • Aero ducts will be used at the rest of them.

*Note: NASCAR regulates the spacer/restrictor plate, not the horsepower. 

Since different horsepower means different mileage, NASCAR will require teams to block part of the fuel cell so that the number of laps run between full fuel runs should be the same.

Let’s see if we can’t make this clearer with a graphic.

You may wonder about my choice in how I listed the tracks. They’re listed in order of most recent pole speeds for each track. Most pole speeds came from 2018, but some qualifying sessions were rained out, so I went to 2017 and, in one case, 2016.

I put Sonoma at 2.52 miles because they’re changing it for next year, even though the pole speed was for the shorter track.
  • Tracks with the 1.170″ tapered spacer and no aero ducts have pole speeds ~160 mph and below
  • Track with the 0.922 tapered spacer and no aero ducts have pole speeds 173-184 mph
  • Tracks with the 0.922 tapered spacer and aero ducts have pole speeds 185 mph and up.
  • Chicagoland looks like an exception, but the pole speed there this year was anomalously low, so I understand why they put it with the last group of tracks.

Lemma: Doesn’t Pole Speed Scale with Track Size?

Sort of. In the graph below, the three configurations are represented by the same colors as I gave them in the table above. You could make an argument that speed is somewhat linear for the short tracks. (I did use five or six speeds for each track and they’re pretty consistent.)

But our 1.5-mile tracks range from 173 mph to 201 mph, and the superspeedways are already artificially restricted.

Tapered Spacer vs. Restrictor Plate

The All-Star Race package used restrictor plates to throttle the engine back to around 400 horsepower. Most fans liked the All-Star Race, but a few drivers (notably Brad Keselowski) objected, saying that the pack racing that resulted put less control in the drivers’ hands. 

It’s hard to compare All-Star Race data because they change the rules every year. Some years require a pit stop during qualifying. However, in 2013, 2014, 2015 and 2017 (2016 was rained out), the pole speed was between 144 mph and 147 mph. The pole speed for last year’s All-Star race was 127.644 mph.

How Plates/Spacers Work

A restrictor plate (or the tapered spacer) slows cars down by preventing them from bring air into the engine as quickly as without the plate or spacer. Remember that aerodynamic forces go like the square of the speed: double the speed and you quadruple the force. 

When cars are so dependent on aerodynamics, however, it’s hard to pass. Lower speeds, along with the aero ducts creating bigger wakes behind the car is theorized to improve passing. 

The Chemistry of Fast

Combustion is the chemical reaction between fuel and oxygen that releases energy. It’s very similar to another chemical process called respiration, which is how your body converts food to energy.

For example, to combust two octane molecules, you need 25 oxygen molecules. Not 24, not 26, but exactly 25.


So if reduce how many air molecules you have in the cylinder, you have to reduce how much gas you put in the cylinder. Otherwise, you’re just wasting gas.

But tapered spacers and restrictor plates work differently when you get down to the details. Below, on the left is a restrictor plate. It is 1/8″ thick and really nothing more than a plate with four holes on it. On the right is a tapered spacer, which is on the order of an inch thick. It also has four holes, but the holes are conical.

In fluid or aero-dynamics terms, the restrictor plate is a set of orifices, while the tapered spacer is a set of nozzles.

Both fit over the spot where the carburetor used to be.

Some Differences

There are a couple minor differences between these two parts. Restrictor plates are stamped: A big die comes down and punches out the hole, leaving a bit of a chamfer on the side the air enters and a bit of a burr on the side the air leaves. This significantly affects the way the air travels into the engine. One engine builder told me that the four outer cylinders get about ten times less air than the central four cylinders with restrictor plates. Tapered spacers, on the other hand, are machined parts and provide for much more even distribution of air.

Because the restrictor plate is so thin, any imperfection makes a big difference. A scratch can mean more horsepower. Tapered spacers are much less sensitive.

The Big Difference

While the distinction between the two seems minuscule, air molecules see two very different things. The next two graphics show the airflow through an orifice and a nozzle. The air comes in from the left.

The animation I took these clips from shows the motion, but you can still see that there’s much more turbulence with an orifice than a nozzle. Some of the arrows to the right of the orifice point away from the orifice, while others point toward the orifice. The flow lines are messier, also.

Compare that to the nozzle (below). See how much cleaner the flow lines are? And all the arrows point away from the nozzle. There is much less turbulence with a nozzle than with an orifice — meaning that the tapered spacer provides air to the engine in a very different way than a restrictor plate does.

When an air molecule passes through an orifice, it essentially has to take a right-angle turn. The flow of the air makes the effective diameter of the orifice smaller than the actual hole diameter.

The walls of the tapered spacer NASCAR uses are machined to be at a 7 degree angle. That’s the maximum angle at which air can travel without separating from the surface. This minimizes turbulence.

Simulations are useful, but there is nothing like being able to see fluid flow. Luckily for us, air and water are both fluids and a five-gallon water bottle provides the perfect illustration of the differences between a tapered spacer and a restrictor plate. 

A hole — the same size as the hole at the top — is cut into the bottom of the five-gallon jug. The hole in the bottom is like a restrictor plate and the top is like a tapered spacer. 

Now watch how the water empties differently.

Why is NASCAR Reducing Horsepower?

NASCAR is all about speed, but high speeds mean high dependence on aerodynamics (difficulty passing) and requires harder, stiffer tires (less opportunity to engineer fall-off into the tire).

More Tire Falloff.

When I talked with Goodyear’s Greg Stucker, he noted that race length doesn’t really factor into tire design because a tire only has to last for a fuel run. That forces teams to change tires (or chance not changing tires).

Corner entry speeds have become so high that Goodyear has to make relatively hard tires — which means they don’t wear as quickly. Lower corner entry speeds will allow Goodyear to go to softer compounds and different constructions. That will allow for more strategy.

The Future of the NASCAR Engine

Formula E, in its sixth season, has eleven manufacturers. The overwhelming interest in what is currently a niche series can be attributes to manufacturers looking to remain relevant in the future.

NASCAR’s been very clear that the eight-cylinder eight-hundred+ horsepower engine is a barrier to entrance for other manufacturers because it’s so far removed from current production cars. 

“it gives us the option to be more relevant. It gives us that option to look at new technology in the future and our current package doesn’t do that.

Steve O’Donnell (via NBC Sport)

So why not just mandate a new engine and not worry about tapered spacers? Change costs money and takes time. There are parts inventories to be considered, especially as teams struggle for sponsorship. There’s an additional issue for engine companies because NASCAR is requiring engines to be used for multiple races. That means fewer engines built.

NASCAR is the proverbial aircraft carrier trying to turn. The inertia is huge.

Aerodynamics and Passing 

Every engineer I’ve consulted says that their simulations tell us to expect pack racing at most of the 1.5 mile tracks next year. They expect drivers will need to be full-on the throttle around the track, although that may not be the case with less-banked corners and/or if tires have a lot of fall off. 

Pack racing gives you passing, but it’s a different kind of passing. If the inside line passes the outside line on the frontstretch, then the outside line passes the inside line on the backstretch, that seems to me to be a wash. 

So Will It Work?

Most drivers are taking a wait-and-see approach to the new package. Even Kyle Busch has been restrained in his remarks after the new package was announced. Everyone agrees that NASCAR is trying to improve the racing, even if they don’t agree with the precise way they’re doing it. 

The aerodynamic changes and the horsepower changes together are a pretty big change. There’s a test with the new package at Charlotte on October 23rd. We’ll see what happens, both on the track, and with driver reactions.

And there’s still time for changes. Goodyear can tweak tires and teams have time to experiment with different set ups. It’s all part of progress. You try things and you see if they work. This is the nature of research.

I’m along with Joey Logano on the change for the moment:

“You make change, and not every change is good, but you learn from every change. If you just sit still, you never make any progress forward. You don’t learn what’s wrong, you don’t learn what’s right, you’re just there… 

we will learn from this decision one way or the other, and I think as a society we need to be open to do that, not just in our sport, but in life. It’s a good thing for us. It’s healthy.”

Joey Logano (via NBC Sports)