Hands-On With Davis Technologies’ Vehicle Position Sensor

Hands-On With Davis Technologies' Vehicle Position Sensor

In July of 1969, man stepped onto the lunar surface of the moon for the first time, utilizing technology and instrumentation archaic by 21st century standards to inform not only the craft’s occupants but those situated 250,000 miles away of its precise coordinates, its roll, yaw, and pitch angles, and its speed, among countless other variables. Decades later, many of the technologies that made that feat possible are still not available or refined in society, even in an era where a supercomputer fits in the palm of one’s hand. 

How could that be?

In many cases in our world, and certainly in reference to the automotive industry, it was a matter of the proper operating conditions to exist to utilize that technology. And today, they do, ushering in a swath of high-tech advancements that have entirely changed automobiles and auto racing. With the proliferation of electronic fuel injection and the advent of more featured ignition systems, ideas used an entire generation ago have been made possible — borrowing on age-old technology and concepts, but groundbreaking, to be sure.

Davis Technologies, consistently at the sharp end of technological advancement in auto racing, is one of the first to utilize gyroscopes and accelerometers — the former dating back to the 1700s and integral in both air and spacecraft operation and the latter with uses from medicine to transportation to structure monitoring — to create a safer racing environment with a whole new subset of valuable data at a racers’ fingertips.

Davis’ newly-released Vehicle Position Sensor (VPS), a project three years in the making by silicon samurai Shannon Davis, is one of the most fully-featured gyroscopic devices available in drag racing, delivering a host of benefits to drag racers of every rank, not the least of which are a variety of programmable checks and balances designed to protect a vehicle and its driver.

Dragzine dove into the concept and the features of the VPS last year while in the midst of field testing and refinement, and now, with the units in the hands of the racing community, we’re taking a closer look at the real-world benefits of this device.

Other devices out there gloss over sudden losses in g-force. The algorithms don’t show sudden, little drops in G. This thing is accurate enough that it can give you a virtual time slip that’s almost dead-on to the timing system. – Shannon Davis


The VPS utilizes multiple gyro-meters, accelerometers, and magnetometers, Davis noting there are “different physics involved in various types of accelerometers, all of which have their pluses and minuses — maybe one is good for missile guidance, but not for something constantly changing its propulsion.” By combining several types of sensors to fuse their data — sensor fusion is the industry term — an output is produced that is as good as it can get for automotive purposes. Davis uses the term “voting rights” to describe how the various sensors work in unison and deliberate internally to arrive at the correct output.

One of the primary challenges in the design of the VPS, however, is the innate environmental effects on the sensors. Magnetometers, which read the magnetic lines of the earth, are super-sensitive to nearby objects like ignition systems and steel objects. Gyro-meters are typically susceptible to changes in temperature and accelerometers to vibration. To alleviate that, Davis created an oil-filled casing that serves two purposes: vibration-dampening and temperature control, targeted at creating a stable operating environment. Further, Davis borrowed a concept from one of his favorite pastimes, RC helicopters, to create a proprietary phase-shift mounting clamp based on the idea of a swash plate (a device that translates the motion of a rotating shaft into reciprocating motion) to tune the VPS as a whole to the typical vibrations found in a racecar. 

The device is universally-mountable, intended to be situated in the car face up or face down, and connector forward or connector backward. As he puts it, “the better you mount it, the better the data results you’re going to get.” As you might imagine, at obscure angles, some of the axis data will bleed into another axis. 

Wired to the transbrake button, the VPS automatically zeroes when depressed, setting the orientation at 0-degrees while on the starting line; this can help mask some changes in rake or ride height, but if mounted at an extreme angle, the axis will, again, start to blend into another. It also resets the device at zero in the event of a 45- or 90-degree turn out of the staging lanes that may have thrown off the orientation of the sensors (in theory, as we’ll note later, this turn could kill the ignition and throw the parachutes depending on your programming).

Thanks to the efforts on the hardware side by Davis and his team, and combined with proper use by the end-user, the data emitting from the VPS is well on its way to becoming the gold standard.

“When you take these sensors and stick them on a circuit board that’s subjected to the vibration of the racecar and then filter the data heavily with mathematics, you end up with data that’s a joke, but it looks good,” Davis explains. “This is very detailed data.”

Data, Data, Data

The VPS is a highly-valuable device for the purpose of safety, which we’ll get to shortly, but it’s also earned the praises of tuners, who have found the accuracy and detail of the data to be incredibly useful.

The data isn’t nice and smooth, but it is accurate. The green line below represents pitch; as you can see, there’s a slight rise at the hit and then the nose is gradually pushed at a negative angle toward the ground under the weight of the rushing air, with slight undulations in the racing surface evident.

The unit is accurate to 1/10 of a degree of angle or G-meter reading on all axis, and updates at 200 times a second. And where other sensors on the market give “pretty” data — graphs with nice, smooth lines — it’s the “ugly” data the VPS outputs that defines the accuracy of the device. And that is where tuners are gravitating (no pun intended) to the VPS.

You may wonder: if built-in or standalone traction control devices can already pinpoint the most minuscule of traction losses, why you’d need another device. Wouldn’t the data look the same? Not so.

“It does mimic the data, but in higher resolution. It’s more accurate data,” Davis says. “Other devices out there gloss over sudden losses in g-force. The algorithms don’t show sudden, little drops in G. This thing is accurate enough that it can give you a virtual time slip that’s almost dead-on to the timing system. 

“A tuner needs to be able to see that, to see when the tire slipped 2-inches,” he adds. “We were trying to see if when we hit the Profiler and lost timing, did I need to? Or did I just have the profile too low? The shocks compressed in the front, the nose is coming down, the ride height is coming down…it’s because it lost G. It slipped the tire.”

With the VPS, we’ve found that it’s not as pretty of a picture — the G data is often jagged to look at. But we’ve found that it’s accurate. When it says this is what’s happening, it is what’s happening. It shows very small fluctuations in G that are correct. – Pete Harrell

Pete Harrell, who tunes for radial-tire racers Lyle Barnett, Brad Edwards, Justin Martin, and others, has been one of the early adopters of the VPS, utilizing it for both data and wheelie control purposes on his clients’ cars. 

“A lot of tuners, myself included, we watch the G-meter pretty close, and that’s a big tool in our toolbox,” Harrell explains. “For years we’ve used other devices but nothing really worked well because in a racecar there are a lot of vibrations and things going on. With the VPS, we’ve found that it’s not as pretty of a picture — the G data is often jagged to look at. But we’ve found that it’s accurate. When it says this is what’s happening, it is what’s happening. It shows very small fluctuations in G that are correct. Some devices and software smooth things out, but they aren’t telling you the whole picture. It’s a super-accurate representation of what the car is actually doing. If it slips a little for just a tenth of a second, that would be smoothed out by software or missed in inefficiencies of the device.”

Harrell traditionally views the VPS data after a run to see correlations to the driveshaft RPM readings and how it corresponds to the Profiler. “If the Gs go down for a tenth, a lot of times it will correspond directly with a driveshaft spike and a corresponding timing retard from the Profiler. It all jives,” he says.

Another ingenious feature of the VPS, as previously noted, is the virtual time-slip. By calculating velocity multiplied by time — and utilizing its incredible accuracy — the VPS can produce an elapsed time to a given distance down to the inch. This is highly valuable in instances where one leaves before the tree is activated and gets no time, or for those making runs away from a timed course.

Harrell has been working with a client of late testing a vehicle on an airport runway, and notes the virtual time slip is incredibly helpful to assessing performance and making changes as a result of the numbers provided…numbers that could not be acquired any other way. The virtual time slip feature presently includes 60-, 330-, and 660-feet, along with 660-foot mph.

By calculating velocity and time, the VPS can produce a relatively accurate virtual time-slip — we say relatively because one’s position in the stage beam will have an effect on the numbers.

The VPS is compatible with any ECU with a 0-5 volt input, sending the data out via analog channels. FuelTech, Holley EFI, MoTec, and Haltech are among those; these modern ECU’s can also manage the wheelie control operations directly. Any axis can be assigned to any of the outputs on said devices, along with commands for wheelie control or traction control. CANbus connectivity (simple power/ground/CAN) is planned soon as the ECU manufacturers complete work on their end.

Those who own a Davis Profiler can program and set parameters for the VPS on its LED display, or a dedicated hand-held display can be purchased with the VPS to do so. The VPS can also serve as a self-learning traction control device, if the option is purchased; what is essentially a TC-3-SL is built into the unit to make it all-in-one that operates via traditional loss of acceleration via the driveshaft.

Devin Vanderhoof Walks Through VPS Setup With A Holley EFI System

Wheelie Control

It stands to reason that if you can measure the angle of a vehicle — very accurately at that — that one could also program responses to those measurements. That concept brought about one of the most sought-after features of the VPS: wheelie control. In utilizing this technology, the tuner can program if-do variables to retard ignition spark, cut the ignition, shift the transmission, or throw the parachutes to prevent a catastrophe in the event of a higher-than-planned wheelstand. This can be set up in tables via your compatible ECU or the Profiler/handheld screen.

We were one of the first teams to get ahold of the VPS and we’ve found it to be a much smoother way to manage the pitch of the truck. It sets it down much softer and is more manageable and accurate. – Bruce McConnell

“You set up a start point on the wheelie control — a starting angle — and a rate at which it is going to make the correction. Then you set up another point at which it will start dropping cylinders as needed. Two to 2-1/2 degrees of pitch is very popular among radial-tire racers for a starting point,” Davis explains. “So at that point, your example configuration might start retarding 2- to 5-degrees — depending on nitrous or turbo — per degree of rise. By the time it gets to 5-degrees of pitch, it’s got 15- or 20- degrees out of it depending on the combination, and if it’s something they’re willing to do they can start dropping cylinders with our Smart Drop. And that’s what sits them down nicely. All of this also has a start time, so it won’t start doing any of this until the car gets a predetermined length out from the starting line, since some cars will snatch the front end up on the hit. It’s when these cars come up at half track that it’s a problem … you don’t want it to kill a bunch of timing right off the line if you don’t need to.”

Bruce McConnell’s ’48 Dodge.

West coast racer Bruce McConnell campaigns a popular 4.8-second, 1946 Dodge pickup sporting a 410-inch, single turbo combination that’s prone to awe-inspiring wheelstands. McConnell, who races for the joy of it, linked up with Davis early in the development of the VPS in hopes of taming his bright orange truck to keep it out of potentially damaging touch-downs. Equipped with a Profiler and a Holley EFI, McConnell has found the VPS both highly useful and relatively simple to set up.

“When we first started this whole thing five or six years ago, we were looking for a way to stage the truck better. We were pointed to Shannon’s Bump Box, and were so impressed that I bought a traction control system. I later got a Profiler and worked through that and then we started using a ride height sensor to help with wheelstands. The problem with a ride height sensor is that when it drops out of range it drops back to zero and so we couldn’t control it,” McConnell shares. “We were one of the first teams to get ahold of the VPS and we’ve found it to be a much smoother way to manage the pitch of the truck. It sets it down much softer and is more manageable and accurate. The nice thing about the Profiler is we can define all of the situations and events, so when it’s at a given angle, this is what we need to do.”

In this real-world data from a radial-tire car, you can see the correlation between pitch, G, and time retard as the car hikes the front end early in the run.

Properly configured, McConnell’s driver, Doug Driggers, is able to keep his foot in the throttle and trust the system to keep the truck from reaching dangerous pitch angles. 

“Doug and I laugh all the time about this, because when it does go down the track and carries the front end 10- or 12-inches off the ground out at half track, Doug is always saying to himself, ‘c’mon Shannon I’m waiting on you, I’m waiting on you.’ The instinct of a driver is to lift when he feels it, so he had to get over that mentality and allow the Davis stuff to do the job. Now you don’t lift, because you’re pretty certain the system will handle it. Doug says he can hear and feel the engine pull down in the cab,” McConnell adds.

Hey Yaw, Let’s Roll

Davis envisioned the VPS going beyond simple wheelie control in regards to safety by utilizing the programmability of the yaw and roll axis of the device. In doing so, one can set parameters to, for example, kill the ignition and throw the parachutes if the vehicle’s yaw angle become too extreme — in other words, if the car is out of shape and sideways — to help the driver regain control. The VPS’s sensors can even detect and calculate deviations from zero in forward heading, allowing one to program the same actions if the car is drifting out of the groove into the marbles or on a collision course with the wall.

Example High-Yaw Scenarios Utilizing Holley EFI To Release Air-Assisted Parachutes And Shift Lever

“If you turn 15-degrees, you’re going to hit the wall pretty quick,” Davis explains. “But if you’re on the interstate and you barely turn your wheel you’re eventually going to run out of your lane. Well we know the velocity, we know the feet traveled, we know what a 3-degree deviation is going to do, so then you can fairly easily calculate that in 90-feet of travel the car is going to move 10-feet sideways and there’s a wall there. So then it’s up to the user to set up how much lateral deviation to allow from the starting point,” Davis explains.

To combat user error where turns through the pits or staging lanes could potentially kill the ignition or release the parachutes, one can either disarm the VPS until staging, or program the ECU to only enact the do-if actions once driveshaft speed is above a certain parameter, so the actions won’t occur until the car is under power on the track.

Screenshots using Holley EFI software to illustrate example settings for wheelie control and Yaw angle scenarios with the VPS. Sample data provided by Devin Vanderhoof.

One can program angle and time, so if it’s excessive yaw or G-meter reading for, say, .25-seconds, it will do whatever actions were assigned. This would keep the ECU from responding to a small wiggle versus a big move left or right.

With a Holley EFI as an example, you can use speed, time, or driveshaft RPM variables to program the do-if actions from the VPS.

Out of the box, the VPS is defaulted at +/- 12-degrees of angle on all three axis but can be reprogrammed for a wider degree of range. Davis, shares that with a 100-inch wheelbase car, 5-degrees is approximately 10-inches of deviation, so you’re unlikely to need more, but it’s there if necessary.

Davis’ optional handheld touchscreen for the VPS. One can program all of their parameters right on the hand-held.

“It’s not something super cheap that relates itself to bracket racers, but for any serious heads-up racer it’s invaluable data,” Harrell says. “Anybody that has been racing for a while will tell you the more data you have and the more accurate it is, the better off you are. That’s how you make a car fast. For me personally, it’s irreplaceable.”

For many, irreplaceable is precisely the word to describe the VPS and the functionality that its technology has brought to the table. Sure, we got by for decades without detailed position data and wheelstand control, but anything that makes our sport safer and gives a driver added insurance at 200-plus mph is a positive step. While not privy to extending any details, Davis alludes to greater utilization of the VPS within his product ecosystem in the future, only going so far as to say, “there are definitely more uses for this device … people know us first and foremost as a traction control company, but that’s all I’ll really say right now.”

DragzineDragzine – Hands-On With Davis Technologies’ Vehicle Position Sensor

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