Some seven years after it was first put into development and four years after its release to the public for further exploration and exploitation by end users, Davis Technologies’ Vehicle Position Sensor (VPS) is no doubt the standard by which all position-sensing devices, present and future, are measured by (pun not intended).
For the uninitiated, the VPS is a highly accurate gyroscopic device, utilizing gyroscopes, magnetometers (measures the earth’s magnetic field), and accelerometers to provide yaw pitch, roll, and g-force data that can aid drivers and tuners in an array of powerful ways. For one, it can be a secondary tool for monitoring traction losses, with incredibly accurate and detailed g-force readings to indicate even the most minute changes in momentum. To put it into numbers, the unit is accurate to 1/10th of a degree of angle on all axis, and updates at 200 times a second. It is t so sensitive, in fact, that the device can detect changes in yaw, pitch, and roll values from foot traffic around the vehicle.
It’s also the tool that many racers — particularly those in no-prep and no-time racing — utilize to obtain virtual time slips. The VPS can calculate velocity referenced to time and produce an elapsed time over a given distance, down to the inch. We did a deep dive into what the VPS does and how it creates virtual time slips here.
But what it can also do — which wasn’t one of the first features that Davis considered when he began drafting the concept for the VPS — is improve driver safety.
Because the VPS can sense yaw, pitch, and roll data so quickly and accurately, it can be used to save a drivers’ bacon faster than he or she can even react. The most obvious use that comes to mind is wheelie control. With the VPS properly mounted in a level position inside the cockpit, it can sense wheelstands and work with an ignition box or EFI system to pull power.
Wheelie Control with Davis VPS
We caught up with Street Outlaws no-time racer Lance Knigge at Muscle Cars at the Strip, in a rare occurrence of small-tire racing with his twin-turbo ‘67 Nova. Lance said he doesn’t even have shock-travel sensors, and purely relies on the VPS in combination with his Holley EFI system for wheelie control. Unfortunately, as Lance found at the MATS race, there is still a human element to setting up the wheelie control. When switching between big tires and small tires, he had it set to come on too late and had to pedal it in his most eventful pass of the weekend.
Lance Knigge walked us through the setup on his twin-turbo Nova (left to right): here you can one table is set up to enable when the transbrake has been released the and throttle hits 70-percent. It pulls as much as 15 degrees of timing when the pitch is at or greater than 5 degrees and 1.33 seconds. This is off the initial starting line launch. The X-axis is setup as time and the Y-axis as VPS PITCH. Another table is set up similarly to prevent a power wheelie at 80-percent throttle or more. This table pulls as much as 15psi of boost (not timing), starting at 2.64 seconds and 5.20 degrees of pitch. These two tables overlap, so that if the Nova hits over 5.00 degrees of pitch and retarding timing by 15-degrees doesn’t bring the front wheels down, the Holley EFI system starts pulling boost.
While the trusted method of using a driveshaft-speed sensor as a measure of wheel speed is still relevant, the VPS takes things to a whole new level.
“It does mimic the data, but in higher resolution. It’s more accurate data,” states Shannon Davis, owner and engineer at Davis Technologies. “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 two inches,” he adds. “We were trying to see if when we hit the Profiler and lost timing, did we need to? Or did we 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.”
Here you can see the Davis VPS putting in work. As the VPS Pitch exceeds 5 degrees (green line), the wheelie ignition cut (yellow line) and then wheelie boost (purple line) drop precipitously.
Crash Prevention with Davis VPS
Street Outlaws competitor Chris Rankin has utilized the VPS on his fleet of Chrysler Conquests, including his newest machine purpose-built for the No Prep Kings series. With the surface he races on, combined with the short-wheelbase characteristics of the car, Rankin and his tuner, Greg Powrie of GP Tuning, found he could benefit from the use of yaw data to release the parachutes — should the car quickly pitch to one side or the other. Rankin got his Conquest uncomfortably out of shape on the street previously with a VPS onboard, and thus had yaw angle data he and Powrie could build upon. So Powrie got to work building out a table in the Holley EFI software, which has yaw angle (positive and negative, or left and right of center) on the Y-axis. On the X-axis, Powrie has used driveshaft RPM as his variable.
From there, Powrie can enter a percentage value as an outcome of this table, which in this case correlates to a percentage of air pressure from the CO2 bottle that is allowed to enter the air cylinder that activates the parachute release handle. Once the conditions have been met (yaw exceeds the desired angle), the cylinder activates and out come the parachutes.
“We haven’t gotten a run where the car has actually moved around more than he would necessarily like to figure out what the proper yaw value actually is,” Powrie says. “We did verify function by setting it up very tight initially, and it does work — it does throw the parachute. This table you see here is a little more broad right now, so it would have to get pretty out of shape for him to get into it. It just takes some fine tuning.”
The Wrap Up
They say an ounce of prevention is worth a pound of cure. In a world where power increases with each season while tire size and traction compound decrease, having electronics like the Davis VPS on board is worth its weight in gold. Even a good pass on an un-prepped surface has 1,500-horsepower cars skating down the lane like Apolo Ohno, and we’ve seen more than our share of life-threatening injuries (and worse) as the result of high speed crashes at these events. Proving that prepped surfaces are not immune, we saw another Street Outlaws competitor take flight at the very race we caught up with Knigge’s Nova. While traction control may not be legally allowed in all classes, perhaps it should be, when it proves so valuable in preventing senseless harm to racers.
https://www.dragzine.com/tech-stories/ignition-electronics-efi/davis-vps-proves-valuable-safety-tool-street-outlaws/
