Dakota Digital Explains Inner Workings of Ultraprecise Instrumentation

Do your gauges measure up?

Stephen Kim Jun 28, 2013 0 Comment(s)
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Nitrous bottles, big blowers, and lumpy cams are the usual suspects to look for when smoking a hot street car out of a dimly lit alley, but why not just look at the gauges? As a hot rodder's general rule of thumb, the more heat a car is packing, the more heavily it relies on quality instrumentation to precisely monitor things like coolant temperature, oil pressure, boost, rpm, EGTs, air/fuel ratio, and inlet air temperature. It's the difference between maximizing performance and blowing up, but even street machines that rarely see track use need quality gauges for one simple reason: Factory gauges flat out suck. Some of it has to do with antiquated sending units, and some of it has to do with suspect circuitry and decrepit wiring. To help us understand just how far instrumentation technology has come over the decades, and what kind of features are packed into the modern crop of aftermarket gauges, we interviewed Greg Karpe of Dakota Digital. We got an enlightening earful on subjects ranging from GPS-based speedometers to products that eliminate the gauge headaches associated with engine and transmission swaps, so here's the scoop.

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OE vs. Aftermarket Gauges

OEM instruments are inaccurate for a variety of reasons, including inexpensive or out-of-date sending units, poor vehicle grounds, low-quality gauge movements, and hokey instrument panel circuitry. Dakota Digital uses industrial-grade, solid-state sending units with dedicated ground wires. This alone solves a majority of tech problems we encounter that are caused by inadequate grounding. The harnesses we include for our oil pressure, water temperature, and speed sensors feature weather-pack connectors in which all wires in the harnesses connect directly to our control box. One solid ground connection to the box is all you need. Of course, proper vehicle grounding is still very important whether it's body to engine block, frame to engine block, or battery ground terminal to engine block. Furthermore, Dakota Digital's VFD3 digital systems use vacuum fluorescent displays that react very quickly and are able to display information very precisely

Our VHX analog/digital hybrid systems utilize precision stepper motors for gauge needle movement. These motors are also extremely accurate in terms of readout, as well as incredibly dependable. The motors are rated for about 10 million sweeps, but we have an ongoing test unit that has registered well over 75 million. Perhaps the biggest issue with OEM gauges is that they must be produced inexpensively and quickly in very large quantities, often in several different locations. Dakota Digital instruments, on the other hand, are tailored specifically for hot rods and street machines, built in the United States, and backed by a lifetime warranty.

One Control Box

One unique feature of Dakota Digital gauges is that they use a central control box that interfaces with the sensors, which greatly simplifies the wiring and installation process. The central control box has been a feature since the beginning, and we strongly believe in its benefits today. The main benefit of the remote control box is that it allows the installer to choose a convenient location to make the wire connections, and reduce the amount of wiring crisscrossing underdash. With a single-ribbon cable or CAT5 networking cable going to the instrument cluster, the amount of wires and confusion is greatly reduced. Our system eliminates the large bundle of wires going all the way to the cluster and makes for simpler connections and troubleshooting. Simple power and ground connections get you up and running, and each indicator or gauge is just one more terminal connection away. The control box breaks down the installation job into a less intimidating process. Another advantage the control box offers is more real estate for circuitry, thereby adding functionality and reducing the size of the instrument display.

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Extreme Precision

While gauge readings can vary slightly for several reasons, such as sensor location, Dakota Digital instrument systems are engineered to perform as precisely as possible. Our voltage readings are accurate to within a tenth of a volt, oil pressure readings are within 2 psi, and temperature readings are within 4 degrees. Likewise, engine rpm is displayed by tens, and speed by a single digit. Fuel level senders by nature are not precise, but our instrument systems have seven common senders curves pre-programmed, along with the capability to learn a custom curve for a sender not on our list. To combat some of the fuel gauge frustrations we've all encountered, both our VFD3 and VHX systems use an averaging strategy on the fuel reading to prevent the gauge from sloshing when taking a corner.

GPS Speedo

The recent development of GPS-based speedometers have opened up a new world of possibilities for hot rodders. A GPS receiver feeding an automotive speedometer provides an accurate speedometer reading in cases where a race-bred transmission has no provisions for a cable or a vehicle speed signal output. An increasing scenario we're seeing is older transmissions being swapped into newer vehicles, primarily '88-98 GM pickups or even a Powerglide into a late-model race car. The VSS requirements of these trucks are very high, and difficult to reproduce with aftermarket components. Our GPS-50-1 receiver features a 128K VSS output for vehicles originally equipped with an automatic as well as a 54K VSS signal for vehicles that came with a Tremec T5 or a T56 manual transmission. When using a GPS-50-1 in conjunction with a current-model Dakota Digital instrument system, you'll have a spot-on speedometer reading regardless of gearing or tire size, an auto-adjusted clock, as well as compass and altimeter information. All of these additional readings will be displayed in the message center of the instrument system.

GPS Accuracy

Most people familiar with GPS-based speedometers in their TomToms will immediately have concerns about how quickly an aftermarket GPS speedometer can acquire satellite signals, and how quickly it can react to changes in velocity. Fortunately, Dakota Digital has been able to overcome these inherent challenges to ensure accuracy and seamless performance. There are roughly 30 functioning GPS satellites in orbit right now, constantly moving. This isn't a problem while in use, but when you power down your TomTom for the night, all of the satellites it was tracking are gone the next time you turn it on. That's why your handheld GPS unit takes so long to get its bearings when you first power it up. To avoid a 10-minute lag before your speedometer starts moving, Dakota Digital's GPS-50-1 speed sensor is programmed to "wake up" every 15 minutes to take a snapshot of current satellite locations. Once the unit gets a fix on the satellites, it goes right back to sleep, thereby minimizing the amperage draw. What this means to you is that when you hit the key in the morning, the GPS-50-1 already has a good idea of where the satellites are located, and getting a fix takes seconds instead of minutes. For best results, including cruise control operation, we like to see 10-12 satellites being tracked, and six is the minimum threshold for speedometer operation.

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What happens to your phone call or satellite radio when you drive through a tunnel or under heavy tree cover? The signal gets weak or interrupted entirely. The same thing happens with GPS-reading devices. With a navigation unit, the interruption is hardly detectable, but when your speedometer and cruise control are using the signal, any disruption is a large one. To make this system work, we added internal accelerometers to fill in the gaps inherent with GPS signals. For example, with your typical GPS-fed cruise control set, as you drive into a tunnel, the signal will falter and eventually drop out. When the cruise control sees these fluctuations, it interprets them as a declination in vehicle speed and attempts to increase speed, sometimes very abruptly. With a GPS-50-1 controlling these components, the accelerometers act as a double-check system, and take a look to see if the vehicle speed actually changed. If not, the cruise control speed is held constant. Speed information from the satellite is updated within the GPS-50-1 every tenth of a second, which means that changes in vehicle speed are instantly reflected in the speedometer.

Solid-State Sensors

All Dakota Digital gauges utilize solid-state sensor technology. A solid-state sensor is a digital meter that gives more accurate, repeatable readings since it has no moving parts to get stuck or wear out. For example, our solid-state oil pressure sensor no longer has a wiper inside that measures the pressure. Another big improvement over traditional sending unit technology is that each solid-state sensor has a dedicated ground wire. No longer are we relying on the sensor grounding through its threads and in turn through the engine. All sensor grounds are run directly to our control box, so you no longer have to fear thread sealant.

More Information

Dakota Digital instrument panels, like the VFD3, are more like information centers than simple gauge readouts. The VFD3 systems offer an odometer, which also has a one-time preset option, so you can start the new odometer where the original left off, if desired. Many times the instrument system is upgraded at the same time as the drivetrain, so many customers choose to leave the odometer start point at zero. There are dual trip odometers in each system, in addition to a service meter, which allows the user to pre-program a desired service interval, such as 3,000 miles for oil changes. The instrument system treats this as a reverse-odometer, and the meter counts backward from the set point and alerts the driver when the service is due. Additional readings in the performance category include high speed and rpm recall. Also present in the system are indicators for turn signals, high beam, check-engine light, parking brake, and cruise control. All indicators are hidden, so if you opt to forego a few, you won't even know they're there.

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Integrated Performance Meters

A very fun feature of our digital gauges systems is that they offer built-in performance meters. Both the VFD3 digital and VHX analog instrument systems keep track of high speed and high-rpm recall as well as measure 0-to-60 times, and quarter-mile e.t. and trap speed. While they sound quite complicated, most of these readings are derived from the speed signal being sent to the Dakota Digital control box. These readings are accurate as long as the customer has the speedometer calibrated. There are two ways to calibrate the speedometer, both of which take just a few minutes and are very simple and effective. Due to the way the information is gathered, you have to keep the wheelspin to a minimum, though our GPS-50-1 speedometer interface will eliminate that variable for the traction-challenged.