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Dakota Digital Explains Inner Workings of Ultraprecise Instrumentation

Do your gauges measure up?

Stephen Kim Jun 28, 2013
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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OEM instruments are inaccurate for a variety of reasons, including inexpensive or out-of-date sending units, poor vehicle grounds, low-quality gauge movements, and hokey instrument panel circuitry.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.

Expansion Modules

Dakota Digital's VFD and VHX instrument panel assembly can accommodate a host of expansion gauges with our BIM expansion modules. The idea for these modules was hatched after identifying the need for additional information as well as recognizing people's reluctance to cut up vintage dashboards. With the redesign on our instrument system control boxes, as well as VHX release in July 2010, we added a data port that allows the new BIM expansion modules to plug into the control box for simple connectivity for nearly limitless growth. The most commonly added readings via the BIM series are auxiliary pressure and temperature gauges, engine boost gauges, and compasses. We also offer modules for air temperature, airbag suspension, auxiliary voltage/amp current, EGT, cylinder head temperature, and wideband air/fuel gauges. Up to 16 additional readouts can be displayed in the message centers in the instrument system.

Analog Gauges

In addition to our well-known line of digital gauges, Dakota Digital is very excited about our new analog VHX lineup as well. A classic look with thoroughly modern technology is really the calling card of the VHX series. They feature precision stepper motors for accurate needle movements, LED backlighting for the utmost visibility day or night, and high-contrast LCD message centers for nearly unlimited expandability. While the look is analog, the technology is digital. All sensor and informational inputs connect to one central control box, and a single CAT5 networking cable connects to the cluster. Solid-state sensors for oil pressure, water temperature, and speed are included, and the system has the ability to learn a custom fuel level sensor if yours is not on our pre-programmed list. The supplied sensors combined with direct-fit compatibility make installation a breeze, plus you won't have to cut up a classic dashboard for better instrumentation.

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Fluorescent vs. LCD vs. LED Displays

Dakota Digital utilizes several different methods of display illumination, and we got our start with vacuum fluorescent technology. These are glass displays that energize a fluorescent gas to emit light. Each display has seven-segment digital numbers or symbols, and the software program dictates what a given display will be. We use this type of display for our VFD3 instrument systems. The display color of our VF displays is a light bluish-green color, so we use a colored acrylic lens to make the instrument systems more visually appealing. In contrast, our VHX instrument systems utilize liquid crystal displays known as LCDs. The advantage of an LCD display is that it can be seen in sunlight with no other light source, as it reflects incoming light through multiple filters. The downside is that LCDs require backlights for improved low-light visibility. Consequently, all VHX instrument systems have LED-backlit LCDs that match the rest of the LED lighting. Another feature that makes the VHX series noteworthy is that we use a special type of LCD known as a trans-reflective LCD. Not only can it be backlit, but this style reflects incoming ambient light, making the contrast even stronger. As a result, the visibility of the VHX message centers gets better in very bright situations. Dakota Digital currently does not offer LED-display instruments for automotive applications, but that technology has proven very successful in our motorcycle line. Light-emitting diode displays are made up of seven-segment displays, lit with monochromatic color. The contrast of an LED display is quite good, making them a great option for a motorcycle application.

Engine Swaps Simplified

LS engine swaps are not going away, and builders expect their hot rods to do everything, and for good reason. In response to this changing marketplace, we have developed a few products that take a lot of the headache out of a late-model powertrain swap. The first product is the BIM-01-1 OBD-II/CAN interface, which plugs directly in to the diagnostic port for an OBD-II system. With this piece, we're able to output speedometer, tachometer, temperature, and trouble code information directly to our control box with a single data cable. This is especially helpful with new applications where getting a tach signal can be nearly impossible, and it also streamlines the growing number of gas trucks with diesel swaps we're seeing. Our other product designed to simplify putting a new engine in an older car is the STA-1000. Similar to the BIM-01-1, the STA-1000 plugs into the diagnostic port, outputting a traditional speedometer, tachometer, and trouble code signal to your choice of aftermarket gauges outputs. We realize that a lot of these late-model conversions are happening to existing hot rods, and changing up the dashboard isn't always in the cards for a finished car. The STA-1000 allows hot rodders to retain the existing aftermarket instrumentation and helps the gauges communicate with a modern drivetrain.

Speedometer Calibration

New speedometers must be calibrated due to the multitude of gearing and tire diameter combinations possible in a hot rod. Dakota Digital instrument systems offer two methods of speedometer calibration: Auto and Adjust. Auto is the preferred process, and it's as simple as driving exactly one mile. With a stretch of road that is known to be exactly a mile, such as section roads, start the instrument system in setup mode, select Speed Auto, and start driving. The system will be counting pulses in the message center as you drive, and it doesn't matter if you stop, just try to keep it in a straight line and don't spin the tires. The other method is Adjust, in which you can pace yourself against another car with an accurate speedometer or a handheld GPS unit. Using the supplied push buttons, you can adjust the speedometer reading up or down until it's right on. You have the option at any time to recalibrate the speedometer to account for rear gear swaps or different height tires. All settings are saved in the hard memory of the system, so disconnecting the battery won't do any harm.

Custom Gauges

We have a very capable custom shop that can adapt our digital instrument systems to nearly any instrument cluster. If there is any restoration, paintwork, or chrome plating to be done to the cluster, we ask that this is completed before sending the components to our facility. Once on site, the bezel and instrument housing are carefully measured and drawn in a CAD program. With a digital rendering on screen, our technicians determine if any existing display layouts will fit the opening. If not, a custom board arrangement is drawn up, vacuum fluorescent displays placed, and a custom acrylic lens is drawn. With the display windows and engraving completed on the laser, the one-off instrument system is assembled into the customer's dash components. Since the system will run off of our standard control box, required sending units are included, and as always, even the custom-built systems are covered by a lifetime warranty.

LED taillights

Although Dakota Digital is best known for gauges, we have also started offering LED taillight kits. The feature that draws a lot of people to LED taillights is the brightness. Old hot rods have comparatively very small taillights, sometimes in precarious locations that coffee-slinging, text-reading drivers aren't looking for. And while our LED taillight systems, whether single or multiple-emitter style, are certainly brighter than an incandescent bulb, the speed is what really excites us. Our LED taillights illuminate 200 milliseconds faster than a normal lightbulb, which doesn't sound like a lot, but at 60 mph, that equates to about 19 feet when you take driver reaction time into account. On paper, that gives the driver behind you 19 more feet to get his Prius stopped before driving into and through your prized Bow Tie. There are, of course, other perks to converting over to LED lighting, such as reduced current draw, internal voltage regulators that maintain brightness throughout a range of 8-18 V, and never having to replace a taillight bulb again. We currently offer direct-fit, specifically engineered LED taillight conversion kits for '67-77 Camaros, '64-72 Chevelles, '59-90 B-bodies, and '55-57 Tri-Fives. chp

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