Behind the Speed: Automotive Instruments

A visual walkthrough at what makes an automotive gauge tick.

Besides the most important visual aid of driving a car—looking out the window, duh—automotive instruments, or gauges, provide a direct connection to the vitals of your car and what’s happening at a moment’s notice. Everything that your car is doing, from the speed at which the crank is turning, to what temperature the oil is, or how fast the driveshaft is spinning can be analyzed with the proper gauge. The more you modify a car—and what performance characteristics you are striving for in the long run—the more that gauges can play an integral part of how you tune, enrich, and monitor your setup.


You can have a lot of gauges or a little. As cars have progressed, dashboards have become supercomputers full of information. Not only is every parameter able to be accessed via a stalk on a steering column or wheel, but you can access navigation, stereo, weather, and even text messages (which is a terrible idea). Most modern cars have gauges for nostalgia reasons, as everything is controlled by computers and diagnosed within milliseconds. Analog gauges, unfortunately, are being phased out by technology.


 Example of a mechanical boost gauge where air pressure forces the metal tube to bend, triggering the needle to move.


But don’t fret, because the need for highly accurate gauges becomes more of a necessity once you get into cars with modifications that require the same level of information, but you don’t necessarily need (or can’t solely rely on) the computer aspect. The texts from your friends aren’t nearly as important as boost pressure in a 9-second racecar.



Example of an Auto Meter Digital Stepper Motor


This is why having an accurate and purposeful gauge is important. Some are better at a specific task than others, whether street or strip. It will be hard to beat a direct connection via a mechanical gauge for racing since you always have a constant source of information. And nothing will be as accurate as a digital gauge that is equipped with a microprocessor; especially when you consider the amount of information modern cars must process. But what’s the difference between them and why does it matter? Continue reading to find out.



When you’re in a racing situation and need to constantly know the vitals of your car with an accurate, and direct connection, mechanical gauges—ones that offer a literal direct line to engine parameters where they take their measurements directly—still work without any electrical connection to the car being applied. For instance: an oil-pressure gauge has an oil line passing through the firewall onto the back of the gauge. If the electrical connections stop working for some reason, the oil pressure will still be registered and therefore still monitored. This is great when you know the inherent risks of racing, but bad when you’re in a street car and something starts leaking at 7,500 rpm making oil spew throughout the cabin. General consensus is that mechanical gauges have an accuracy range of +/- 2-percent variance. Diehards will remark that mechanical gauges offer a more direct, and seemless sweep with no stutter, as seen on stepper motors. So while they're reliable, they're also accurate, however, their direct connection might not be needed for street applications as any sort of leak in the line will cause a malfunction.


Example of a mechanical gauge connection. Photos via:


The solution to saving face (your face, in the case of hot oil), literally, is stepping up to electric gauges that have senders, which process input signals directly to the gauge. Otherwise known as ‘stepper motors,’ these units from companies such as Auto Meter and AEM Electronics use electric signals via a sensor (a sending unit) in the engine compartment. They take signals, depending on what component you're measuring, and convert them to a numerical unit on the gauge via an analog tach sweep, digital numerals, or both. These are highly accurate (around +/- 1-percent)a bit safer than traditional mechanical gauges because there is no fluid entering the cabin, and have more fail-safes. They offer a great compromise between a mechanical gauge and going fully digital, which we'll cover next, but they are more expensive.



Modern gauges now have the ability to house microprocessors inside the gauge for access to many different facets of information such as recall functions, warning displays, and even the abillity to reset itself back to zero after each startup; making for an incredibly accurate reading from day 1 to day 1,000. Digital stepper motors offer the ability to plug these directly into the ECU for data logging capabilities. With solid state internals, they're incredibly robust and can absorb vibrations without ill effects. Like many other modern computers, they can be dialed in to perform almost limitless combinations of colors, displays, sweeps of 270-degrees, and can also access Wi-Fi so you can connect to smartphones for even more functionality. If you have an unlimited budget and are looking for the top of the line products, these are your go-to. 



Auto instruments deliver the vital information of your vehicle at a moment’s notice or a quick glance. What they tell you can be instrumental to making sure your vehicle is running like a top, or needs a bit of adjustment in a particular area. Monitoring gauges and tuning to your preference will help make critical choices easier, and in the end your car more efficient, faster, and powerful. Your budget, technological needs, and cool factor will all play into which choice you make, but in the end, you'll be staring at better data than you had before. It's like the difference between buying an Omega watch and an Apple Watch: they both do roughly the same thing, but the price difference can be staggering and features might wow you in the beginning, but an analog watch will probably outlast a digital watch by many year. Consider your needs, wants, and how much information you realistically need before making the purchase decision.

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