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Rebuilding Engines As A Side Business? What Should You Know About Dyno Testing?

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If you're currently working as a mechanic at a dealership or private shop, you may be growing tired of the divide between your billable hourly rate and your actual pay. For those who have the skills to rebuild engines and transmissions from the comfort and convenience of their own garages, transitioning from a W-2 wage worker to a small business owner can be a wise choice. However, there are still many factors you may need to consider before pulling the plug on your day job -- and having a reliable way to test the horsepower, emissions, and overall function of the engines you rebuild is one of them. Read on to learn more about dyno testing and when you may want to invest in your own dynamometer. 

What is dyno testing?

Dyno testing involves the use of a dynamometer to measure engine output and performance and troubleshoot any potential problems. This specialized piece of equipment can be used for everything from "breaking in" an engine so it can achieve maximum horsepower to ensuring that the engine complies with all federal and state emissions standards. If you're planning to build specialty engines (like racing or pulling engines), having these engines dyno tested before sale is a must -- but this testing can also be used to improve performance of smaller passenger engines.

When an engine is dyno tested for the first time, it's generally hooked up to the dynamometer to idle for a few minutes so that a baseline can be achieved. The dynamometer will then increase pressure on your engine by raising and varying the number of revolutions per minute (RPMs) to simulate actual driving conditions. Throughout this process, the dynamometer is keeping careful track of your engine's metrics, including fuel economy, average horsepower, and torque output. You'll then be able to review these measurements to determine whether your engine requires further tuning (and another round of dyno testing) to achieve your goals or if it can be sold or installed as-is.  

Should you seek local dyno testing services or invest in your own dynamometer?

Many areas, particularly those in regions where amateur drag racing is popular, have one or more dyno testing facilities where mechanics and hobbyists can bring engines to be tested. These facilities will generally charge a flat hourly or daily fee. This charge often includes professional assistance in reading the dynamometer results, as well as help in fine-tuning your engine to respond to the readings you're getting. Because these facilities can charge anywhere from $500 to $2,000 per day, it's often worth your while to bring several engines to be dyno tested at once to ensure you get your money's worth.

However, if you find yourself traveling to the dyno test facility on a regular basis, you may begin to wonder if you wouldn't be better off purchasing your own dynamometer so that you'll be able to evaluate and adjust your newly-built engines at home. This can often be a pricey prospect for those dealing with relatively inexpensive engines and a low profit margin, as a full dyno testing setup can eclipse your startup costs, running $50,000 or more. Fortunately, you may be able to construct your own home dynamometer for a substantially lower cost -- at least one set of plans allows you to build a dynamometer for less than $2,000

Ultimately, your dyno decision will depend on a few key factors. If you already have the space for a home dynamometer and the skills to build this testing equipment at a relatively low cost (combined with frequent visits to your local dyno testing facility), you may find that avoiding the regular dyno testing fee can save you a substantial amount of money. This can also be a good option if you live in an area without high-quality dyno testing facilities available.

However, if you're already struggling to keep your tools and equipment confined to your garage or outbuilding, or if you dyno test engines so infrequently you're unlikely to spend more than a few hundred bucks a year on this service, you may be better served by saving your money and investing in professional dyno testing rather than purchasing or constructing your own device.

For more information and details, visit professional dyno testing facilities or websites like