Engine dynamometer testing is an important and integral part of an engine development program. The ability to accurately and repeatedly measure, control, and monitor the engine is the hallmark of the engine dyno. No other piece of shop equipment can match the overall test capabilities of the engine dyno.

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Our facility is equipped with a Stuska Model 800 water brake dynamometer. Data acquisition and processing is handled by a Depac data logger. Recorded data is stored and displayed on a PC running Depac software. The Stuska Model 800 water brake is capable of absorbing 800 hp at 8,000 rpm.

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With the rise in popularity of the chassis dyno, many people consider engine dyno testing expensive, unnecessary or redundant. A comparison of engine and chassis dyno capabilities can help determine which dyno will meet your objectives. Our engine dyno test package includes free chassis dyno testing to verify “installed” engine performance expectations.

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What is an engine dynamometer? The engine dynamometer is a device used to measure engine power developed at the flywheel. A typical dynamometer consists of a chassis or stand to hold the engine, a brake to load the engine and a strain gauge or load cell to measure the torque applied to the brake. A cooling system maintains engine temperatures and a data acquisition system monitors and records various sensor outputs such as rpm, torque, water and oil temp, oil pressure and so on. Recorded data is stored for output in graphical and numerical formats. The dyno is installed in a purpose built test cell with considerations for noise, air intake, exhaust and cooling. The control room is at the forward end of the test cell where the remote throttle, load control, instrumentation and computers are located. The test cell is visible from the control room through a viewing window.

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The term brake horsepower (bhp) refers to the horsepower measured at the dyno brake. It is generally assumed the dyno brake is directly coupled to the flywheel or crankshaft. Therefore, bhp usually represents power measured at the flywheel although this is not always the case. For example, motorcycle engines may have the dyno brake coupled to the transmission output shaft or outboard marine engines may have the dyno brake coupled to the prop shaft on the lower unit. In the preceding examples, the measured bhp would not be representative of flywheel or crankshaft horsepower due to transmission or driveline losses.

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Technically speaking a dyno does not directly measure horsepower. The dyno measures engine rpm and brake torque. Brake horsepower is then calculated using the formula bhp = (rpm*torque)/5252. Dyno’s equipped with electronic data gathering and processing make this calculation transparent to the operator.

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How is the dyno used for engine development? The engine dynamometer is a device designed to measure engine power output. The basic premise in engine development work is a comparison of engine output in different configurations. An engine is tested in configuration X, changed to configuration Y and tested again. The recorded power and torque of the engine in both configurations is compared. A judgment is then made as to the efficacy of the configuration changes as it relates to the performance objectives. Configuration changes can be as simple as ignition timing or as complex as cylinder head and manifold changes. Often the same tests are run several times to ensure repeatability. In general, the idea is to minimize the number of variables between tests so the effects of a change are readily apparent. This methodology is the basis for the dyno-testing portion of an engine development program.

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In addition to changing engine configurations, different test methods may be used. An engine may be tested steady-state (holding set rpm’s) or accelerated through a range of rpm’s. Prior to the use of electronic data gathering, step testing was necessary to allow time for the operator to record torque and rpm readings. The brake load would be adjusted to hold the engine at specific rpm points. When the readings stabilized they were manually recorded. Brake horsepower at each step was then calculated from the recorded torque and rpm. Current dyno’s record test data as the engine speed is changing. This method can approximate an engine accelerating in a vehicle. More sophisticated dyno’s can be programmed to simulate road loads as though the engine were installed in a vehicle.

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The engine dyno also serves as a quality control tool. Program or “spec” engines are tested to verify power output. For example, rebuilt engines are tested prior to shipping to confirm expected performance.

Advantages of the engine dyno over other methods of measuring engine output e.g., chassis dyno, g-meter (accelerometer), time/distance are:

• The ability to maintain a continuous load on the engine for endurance testing.

• Control over engine water and oil temperature set points.

• Monitor numerous operating parameters e.g., air-fuel ratio, manifold vacuum, EGT’s, fuel flow.

• No wear and tear on the vehicle driveline.

• Complete access to the engine for changing out or modifying components.

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Can any engine be tested? Virtually any type of piston or rotary engine can be tested on our engine dyno. The engine should be greater than 30 bhp and less than 800 bhp with a maximum speed less than 8,000 rpm. Unusual engines may need special driveshaft adapters and mounts.

Is engine testing expensive? The engine dyno is operated on a per hour basis that includes engine installation, testing and removal. Additional expenses include consumables and materials e.g., fuel, oil, spark plugs. Total test time is dependent on the test plan. Minimum test time is 8 hours. This generally allows for break-in and basic fuel and spark calibration. Call 757-363-8878 or e-mail for additional information.

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If you plan to use your engine for competing in a sanctioned performance series where significant modifications are permitted, an engine development program including dyno testing should be considered.