Engine Dyno Testing - On The Pump

A very good friend of mine, noted engine guru, and PHR contributor David Vizard, was once being queried about some aspect of engine theory. The interesting part of the exchange was when the fellow asking the questions summed up the discussion with the words, "So, in your opinion..." Vizard interrupted, "I don't have an opinion, I have a dyno." The point was that the information being presented was not based upon conjecture or opinion, but rather was derived from empirical testing on one of an engine builder's most important tools: the dynamometer. In those days, facilities equipped with engine dynos were few and far between, and some of the widely accepted engine building practices were based as much on wives' tales and hearsay as on fact. In more recent years, the accessibility of the engine dyno has expanded to the point where dyno testing has become a relatively routine punctuation to a performance engine build-and for good reason.

Why Dyno Test?The reasons here can be varied, depending upon the final objective, be it an involved development program, or a one-off test of a completed engine, but the underlying objective is to get the most from an engine package. Building an engine without testing is somewhat like playing baseball without keeping score. You'll likely have some fun in the process, but it's going to be impossible to evaluate the stats. A dyno test will provide a wealth of information that will sharpen both the engine's performance, and the builder's skill. What are some of the things the dyno can tell you?

Horsepower And TorqueOil And Water TempsOil PressureMechanical EfficiencyBrake Mean Effective Cylinder PressureBrake Specific Fuel ConsumptionExhaust Gas TempsFuel PressureFuel FlowManifold Pressure Or VacuumAir Temp For Best PowerEngine AirflowVolumetric EfficiencyFuel EfficiencyRPM Range

Besides the detailed information on the numerous running parameters of the engine, the test will also allow the builder to find the optimal tuning setting for best power and/or economy. This can be as simple as finding the basic timing and jetting requirements, or it may be more involved, including detailed tuning of the fuel and spark curves to really dial-in a combination. The dyno makes it possible, providing instant feedback to various changes. Running the engine on the dyno will also provide an opportunity for more basic adjustments and checks of the engine's operation. The cam and rings can be broken-in, and the valves given a final adjustment on the dyno, and running the engine under load can assure there are no mechanical problems or leaks before the engine is bolted into a car. This alone can be worth the cost of a test.

Before The TestOf course, the greatest advantage of a dyno test is that it can provide a roadmap to making more power, if you know how to find it. One of the key elements here has less to do with equipment than with personnel. An experienced and knowledgeable dyno operator will add immeasurably to the value of a test, and the operator will usually be the point man when it comes to finding that "magic tune." Experience plays a key role here-remember, you are paying for the operator's time as well as for the time on the machine. It is worthwhile to make some inquiries both at the shop and within the local performance community to get an insight into the facility being considered for a test. A skilled operator will be an asset in evaluating the data from the dyno and making interpretations that can lead to improved performance. Just as importantly, a skilled operator will often detect and head-off problems before they develop into serious trouble and help find faults if they occur.

Preparing for a dyno test should begin with a conversation with the dyno operator. It's important that everyone is clear on what the objectives and goals of the test will be, and that everything required is identified ahead of time. Besides discussing the basic engine combination, it is important to be clear about what additional testing you'd like to accomplish. You'll need to know what components in addition to the engine assembly will be required for testing, which will vary from shop to shop. You may need to supply a set of headers, though in some cases the shop will have dedicated dyno headers, often set up to accept exhaust gas temperature probes. The dyno may be equipped with an ignition system, or you may elect to run the system that will be used in the car. It's important to discuss the requirements and capabilities of the shop to run ancillary equipment, such as nitrous, blowers, or a dry sump. Find out what equipment and supplies the shop has on hand before showing up on test day. Things to consider include:

Prelube AdapterCarburetorFuel Lines (Especially For Multi-Carb Induction)HeadersMufflersIgnition SystemFuel PumpSparkplug WiresFlywheelOil And FiltersFuelTuning Parts (Jets, Sparkplugs, Etc.)GasketsSpecial Tools

Testing an engine provides the opportunity to try a variety of equipment and the dyno results can provide the basis for component selection, based on the results. You might wonder, is a 1 7/8-inch header an advantage over a 1 3/4-inch set? Is a 750-cfm carb the best, or would an 850 prove better? Single-plane or dual-plane intake? The dyno will help answer these kinds of questions for your particular engine combination. Just be sure to discuss the testing ahead of time, so that the operator can provide some insight on what can be accomplished in the allotted time, and how the test will be structured to make the best use of that time. Don't expect to show up on test day and surprise the operator with 12 intake manifolds. Explain to the shop what you'd like to test and work out a plan to get that testing accomplished. You'll need to consider what additional items will be required to get the parts swapping done, such as gaskets and sealants, fasteners, or special tools the shop may or may not have. Communication here is vital to a successful day on the dyno. It's good practice to prepare a checklist of what you'll need to bring.

Hunting For PowerIf the groundwork has been done in advance, the test can be an efficient way to find power. Normally, once the engine is started, it will be inspected for any signs of problems, such as abnormal gauge readings, or noises. If a problem is suspected, the engine should be quickly shut off to make repairs or corrections, if needed. The coolant flow will be confirmed, as will oil pressure, mixture, and ignition timing. If it is a new engine, a break-in cycle will be initiated, and the engine brought to operating temperature. If you have specific requirements on running or break-in, make sure to inform the operator in advance. For instance, if the engine contains a radical high-lift mechanical camshaft, it may have been assembled with light break-in springs, which will be swapped for higher rate units when the wear pattern is established. In this case, the engine might require keeping the engine speed below a certain upper limit until the springs are installed. Don't assume the operator will know your engine's specific requirements-tell him in advance. After the warm-up and run-in, the engine is often shut down to make some additional adjustments, such as the hot valve lash, before any power pulls are made.

Though the temptation is there to just let it rip to see what an engine will do, a more prudent approach is to initiate the testing with a series of static pulls to collect initial data. In a static test, the engine is brought up to wide-open throttle, while the dyno holds the load to a constant rpm. Normally, the first static pulls will be at the lower end of the operating range. The static pulls will provide data on the air/fuel ratio, and uncover calibration errors before a full dyno pull is made. If a problem such as too lean an air/fuel ratio or audible detonation are apparent during the static test, an experienced operator will quickly abort the test, and corrections will need to be made. If the readings look good, the static rpm level will be raised, making similar checks higher in the operating range. After confirming that all is well in the static pulls, it's time to establish a baseline.

In a sweep test, the dyno is set to test the engine over a specified rpm range and acceleration rate. Modern dynos, such as the DTS, will automatically control the load to allow the engine to accelerate through the rpm range as specified by the control settings on the console, while measuring torque and deriving power output. At the same time, the dyno will be gathering other data through various channels, depending how the dyno is equipped and instrumented. If the first sweep test is completed successfully, a baseline has been established, and the numbers and data from the baseline can be used to compare with results of subsequent tests. A DTS dyno can provide this information graphically or in detailed numerical charts.

Once the baseline is established, changes can be made and the engine re-tested to determine if the change results in an improvement. Typically, the first changes will be related to the tune-up, including the mixture and timing, however, only one thing at a time should be changed. If the mixture is looking in the zone for what normally produces best power with similar engines, a timing loop may be the first tuning step. The conservative approach is to remove timing, which is always safer, and then re-test and compare the outcome to the baseline. If the power is improved, more timing may be removed, however if power declines, the next test may be to try more timing than the baseline setting. Using this procedure, the optimal timing can quickly be established. Similarly, the mixture can be addressed with a mixture loop. Again, the conservative approach is to start by trying a richer mixture to see if that direction improves output. If not, jetting is taken in the other direction, leaning the mixture and again zeroing-in on the optimal setting. It's not unusual to find substantial power improvements in the timing and jetting loops. If parts swapping is not part of the program with the tune dialed-in, the basic dyno test is completed. Additional tuning may be performed to dial-in the part throttle and ignition curve advance rate.

While simply running a completed combination for a number is definitely worthwhile, one of the greatest assets of dyno testing is the ability to perform comparative testing. Here we are talking about parts swapping, be it various headers, intake manifolds, carbs, or even more elaborate components such as cylinder heads, camshafts, or valvetrains. In comparative testing, you are only limited by your imagination, the available time, and the parts on hand. Again, it is important to discuss plans for additional testing with the dyno facility, to coordinate a testing plan. Sometimes certain parts will be optimized with the addition of further components, so the sequence of the changes is important. Here, the value of an experienced dyno shop adds value in the planning and execution of the testing. Whether you just purchased an engine, or if you're an aspiring builder or a seasoned pro, there is always something to be learned on the dyno.

Own Your Own DynoThe DTS is the official dyno for our Engine Masters Competition and with its proven track record in our event, it has demonstrated its worth. Who should consider owning a dyno? If you are a professional in the field of engine building, or even an amateur with the resources to make it happen, a dyno may well prove to be the most valuable resource in the shop. Besides being able to really dial-in an engine combination, spending time on the dyno has the effect of dialing-in the user. There is nothing like time on the dyno to really learn the characteristics of engine operation, and seeing the cause and effect relationships in making power is a teacher like no other.

DTS has stepped up to the plate with a specific dyno package named for our engine competition, the EM-2000 Engine Masters series dynamometer. We had a look at the rundown of features included in this package and came away impressed. The base price of $39,870 buys quite a substantial level of equipment. Optional and additional equipment makes the machine even more versatile, and the upgrades can be added as required. We thought it would be worth a look to see what it takes to be DTS-equipped.

The Dts Em-2000 Engine Masters Series Dynamometer:*Dual-Rotor Dynamometer Power Absorption Unit, 2-Inch Stainless Steel Mainshaft, 1,000 Hp, 10,000-Rpm, 1,000 Lb-Ft Continuous Capacity Rating, Bi-Directional High-Speed Torsionally Compliant Driveshaft*Fixed-Base Dynamometer Stand With Driveshaft Safety Guard*Engine Starting System With 2kw Starter*Heavy-Duty Engine Docking Cart With Four Adjustable Jack Screw Uprights*Digital Dual-Valve Dynamometer Control System*Torque Calibration Arm*Thermostatically Controlled, Wall-Mount, Heavy-Duty Engine Cooling Column*Two Control Joysticks (Dyno Speed And Throttle Position)*Electronically Controlled Remote Throttle Actuator System*Switch Panel (Power, Ignition, Engine Start, Emergency Stop, Hp Range, And Throttle Travel Adjust)*Six Switching Relays*High-Speed Industrial Computer System*17-Inch Flat-Panel Color Computer Monitor*Computer Keyboard*Dts 4000g Comprehensive Data Acquisition And Control System*Graphical Software Environment*Powerful Integrated Data Analysis And Graphing Package*17 Calculated Channels*Variable Speed, Inertia-Corrected Sweep Testing*High-Speed Modem*Dynocom Customer Support Software Package*Hewlett Packard Deskjet Color Printer*All Connecting Cables (35 Feet Standard)*Measured Channel Configuration (Each With High/Low Warning And Shut Down)*Engine Rpm*Engine Torque*Fuel Flow 0-80 Gph*Fuel Pressure*Oil Pressure*Oil Temperature*Engine Coolant Temperature*Fuel Temperature*Dynamometer Outlet Water Temperature*Three-Channel Automatic Weather Station (Percent R.H., Barometric Pressure, And Ambient Air Temp)*Training - All Dts Systems Include Two Days Training At Their Facility In Shingle Springs, California; On-Site Training Is Available By Special Quotation*Ongoing Support Is Available Direct From The Factory Via Dynocom At No Charge

Options, Additional Equipment And Cost:*Pm-15d Upgrade To Aluminum Bronze Powermark Absorption Unit 2,000hp,15,000rpm, 1,500 Lb-Ft, Continuous Capacity, $850*Dts - Dcs Additional Engine Docking Cart, $2,450*Dts - 1633 Engine-Mounting Kit One Each, Rear Engine Mount, $1,485*Dts - 1204 Universal Flywheel Drive Adapter, $475*Dts - 1095 Additional Starter, $625*Dts - Rear Engine Mounts, Various Block Patterns Available, $750*Dts - 1007p Pressurized Engine Cooling Column (In Exchange For Standard Column With System), $1,900*Dts - 1240 Tilton Flywheel Drive Adapter, $495*Dts -1248 Gm Crankshaft Inertia Drive Adapter, $550*Dts - 1212 Gm Crankshaft Adapter Button, $375*Dts - 1650 Additional Cv Joint, $850*Dts - Lmd Lambda System For Fast And Accurate A/F Ratio (Price Per Channel), $1,825*Dts - Eaf Air Flow System For Engine Inlet (Connecting Hose To Engine Not Included), $5,800*Dts - Jtb Engine Blow-By System, $2,850*Dts - 1420 Additional Pressure Transducer, $330*Dts - 1493 Vacuum Transducer -15/+15 Psi, $330*Dts - 1438 Additional Type "K" 6-Inch Thermocouple W/Armor Shield, $85*Dts - 1616 Additional Flow Transducers Consult Factory (Water, Oil, Different Fuels, Etc.)

Terms And Conditions30 percent due with purchase order70 percent due at time of shipmentAll sales are FOB Shingle Springs, California, for domestic use onlyFreight charges are collect unless otherwise arranged Prices do not include any taxes that may be applicableAll orders are subject to acceptance by factory, Shingle Springs,California

The Dyno ChallengeA discussion of dynos would seem incomplete without a word about our experience with the DTS dyno products used for testing in the Engine Masters Challenge. The heart of the World Products testing facility is made up of three dedicated test cells, each equipped with a DTS dyno. While the Engine Masters event is a test of engine-building skill, behind the scenes it is also a test of an engine dyno's capabilities-and that is a challenge unto itself. We walked away impressed with the stats surrounding the equipment. With over 650 dyno pulls in the course of two years' competition, the events proceeded without a single aborted run or dyno-related problem-quite a testimony to the durability of these units.

Durability is important, but accuracy is absolutely vital in an event such as this. Competitors need data to find the smallest change in power during the "tune-up" phase of the event, and the equipment needs to be up to the task of pointing the competitors in the right direction with accurate information. Here again, the DTS dynos at World Products were up to the task, clearly showing the effects to the power curve resulting from the often-hectic tuning efforts. Just as importantly, the repeatability has to be outstanding to provide quantitative information on changes, often on the basis of a single dyno pull. Repeatability also comes into play when comparing data from day to day, and probably most impressively, from test cell to test cell on different dynos. We saw first-hand the repeatability here, as the engines moved from their qualifying cells, to the second cell for the finals.

Another point that became evident at the Engine Masters event was the ease of use encountered with the DTS configuration. The crew at World had rows of engines to test in qualifying, with only days to work through the field. The engines in the competition ranged over virtually every type of big-block put out by the Big Three, including Buick, Cadillac, Pontiac, Mopar's wedge, Ford's 385-Series and FE, not to mention the ubiquitous Chevy rat. The flexibility and ease of use of the DTS platform, aided by the versatile docking cart system, was a big help in getting through testing these different engine types in a remarkably efficient manner.