MORE THAN A SMOG CHECK MACHINE

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Lilian Booker
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DYNOS: MORE THAN A SMOG CHECK MACHINE BY BOB CERULLO If you re using your dyno only for smog checks, you re missing out on some great, profitable service opportunities.

1 DYNOS: MORE THAN A SMOG CHECK MACHINE BY BOB CERULLO If you re using your dyno only for smog checks, you re missing out on some great, profitable service opportunities. Dynos in auto repair shops were pretty much unheard of prior to the introduction of stricter government-mandated emissions standards resulting from the passage of the Clean Air Act amendments. It wasn t until various state smog inspection programs went from requiring static emissions tests to loaded-mode testing that the term dynamometer became a household word in shops located in areas of heavy air pollution. When this legislation was passed, there wasn t any real choice given to repair shops in some states, like New York, that were already doing state motor vehicle inspections. If they wanted to stay in the inspection business, they had to invest in a dynamometer programmed to work with a computerized emissions-testing machine. However, having a dyno in your shop 42 November 2000

2 Photo courtesy Environmental Systems Products November

DYNOS: MORE THAN A SMOG CHECK MACHINE The eddy-current brake is the heart of the modern dynamometer. It absorbs horsepower without overheating to help simulate road conditions.

3 DYNOS: MORE THAN A SMOG CHECK MACHINE The eddy-current brake is the heart of the modern dynamometer. It absorbs horsepower without overheating to help simulate road conditions. can be a huge blessing in disguise. It can provide exciting opportunities for those shop owners willing to explore the diagnostic possibilities beyond inspections of even a basic unit. Types of Dynos Actually, there are all sorts of dynamometers, from those designed to test automatic transmissions and engines on a test stand to units on which anything from a motorcycle to a giant multiaxle truck tractor can be driven under simulated road conditions. Special dynos are available to test braking and steering systems, as well. But it s the chassis dynamometer that can now be found in thousands of repair shops across the country, thanks to the various state smog programs currently in force. Essentially, a chassis dynamometer is designed to simulate the conditions a car would encounter on the road. The term indoor road is as good as any to describe the basic concept. The typical chassis dynamometer is a two-roller system, comprising a drive roller and an idler roller. The drive roller drives a brake through a coupling. In years past, chassis dynamometers were designed with water brakes that created resistance by the use of cumbersome pumps controlled by valves and attached to the rollers to effectively absorb power. Practical use has proven the modern eddy current dyno more reliable and simpler to build and use. The eddy current dynamometer uses a magnetic brake that s particularly effective because it s almost impossible to overheat. It resists heat so well because the braking effect decreases as the temperature rises. And since it s basically an electric magnet, it can be turned on and off as needed and is readily adaptable to computerized controls. The idea behind the eddy current dyno is to simulate road-testing under a variety of driving conditions uphill, downhill, rapid acceleration, slow acceleration, etc. It s the answer to the mechanic s prayer of being able to quickly simulate conditions that existed when a problem occurred, which you re now trying to duplicate in the shop. Three Major Systems Modern chassis dynos have three major systems power absorption, vehicle support and rollers, and control and measurement. Let s look at these systems individually. Photos courtesy Snap-on Diagnostics Power absorption. This is what makes the difference between simply running a car with the wheels off the ground and running it on a dynamometer. Power absorption is accomplished using the eddy current brake, which has the capability to absorb more power than any vehicle can be expected to deliver. Vehicle support and rollers. On most two-roller systems, the tire sits down on and between the drive roller, which drives the eddy current brake, and the idler roller, which supports the vehicle. An elevator is positioned between the rollers to make easy entry and exit from the dyno possible. Control and measurement. These functions are generally programmed into a controlling computer. In the case of state-mandated testing, the software program is specified by the various states for their required tests. However, many basic motor vehicle inspection dyno systems can be used in an operator training mode or in other modes, depending on the make and model, for testing outside the realm of a smog check or for pinpointing problems that may have caused an inspection failure. In addition, there are optional programs and equipment now available as add-ons, and others soon to come, that offer additional capabilities. These features greatly enhance the diagnostic capability of the dyno for vehicle performance testing. Big-Time Versatility The dynamometer is a multidimensional machine that can perform a variety of functions apart from a standard emissions inspection. Some of them are: Preconditioning. Let s say a customer complains that his front-drive car is running hot and there are no obvious coolant leaks. By running the car on the dyno with a light load typically 5 to 10 hp the engine can be brought up to operating temperature quickly. This allows you to check the operation of the electric cooling fan, along with overall cooling efficiency, without the risks to the transmission inherent in power braking or a potentially abusive road test. This same pro- 44 November 2000

4 cedure can be used to quickly get the feedback system into closed-loop, for analysis. You can save considerable time getting the catalytic converter to light off using the dyno, as well. Speedometer check. Without performing an actual state inspection, a mechanic can run a car through a full range of speeds while comparing the reading on the car s speedometer with the reading shown on the inspection machine s monitor. Thanks to the demands of state emissions programs, these readings are quite accurate, and can pinpoint inaccuracies in the vehicle s speedometer. Driveline vibration. Suppose a customer with a rear-drive vehicle complains that at 45 mph, he feels a driveline vibration through the seat. Doing a sustained 45 mph usually requires the car to be driven on a highway. But, not if you put the car on the dyno and run it up to 45 mph. Doing this on a rear-drive car can rule out the front suspension as the cause of the problem and narrow your search to the drivetrain. Intermittent driveability problems. Technicians are often called upon to diagnose conditions that simply can t be duplicated in the shop. Part of effectively using a scan tool during a road test is to try to catch a snapshot recording of key data as a problem occurs, then play it back at the shop to determine the likely cause. This requires driving while attempting to push a button on the scan tool to begin a movie. On a dyno, a mechanic can concentrate on the scanner without worrying about running into a tree. He can also accelerate or decelerate at will, then trigger the scanner at just the right moment to get the before-and-after recording of what s happening when the hiccup occurs. Quality control. One great use for an inspection dyno is as a general check of how well a vehicle is performing. This can be a prevacation check, a prior-to-purchase used car check or simply a quality control check to be sure that once a vehicle is repaired, all systems are go. This can be used, for example, after a major engine overhaul or transmission rebuild. Before-and-after testing for driveability problems, meanwhile, provides an assurance previously possible only while road-testing. Setting up and running a car on the dyno through a full emissions inspection in the operator training mode assures the tech and the owner that the feedback system is operating correctly and that a MIL won t illuminate the first time the customer takes the car out on the road after a repair. This type of check can be performed in less than 15 minutes, as opposed to the time it would take to actually drive to the nearest highway and perform the same test, without having the November

DYNOS: MORE THAN A SMOG CHECK MACHINE Dynos have often been called an indoor road for their ability to simulate road conditions without a mechanic ever having to take the vehicle out of the shop.

5 DYNOS: MORE THAN A SMOG CHECK MACHINE Dynos have often been called an indoor road for their ability to simulate road conditions without a mechanic ever having to take the vehicle out of the shop. Hooked to a good emissions machine or engine analyzer, its capabilities are virtually endless. benefit of an actual emissions report in hand. In the case of a prior-to-purchase used car check, doing an emissions test on the dyno ensures that the owner won t come back to complain that a car that looked good failed its smog inspection. Being able to advise the customer beforehand that a particular vehicle will not pass a smog test provides good information for the prospective buyer, and an opportunity for your shop to get the job of correcting the emissions problem. Isolating driveline-related vs. engine-related vibrations can be accomplished easily on a dyno by first running the vehicle up to the speed at which the vibration is noticed. Note the mph shown on the computer monitor and the engine rpm. Then shift to another gear and bring the speed up to the same shown on the monitor during the previous test. If the problem occurs at the same engine rpm, it s likely to be engine-related. If it occurs at the same dyno mph, the problem is more likely driveline-related. Transmission shift points, kickdown and slippage often become obvious during the acceleration and deceleration cycles required by some states drive cycle. Retesting after a TV cable adjustment or major repair can be done quickly and safely on a dyno. Tires that have broken belts or an out-of-round condition will show up immediately on the dyno as they roll against the dyno s smooth rollers. You ll hear the noise and feel the vibration in the steering wheel. Distorted tires will cause a vehicle to move from side to side on the dyno, sometimes violently, as the tires fight the restraining belts. Transient test results, when printed out, provide a graphic depiction of where emissions should be at specific rpm and mph readings during an actual or simulated smog inspection. By printing out the results, your tech can get a good idea of when the failurecausing problem occurs. Other Diagnostic Capabilities Typically, basic state inspection dyno systems are designed to do what each state requires for its test. In some cases, trying to do too much outside of a dedicated system procedure may result in a tampering condition. But with a little know-how, you can use most machines for diagnostics outside of the realm of an official state smog program. For example, with the ESP SystemOne unit, after you enter engine size, number of cylinders, vehicle weight and emissions limits, you can enter into an ASM 5015, ASM 2525 or RG240 mode to obtain emissions levels that will provide a baseline. Then use the dyno to perform diagnostics without going through an official smog inspection. Once the repairs are done, this same method can be used to verify that they ve been successful prior to actually running an official emissions test. Snap-on Diagnostics SIS 900 Service Inspection System is fully capable of state inspection dyno testing, while also being able to accomplish general repair diagnostics, including gas analysis, compression testing and ignition and charging system diagnosis. On the machine s control panel, various dyno modes can also be entered, including Road Simulation, Incline, Power, Speed Control, Constant Torque or None, which is essentially freewheeling. Bear/Allen Emissary Series machines from SPX Corp. also offer choices beyond the basic requirements of state emissions tests. Coupled with the company s Exxam engine analyzer, they provide a wide variety of diagnostic capabilities right in the shop. It s important to read the operator s manual carefully to understand what your dynamometer can and cannot do. Better yet, call the manufacturer of the dyno you presently own or plan to own to discuss capabilities and upgrades. Some makers we talked with have plans in the works for additional software that will provide fuel mileage checks so that actual fuel 46 November 2000

6 economy tests can be provided for customers. Future OBD II systems may call for clearing trouble codes by actually driving the vehicle. Software should soon be available to perform manufacturer-specific OBD II drive traces that can be run on the dyno to accomplish that objective. Safety First...and Always Always take precautions with a dyno. Use the restraining belts, block the wheels and inspect the tires before running up to speed. And know the limitations of your machine. Note that certain laterally adjustable dynos (LADs) cannot be used for some of the tests mentioned earlier. Keep everyone clear when a dyno is in operation. Remember, a stone or wheel weight spun off a wheel spinning at 55 mph can be as dangerous as a bullet. To avoid overheating, use a good-quality fan to provide the kind of airflow to the radiator that would normally occur when the vehicle is driven. Some manufacturers have fans available that do a great job, and these can be wired directly into their equipment. When it comes to buying and using a dyno, there are some really exciting possibilities. Once you get a taste of using your basic smog test machine for more than just inspections, there s a strong likelihood that you ll soon want to expand to a higher-performance dyno, which can handle far more testing scenarios and is designed for greater power absorption. As dyno expert Tom Fudali from Snap-on Diagnostics points out: Your dyno should be working 80% of the time doing inspections or diagnosis. If it s busy only 50% of the time, you need to think seriously about advertising and expanding the use of the equipment. When you get the word out that your shop provides the kind of quality work dyno testing makes possible, the business will come. I guarantee it! For a free copy of this article, write to: Fulfillment Dept., MOTOR Magazine, 5600 Crooks Rd., Troy, MI Additional copies are $2 each. Send check or money order. November

DYNAMIC DUO. Lab scopes and current

DYNAMIC DUO. Lab scopes and current DYNAMIC DUO Combining the data acquisition capabilities of a lab scope with the versatility of a current probe gives you a powerful diagnostic tandem that s awfully hard to beat. BY MARK WARREN Lab scopes