The opening topic of this year’s Advanced Engineering Technology Conference came from SuperFlow’s Bret Williamson, who covered a wide range of issues related to engine builders and dynamometer operators.
Over his career, the 17-year veteran of engine testing and data acquisition systems has seen plenty of things to do and many things to avoid when working with customers, ranging from the “do” of providing the dyno cell with plenty of fresh air and water for the dyno brake to customers building a dyno cell with the operator’s area right in the line of fire of a potential flywheel explosion. He also discussed many ways to achieve successful engine dyno testing and a variety of variables.
In addition, he discussed a wide range of ways to achieve the best results from the tool, giving operators a full arsenal of ideas moving forward.
“There are some important things you need to know about test cells,” he explains. “When I go into the field I see a lot of good test cells, and a lot of bad test cells, and why these things make a big difference in the results.”
He recommends that no matter which dynamometer manufacturer’s products you’re using, one of the largest problems he encounters is test cell design. Pre-fabricated dyno cells are a large part o the marketplace, which work very well and are very quiet, according to Williamson. A pre-fabricated cell can be built very nice and quiet. Often, he finds cells that have been built by the customer, and these have both good and bad qualities. Many times, the cells aren’t equipped with the proper wiring, or aren’t clean and organized – all of these issues can prevent the cell operator from achieving quality results.
Airflow in the dyno cell must be foremost in the operator’s mind during construction. If there isn’t enough flow in the dyno cell, the engine will be sucking in its own impurities and the test results will not be repeatable.
“With a dynamometer test cell, we want the air to change eight to ten times a minute, and it needs to go across the engine. I’ve been in test cells before where I walk around and the air comes out of the ceiling, goes straight across the floor, and out the back – the engine never sees it. You need to figure out the cubic feet of the room and multiply it by ten to determine the volume of air you need to properly feed the engine,” he notes.
36 to 42-inch fans, with eight to ten horsepower motors are what’s required in many instances. Of course, test cell construction can also come down to the amount of available funds, and he says that a dyno operator should expect to pay at least as much for the test cell as is spent on the dyno itself.
An operator must take into account the types of engines that will be tested, and outfit the cell with the proper equipment to do so. For example, he recommends using a DC power supply for operators that do a lot of fuel-injected engine testing, as the ECU components and other electronics don’t like to see power fluctuations.
He spent much of his seminar time discussing test results and how to achieve repeatable, consistent performance over and above ensuring that the cell has the proper amount of airflow. Measuring pressure drop in the cell is an oft-overlooked aspect of cell design, and he says a simple manometer can be used to achieve this.
“The exhaust is going to have impurities in it, and we need to isolate the exhaust and make sure it’s not going into the engine. It’s important to manage the exhaust so that you’re not affecting the engine’s power because you’ve put some sort of restrictive exhaust on it,” he says.
A good rule is to ensure that the muffler on the end of the collector is at least double the diameter; for example, a four-inch collector should have eight-inch tubing running out of the cell to ensure that there is no additional restriction posed by the test equipment.
There are four main rules of test cell design – quality air flow across the engine, ensuring that the engine’s intake air is sealed off, the exhaust system is sealed and offers an acceptable level of noise reduction, and the capacity of the water system in a water brake dyno.
Williamson spent quite a bit of time discussing this last point. There are a variety of ways to ensure that the water system flows enough capacity to hold the engine at the proper level, and cooling the water is often the most overlooked aspect of system design.
Some customers that have built a total-loss system, and don’t need to be concerned with heating up the water in the brake system, but for customers who have recirculating systems, managing water temperatures ensure repeatable results. Any rise in temperature above 100 degrees Fahrenheit can cause issues with repeatability. A single large storage tank, a couple of water pumps that can keep up with demand, and a filter should be enough, according to Williamson.
The operator console area should also be considered; clean, neat, and organized is the order of the day, so that the operator is not constantly chasing his or her tail trying to find important items during the testing process.
Maintaining consistent engine intake air is also a critical factor of the testing process, as is data acquisition. The software must fulfill four critical parameters; be easy to use, be configurable for the combination being tested, adapt to the operator’s needs, and must make data analysis convenient.
Williamson also provided a simple list of tuning tips for the testing process.
- Calibration of Sensors
- Keep oil and water temperatures consistent
- Fuel system flow, pressure, and temperature consistency
- Measure airflow
- Optimize test methods for engines being tested
- Be consistent as an operator, with smooth throttle transitions
- Optimize air/fuel ratio for atmospheric conditions
- Minimize testing on bad air days
- Tune for maximum torque
- Keep spare parts for the dyno
And most importantly, back up all computer files.