As for engines themselves, testing continues to take on greater importance as off-highway OEMs and suppliers work toward achieving Tier 4 emissions targets. Many labs are already heavily engaged with testing to meet the Tier 4 Interim phase targets of 2011 and will only increase the proportion of work for Tier 4 as the final phase approaches in 2014.
“We’ve got quite a bit of pull-ahead work, in fact, for Tier 4 Final, so we’re actually overlapping two standards, doing the development work concurrently,” said Robin Woodward, General Manager of Perkins Engine Co. Ltd.’s Global Engine Development (GED) center. “We’re still growing, and the foreseeable next five or six years are going to be really flat-out on Tier 4.”
As part of its £19 million test facility investment, Perkins will be installing 12 new mechanical validation cells and five endurance cells at its GED in Peterborough, U.K., over the next two years.
GED currently has around 20 performance and emissions test cells equipped with data acquisition systems supplied by D2T of France. To make room for the 12 additional cells, Perkins is reallocating space previously used by other test cells and stripping out the old equipment and replacing it with all new systems.
The GED has always conducted engine development tests; however, as aftertreatment and associated control systems have become necessary, complexity has grown and led Perkins to invest in these additional cells.
“If you’re using, for example, an EGR system and a diesel particulate filter kind of system, there’s a lot of extra data that you really want to collect as you go along, so data richness is a critical requirement for us,” Woodward said. “And that will become even greater when we have further NOx reduction systems at Tier 4 Final.”
This added complexity and often around-the-clock test cell operation has made maintaining the data quality resulting from these tests increasingly difficult.
“As the test throughput goes up, you’ll find that people are less and less able to keep an eye on what’s happening,” Woodward said. “You have to have some real technological help to enable you to detect anomalies that are going on in the data collection. Equipment goes wrong every now and again, and you need to be able to detect those things before you collect a lot of data that is of poor quality.”
With all the changes being made as a result of Tier 4, there can also be a great impact on the engine’s NVH characteristics. In response to this, GED also upgraded some of the data acquisition systems of its hemi-anechoic noise chambers.
Once basic calibrations for the engine have been selected, engines are placed inside the chamber, data is collected on the noise, and a noise ranking is determined. To determine the proper noise characteristics for an engine, there is a lot of interaction with outside clients.
“We work very closely with our customers, many of whom are internal customers to us now within Caterpillar, to really get a package of a machine that works from a noise, vibration, and harshness perspective,” Woodward said. “You can do a lot with the engine, but when you install things, you can actually either undo some of that good work or you can improve a situation a lot just by paying attention to the right things in the vehicle itself.”
Woodward said that while engineers are getting better and better at predicting overall engine noise, noise character is not something that can be very well predicted.
“[Noise character] is one of the things that, more subjectively, people are interested in,” Woodward said. “That’s something you can’t really do through simulation. There are some rules of thumb that you can use, but you really need to get in there and test it.”