LOVELAND PASS, CO – At the halfway point of a two-week “summer road test” conducted by Freightliner LLC engineers, over half a dozen of the company’s trucks are trundling up and over the 11,900-ft Continental Divide. Onboard computers record in minute detail between 75 and 100 data individual streams of data – engine temperature, road speed, fan on/off time – all in an effort to gain insight into the issues that could face truck OEMs as the 2007 emission rules draw ever closer.
“The real focus of our summer tests this year is to gain more knowledge about the performance and cooling needs of 2002 and 2004 emission-compliant engines, so we can apply what we learn to what’s facing us in 2007,” said Ramin Younessi, chief test engineer for Freightliner. “We’re also looking at HVAC performance and the integration issues between the engine and transmission and how those two factors will impact what may happen in 2007.”
Journalists invited by Freightliner to join part of the two-week summer test traveled from Rock Springs, WY, to Frisco, CO, and then spent a day at Loveland Pass. There Freightliner’s test engineers drove several different configurations – Western Stars pulling dry van tractor-trailer, Sterling tractors hitched to tanker-trailer, M2 Business Class straight trucks, Sterling Acterra straight trucks – over the pass to record high-altitude performance data.
“Getting real-world road mileage under these conditions is extremely important for our ’07 research,” Younessi said. “We’re also fine-tuning our current models as we record and examine temperature and cooling flow, looking at threshold points we’ll need to watch under heavy load situations.”
The second half of the summer test takes place in Laughlin, NV, where the trucks run up a 12-mile, 6% grade in 110 to 120 degree Fahrenheit conditions. Not only will those tests involve a variety of experimental technology – turbochargers and fuel injectors to name just two – but will also test one potential strategy for handling the higher heat loads generated by post-’02 engines: de-rating.
“The cooling system can handle only so much heat, so under extreme loads, we’re looking at ‘de-rating’ the engine in increments to reduce the chances of overheating,” Younessi explained. “This involves reducing the available horsepower slowly. The rule of thumb is you can reduce available hp by about 10% before the driver notices it. So our goal will be to see how much and how smoothly we can reduce it—so the driver doesn’t feel it.”