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Alot of bad things happened in 2002... If you were one of the unfortunate fleet maintenance managers who experienced heat-related component failures in post-October, 2002 trucks, you probably have a lot of bad memories from that time. And you probably have taken steps to avoid dealing with 2007 engines, for fear of reliving the nightmare…
Well, the bad news is that underhood temperatures will be going up on 2007 trucks. Fortunately, there are a lot of people in the industry who are working hard to make sure that higher underhood temperatures will not be causing component failures like they did a few years ago.
TEMPERATURE'S RISING
"I think sometimes the estimates of how much the temperatures are going to increase in 2007 are overstated," says Jim Benson, applications engineering manager for BorgWarner Thermal Systems. "But I can tell you that, based on our field testing, it is a real concern, and underhood temps are going up. Exactly how much is very application-specific, and even engine-specific: some of them will see in the range of a 15 to 20 percent temperature increase, while others may be in the range of 12 to 17 percent. But there is a sizeable double-digit heat increase across the board."
Benson cautions that the increase in underhood temperature shouldn't be confused with the increase in engine heat rejection, the amount of heat radiated by the engine, which is projected to rise by 20 to 30 percent in 2007 engines. It's that increased heat rejection by the engine, Benson explains, that will lead to higher underhood temperatures.
"We try very hard to understand the airflow paths underhood, because if we have a very restrictive vehicle, what that leads to is higher underhood temps," he says. "If there's no exit path for the air to go to, then much of that heat that's generated stays underhood.
"Our goal is to manage that airflow, to make sure airflow gets to the components that need it, and also to direct it out and exhaust it from under the hood," Benson says. "So having enough flow path decreases that overall system resistance."
That being said, Benson stresses that the old methods of increasing underhood airflow may have reached their limits in 2007: "You can't just keep running higher and higher fan speeds, and increasing noise, and stealing all that horsepower, without doing something about it," he insists.
