The engine maker says 74,139, or 88% of the 83,841 Series 60 engines it shipped last year were rated at over 430 hp. Of those, 23,500 were rated at 500 hp.
Bill Westcott, manager, Series 60 remarketing, attributed the steady power growth to higher gross weights, higher speeds, longer trip lengths, the need to retain drivers, and maintaining residual values.
The trend to more power led to a big drop in demand for the company's 11.1-liter Series 60 model. In 1988, when Detroit Diesel introduced the Series 60, sales were split 50/50 between the 11.1-liter and the larger 12.7-liter model. By 1992, 60% of sales were 12.7-liter models and last year they rose to 95% of the total.
With demand so low, the company decided to discontinue the 11.1-liter model for highways applications this year. It is still available for off-highway applications such as construction and marine.
The two 11.1-liter ratings (330 hp and 365 hp) have been tacked onto the 12.7-liter model, so you can now order a 12.7 liter in ratings from 330 hp to 500 hp. A 14-liter version of the Series 60 is offered at 550 hp and 575 hp, the latter rating for Freightliner buyers only.
Westcott said engine torque ratings have also climbed steadily. Over 78% of last year's Series 60 production was rated at 1,550 lb-ft or above. But the top end has plateaued at 1,850 lb.ft he said.
"We aren't going to offer engines higher than 1,850 lb.-ft because we believe that's the cost-benefit limit," he said. "If you go higher than that, you have to spend $10,000-15,000 extra to beef up the driveline and it's hard to get that back."