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Take, for instance, a pumper at 42,000 pounds GVWR with a 500-hp diesel versus a 475-hp diesel. With the 500 hp, you will get a better power-to-weight ratio, and bigger is better, right? Not necessarily. Power-to-weight is often a metric kicked around by sports car buffs, but it won’t necessarily get you better performance off the line. Focus in on the low end of the torque curve and you will find that because the 475-hp engine reaches its peak torque of 1,700 lb./ft. at 200 rpm earlier in the curve, it moves out just as fast as the 500-hp engine, which reaches 1,650 lb./ft. at 1,200 rpm.
This approach to evaluating power performance characteristics will help departments better spec apparatus engines. It will help identify the benefits of low-end torque capabilities, which in turn will help reduce response times.
Because every second counts. Response time standards from the NFPA and the Commission of Fire Accreditation International (CFAI) call for engine companies to arrive at fire and EMS events in as little as four minutes. That’s 240 seconds. Low-end torque will help shave precious time from runs, especially those with many instances of “slow-n-go” at intersections and traffic blockage.