2014 Ultimate 1 Ton Challenge results

AH64ID wrote:


The second comment is also about a chassis dyno and how they are effected by engine loading. To make 50 more ft/lbs of torque at 2500 rpms takes 35 more hp, you know the equation since you posted it. So you should have no problems understanding that at 2500 rpms 800 ft/lbs is 380 hp, and 850 ft/lbs is 405 hp... A difference of 35, weird right!. There you go , gears made hp... Um no, not really the point if that was to show the issues of a loading the engine on a chassis dyno, not real world power production. On a chassis dyno taller gearing allows the engine to make more hp, and more torque.. Not because of the gearing but because the load required to spin the tires is higher.

If a vehicle on the dyno is ran in 5th and makes 415/800 and then ran in 6th and makes 425/850 the hp curves are not identical. Which one do you think is more accurate? What do you think made the extra hp in the middle of the rpm band? I can tell you the gearing didn't do it, it just facilitated it.

Think about it from the engine's perspective. An engine is placed on a bench and is running at full throttle and loaded down to 2500 rpm. The power output is measured at the crank and determined to be 500 HP. Now hook it up to a driveline and load it down to 2500 rpm. The engine has no knowledge of what happens down stream of the crank. The power measured at the rear wheels will be less than 500 HP due to inefficiencies in the driveline. If in 5th gear you happen to measure less power than 6th gear it is because more power is being turned into heat while running through 5th or because your dyno is not capable of taking accurate measurements at different wheel speeds or a combination of the two. So you could say gears make heat ... therefore consume power.