Part 4: Understanding Droop

One question I get sometimes is what does the droop setting do on the E23 and E18 transmissions? In this video we will explore the purpose of the droop setting. The droop setting is the amount the engine is allowed to be lugged down when the tractor is at full load before it downshifts to prevent over lugging or stalling the engine. At the top of the custom settings page you can see we have two droop settings. One for when the PTO is on and one for when the PTO is off. You can see these settings are a percent instead of a specific engine speed setting. The reason why is because the droop setting is based on the maximum allowed engine speed. For example, I have a PTO off droop setting of 20%. When FieldCruise is turned off, the droop setting is 20% of 2100 RPM or about 420 RPM. This means under full load, the tractor will lug down about 420 rpm before it begins to downshift. When fieldcruise is on with a setting of 1800rpm, the droop setting is now 20% of 1800 or about 360rpm before it begins to downshift. You can see by using a percent setting, the transmission can automatically recalculate the shift points when maximum engine speed is adjusted. This chart shows the relationship between engine speed, wheel speed and load. Now this chart shows smooth lines to help show our illustration. But in reality, since the E18 and E23 transmissions are still gear type transmissions, these smooth lines will look more like stair steps. This is because the tractor is monitoring changes in actual engine speed due to changing loads and for how long those changes last before it decides to make a shift and adjust engine speed. The idea of this logic is to maintain efficiency and a consistent ground speed as often as possible. Starting at the left with a light load, the tractor will shift up and throttle back to a low engine speed while maintaining a constant wheel speed. As the load on the tractor increases, the tractor will compensate by increasing the engine speed and and downshifting the transmission while maintaining the constant commanded wheel speed. The engine and transmission will continue to shift down and throttle up as the load continues to increase until the engine reaches the maximum engine speed. At this point, if the load increases even more, the engine will remain commanded to maximum speed, but the actual engine speed is decreasing because it is being lugged down by the load. The transmission will not shift down anymore, which means we are also losing wheel speed. When the engine is lugged down to the droop setting, the transmission will begin to downshift, sacrificing ground speed to make sure the engine speed does not decrease any further. In closing, remember, the droop setting is the amount the engine is allowed to be lugged down when the tractor is at full load before it downshifts to prevent over lugging or stalling the engine.