X15 Cruise control droop and engine brake response.

[Chamberpains]

To the OP, is your speedo right? Are the tire rotations in the ECM correct to what size tire you have.

**edit** I see now that you have the lower droop set to 2 mph. Yes, zero out the lower drop. Its giving you an extra 2 mph above the set speed. I also max out the upper droop to 3 mph. It keeps the cruise from being so aggressive when confronted with a slight uphill out on the flats with CC on.

I believe that LRT1549 has which droop is which backwards. If you can correct this, it'll keep the quick answer readers from getting it backwards as well.

I pulled this for any one wondering what droop is. (It used to be simply googled and found on cummins site but not any more)

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Cruise Control Lower Droop:

During normal operation, as a vehicle negotiates a down-hill grade, the fueling required by the engine to maintain the set vehicle speed will progressively decrease. By slowing the reduction in fueling and allowing the vehicle speed to exceed the cruise control set speed limit by a small amount, the positive effects of momentum can be utilized in anticipation of the next up-hill grade. Cruise Control Lower Droop refers to the increase in speed above the set vehicle speed that the vehicle may travel in down-hill circumstances. The available Cruise Control Lower Droop range is between 0 - 3 MPH. Setting Cruise Control Lower Droop to 3 MPH will allow the vehicle to exceed the set vehicle speed by 3 MPH before limiting fueling and provide the maximum benefit that may be gained from vehicle momentum. Setting Cruise Control Lower Droop to 0 MPH will minimize the effects of momentum but will provide the best speed control during these circumstances.


Cruise Control Upper Droop:

During normal operation, as the vehicle climbs an uphill grade, the Electronic Control Module will provide progressively increasing fueling to the engine in order to maintain the set vehicle speed. Continued up-hill climbing could eventually result in the maximum fueling rate being attained with little to no positive impact on vehicle speed. Cruise Control Upper Droop can minimize fuel consumed in these circumstances by automatically reducing the set vehicle speed by between 0 - 3 MPH. The time the engine spends at maximum fueling is thus reduced and fuel economy positively influenced. Setting the Upper Droop to 3 MPH will provide the best fuel economy benefit, while setting it to 0 MPH will provide maximum performance in these circumstances with no positive effect on fuel economy.