Originally Posted By: jorton
Our 2012 Patriot has been difficult for me to get used to, but on a recent trip I found out a little more. This a 3000 pound small SUV with a 2.0l 4 cylinder engine. On a stretch of highway with several long up hill down hill grades she shined. With speed control on the engine never raced going up hill but if I tried to maintain speed manually the engine raced to 4000+ rpm. I was surprised that the the computer can maintain speed on long up hill grades without racing the engine, but I could not maintain speed manually without racing the engine. Just wanted to share an observation.
While our MDX doesn't vary its operating to that degree, it does seem that the torque converter stays engaged more while in cruise control than without. I have a theory that explains it. I don't know if it's right, or even if my perception about the torque converter is accurate, but nonetheless...
If you're not using cruise control, the computer doesn't know what's coming next, so to speak. You could suddenly call for more throttle and it needs to be ready. It could downshift, or move to a shorter ratio in the case of a CVT, but that would take time. It's my theory that in hilly environments, and if cruise control is not being used, the computer is a little more conservative with transmission operation, for faster response on the go-pedal if required. In other words, it stays poised to provide more sauce if you want it.
On the flip side of that coin, if you are using cruise control, the computer can at least make an assumption that its directive to maintain that set speed won't change, and it doesn't expect to have to suddenly provide more power, so it can be a little more liberal with tieing the engine down to a lower speed to save fuel...just enough that it can maintain speed, but without much power in reserve.
