Question of Cruisecontrol

yea, the CC is not designed for various terrain efficiency. I find compensating for hills like you described more efficient. Like most cars, the CC is designed to maintain the desired speed.

Although, it can be more efficient if the freeway is relatively flat since the CC gives ONLY enough power to keep your speed.

 

From my experience, CC is much worse.

 

I used my cc to travel from Orlando Fl to Bryan Tx only stopped 2 times for fuel, speeds varied from 60- 75mph...

I found it didn't change the mpg, except when I came off of overpasses the ICE would shut off and the EV would keep me at the set cc speed..

I did have the ice shut off a few times during the trip on flat sections and again the EV kept me at speed for approx. 5 miles or until I hit another grade .

The highlights to the trip where all the stares from other drivers trying to figure out what kind of car I was driving, remember this was Aug/05, there wasn't a lot of PriusII's on the roads around here I only saw one other Type II Prius on the trip and that one we played follow the leader from mobile to bilouxi (a real hottie college chick driver)..

I guess it just boils down to your driving habits for MPG's

 

Perhaps I'm still leraning how to drive a Prius, but in mycase, CC does a good job on the interstate.

I use it when traffic thins out enough so that I'm neither blocking traffic nor wildly weaving to get around traffic moving slower.

Usually 52 mpg when I drive, and 54 when CC drives.

 

On my Classic Prius, CC always produces worse mileage than I can get by driving manually, but I still occasionally use it on long trips because I get tired easily when driving and the cruise helps a lot with that..

As Mike described, the CC seems to apply gas to maintain speed and then switches to compression braking to slow down, which seems to me to be a very simplistic control loop that should give quite poor mileage.. In real life driving, you vary the amount of gas pedal depending on how fast you need to accelerate (ie, if you drop only 1 or 2 MPH, you don't need to go to full throttle to accelerate- you'd either just let it go or very gently touch the pedal and accelerate slowly to get back up to speed), but in comparison, the CC seems to apply a fixed amount of throttle to get the car back up to speed fairly quickly- in terms of acceleration, the CC could probably benefit from a wider speed range (perhaps 3-4 MPH variation vs. the tight +/-1 range) as well as variable throttle. In terms of overspeed condition, in real life, if you're going a bit fast, on the Prius, you'd just let off the gas pedal and the regen will bring you back down quite quickly, while you also benefit from the regen. The CC in this case controls the engine RPM to get compression braking, and you use gas to slow down without getting anything in terms of regen (according to my Miniscanner display- there is still current drain vs. charging when the CC compression brakes)..

In short, the behaviour of the CC seems to me, to do exactly the opposite things needed for optimizing mileage so I'm very surprised that people are actually getting better mileage with the cruise- as I said, every time I use it, the thing gets much worse mileage than I can do by driving manually..

 

<div class='quotetop'>QUOTE(c4 @ May 1 2006, 10:51 AM) [snapback]248027[/snapback]</div>

I've generally gotten the best mileage using CC, which surprised me too. One reason must be the roads I use it on.

 

I have not done as well with cruise control, but I am typically in busier traffic.

 

<div class='quotetop'>QUOTE(c4 @ May 1 2006, 12:51 PM) [snapback]248027[/snapback]</div>

I think your description applies to somewhat hilly areas. If you're on a flat interstate or at least one with very long hills, then the CC doesn't hinder as much. I have never used CC much even in other cars, just for long drives on the interstate. Besides your description of the technical aspects, CC cannot look ahead and make proactive changes for an upcoming hill or bunch of brakelights coming on. OTOH, it does keep you from creeping up to speeds higher than you intended, and can be very valuable in that regard.

nerfer

 

I get my best mileage using cruise control. Maybe it is because I do not drive very long on surface streets. It is true, though, that Cruise Control has a problem with hills.