2nd Gen Non-Engine/Transmission Why would cruise control lower MPG?

[AKDrifter]

Just full of basic questions are'nt I. So why would cruise control lower MPG, how does CC work?



Someday I'll answer all these basic questions once I've learned. Take some of the heat ofk you regulars. Thanks, Paul

 

[Gary - K7GLD]

CC will increase average fuel consumption because it cannot anticipate proper speed when approaching hills, or properly adjust throttle setting for headwinds or inclines - it merely senses that speed has dropped below the set speed, and stupidly increases throttle as much as it can to maintain set speed. A driver, on the other hand, can estimate speed needed to maintain a reasonable speed up an approaching grade, and then only apply as much throttle as needed to maintain that speed properly. CC is not bad on flat travel, without wind to adjust for - but in changing landscape and wind conditions, the CC "luxury" can cost you - not a lot, but some fuel consumption...

 

[moparguy]

When you drive by wire (or hose as with cruise) the cruse control tries to maintain the exact speed you've programed. If it starts up a hill, it'll go to full fuel. If you were doing the driving, you would likely speed up on the down hill side, then let your speed drop as you approach the top of the hill, using less fuel than if you had maintained say, 60 mph.



Clear as mud? Just trust, if driving in hilly country, you can beat the cruise. If however you're in flat Kansas country, the cruise is the better choice.



The main thing is "Enjoy the trip".



RJR

 

[moparguy]

Dang, beat out by "Fast Fingers Gary".

 

[illflem]

What the others said plus the cruise on our trucks is too sensitive, you set it on 60, it stays at 60. Diesels are at their top efficiency when the throttle is set in one position and left there, none of this up and down business the CC does.

I slowed down my cruise by restricting the vacuum hose to the throttle actuator and gained average 2 mpg in in cruise, about the same as it is while driving by foot. The speed varies by about 5 mph now and is slow to return to the set speed if you punch reset but you can help it with your foot.

A throttle cable like a tractor has would net even more mpg but could be dangerous.

 

[AKDrifter]

Thanks for the input guys but, I already knew that. I rarley drive in the hills/ mounians on CC for those very same reasons.



Mabey I was thinking along the lines of some computer controlled something or another, hell, I don't know what I was thinking, just reading more into it than needed. But thank you all for your time.



Paul

 

[dflack]

throttle actuator hose restriction?

OK, I'll bite... please provide further technical data as to procedure to restrict/modify the throttle actuator hose. I have tried to document the cruise control penalty, my belief is at least 1 mpg. I would be willing to sacrifice some speed wander to make this up... .

 

[Steve Campbell]

I think I copied this from Illflem once....

"To solve this problem, you will need a precision adjustable needle valve to put into the vacuum line to the vacuum servo on the servo control module that set under the battery. By turning it almost all the way off and allowing only a minute amount of vacuum to take place, you will slow the throttle affect and thereby dampen out your surge affect. "

 

[lschultz]

I know how the cc works on these trucks but it don't make no difference on the vw whether its straight roads,hills,wind they get better mpg with the cc-53 mpg best yet.

 

[illflem]

I just used a 5¢ barbed 1/4" hose coupling filled it with glue then poked a hole though it with a needle, the hole needs to be very small, a 1/64" drill bit didn't do it. Then cut the vacuum line going to the CC actuator under the driver's side battery and put it back together with the modified coupling. That's it.

Now when the PCM calls for more throttle the actuator moves so slowly that the pcm is usually calling for less throttle before the actuator has a chance to move the throttle much.



Somewhere along the line the actuator was replaced by electronics, not sure which year though. If yours is electronic you're out of luck.

 

[Gary - K7GLD]

YUP - my CC on the '02 is electronic - no vacuum lines or actuator - works VERY smoothly, and big improvement over the mechanical types I've had in the past - dunno if they're any better economy-wise in varrying terrain tho...