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Chat Area => General Car Chat => Topic started by: Terbs on 07 November 2012, 14:28:04

Title: To cruise or not to cruise
Post by: Terbs on 07 November 2012, 14:28:04
Straight question, chaps and chapesses.........

What is the most ecnomical type of driving....Self or cruise control !!!!!!!!

I had always assumed cruise control would be best, but it seems when I knock it off, the screen seems to give me a better readout :)
I have not put this to the test on a motorway yet, but as I have to go to Brackley every Monday, I shall have the oportunity to test.

And before TB comes in with a wisecrack...yes I do know which button to press..........(well, most of the time) ;D ;D ;D ;D
Title: Re: To cruise or not to cruise
Post by: Kevin Wood on 07 November 2012, 14:32:50
It's the same engine hauling the same car, cruise or not. Not worth wasting your life worrying about it, TBH, because the difference will be minimal.

At least on cruise you aren't tempted to gradually increase speed, which can be a problem with a V6, since 70MPH is no less noisy than <mumble> MPH. :-[

Then again, cruise can't anticipate hills, so might be worse then as it has to change down late.

Swings and roundabouts.
Title: Re: To cruise or not to cruise
Post by: tunnie on 07 November 2012, 14:36:37
I'm lazy, so use cruise. Balls to fuel use!  ;D
Title: Re: To cruise or not to cruise
Post by: Andy B on 07 November 2012, 14:36:48
Agreed with KW.
The trouble with cruise is that if you knock it off for whatever reason, it's too numb to accelerate gently till it reaches the previous speed. It has to get you back NOW! And that uses more fuel than if you gently accelerated back. Over a journey though, the difference would be minimal and once set, you don't then need to look at your speedo to check.  ;) ;)
Title: Re: To cruise or not to cruise
Post by: tunnie on 07 November 2012, 14:45:26
Will add the other problem with Cruise is you pull out to overtake, guy in front will often speed up and slow down where you are a constant speed.
Title: Re: To cruise or not to cruise
Post by: aaronjb on 07 November 2012, 14:51:32
The trouble with cruise is that if you knock it off for whatever reason, it's too numb to accelerate gently till it reaches the previous speed.

How do you get it to 'resume'? The manual talks about it, but I've never been able to get that to work in my car.. it appears all I can do is 'set current speed as cruise', 'cancel cruise' or when cruise is active speed up/slow down..

Tunnie's point is very valid - I've had that so many times on the M40 and it drives me absolutely bonkers.
Title: Re: To cruise or not to cruise
Post by: omega3000 on 07 November 2012, 15:11:54
Throttle response is much better using the stalk buttons but not as good as the carlton manual box .
Title: Re: To cruise or not to cruise
Post by: Kevin Wood on 07 November 2012, 15:49:27
The trouble with cruise is that if you knock it off for whatever reason, it's too numb to accelerate gently till it reaches the previous speed.

How do you get it to 'resume'? The manual talks about it, but I've never been able to get that to work in my car.. it appears all I can do is 'set current speed as cruise', 'cancel cruise' or when cruise is active speed up/slow down..


With cruise cancelled, the "slow down" button will resume the last cruise control speed selected. You need to be doing around 20MPH or more for it to kick in from memory.
Title: Re: To cruise or not to cruise
Post by: Terbs on 07 November 2012, 16:12:20
Hmmmmm, very interesting points :y

I will say, that getting on the M40 at Wycombe and going up to M42, I set at 70mph, and by the time we got to M42, the range readout had incread by a fantastic amount....I mean a few hundred miles !!!!!!! Obviously, I thought this must be economical sense. The motorway was quiet, so I did not have to vary much :y
But coming back from Brackley on Monday, the cruise was set, and seemed constant at 30mpg, but when I knocked it off, I seemed to have a readout of up to 38mpg steady....dropping for uphill, and rising dramatically for off throttle, whereas on cruise, the going downhill consumption did not drop as much, and never up to the 999mpg you get when coasting

Hope that made sense ;D ;D
Title: Re: To cruise or not to cruise
Post by: aaronjb on 07 November 2012, 16:17:23
The trouble with cruise is that if you knock it off for whatever reason, it's too numb to accelerate gently till it reaches the previous speed.

How do you get it to 'resume'? The manual talks about it, but I've never been able to get that to work in my car.. it appears all I can do is 'set current speed as cruise', 'cancel cruise' or when cruise is active speed up/slow down..


With cruise cancelled, the "slow down" button will resume the last cruise control speed selected. You need to be doing around 20MPH or more for it to kick in from memory.

I'll try that again next time I'm on the motorway  :y I'm sure that's what I was doing.. or maybe I was pressing the 'increase speed' button  :-[
Title: Re: To cruise or not to cruise
Post by: Terbs on 07 November 2012, 16:23:05
You got me thinking now about the 'resume speed'....I'll try that Saturday....I'm off to Swindon for a few days down the M4 :y Cars will be idle till then
Title: Re: To cruise or not to cruise
Post by: brendan1983 on 07 November 2012, 16:51:26
Cruise will use more fuel - however the difference will be minimal... You'll notice more of a difference in an area with lots of hills/long gradients.

Best is to allow the car to speed up slightly on downhill sections and then allow it to slow gradually with a fixed throttle position.
Title: Re: To cruise or not to cruise
Post by: henryd on 07 November 2012, 17:38:50
Older cruise systems are not so good,my disco is vacumn/mechanical and you can feel the throttle pedal going up and down much more than it would if I was driving normally,DBW systems should be much better
Title: Re: To cruise or not to cruise
Post by: 05omegav6 on 07 November 2012, 18:02:39
Never seems to get much over 165mpg on overrun in top, drop a cog, foot off throttle and straight up to 999 ::) guess that in top the engine has to 'work' in order to compensate for less available torque below 2000rpm :-\

The MK3 Granada system was a Vacuum/mechanical system. Was a bit strange when you set a speed because the system used to pull on the throttle cable, pulling the pedal down and away from your foot. DBW, being ECU controlled doesn't do this and also doesn't seem to control downhill speed anywhere near as well as the old Ford set up :-\ (found this to be the case in the Vectra C as well).
Title: Re: To cruise or not to cruise
Post by: Kevin Wood on 07 November 2012, 18:24:59
Never seems to get much over 165mpg on overrun in top, drop a cog, foot off throttle and straight up to 999 ::) guess that in top the engine has to 'work' in order to compensate for less available torque below 2000rpm :-\

The MK3 Granada system was a Vacuum/mechanical system. Was a bit strange when you set a speed because the system used to pull on the throttle cable, pulling the pedal down and away from your foot. DBW, being ECU controlled doesn't do this and also doesn't seem to control downhill speed anywhere near as well as the old Ford set up :-\ (found this to be the case in the Vectra C as well).

999 MPG means it's in overrun cutoff. In top gear it may not be above the RPM threshold for overrun cutoff, hence the high (but not silly) MPG figure.

Not sure what the threshold is for a manual setup. It's around 1000 RPM for an auto, but can believe the manual config will set it higher to stop the engine stalling if you suddenly knock it into neutral.
Title: Re: To cruise or not to cruise
Post by: TheBoy on 07 November 2012, 19:07:11
I have done some fairly extensive testing in my 3.0l on this, and cruise does use more fuel.

Not tried with the 3.2, as too many 'tards on the roads now in the UK to make much use of cruise.
Title: Re: To cruise or not to cruise
Post by: 05omegav6 on 07 November 2012, 19:16:01
Came in useful on the truck what which I drove from Shoreham to Ashford and back :y 56mph all the way there, and 56mph all the way back ::)
Title: Re: To cruise or not to cruise
Post by: Entwood on 07 November 2012, 20:21:33
Cruise can save you money .... and not just on speeding fines !! 

I agree that IF you are able to sit and control the speed accurately using the throttle you will get better mpg than using cruise, which as said is a little harsh at times.... however, if - like me - the tendency when not using cruise is to slowly speed up as the car is so responsive and fun to drive, then the mpg will be worse because quite simply .. the faster you go the more fuel you use .. :)
Title: Re: To cruise or not to cruise
Post by: 2woody on 07 November 2012, 20:28:17
using cruise will probably cost you 5 to 10% over doing it the "normal" manual way, more if you aim to drive economically.
Title: Re: To cruise or not to cruise
Post by: VXL V6 on 07 November 2012, 20:31:35
Well Not much opportunity to use cruise on my Journey this Afternoon - Worcester to Hastings, but from a full tank of fuel last night (at home - Solihull) I have done 240 miles and have a range of 494 miles....  8)
Title: Re: To cruise or not to cruise
Post by: Terbs on 07 November 2012, 21:07:26
Forgive my ignorance :y

But...with my V6 (2.5 or 2.6) irrespective of the comparison against each other.....if I set cruise control at 30mph, you are saying I would use less petrol than setting cruise at 60mph :)
I know the logical answer is yes, but I was led to believe that with these type of engines, a higher speed was more economical. (speed within sensible parameters, obviously)
Title: Re: To cruise or not to cruise
Post by: Entwood on 07 November 2012, 21:56:32
Forgive my ignorance :y

But...with my V6 (2.5 or 2.6) irrespective of the comparison against each other.....if I set cruise control at 30mph, you are saying I would use less petrol than setting cruise at 60mph :)
I know the logical answer is yes, but I was led to believe that with these type of engines, a higher speed was more economical. (speed within sensible parameters, obviously)

30 / 60 are too far apart to use as comparisons, as the car would not be in the same gear for a start !! At 30 you will use more fuel than at 60 for sure .. due to gearing !!

A better comparison is 60 / 80 ... air resistance (drag) increases in proportion to the square of the speed .. so if we make up a few units .. drag at 60 = 3600 units, drag at 80 = 6400 units ...  the drag has almost doubled for a 20 mph increase... so the amount of energy needed to overcome the drag has also almost doubled !! That energy can only come from extra fuel burned.

If cruise keeps you at 60 you use less fuel than if manual driving starts to edge towards 80 .. :)

Title: Re: To cruise or not to cruise
Post by: henryd on 07 November 2012, 22:33:28
As government fuel figures centre on the 56mph reading that is where most cars are set up to be at there most fuel efficient.
Title: Re: To cruise or not to cruise
Post by: TheBoy on 07 November 2012, 22:37:35
As government fuel figures centre on the 56mph reading that is where most cars are set up to be at there most fuel efficient.
Probably more 90kph, as the Euro market is more important. Oh yeah, thats 56mph ;D
Title: Re: To cruise or not to cruise
Post by: Terbs on 07 November 2012, 23:28:33
Thanks fellas....most enlightening :y
Entwood....sit down mate, and take a pill ;D ;D ;D ;D
Title: Re: To cruise or not to cruise
Post by: plym ian on 07 November 2012, 23:36:09
The trouble with cruise is that if you knock it off for whatever reason, it's too numb to accelerate gently till it reaches the previous speed.

How do you get it to 'resume'? The manual talks about it, but I've never been able to get that to work in my car.. it appears all I can do is 'set current speed as cruise', 'cancel cruise' or when cruise is active speed up/slow down..


With cruise cancelled, the "slow down" button will resume the last cruise control speed selected. You need to be doing around 20MPH or more for it to kick in from memory.

I'll try that again next time I'm on the motorway  :y I'm sure that's what I was doing.. or maybe I was pressing the 'increase speed' button  :-[
don't do what I did, on motorway cruise on at 70mph came off motorway got to top of slip road came off brake to pull out as was clear whent to indicate and caught resume button. brown pants time as car was at 30mph trying to accelerate to 70mph again