Does cruise control use more fuel?
This applies to modern cars.
This is my style of driving a car without cruise control. I accelerate gently, not sluggish or harshly. When i get to my desired speed i lift my foot slightly off the accelerator so that i am cruising at the desired speed using as less fuel as possible. When i go down a hill i lift my foot off the accelerator and let gravity do the work. Only apply accelerator when required. (No i am not the type who does 56.00 mph on the motorway, i do like to drive my car to the full within legal speeds of course ;-) )
Imagine you are on the motorway with the cruise control set at 70 mph. You have to apply brakes which automatically disengages the cruise control. When you press resume does the cruise control make the car accelerate harder than normal hence using more fuel?
On a long journey is it economical to use cruise control compared to manual input (your right foot)?
|
>>>Does cruise control use more fuel?
Yes.
>>>When you press resume does the cruise control make the car accelerate harder than normal hence using more fuel?
Yes.
Problem is it can't anticipate as it sees the moment rather than your view of what is happening ahead.
|
I look upon cruise control as a device that lets your right foot take a break on a long journey.I also use it as a speed limiter on roadworks.Other than that its best to use your right foot.
|
>> On a long journey is it economical to use cruise control compared to manual input (your right foot)?
>>
Yes, I find it more economical.
M
|
|
If you have used CC you will know how much cars not on CC vary their speed. I find it more economical on long journeys, it shuts off the fuel on downhill bits, (diesel, don't know about petrol engines), which compensates for maintaining speed on uphill bits. Does slowing down when going uphill save fuel? If it does it must be so little I don't care, one motorway slip road acceleration will burn off far more anyway.
|
I think cruise uses more fuel on undulating A roads.
I can feel the CC3 'pulling' when I wouldn't be accelerating on manual throttle.
There's an obvious answer, but I rather like using cruise at moderate speeds on A roads.
Using the 'Res' button, it's even possible to set the car up for a bend reasonably well and accelerate gently from the apex.
One thumb control - very satisfying.
|
|
People who enter economy contests dont use cruise control. There is your answer.
|
>> People who enter economy contests dont use cruise control. There is your answer.
>>
You mean the ultimate mimsers. :-)
I assumed we were talking about real world day to day driving.
Last edited by: Old Navy on Wed 23 Jun 10 at 10:16
|
|
Merely answering the question.
|
>> Merely answering the question.
>>
No problem. :-)
HGV's use cruise control, (in my day it was a house brick or suitable length of wood :-) ). Hgv operators monitor fuel use, and would not have it fitted if it wasted fuel.
|
I use it on motorways and dual carriageways in the lorry.
Had one on the Hyundai Coupe but found it jerky, didn't like it. The one on the lorry (Volvo) is much smoother.
I tend to find that those lorry drivers who decry CC are the same ones who would welcome the return of crash gearboxes, double de-clutching and roped and sheeted flatbed trailers. Myself, I'm glad that I was around to learn the skills, but I don't miss 'em in daily use.
|
''would welcome the return of crash gearboxes'',
Sun was a blinder today, my ears got burned.
Anyway i use CC every day in truck, set at 50mph dual and m'way...hourly paid.
CC in the pick up can be a pita, on undulating roads it causes kickdown to kick in too easily where a gentle increase in throttle will easily power up hills without a downchange.
Now if only modern trucks came with a proper crash box, few would be able to drive them and wages would be back where they should be.
..;)
Last edited by: gordonbennet on Wed 23 Jun 10 at 22:49
|
Cruise control keeps your speed constant by varying the throttle (more on uphills, less on downhills).
Driving for economy is the opposite on mway - keeping the throttle constant and the road speed changing for hills etc. ease off the throttle on steep enough downhills.
|
CraigP>> Driving for economy is the opposite on mway - keeping the throttle constant and the
>> road speed changing for hills
I agree it feels logical, but does anybody KNOW this to be the case?
|
>> I agree it feels logical, but does anybody KNOW this to be the case?
Yeah, I know the case for my car. For the Bosch MED (Motronic, Electronic Ignition, Direct Injection) ECUs as fitted to various VAGs, BMWs etc. the ECU is designed to run the engine based on torque requirements.
It calculates the required torque based on various inputs:
- throttle position
- traction control
- auto gearbox shift point
- air con compressor
- cruise control
It's more complex than that, it's also paying attention to other (relatively) special case stuff like engine temperature, are we in catalyst warm up mode?, idle speed regulator, lambda control etc. but the above does for a general idea.
Once it works out the required torque, it goes about getting that via 2 methods:
- cylinder charge (long term trim, these engines are often mated with forced induction)
- fuel quantity, ignition point (short term trim)
It's a bit more complex than this again, these engines will run in different modes depending on various inputs. With these engines, they'll switch between stratified charge mode, homogeonous charge mode and homogeonous lean charge mode.
Back to the cruise control case - the input to the ECU from the cruise control speed selection means it will work as i said above, and when you disengage CC and go manually, it'll work like i said too.
Please send me £50 via paypal for this lecture you have enjoyed ;-)
Bibliography:
- VW SSP 253, Direct Petrol Injection System with Bosch Motronic MED Design & Function. (Google it, it's available on t'internet)
|
I would guess there is a complete spectrum, from a perfectly level road with no traffic where CC will obviously be better at maintaining a constant throttle position than a human foot, through to an undulating road with traffic where CC will virtually always be doing the wrong thing, because anticipation is of prime importance.
Somewhere in between, depending on actual conditions, comes ordinary driving.
Things it won't do:
Spot traffic bunching half a mile ahead and ease off so as to maintain a constant but slightly lower speed.
Let the car rip on a long clear downhill section, knowing the momentum will be useful on the next hill.
Ease off and let the car slow up on a hill, rather than opening the throttle to pour in petrol to maintain speed wastefully.
Watch the brake lights of the cars ahead of the cars ahead.
Tell you the car in front has done an emergency stop.
Some of those things must be easily achievable with current technology - are there any systems with built in intelligence, able to learn from experience?
|
>>
>> Some of those things must be easily achievable with current technology - are there any
>> systems with built in intelligence, able to learn from experience?
>>
Most are available. Look up "adaptive cruise", or if it's Honda, ADAS, or if it's Ford or Jaguar, "forward alert", or if it's Mercedes, "distronic" or "distronic plus"...etc etc.
|
Another aspect of CC is the reduction in mental effort, it is sub conscious but you are constantly calculating your speed, the relationship to the speed limit, to other traffic, and adjusting your speed as appropriate.
If you can remove some of this effort, even just calculating your speed and adjusting it to near the speed limit on an empty road you will be less tired on a long journey.
I have frequently driven between London and Scotland and have found it far less tiring in a CC equipped car, I fact I have not bought a car without CC for many years and won't in the future.
|
|
This reduction in mental effort is a major problem as I see it. When driving as a passenger in a car equipped with CC, they invariably drive a lot closer to the car in front than I would, since they let the CC control the car, instead of lifting off at the appropriate time.
|
|
My present car has cruise. I hardly ever use it. It doesn't drive any more economically than I do. It's a bit of a nuisance.
|
>> This reduction in mental effort is a major problem as I see it. When driving
>> as a passenger in a car equipped with CC, they invariably drive a lot closer
>> to the car in front than I would, since they let the CC control the
>> car, instead of lifting off at the appropriate time.
>>
Simple, choose a better driver. Who in their right mind is going to let CC drive them into a problem? CC does not over ride anticipation, although I know some drivers only plan as far ahead as their windscreen wipers.
Last edited by: Old Navy on Wed 23 Jun 10 at 12:49
|
|
I suspect many drivers who regularly use CC switch off their brain, and cease to have proper control. I think this is how these people get themselves into a tailgating situation in the first place.
|
|
I miss CC. Nothing like it for relaxed driving on even a fairly populated motorway. ON a good CC system you can adjust your MPH up and down with a press of a switch, usually in 1 mph increments. No need to drive up to the bootlid of the car in front.
|
No, if I use it to keep my speed down on a relaxed trip. Like Zero, if you have the time you can fine tune your speed.
|
|
I agree with the last two people. I think it is more economical on the motorway as there is no "driver demand" input the the ECU, which can be a rather noisy input due to repositioning one's foot or going over a bump.
|
>>Please send me £50 via paypal for this lecture you have enjoyed ;-)
Not sure I understood it, but I'm happy to believe that you know the answer to be "yes".
|
As usual when this topic, the question at the top is incomplete;
"Does cruise control use more fuel?"
Use more fuel than which case?;
1) A comparable journey with zero difference in total duration?
2) A comparable journey where a driver matches the speed as closely as possible all the time?
3) A journey where the driver can choose to speed up or slow down as he thinks fit to take best advantage of the terrain regardless of journey time?
etc, etc,
If you imagine the case where the car using cruise control is paced by a car being driven by a driver, and the two cars always do very nearly the same speed, then, there will be very little difference - cruise control doesn't fundamentally change the way the car works, or how the engine management fuels the car - it simply adjusts the demand made of the engine to keep the car traveelig at a set speed - there's a one to one relationship between the power required and the vehicle's speed, and using cruise control or a driver's right foot can't change that.
|
|
Swings and roundabouts, if it's use costs a few pence more it is well worth it.
|
I happened to catch Top Gear on Dave today, the episode where Clarkson attempts to drive from Edinburgh to London and back on a single tank.
Just so happens that he mentions the cruise control and a lot of the points that have been made above (e.g. importance of anticipation, hills, concentration required etc).
tinyurl.com/25yytoe
Last edited by: SteelSpark on Fri 25 Jun 10 at 01:11
|
Not sure it does? But on long drives on French Autoroutes it does make it a nice smooth journey, cruising along at 83mph, and about 52mpg diesel consumption.
In the UK i use it to ensure I keep to the speed limit since its so easy to drift upwards and then get caught by a mobile scamra - even possible on the M25.
|
|
I'm not sure I really see the point of cruise control. I've had it on my past two cars and seldom use it. Don't find it difficult to maintain a constant speed without it and alway have a feeling of being slightly "not in control"l when using it. I appreciate others like it . It's just not for me.
|
I couldn't be without it. Any extra fuel it uses is more than worth relieving the monotony of keeping a steady right foot in a position that isn't relaxed.
|
|
On a long journey its nice to click the cruise on, and move the right leg and ankle around for a bit of relief.
|
|
CraigP - I certainly enjoyed the lecture - it was worth scanning through for that alone. I've got my first CC on the Octavia. Love it. I can drum with fingers and feet now.
|
I use cc north of Penrith and south of Dover. In between it's a bit redundant. ( rubbish drivers in the main, especially those with yon daft flags on their cars ).........
:-)
|
|
I have done the Glasgow / Penrith or return run several times on CC all the way, the bit that requires serious anticipation is the two lane section north of Abington.
|
|
Anybody else noticed that this question got 35 replies here but only 13 on HJ's site?
|
>> Anybody else noticed that this question got 35 replies here but only 13 on HJ's site?
I would say the number of views is more important (to us anyway)
Currently:-
HJ = 893
C4P = 1211
|
>> Currently
You've gone and ruined his night now, he'll be clicking till the wee hours...
|
Maybe with this level of competitiveness the England team should have been picked from car4play?
Pat
|
I'm not convinced that CC users are any better or worse than non CC users for tailgating!
Personally I'm in agreement with many others... wouldn't do without it!
|
>> I would say the number of views is more important (to us anyway)
>>
>> Currently:-
>>
>> HJ = 893
>> C4P = 1211
Based on the number of replies (13:35) I'd suggest that HJ is getting a higher number of unique vistors.
|
Cruise control really comes into its own when you are travelling late at night
I was marshalling at Blyton Race Circuit a couple of weeks ago near Gainsbrough – approx 110 miles away from Darlington
The even finished at 00:30 and once I got onto the M180/M18 Cruise control set to 70mph all the way to leeds, and then again all the way up the A1 to Darlington never switched it off unless changing motorways. – More fuel or not, its so easy and now a must have for any future car purchase.
|
Late at night it can be quite scary, I think. I won't use it if I'm not 100% bright and fresh as in some ways it takes more concentration than not using it.
If coming up to another vehicle, it is instinct to lift off with the foot; using CC that instinct doesn't happen.
|
>> If coming up to another vehicle, it is instinct to lift off with the foot; using CC that instinct doesn't happen.
You only have to tap the pedal with your foot to disconnect the CC, and that soon becomes instinct I find. But I still hardly ever use the thing. It's for wide open spaces, not the vehicle-infested South East.
|
|
I think that a careful driver will always get better consumption than cruise, but for the majority, whose ability to keep any sort of constant speed within even +/-5mph of a set speed is something totally alien its probably more efficent for them!
Last edited by: hobby on Tue 29 Jun 10 at 16:42
|
Does cruise control use more fuel? - Fenlander
