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Freewheeling to save money

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  • Iceweasel
    Iceweasel Posts: 4,882 Forumite
    Part of the Furniture 1,000 Posts Photogenic Combo Breaker
    So called 'drifting' and /or smoking tyres is not what I was meaning at all. I detest all these young folks who leave the doughnut circles in car-parks etc.

    I was hoping only to show the inaccuracy of the statement that 'any skid is a loss of control'.

    Top notch rally drivers do not seek to have smoking tyres.

    Neither do instructors at skid-pans where deliberate use of opposite lock is taught as a means of car control not a loss of it. Albeit usually in the context of recovering steering direction once a slide has started due to ice or a diesel spill on the road.

    Many Scandinavian driving instructors teach such 'sideways' skills as a matter of car control - certainly not a loss of it.

    As for the free-wheeling I can still see no point in it as there is absolutely no savings to be made unless you have a car over 20 years old or so.
  • Weird_Nev
    Weird_Nev Posts: 1,383 Forumite
    Another question to consider is would you prefer to put more strain on the engine (slowing down in gear) or the brakes (slowing down out of gear). Although for the brakes, you will still use them to stop no matter if you are in or out of gear.
    Gears to go, brakes to slow.
    It's not the engine that "takes strain" when you use engine braking. At least it shouldn't. It's more that if you try and downshift and then let the engine absorb the kinetic energy of the moving car, then the clutch will take heavy wear doing that.

    You can slow to about 10-15mph in FIFTH in most cars without the engine stalling or laboring. You slow in whatever gear you are in on the brakes (and since you're off the throttle the engine does assist with braking) until you're at the correct speed for the hazard, then you select the right gear for that road speed and negotiate the hazard.

    Brake pads are cheap, clutches are expensive.

    Iceweasel: I think we can accept that when 99.9% of drivers experience a skid, they have lost control of the car. I include myself in that. those that do it deliberately do it in controlled circumstances most often in a motorsport environment, or else they're 'tards.
  • Iceweasel
    Iceweasel Posts: 4,882 Forumite
    Part of the Furniture 1,000 Posts Photogenic Combo Breaker
    I see free-wheeling as a problem if due to some unforeseen circumstance you need to swerve or take avoiding action.

    I doubt if anyone would choose to free-wheel round a corner, but you never know when the proverbial child, dog, bicycle or whatever pops up.

    Back in the day the free-wheeling 2-stroke Saabs and Wartburgs were still in gear and ready for an instant return to power if needed.

    I did drive such a Saab many moons ago but cant recall free-wheeling down any hills or round any corners.

    I have an inkling of a memory that the free-wheel may only have been on 1st gear though.

    Anyone have a better memory of those by-gone days when fuel was six shillings and fivepence ha'penny a gallon? LOL ;)
  • goonarmy
    goonarmy Posts: 1,006 Forumite
    alastairq wrote: »
    Because the wheels & tyres are intended for gripping the road surface.

    Therefore if they don't grip the road surface, there is a 'loss of control'....ie, a skid.

    All skids occur as a result of driver input.

    [Especially if said driver fails to identify, and act upon, the sight [or suspicion ] of a less than suitable road surface.]

    Whether that input is intentional [as with rally drivers using the skid to scrub off speed and point the car in a new direction]...or unintended...the fact that the wheels/tyres are not doing what they are intended for, means a control-loss.

    As I have said, where a skid is deliberately induced, the skill of the driver [at vehicle control, not interaction with other road users....let's not confuse the issue?]......lies with managing that loss-of-control.

    For the rally driver or circus-trick driver, should the situation change, recovery from the loss-of-control is another thing altogether.

    You seem to say that loss of traction is lack of control. That is not the case.
  • Ultrasonic
    Ultrasonic Posts: 4,265 Forumite
    Part of the Furniture 1,000 Posts Name Dropper Photogenic
    Retrogamer wrote: »
    I know coasting / freewheeling won't save fuel on a modern petrol car due to the ECU cutting fuel on the over run but what about diesel cars?
    What you 'know' is incorrect, but the same applies to diesels as petrols - both cut fuel when slowing down in gear with foot off the accelerator, provided engine revs are above a certain threshold.

    Let me have my stab at explaining this...

    Yes when you slow down in gear your car can do so whilst burning no fuel at all. As you do this the effort of the wheels turning the engine causes a braking effect, which slows the car down more rapidly than when slowing down in neutral. So you're comparing situations of, say, slowing down in neutral over 500 m to driving normally for 300 m and then decelerating in gear over 200 m (completely made up numbers but it gives an idea). To work out which is more fuel efficient you need to compare the total fuel used for each method to cover 500 m, not just focus on the zero fuel used for the in gear braking part.

    Which of the two methods above gives best mpg is not obvious, and I can't write something to prove which is better. But advice from people who take considerable effort to maximise mpg is that coasting in neutral is optimal, and I find the same.

    I would also point out to doubters that if you've never tried seeing how far it takes to slow down in neutral you may be surprised - cars can roll quite a long way like this! More so for heavier cars I suspect.
  • Retrogamer
    Retrogamer Posts: 4,218 Forumite
    Part of the Furniture 1,000 Posts Name Dropper Photogenic
    WTFH wrote: »
    If you're talking about modern diesel cars, same rule applies. The ECU will cut the fuel if none is required

    I was skeptical of this but when i moved my car earlier i tried it and you're 100% right. On the overrun there is noise from the engine being turned over, but no chatter. As soon as foot goes back on the accelerator you can hear the chatter from the injectors & combustion again
    Ultrasonic wrote: »
    What you 'know' is incorrect, but the same applies to diesels as petrols - both cut fuel when slowing down in gear with foot off the accelerator, provided engine revs are above a certain threshold.

    Let me have my stab at explaining this...

    Yes when you slow down in gear your car can do so whilst burning no fuel at all. As you do this the effort of the wheels turning the engine causes a braking effect, which slows the car down more rapidly than when slowing down in neutral. So you're comparing situations of, say, slowing down in neutral over 500 m to driving normally for 300 m and then decelerating in gear over 200 m (completely made up numbers but it gives an idea). To work out which is more fuel efficient you need to compare the total fuel used for each method to cover 500 m, not just focus on the zero fuel used for the in gear braking part.

    Which of the two methods above gives best mpg is not obvious, and I can't write something to prove which is better. But advice from people who take considerable effort to maximise mpg is that coasting in neutral is optimal, and I find the same.

    I would also point out to doubters that if you've never tried seeing how far it takes to slow down in neutral you may be surprised - cars can roll quite a long way like this! More so for heavier cars I suspect.

    I was wondering this myself. Having previously been a freewheeler at most oppertunities i think i'll reserve it now only for the very long hills, or if not so long just pop it into 6th so to reduce the slow down effect from being left in gear
    All your base are belong to us.
  • Ultrasonic
    Ultrasonic Posts: 4,265 Forumite
    Part of the Furniture 1,000 Posts Name Dropper Photogenic
    Bongles - sorry it's taken me a while to get round to replying to your post. Let me have a stab at answering your questions.
    Bongles wrote: »
    However, it seems theoretical rather than practical to me. I can't picture a real life situation where you might do c.

    On my drive home I have a long straight road with a 60 mph limit leading up to a large roundabout, which I would ideally want to reach at about 25 mph in 3rd gear (it's open so you can see if other cars are approaching the roundabout from other directions). If there are no cars behind me then I can stick the car in neutral and slow down over a much longer distance than I would under more normal traffic conditions with cars behind where I would start to slow down later in gear, and decelarate more rapidly. The fact that the road is straight means I can see if there are no cars for a considerable distance behind me.
    Trying to picture this one. I think you must mean a moving queue - presumably moving at fairly constant speed (rather than a stationary or stop-go queue)?
    To maximise mpg you want to try to never completely stop. So if you can manage it then crawling along at a very slow speed is better than lots of accelerations followed by braking. I would suggest that most drivers do a bit of coasting with the clutch in when queuing, it's just a quesiton of how much you do this. My aim is never to have to brake when queuing, although obviously this isn't always possible.

    You might have come across the hypermiling technique of pulse and glide? This combines high load (fast) acceleration with long periods of coasting. This improves mpg because of the higher engine efficiency at high loads (Google BSFC). I DO NOT do this for normal driving, but effectively do in queuing traffic. A short acceleration followed by rolling along in neutral rather than crawling along in 1st gear.
    Do you not find that on approach to the hazard you also need the brakes at some point? Are you really starting to slow from even further away than the distance your momentum would take you if you lifted off and stayed in gear?
    Yes, for coasting in neutral you want to be starting to slow down much earlier to arrive at the junction at the same speed as you otherwise would. This is not practical with other traffic around but can be when roads are quiet.
  • EdGasket
    EdGasket Posts: 3,503 Forumite
    edited 26 September 2013 at 10:26PM
    I coast to save money, reduce pollution, reduce noise and reduce engine wear. Don't believe the other posters that say you won't save anything; not true. If you stay in gear with your foot off the accelerator, the engine will slow you quite rapidly and you'll need to use fuel to keep going. Coasting in neutral will get you quite far especially on a downhill gradient. Some Saabs and Land Rovers have freewheel transmission or hubs fitted as standard for economy; proves the point.
    Re. the previous post; I don't see why slowing down earlier is 'not practical with other traffic around'; seems very safe and sensible? If other drivers want to drive as fast as possible and slam on the brakes at the last minute then that's their problem not mine. I am happy to approach junctions and roundabouts gently decreasing speed and yes, coasting where appropriate.
  • Gloomendoom
    Gloomendoom Posts: 16,551 Forumite
    Part of the Furniture 10,000 Posts Combo Breaker
    EdGasket wrote: »
    I coast to save money, reduce pollution, reduce noise and reduce engine wear. Don't believe the other posters that say you won't save anything; not true. If you stay in gear with your foot off the accelerator, the engine will slow you quite rapidly and you'll need to use fuel to keep going. Coasting in neutral will get you quite far especially on a downhill gradient. Some Saabs and Land Rovers have freewheel transmission or hubs fitted as standard for economy; proves the point.

    Not in the case of Land Rovers because only the front wheels freewheel when running in 4x2 mode, the rears remain firmly connected to the engine unless the gears are knocked into neutral or the clutch is dipped.
  • Weird_Nev
    Weird_Nev Posts: 1,383 Forumite
    Good god.

    Reading this thread has made me glad I used to have knocking on for 300bhp at my disposal for quick clean overtakes.

    Are we really at a point where saving a few drops of fuel is more important that the fundamental function of a car, that is getting from A-B quickly and in comfort? Saving 10% or even 20% on your fuel bill by driving bare foot with your panel gaps taped over is nothing compared to the overall cost of owning or running a car. By all means, buy an efficient model, keep it maintained and drive with a nod in the direction of economy and smoothness.
    The moment you pull the car out of gear going down hill, pulse and glide, put the clutch out for extended periods of time in the name fo fuel saving, you've gone too far.

    I take it the hypermilers walk journeys of less than 2 miles and cycle journeys of less than 15? I do, so that I can enjoy 3.8 litres of auto boxed goodness for the rest of the time. I struggle to make 17mpg. :)

    Re: in built freewheels: They were never common place. Rovers had them, Saabs had them. LAndrovers have them 1948-1951 apparently, but only on the front axle to allow a permanent 4x4 system without transmission wind up. Guess what? They were dropped due to unpredictable handling.
    Other manufacturers stopped using them because of difficulties with brakes overheating (surprise surprise) and customers not liking the feeling of the car "running away" surprise surprise.

    Please, Safety first, fuel economy second. If you're that het up about fuel economy, remember a car left on the drive uses no fuel at all.
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