I coast all the time, except down long hills to stop the brakes from boiling.
Why exactly is it illegal / unadvisable again?
Why exactly is it illegal / unadvisable again?
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General strategies for best economy
Out of gear and coasting - you're not fully in control of your vehicle.
I'm always too scared that leaving it in gear will cause it to 'bunnyhop' or worse, stall
In gear rolling without depressing the accellerator takes no fuel at all in a modern fuelinjectioncar. Coasting out of gear takes fuel.
gr J
gr J
That's true, but coasting can sometimes still save you fuel, just not in all situations.
If you coast in gear, you won't burn any fuel* but you'll lose energy due to engine braking. If you coast out of gear, you'll go much further from a given speed than if you coast in gear, so you'll save fuel by coasting downhill providing you don't have to brake at the bottom. If you have to brake, you'll likely use less fuel coasting in gear.
Coasting has its place as an ecodriving technique, but safety must always take priority. If you coast out of gear and have an accident as a result, they'll throw the book at you. So please don't try this at home
.Being able to coast out of gear safely and competently is an advanced dricing skill which might even save your life if you are unfortunate enough to experience catastrophic engine failure in the fast lane one day. Knowing what you can do with the energy you have can sometimes be very useful.
*providing you keep above 1400-1600rpm; below this, the ecu will start feeding in fuel to keep things turning smoothly.
I feel like when slowing down in gear I'm straining the engine, is this true or is it so minimal it won't matter?
Whilst it does put some additional load on the engine (and more particularly on the gearbox and transmission), the car is absolutely designed to cope with this and you shouldn't worry unduly about it.
It's more of an issue on aircraft piston engines, particularly those with geared propellors; engine life can be drastically shortened by incorrect operation and on some types particular care must be taken not to allow the propellor to drive the engine.
It's true that coasting out of gear puts less stress on the engine and transmission, but the effect isn't great and safety must be your priority. Coasting out of gear on steep hills puts a great deal of stress on the brakes and can't be recommended. If you need to use the brakes when coasting, you'd be better off from every perspective to leave it in gear.
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The engine in overrun imposes a small fraction of the force it delivers when driving.
Coasting is alleged to save energy but the main reason for coming off power is to slow down. We either use engine braking or we apply the actual brakes. Both absorb energy of motion.
Another issue is the load reversals when gears are shifted. These are normally well with reasonable limits as the engine and gearbox revs are similar. Now put the box into neutral and coast for a while. At some point you need more power what gear should you use and at what revs? Most people shove the lever into any gear and expect the mechanism to cope. It usually does but the internal forces are considerably higher than for a normal up or downshift.
There is also a safety issue. What if you are coasting along, head in the clouds, when you realise you need to get a move on. Oh booger what gear do i need etc etc. Too late someone hits you. Another time happily coasting down you need to emergency stop and slam on the brakes. But you fail to stop in time and hit that errant child. Had you been in gear the additional engine braking might have been just enough to stop you in time.
Last of all - vehicle stability. Drive around any bend coasting and note how stable the car feels. Now drive around the same bend at constant speed under power or even accelerating slightly. The car will feel like its holding the road better because it is more stable under power.
Today's computer controls allow cars to maximise the benefits of coasting when its appropriate but cars like the Panda are a long way from enjoying any such benefits. I would also suggest that very few cars that make such claims are actually doing anything more than using computers to cover up for less than ideal design. Systems like ASC use the brakes to keep a car from over or under steering.
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True, but those forces are acting in the opposite direction to which the engine & transmission was designed to run. It's a big problem with some engine designs; fortunately those engines aren't normally used in cars.
That said, a pretty good and concise summary.
Most folks would do best to forget about the idea of coasting out of gear; the inexperienced could get into difficulties and may end up doing more harm than good.
I'd hate to think of anyone experimenting and ending up in trouble as a result of something that's been posted here.
Sweetsixteen
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Following JR's comments, re coasting for economy - both in fuel savings and in lessening strains on engine and transmission - it is definitely an art.
Slipping out of gear to coast in neutral, and mentally keeping a running tally of engine revs/road speed so that the right gear can be re-engaged at the right moment with absolute smoothness, is an advanced technique.
The driver who can do this is also the driver who is very alert to surrounding conditions, and is often in a better position to take fast avoiding action if any emergence arises than the half-asleep driver who often forgets what gear he's in.
Slipping out of gear to coast in neutral, and mentally keeping a running tally of engine revs/road speed so that the right gear can be re-engaged at the right moment with absolute smoothness, is an advanced technique.
The driver who can do this is also the driver who is very alert to surrounding conditions, and is often in a better position to take fast avoiding action if any emergence arises than the half-asleep driver who often forgets what gear he's in.
