Soldato
huh? so easing off/engine braking is a fail now?
im talking about not accerating upto obstructions (lights etc), but trying to ease off to hope obstructions are cleared
What is most likely to cause high fuel consumption?
- Thread starter azmi
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huh? so easing off/engine braking is a fail now?
im talking about not accerating upto obstructions (lights etc), but trying to ease off to hope obstructions are cleared
Why is this?
I've always meant to ask - if you are just in a steady stream of traffic that is going about 30mph, is it detrimental to put the car in 5th and happily cruise along?
depends on the car and gearing. For instance mine copes fine in 6th at 30mph but my old car wouldn't. Its fairly obvious though as you can hear the car labouring if its in too high a gear.
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No, this is fine in a BMW 535d, Audi A6 3.0 TDI or a Mercedes E500.
Yes, this is detrimental in a Nissan Micra 1.0
Soldato
Stands to reason, surely?
Even if the engine is burning fuel much more slowly than when you're travelling at, say, 55mph on the motorway, you're not actually going anywhere so the live economy is always going to be 0.
My 5 series shows the economy as infinite when I'm stationary which I find strange.
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Soldato
My 120d tells me to change down if I'm in too high a gear at 30mph, as it thinks the fuel is being burned inefficiently.
Soldato
thats freewheeling.
Soldato
Cos you spend more time prior to the braking maintaining speed rather than utilising engine braking under fuel cut conditions. Also generally results in overbraking that reading the lights.
Late braking at a red light usually results in you stopping where as if you read ahead and drive steadier you can roll to the lights in enough time for them to go green then you only have to accelerate from 10mph and not a dead stop.
Speed is the main thing. When i drive now though I try to do so without using the brakes, it pays dividends.
Soldato
In a car its typically refered to as coasting.
Freewheeling is something I have only ever seen in reference to a push cycle...
Most car owners manuals will call coasting in neutral... coasting.
If you're gonna coast atleast do it properly with a Forced engine stop
Soldato
Probably doesnt want the engine way off boost and lugging rather than anything else.
The answer to this HAS to be the braking answer, as in all cars aggressive braking will result in inefficient use of the cars momentum.
Driving above 50 is a nonsense answer, my s-class for example is most efficient at around 70mph, 50mph is too slow for top gear hence the car changes down.
Driving above 50 is a nonsense answer, my s-class for example is most efficient at around 70mph, 50mph is too slow for top gear hence the car changes down.
Soldato
If you do a motorway drive it doesnt matter on your braking as you do so little does it? We dont know if agressive means simply quick braking or braking quickly such that you can an overshoot of speed retardation so you end up slower than you intended to be and hence have to accelerate even more after the braking.
Aero drag is the main force a car has to overcome, speed gives this force by result of doubling the speed = 4 times the drag. The engine burns fuel to give this.
There is something odd with your merc if you get less rpm at 50mph. The fact its not in its top gear means nothing regarding the engine efficiency when you might be sat at a better BSFC point at 50mph in 4th than 5th. I guess the main reason is that you dont get direct lock in your auto box in anything other than top gear?
You answer kind of ignores physics and facts using your own opinions, but I guess we're getting used to that from Jez.
Soldato
Its clearly C.
What has braking got to do with fuel economy. What difference does it make if I brake up to a junction gradually, or if I slam the car to a stop suddenly.
What has braking got to do with fuel economy. What difference does it make if I brake up to a junction gradually, or if I slam the car to a stop suddenly.
That may be the answer, i am merely stating the fact that in one particular car the economy shown is greater when cruising at 70mph than it is at 50mph. I see this day in day out when stuck in 50mph specs sections of motorway for example.
It is therefore a nonsense answer, as it totally depends on the vehicle.
Because if you slowly came to a stop using engine braking, then you would not have been using fuel for that last few hundred yards...