The compression of the pistons acts as an effective air brake on the road wheels when traveling at speed with the throttle plate(s) closed ie you slow a bit quicker than freewheeling it is an effect you can use in sync with normal disc braking; or alternatively you can use the hill scenario where you select first role off and will eventually find your acceleration restricted because you have reached maximum engine revolution in that gear.
Coasting vs engine braking
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The compression of the pistons acts as an effective air brake on the road wheels when traveling at speed with the throttle plate(s) closed ie you slow a bit quicker than freewheeling it is an effect you can use in sync with normal disc braking; or alternatively you can use the hill scenario where you select first role off and will eventually find your acceleration restricted because you have reached maximum engine revolution in that gear.
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Perhaps my question was poorly phrased. What I meant was were people sequential shifting or just using engine braking in the gear that they are currently in?
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Well I've been rolling down inclines in neutral for years thinking I'm saving fuel blissfully unaware of this thing called fuel cut off.
Will have to completely change the way I drive now!
Will have to completely change the way I drive now!
Clearly you've not actually read what I've put.
I said, it annoys me that cars read 99mpg when coasting, ie, not in gear, when in fact, it should read closer to 0mpg.
I should imagine it's very difficult to calculate, but, the fact that when coasting in neutral, you will be using fuel (to keep the engine idling), in theory you'd be getting closer to 0 mpg than 99mpg
Lol what. Idle uses hardly any fuel.
On coasting an engine with fuel shut of is doing infinite MPG a it's using ZERO fuel! 99 is just the max of the display.
Idle rolling is irrelevant. And fuel usage is purely related to time. Around 200-300mpg is a good rough estimate when rolling down a gentle slope though
On coasting an engine with fuel shut of is doing infinite MPG a it's using ZERO fuel! 99 is just the max of the display.
Idle rolling is irrelevant. And fuel usage is purely related to time. Around 200-300mpg is a good rough estimate when rolling down a gentle slope though
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So I can get 45mpg whilst at 1/3 throttle at 70mph but if I use no throttle and let the engine idle whilst coasting at the same speed I will get closer to 0mpg?
SkodaMart
SkodaMart
Not just that, but you will also need to replace your brake linings/discs more frequently as you are only using your brakes to slow down.
My cay uses no fuel at all when coasting in gear.
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Deceleration fuel cutoff is usually down to ~1600rpm. You should be able to feel it when it kicks back in. Best economy: depends on the situation. Weigh up the increased engine braking/0 fuel usage of deceleration in gear against increased coasting distance with slight fuel usage while coasting in neutral.
Hah fail
Even my hardly-fuel-efficient Golf will use just 1.2L/hr of fuel while idling, give or take a hundred mls or so.
So.. idling in neutral at 30mph => 113.5mpg. 60mph is obviously double that. Even coasting at a steady 10mph would return around 38mpg..
Not really that difficult to calculate, no
Lots of interesting info here. I'll definitely be listening for this cutoff at around 1500rpm to see if I can tell if it's working.
Although with regards to safety, I recognise that being in gear allows you to accelerate away from danger, if I'm engine braking in 5th at 40mph (to keep the engine quiet) I need to change gear if I want to go anywhere quickly. Also, braking without the inertial force of the engine will allow me to stop faster (although you can always apply the clutch to avoid that problem).
Although with regards to safety, I recognise that being in gear allows you to accelerate away from danger, if I'm engine braking in 5th at 40mph (to keep the engine quiet) I need to change gear if I want to go anywhere quickly. Also, braking without the inertial force of the engine will allow me to stop faster (although you can always apply the clutch to avoid that problem).
Hold on, so what we are saying here is, that my car, any car, in neutral, will achieve more than a mile, or maybe 2 of movement, without any use of the throttle? No, didn't think so.
ie
How do you plan to cover those 113 miles, in neutral?
ie
How do you plan to cover those 113 miles, in neutral?
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Zero, as in youre doing no miles per gallon of fuel used?
off throttle/in gear/sufficient revs, the injectors will close, zero fuel used, infinite mpg for the time youre still moving and the rev are above the cut off threshold.
off throttle/out of gear/idle, the injectors will flow sufficient fuel to idle the engine, ie a small amount. mpg wont be infinite, but it will be high
No, you will tend to stop quicker with less pad wear with the car in gear (for most of the rev range) due to engine braking. As above, if you're at low revs e.g. <1500rpm only then will the engine be fed a bit of fuel which would counteract braking. Besides, you are less likely to lock your wheels under hard braking.
You really don't seem to understand the basics here
We are talking about instantaneous mpg. You don't have to travel a mile at the same speed (or use a gallon of fuel) to work out how many miles per gallon you're doing. This is basic maths.
and you sound like a bawws if you can H&T down the gears too
No, you will tend to stop quicker with less pad wear with the car in gear (for most of the rev range) due to engine braking. As above, if you're at low revs e.g. <1500rpm only then will the engine be fed a bit of fuel which would counteract braking. Besides, you are less likely to lock your wheels under hard braking.
You really don't seem to understand the basics here
We are talking about instantaneous mpg. You don't have to travel a mile at the same speed (or use a gallon of fuel) to work out how many miles per gallon you're doing. This is basic maths.
Yes, it's basic maths, but other than instantaneous, it's not a true reflection. The car will not travel for 113 miles with no throttle. The clue is in the name. Once my car stops coasting, in neutral, and comes to a stop, I am travelling 0 miles for every gallon of fuel used. If I coast in neutral and my car reads 113miles per gallon, my car should be aware that this is not ever likely to happen, and stop misinforming me
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Yet it still remains a poor tool to use.
"OMG 113mpg in neutral #YOLO" said no one, ever.
You dont seem to be getting this. This thread is about Coasting vs Engine braking. All examples used have mentioned going down hill. Whether we measure the MPG over 100 miles or 1 mile we would, in this instance, still be going down hill thanks to mavity. So the car will not come to a stop and a read out of 113mpg would actually be true. The MPG is measured based on current conditions, as if the hill were to last forever, otherwise it would have to be able to see in the future to predict anything else apart from your average MPG over a journey.
A car reading 0mpg would have to be able to read the road ahead and see what you are going to do. If it saw a flat/uphill and knew you will stop and not lightly accelerate then yes, it would read 0mpg, but this would still only happen once you come to a stop. As currently you are getting 0 miles out of a gallon.
MPG is based on current conditions. If current conditions said you were going down hill on idle, then the amount of fuel used to stay on idle would then contribute to the MPG depending on speed. If you were rolling down in 2nd at 30mph with fuel cut off then your current MPG would be infinite miles to the gallon.
Thing is, I've got the hang of it. I'm a realist. Whilst I fully understand your post, you, and most others seem to think that that downhill will last for 113 miles and therefore the car should tell me that I'm "achieving" 113mpg. The hill won't, obviously last for 113 miles and would need to be at a considerable incline to even secure a prolonged 30mph. Yes, I appreciate that the car would have to know what was coming up in terms of flat surface or up hill, but I've never looked at my "instantaneous" mpg, coasting in neutral, and marvelled at my 113mpg. 
Interestingly, the 5 series F10 hyrbid does read the road ahead and uses the engine / electric motors accordingly
Interestingly, the 5 series F10 hyrbid does read the road ahead and uses the engine / electric motors accordingly
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