Assuming one is stuck in a drift but can keep the exhaust clear enough to run the engine, how long would it run at idle with just a few basic services running? Say, for example
Whassat??? I hate snow in the UK - everywhere else is fine, but the UK simply cannot cope with a snowflake without grinding to a halt and some f***er buying all the bread at Safeways...
Until it runs out of petrol ;-)
You need to calculate usage whilst idling, I guess...
yeah, that's kind of what i was asking, albeit not too clearly. I'm not expecting it to the nearest minute, but I have no concept of whether it would be an hour, a day, a week. Consumption would be pretty low no doubt.
I used to have a Vauxall Sintra before I got my present land rover and it had one of those trip computers which used to tell me that it was consuming ablou 4 Ltrs/Hr at idle, that was usually with the radio and air con on and in drive.
||| Until it runs out of petrol ;-) ||| ||| You need to calculate usage whilst idling, I guess... ||| ||| ||| Martyn || || yeah, that's kind of what i was asking, albeit not too clearly. I'm || not expecting it to the nearest minute, but I have no concept of || whether it would be an hour, a day, a week. Consumption would be || pretty low no doubt. || || || || || -- || || Tim Hobbs || || '58 Series 2 88" || '67 Series 2a 109" || '77 101FC Ambulance || '95 Discovery V8i || || My Landies?
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|| Barcoding?
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|| Tony Luckwill web archive at
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OK, let's take a shot...
Round figures: V8, so let's assume 15mpg at 60mph. That's a gallon every 15 minutes at (say) half-throttle and 2500 rpm. At minumum throttle (idling) and 700rpm, how much less would it use? I'd make a wild guess and say 4 times that, or a gallon per hour, minimum. So 16 hours, plus or minus. Enough to see you through a cold night by the roadside.
i would assume it should idle until it runns out of fuel but i would be looking at clearing airflow to the radiator too otherwise it maywell overheat and seaze long before it runs out of fuel or recovery arrives..
Let's try putting a couple of boundaries on it: If you were driving it a steady 25 mile/h, you might get 25 mpg (say). So you'd be using a gallon per hour.
At idle, it will use less than that, since the power to turn the engine and its ancillaries will be the same, but you're not turning all the 4wd gubbins, and you're not using the few kW to overcome tyre rolling resistance. But its not going to be an order of magnitude less, so let's guess it will use somewhere between a fifth and half as much fuel. So on 16 gallons, somewhere between 30 and 80 hours.
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Although not comparable, I read somewhere that the Tdi engine goes through about 0.7 l per hour on idle - does that sound about right to anyone?
I think it was in an article about space heaters (I only add that because Mr Stella Tortoise is kicking in and I wish to sound like I know what I'm talking about)
I would have thought it would go on 4 a long time! i have had 8hrs DRIVING time on the motor way in my disco b4 i had to fill up so i would expect it to last a few days on idle.
The heat generated by the engine i would have thought would have kept the snow away 4 the intake/rad etc - think of the heat that comes out from the viscus then u rev it in traffic!
- Assume that, at idle, you're putting out 5 hp (3.75 kW).
- Assume that, as an old-school V8, you're getting 15% thermodynamic efficiency. So you're burning 25 kW of petrol (25 kJ/sec).
- Petrol has a calorific value of 48 kJ per g:
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So you're burning (25/48=)~0.5 g of petrol per second.- Petrol has a density of 0.74 kg per litre.- So you're burning )0.5/0.74=) ~0.7 ml of petrol per second.- You've got (16 x 4.5=) 56 litres of petrol.- So your petrol will last (56000/0.7=) 80000 seconds. That's 22 hours, ish.
Of course, if either of my initial assumptions are wrong the result will be equally inaccurate ...
I think your final answer is probably about right, although your maths is a bit off in the middle!
16 gallons is a bit more than 56 litres. I make it 72. So I'm as wrong as you are, because I thought I had a 16 gall tank in the Disco. But I know I can get 91 litres in it, so it must have a 20 gallon tank. Either way, the answer would be 'long enough'.
16 gallons of fuel? Don't forget to calculate the fuel consumed getting to the snow dift as well as the amount of fuel you use trying to get out of it before deciding that you are stranded.
The main thing is to keep from freezing to death, not to be as warm and comfortable as you would be at home.
On or around Wed, 31 Dec 2003 17:35:57 +0000, Tim Hobbs enlightened us thusly:
erm... running light and slow, you might be getting 20 mpg at 20 mph average... which gives you 320 miles from your 16 gallons, in 16 hours.
so I'd guess at idle you might get 20 hours out of it. Hard to tell really. You could always experiment, by disconnecting the petrol feed (and blocking it, or disabling the pump), and arranging a gravity feed from a petrol tin with say a pint of juice in, and see how long it runs for.
I've got a machine, which I usually just use to mix and rise before bunging it in the oven. Trouble is, our Safeway doesn't stock very good flour for breadmaking (they do have lots of yeast, though).
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