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 Post subject: Fuel Consumption At Idle
PostPosted: Sat Aug 08, 2009 9:53 am 
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I expect to be out in the hot desert for several days and to get through the heat of the day I thought I would start up the CRD and it may run 2 or 3 hours a day if there is a hot spell. I do not think there is an issue for overheating or wear but I wonder about fuel consumption. I have never seen figures for the CRD or any vehicle about fuel use at idle. I want to make sure I have enough fuel, its maybe 70 miles out to a nearby town. Any ideas?


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PostPosted: Sat Aug 08, 2009 9:56 am 
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I used ~3 gals over 8 hours with the heater on and the viscous heater running constantly.

Others have reported what i recall as something like a gallon every 3 hours or so.

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PostPosted: Sat Aug 08, 2009 12:14 pm 
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Location: Somewhere between Heaven and Hell... But it is really hot here on Earth...
Last summer, I used my CRD as a hotel while driving cross-country. I filled it up when I got to a truck stop, 8 hours later I topped it off... 2 gallons exactly with the AC on all night long.


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PostPosted: Sat Aug 08, 2009 1:56 pm 
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I remember reading somewhere that the VM burns through about 1 quart/hr idling...

(obviously more if you're using AC and whatnot)

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PostPosted: Sat Aug 08, 2009 3:16 pm 
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The scangauge reports ~.25 to .3 gallons/hour idling in park, AC on adds ~.15 and in gear adds ~ .15
so it's about .25 gallon/hour but can go over .5

and MrMopar said it can idle through an entire tank with no damage - although there was a lot of concern about the engine getting too cold (this was in an engine for heat discussion)

and the engine heater uses about the same energy as the AC compressor.

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PostPosted: Sat Aug 08, 2009 3:58 pm 
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Interesting comparison of the numbers, and I suspected as much about the long idling not being a problem. As for too cold, thats what a thermostat valve is for.

What I find fascinating *Spock eyebrow* is that I use the A/C _ALWAYS_ and when I was sleeping in the back, the AC was of course on all night. Yet it only took 2 gallons to fill it back up, and I always fill to the top of the neck with no foam... So it is a consistent level. For 8 hours, 2 gallons... .25 gal / hour.

I only hope this new engine does as well the next time.


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PostPosted: Mon Aug 10, 2009 2:17 am 
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For comparison the little 1.9 TDI with PD injection uses about ~0.5-0.75 quart every hour of idling (with all comfort stuff off). It doesn't sound much off for me with the CRD being a 'tad' bigger at 2.8 liters with everything else being bigger as well taking up twice of the little TDI.

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PostPosted: Mon Aug 10, 2009 3:04 am 
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My previous car was a 1.9l TDI VW too, but the older VE pump. Not the PD. Same story, but an earlier chapter - I used that one as a truck stop hotel too, idling all night long with the AC running. Now I know that with the temp selector set at a specific point above the man-I'm-hot-and-want-to-cool-off setting, the compressor is not running all the time. The compressors don't take that much power to turn, and the natural inclination of a diesel is to adjust the mix SUPER-lean when the power is not needed. Air fuel ratios of 200:1 would not be out of the question. The engine only needs *just enough* to keep itself turning, and add that 1/2 HP or so for the AC compressor and the alternator... Its easy to see how on my 1.9, it was using about 20 ounces per hour, or a little more than the .5 quart your TDI did. But like I said, I run the AC all the time. Its too hot out in the south USA to even THINK about just letting the fan blow the outside air in.

So from 20 ounces per hour and about 42mpg average (Ok, I drove it like a go-kart usually) to just about 64 ounces per hour (1 quart, and that was stock computer) and 24mpg... It will be VERY interesting to see what the CRD idles like with the GDE tune. The EVIC seems to have settled down to right at 31mpg, which isn't bad considering I've only done rural-city >60mph with stops and turns since I put it in. The first long trip will be on Saturday, and the first idling overnight is TBD, but probably within about 30 days.


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