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gallons per hour at varying rpm's


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thought crossed my mind after falling asleep in my truck trying to stay dry one night when camping.ended up letting the truck idle for 7 hours before i woke up and realized it :doh:then i got to thinking. has anyone done any research on how many gallons per hour these things use at stock idle speed (800~rpm)? what about with high idle engaged around 1200 rpm's? also is there any danger in idling these trucks for hours at a time at factory idle speed?

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As long as the weather isn't too cold there isn't much harm you can do to it. As for fuel flow rates ISX should know the number roughly speaking.

No clue. A lot of my stuff uses MPG.. GPH can then be derived from it but yeah I have no flow meters to go by. AH64 has a map with idle flow I think. You all have scan gauges cant you put it on GPH and watch :evilgrin:
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http://www.cmdmarine.com/Products/Recreational%20Inboard/QSB/Fr91364_2.pdf Here is a link to a Cummins PDF for a Marine 380hp QSB 5.9. 800rpm=.84gph, 1200rpm=1.84gph All things considered thus is for a new engine in a loaded (prop installed and in water) situation. A 2001 mechanical injector flow is about .76 of what a 380hp QSB is (based on reman specs for the injector flow bench). In my personal experience I get about .8gph to 1.1gph fuel usage (depending on ambient temp and altitude) at 1200 rpm. Stock hx35w turbo, rv275 injectors, 4" exhaust, no programmer, running 2cycle oil (1:128). The numbers are going to vary a little base upon each individual set-up but hopefully this is a bit better than nothing. "Put your hands on a hot pan and a minute can seem like an hour. Put your hands on a hot woman and an hour can seem like a minute. Its all relative."
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If you have an automatic, you need to put it in N if you are going to idle for an extended time. The fluid does recirculate in Park.

trucks a 6 speed :thumbup2:

As long as the weather isn't too cold there isn't much harm you can do to it. As for fuel flow rates ISX should know the number roughly speaking.

if you dont mind me picking your brain a little bit, what's the difference in idling in warm temperatures versus idling at colder temperatures?

No clue. A lot of my stuff uses MPG.. GPH can then be derived from it but yeah I have no flow meters to go by. AH64 has a map with idle flow I think. You all have scan gauges cant you put it on GPH and watch :evilgrin:

does the scanguage show GPH at idle or only when moving?

http://www.cmdmarine.com/Products/Recreational%20Inboard/QSB/Fr91364_2.pdf Here is a link to a Cummins PDF for a Marine 380hp QSB 5.9. 800rpm=.84gph, 1200rpm=1.84gph All things considered thus is for a new engine in a loaded (prop installed and in water) situation. A 2001 mechanical injector flow is about .76 of what a 380hp QSB is (based on reman specs for the injector flow bench). In my personal experience I get about .8gph to 1.1gph fuel usage (depending on ambient temp and altitude) at 1200 rpm. Stock hx35w turbo, rv275 injectors, 4" exhaust, no programmer, running 2cycle oil (1:128). The numbers are going to vary a little base upon each individual set-up but hopefully this is a bit better than nothing.

.8 - 1GPH isnt bad at all i suppose :shrug: had to keep the lady from freezing/complaining! women act like they have never heard of a thing called long johns and bundling up :lol: thanks for all the replies guys :thumb1:
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I remember years ago, a lot of semi's would have a 'low' idle. I swear these things sounded like they were just barely ticking over. 3-400 rpm? Drivers would kick that in while parked instead of shutting it down, especially in cold weather.That was back when diesel was 20 cents a gallon too.. These days I notice most drivers will idle for a cool down period, then kill it. My trucker friend has automatic 'restart' when coolant drops below a certain point.I'd worry about oil pressure at those low speeds, Is there enough to keep the crank, rods, and cam floated?

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didnt catch what you meant there. your saying you worry about oil pressure at the 'low idle' of 300-400 rpms, or the stock cummins idle of 800? i dont want to tear anything up, id rather just turn it off 400 times instead :ahhh:

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didnt catch what you meant there. your saying you worry about oil pressure at the 'low idle' of 300-400 rpms, or the stock cummins idle of 800? i dont want to tear anything up, id rather just turn it off 400 times instead :ahhh:

sorry bout that~ I meant the LOW idle of those older trucks whether they had ample oil pressure @ those very low speeds! our factory stock is fine. Most of my ag tractors have a cable "Pull to shut off engine" and a person can slowly pull it out and reduce idle which the further you pull it out the slower the engine turns... eventually stopping the engine. At 3-400 rpm, my oil pressure is 10-20 sometime less on some tractors. I did this as an experiment years ago, I normally kill em quick!
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Check this out...

http://www.autoblog.com/2011/07/22/worlds-largest-diesel-engine-makes-109-000-horsepower/

The 109,000-horsepower Wärtsilä-Sulzer RTA96-C, which first set sail in the Emma Mærsk in 2006, weighs in at a rotund 2,300 tons, and it's 44-feet tall and 90-feet long. In other words, the TRA96 is the height of a four-story building, and longer than a Christmas Eve line at Sam's Club. Within that massive exterior rests 14 cylinders that each consume 6.5-ounces of diesel fuel every cycle. And, if you like torque, there's enough twist to rip an M1 tank to shreds, though the massive mill churns at only 102 rpm.

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mother of god... :thumb1:

i would love to see that thing in person :pant:

- - - Updated - - -

wonder if it means it will only spin a maximum of 102 rpm's, or if that is idle speed? :shrug:

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I forgot I had a way to calculate engine HP required to turn it. I get 6.87 at 800 RPM. 33% efficiency comes out to 0.407 GPH. I searched the net and found semi trucks are burning twice that at the same RPM. Another guy personally tested it and came up to 0.25 GPH. So I'm just gonna round everything and say 0.3ish.

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and it's 2 stroke to boot! I wonder what the stroke is, ( measured in feet? :lol: ) I'll bet even at 102 rpm, that piston speed is still pretty zippy!

8.2 feet. Average piston velocity in feet per second at 103 RPM is 28. Our trucks are 1.35 FPS at 103 RPM. However, at a speed around 2125, we match piston speeds (about). So very similar speeds at working RPM. http://en.wikipedia.org/wiki/W%C3%A4rtsil%C3%A4-Sulzer_RTA96-C
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