Gallons Per Hour

[DSN46]

X2.

Jim has helped so many of us with very technical issues, I can't remember all that I have read. "Thanks Jim".

 

[Dr. Dyno]

At idle, how many gallons (or fraction of one) do you guys think the 4.0L would burn in an hour?

My guess? Since I'm a real smartass and not just claiming to be one , I'm going to use some science to come up with a true figure. A 4.0L engine idling at 750rpm with a perfect A/F ratio of 14.7:1 will consume 16.5lb of fuel in one hour. Since one US gallon of fuel weighs 6.1lb, that's a consumption of 2.7 gallons/hour.
This does assume 100% volumetric efficiency but the 4.0L engine probably has only 60% volumetric efficiency at 750rpm so the true figure should be roughly 1.6 gallons/hour (6.0 liters/hour for metric guys like me). That would give you about 12 hours of idling time before the tank runs dry.

 

[majic_tech]

I love science ...........good job dr dyno ..........now lets see some more flaming dumbasses.........

 

[MaXJohnson]

My guess? Since I'm a real smartass and not just claiming to be one , I'm going to use some science to come up with a true figure. A 4.0L engine idling at 750rpm with a perfect A/F ratio of 14.7:1 will consume 16.5lb of fuel in one hour. Since one US gallon of fuel weighs 6.1lb, that's a consumption of 2.7 gallons/hour.
This does assume 100% volumetric efficiency but the 4.0L engine probably has only 60% volumetric efficiency at 750rpm so the true figure should be roughly 1.6 gallons/hour (6.0 liters/hour for metric guys like me). That would give you about 12 hours of idling time before the tank runs dry.

good post, Dino. I just gave ya some rep points

 

[majic_tech]

lemmie try something here

 

[majic_tech]

ok I have an idea, what heater fan speed are you using while you are sitting around polluting the ozone layer in the interest of keeping your piggies warm? (dont they heat the building you work in?) what mode? defrost? You want i should factor in the cycling a/c clutch and alternator load too?...... Jump in here anytime Dyno im just trying to have some fun ....................any other ideas?......You chargin a cell phone too? that adds to the electrical load factor........$hit wheres my slide rule and thick glasses??????????? imma get right on it!.......the light at the end of the tunnel is causing your zero miles per gallon to go down dude! *we have an emergency!!!!!!!!!!!!!!!!*

 

[trekker]

Well I have no idea the answer to your question.
But I do have a suggestion for your reading material......

 

[gjxj]

Here's one way to look at it, a quick search shows many environmentalists claiming 1/2 to 1 gal /hour. Given the way the exagerate everything, I'd say its somewhere less than 1/2..

 

[DorkAlert]

Well I have no idea the answer to your question.
But I do have a suggestion for your reading material......


That's a great book....Just for fun maybe he should read Covey's 7 Habits of Highley Effective people...Then he could be more effective in figuring out the answer to his question. I like Dr. Dyno's answer....

 

[the_chief]

i would let my jeep idle for an hour and tell you, but it would probably blow up at the ten minute mark.

I've been contemplating an electric heating solution for my jeep, anyone have any good ideas or experience.

 

[rumblebelly]

My guess? Since I'm a real smartass and not just claiming to be one , I'm going to use some science to come up with a true figure. A 4.0L engine idling at 750rpm with a perfect A/F ratio of 14.7:1 will consume 16.5lb of fuel in one hour. Since one US gallon of fuel weighs 6.1lb, that's a consumption of 2.7 gallons/hour.
This does assume 100% volumetric efficiency but the 4.0L engine probably has only 60% volumetric efficiency at 750rpm so the true figure should be roughly 1.6 gallons/hour (6.0 liters/hour for metric guys like me). That would give you about 12 hours of idling time before the tank runs dry.

I'm a little confused. What exactly is volumetric efficiency? Is it the Air/Fuel mixture? If so, wouldn't less volumetric efficiency raise the gallons/hour? Of course, I could be missing something...

 

[bajacalal]

Its how much air (or air-fuel charge) the engine actually intakes/puts out while running compared to the how much the engine can potentially intake given its displacement. So, its related to the power made by the engine not so much the fuel efficency of the engine. The efficiency is limited by the restrictions (such as size of valves) that slow down the charge intake.

 

[Purple]

Does Tread Lightly apply only to running/moving vehicles?

 

[clean96XJ]

Listening to Car Talk awhile back. Some lady left her little honda ilding (with the key in it and unlocked) and it was dead in 24 hours. I think she had at least 3 quarters of a tank. So.. I would guess (note thumb in air) 4.0 would last about
14-16 hours.

On another note, ever notice how inaccurate you gas guage really is? I have been testing the limits for some time now. Fri I ran the gas guage almost past E. That is almost through E. I got gas when the needle was on top of the lower
left hand corner. (ya I got a pic but its on my phone and I dropped that part of the plan) When I went to fill it, still could only get 19.1 gallons in it.

 

[bajacalal]

It'll go past the E line. Just last week I had run it way too low and pulling out from my house it started sputtering but I accelerated slowly until it sputtered then pulled it out of gear, coast, avoided hills and made it the 1/2 mile to the gas station. I'm sure my fuel pump appreciates doing that.

 

[clean96XJ]

maybe my guage is not normal. But I mean almost past the letter E which is behind the line. .E\ that far left corner. where i put the period.

When it gets to the E line, how much gas can you put in?

 

[bajacalal]

LOL I only put half a tank in since I diddn't expect to drive much that week. I've squeezed about another gal past 20 my gauge is way inaccurate. 1/4 tanks seems like 7+ gal.

 

[Pappy]

Volumetric efficiency refers to how efficiently the engine runs. Compare a gas engine idling with closed throttle plates (vacuum) to a diesel engine idling with no throtle plates to restrict air. Gas engine volumetric efficiency varies with accelerator pedal while the diesel runs at a constant 100% volumetric efficiency, unless a turbo is installed.

 

[Dr. Dyno]

good post, Dino. I just gave ya some rep points

Thanks!

For those who wonder why I ask, I live in Chicago, and usally have ten of fifteen minutes to burn before work, so I sit in the car and read. Now that its colder I'm keeping it running for the heat. So I was just curious what it was costing me.

Let's see. If you burn 0.4 gallons each morning before driving off to work, and you work 5 days a week, that's 2 gallons per week or ~100 gallons per year. That's a lot of CO2, CO, HC, NOx, and other pollutants that you'd be pumping into the atmosphere. If everyone living in a cold climate does that, there'll be enough global warming within one year to make it unnecessary to do the same next year. The whole population will also be choking on the smog that'll accumulate. Since gas costs over $3 per gallon, your wallet would be $300 lighter each year and I don't think you'd like that. Let's just say that this wouldn't be a very smart idea.
Since you have 10-15 minutes to burn before leaving for work, I have a better idea. Spend that time doing some exercises in your home. A few push ups, sit ups, and squats will get your circulation going and warm the parts that'll otherwise freeze when you step outside. You'll burn some calories, lose some excess weight (if you have any), feel healthier, your wallet will thank you, you'll save wear and tear on your engine, and the world will thank you for not polluting the atmosphere.
Now that I've given you this wonderful idea, set a couple of beers aside for me and I'll come to drink them.

 

[jmsull]

First, I'd like to thank all of the people who continued to offer a simple answer to my very simple question. Thanks.

Second, my idling for fifteen minutes is not going to destroy the atmosphere. I guess it may account for 0.00000000000000001% of the pollutants in the atmosphere, this year. Incidentally, I don't want to hear one word about polluting from anyone who voted for W the last two elections. It's called The Kyoto treaty, and if you really want to keep the billions of tons of carbon from the atmosphere you would have voted for someone who would have prevented it.

Anyway, I drive a Cherokee, if the environment was that important to me I wouldn't drive a Jeep, I would be in a Civic, if not on a bike. If I never started another internal-combustion engine for the rest of my life, the environment would still be ruined in the coming decades. Not by me or you, but the whole planet acting together (but the US mostly, 4.6% of the planets population, 25% of the worlds emissions). So as soon as the country spends some serious time talking about how to prevent the disaster we are creating, I'll stop idling my car for ten or fifteen minutes a day. Until then, I guess I'm still just part of the problem, just like every one of you.

And last, I don’t need a book on “How to win friends”, I’ve got plenty, what I’ve been doing so far seems to work fine. You may want to read it though, it seems you could use it. I just have a problem with someone putting me down, so they can feel better about themselves, or to try and get a laugh from someone else. If you’re going to make a smartass comment, please by all means do so, I’ll be the first. But I won’t belittle you. And I’ll certainly read and understand the f’ing post before I start making fun of it.

I’m going to go let my car idle for a while.