Engineering Stack Exchange
Engineering Stack Exchange

Questions tagged [fuel-economy]

19 questions
22
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4 answers

How does turning off electric appliances save energy

We all know if we use less electricity we save energy. But the energy we're getting is result of burning (not necessarily the literal meaning) the fuel. Even if we don't use that energy that fuel is gone forever. (Except saving money on bills) My…
ShivCK
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2 answers

While going downhill, does my car consume less fuel when in neutral or in gear?

I once meditated on the fact that a car, in downhill, would consume more fuel when in neutral to keep the engine on, rather than in gear. To keep the engine on when in gear, in fact, you mostly need the gravity and enough thrust to keep it rotating,…
Wes
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9
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10 answers

How can "mpg" be high under low engine load?

Let's say a car at 60 mph requires roughly 20 hp to maintain its speed (i.e., to overcome rolling resistance and drag). If this car makes 240 hp and gets about 34 mpg (not too unrealistic), how is it getting 34 mpg if the engine is only at 0.05…
NumberJuan
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5
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2 answers

Whats the purpose of a main metering system in a carburetor?

I'm confused on how to differentiate mixture control from the main metering system, and why we even need one at all. Let's say we had a large resovior, and a needle type mixture control system. The differential pressure would push/pull fuel from the…
ApolloMission4
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4
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4 answers

Why wont Petrol engine run on Acetylene?

Boiling temperature of Acetylene is -84°C and that of Petrol is 95°C (at Atmospheric Pressure). So the spark is efficient to ignite the compressed Acetylene and run the Engine. But why wont that work ? Is any other factor that I miss or…
Dasaradh M S
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4
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1 answer

What does MM prefix mean in MMtoe?

I was reading documents about energy importation and came across the following: The import was of 5,915.87 MMtoe I wonder if MMtoe = $10^6*10^6$ toe = $10^{12}$ toe. First time coming across a unit expressed like that.
RSM
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4
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1 answer

How does the optimal-gear indicator work?

Some modern cars, including models by BMW, Ford and Audi, have a system on the panel that tells the driver the next gear to use while driving, for optimal fuel economy. How does the vehicle decide which gear provides the best fuel economy? What data…
NG_21
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3
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1 answer

Can we currently achieve 55 MPG on Non-Hybrid vehicles using internal combustion engines?

With recent debates, one frequently hears that it's currently not possible for car manufacturers to meet the 55 MPG energy efficiency rating required by 2025. So, is there something physically impossible about meeting this standard? Is it achievable…
Beliod
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2
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1 answer

does payload weight distribution affect rolling resistance?

Recently came across the following 2-minute YouTube video that claims A Balanced Rig Saves Fuel While nicely done, it is a marketing video. Does anyone know of any unbiased studies that support the claim?
mathematrucker
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2
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1 answer

How much air will an engine use per tank of gas?

Apparently I have a stupid question. I got curious and crunched some numbers to determine approximately how much air an engine consumes in total to burn a full tank of gas. Something went horribly wrong and I feel stupid. So theoretically, I can get…
CDB
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Calculating fuel mixture from injector pulses

I have a simulation of a fuel injection system and the result is a set of pulses that operate the injectors. I know how long the pulses are in milliseconds and I know how much fuel is emitted from a single injector per millisecond. Therefore I know…
user150402
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Which is fuel efficient, roadways transport vs waterways transport?

Which will be more efficient in term of fuel price: Transport via roadways, say truck or motor vehicle. Transport via waterways, say via ship or motor boat. Assumptions: Same caliber engines (same power) are used in either ways. Fuel is same. The…
Anurag Vohra
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1 answer

How to Calculate Approximate Fuel Consumption from Engine Specs

I have a marine diesel engine, and I'd like to calculate the approximate fuel consumption based on the size of the engine, at a given number of RPM - specifically for the cruising recommended cruising RPM of 2880 - 3240. Guidance online varies from…
Adrian K
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Where can I find efficiency metrics for diesel engines?

I am doing long term planning for a small fleet of tugboats. A lot of the engines (propulsion, generators, hydraulics) are Detroit Diesels of various sizes (e.g., 4-71, 6-71, 12V-71). Newer engines are more efficient, but it is not clear to me how…
Gene McCulley
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Can turbine engines really run on "just about anything"?

I often read that turbine engines can run on almost any fuel source. I understand that turbine engines are less "picky" in terms of the fuel source that they can use, but surely there would still be some limitations as to which fuel source can be…
PhysicsGuy123
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