Engineering Stack Exchange
Engineering Stack Exchange

Questions tagged [fuel-economy]

22 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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8
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6 answers

Can we add treadmill-like structures over the airplane surfaces to reduce friction, decrease drag and producing energy?

I am curious about a method to enhance the efficiency of passenger aircraft during cruise speeds by integrating treadmill-like structures on the fuselage and beneath the wings without changing the original shape of the aircraft and the…
Siames
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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…
MatthewSilus
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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.
STOI
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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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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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Why don't cars have manual valve timing?

This really confuses me. On the late steam engines, you let in as much steam as possible to start the engine, and "notch up" as you pick up speed so you waste less fuel. Some stationary engines even had rotary valves. I understand VTEC, but if you…
Ethan Miller
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T-GDI vs NA Petrol Cruising characteristics

I am interested in the real world applicability of vehicles' real world cruising RPMs. Consider two cars' Power Curves: 1.5L MPFI NA Petrol ~ 30hp @ 2000rpm @ 6th gear ~ 1150kg kerb wt ~ runs at 80kph 25% throttle 1.5L Turbo GDI ~ 60hp @…
Abel Rosnovski
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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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