Fuel consumption test methodology

[Matra et Alpine]

This comes up often in discussino about "real" fuel consumption versus published figures to varying standards.

So here's the European version ............

FUEL CONSUMPTION TEST (Directive 80/1268/EEC as amended by 2004/3/EC)
The new test has been agreed internationally and provides results that are more representative of actual average on-road fuel consumption than previous tests. There are two parts: an urban and an extra-urban cycle. The test cycle is the same as that used to determine the official exhaust emission classification for the model of vehicle in question.
The cars tested have to be run in and must have been driven for at least 1,800 miles (3,000 kilometres) before testing.
Urban cycle
The urban test cycle is carried out in a laboratory at an ambient temperature of 20°C to 30°C on a rolling road from a cold start, i.e. the engine has not run for several hours. The cycle consists of a series of accelerations, steady speeds, decelerations and idling. Maximum speed is 31 mph (50 km/h), average speed 12 mph (19 km/h) and the distance covered is 2.5 miles (4 km). The cycle is shown as Part One in the diagram below.
Extra-urban cycle
This cycle is conducted immediately following the urban cycle and consists of roughly half steady-speed driving and the remainder accelerations, decelerations, and some idling. Maximum speed is 75 mph (120 km/h), average speed is 39 mph (63 km/h) and the distance covered is 4.3 miles (7 km). The cycle is shown as Part Two in the diagram below.
Combined Fuel Consumption Figure
The combined figure presented is for the urban and the extra-urban cycle together. It is therefore an average of the two parts of the test, weighted by the distances covered in each part.

[Matra et Alpine]

The EPA fuel economy test consists of two driving routines, or schedules, performed in the laboratory.

City: Represents urban driving, in which a vehicle is started with the engine cold and driven in stop-and-go rush hour traffic. The driving cycle for the test includes idling, and the vehicle averages about 20 mph.

Highway: Represents a mixture of rural and Interstate highway driving with a warmed-up engine, typical of longer trips in free-flowing traffic. Average test speed is about 48 mph and includes no intermediate stops or idling.

The city schedule represents low-speed driving in stop-and-go traffic and considerable idling.

The highway schedule simulates non-metropolitan driving at higher speeds, with no stops and negligible idling.

Test Schedule Characteristics Driving Schedule Attributes

Test Schedule
City ! Highway

Trip Type

Low speeds in stop-and-go urban traffic ! Free-flow traffic at highway speeds

Simulated Distance

11 miles ! 10 miles

Time

31 minutes ! 12.5 minutes

Average Speed

20 mph ! 48 mph

Top Speed

56 mph ! 60 mph

Stops

23 ! None

Idling time

18% of time ! None

Engine Temp. at Startup*

Cold ! Warm

Lab temperature

68-86 ºF

Vehicle air conditioning

Off

* A vehicle's engine doesn't reach maximum fuel efficiency until it is warm.

[Matra et Alpine]

SOrry botu the layout, bty new UCP sucks for tables, It pastes them in OK, but once you save it it screws up

ah well


ANyway, THIS was an interesting note on teh "scientific" EPA method ---- I love fugdge factors -- espsecially as THEN people will make proud claims based on point one differences

"Adjusting Estimates

In the 1980s, an EPA study found that drivers were typically achieving lower fuel economy than predicted by EPA laboratory tests. As a result, EPA required the laboratory-derived city and highway MPG estimates posted on the labels of new vehicles to be adjusted downward by 10 percent for city estimates and by 22 percent for highway estimates to better reflect the MPG real-world drivers can expect."


22 PERCENT !!!!!! lol
So if you have an efficiently designed car with low rolling road resisitance and good aerodynamics the fudge will be MORE than it should be, if you'e a 4x4 SUV shaped like a brick then the fudge factor is in your favour --- hmm and they say the US EPA isn't swayed by the US manufacturers

BTW the US info is taken form the EPA's own fueleconomy.gov web site, including the fudge factor text.

The thing to remember they are all estimates, real world info is more useful ( and praise to EPA for actually having a "My MPG" so folks can share their real world numbers )

[drakkie]

I'd say a ombination of US city cycle and EU highway driving would be a nice combination. However don't run in a laboratory but in the "real jungle". Drive a car for something like 500 miles in city cycle and 500 miles highway for better averages,but drive the same routes. I'm sure someone can figure out a model to adjust the mpg/kmpl stuff to speeds achieved.

By the way, thx for the info, interesting read

[Coventrysucks]

Of course, honourable manufacturers would cite the mpg returned from their pre-release road testing - it wouldn't be comparable to other manufacturers because you don't know what testing they did, but it would be more use to customers.

Of course the whole idea is not to replicate real-world driving, as with several hundred million people across the EU and US, each driving differently, you can't get it right.

The tests merely give a yardstick with which you can "accurately" compare like for like;

If car A gets 5% better mpg than car B according to EPA/EU tests then it should, in theory, get 5% better in the real world.

[henk4]

would it be possible to make a comparison to see how the ECE cycle is being calculated?

[Matra et Alpine]

If car A gets 5% better mpg than car B according to EPA/EU tests then it should, in theory, get 5% better in the real world.

Except for that crazy 22% fudge factor !!!!!

[Matra et Alpine]

would it be possible to make a comparison to see how the ECE cycle is being calculated?

Post #1 ... no fudge factors.
Measured aross the cycle an published.

Was there some other test ?

[henk4]

Post #1 ... no fudge factors.
Measured aross the cycle an published.

Was there some other test ?

oh s..t, I did not even see that....That's what you get when you read the latest post first...

[spi-ti-tout]

This one?

[Matra et Alpine]

The US06 Supplemental Federal Test Procedure (SFTP) was developed to address the shortcomings with the FTP-75 test cycle in the representation of aggressive, high speed and/or high acceleration driving behavior, rapid speed fluctuations, and driving behavior following startup.
The cycle represents an 8.01 mile (12.8 km) route with an average speed of 48.4 miles/h (77.9 km/h), maximum speed 80.3 miles/h (129.2 km/h), and a duration of 596 seconds.

[Coventrysucks]

"If car A gets 5% better mpg than car B according to EU tests then it should, in theory, get 5% better in the real world."

There.

[ruim20]

So... i have king of an impossible problem for you guys to try and help me out, i've been trying to calculate how much fuel my car uses, but i have a major problem lol, i know how many Kms i do but i don't know accuratly how many Lts i spent, because the car just as a neddle to show fuel consuption - and you know how accurate those are...- so i'm asking to know if there is a different method to find out how much it's spending, my rough calculations lead me to believe it's doing 6-7 lts each 100kms...

[henk4]

that is not the most difficult problem. Take a paper and pencil in your car, and everytime you refuel, just note the the current indication on the odometer and the amount of fuel loaded. Over time, you will get a very good idea what your mileage is.

[Matra et Alpine]

If you want a fast answer then fill the tank ... put the nozzle all the way in and fill till it clicks off. ( this sometimes takes one or two cicks ad "slow fill" at the end ) . You now have a known tank level. Reset the tripmeter to 0000.

Drive the car and then at any time go fill it up again using the same procedure above. The amount of fuel added is the amount you've used.
If you use the same pump nozzle and the same method you can get VERY close on the fuel amount added.

Simpe calc of miles/kms on on the trip divided by fuel just paid for