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Old 02-22-2020, 10:06 AM   #1 (permalink)
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Worldwide Harmonised Light Vehicle Test Procedure (WLTP)

The WLTP has now replaced the NEDC (New European Drive Cycle).

As a tool for predicting real world fuel consumption, the NEDC was very inaccurate with many vehicles burning upwards of 45% more fuel than the NEDC test indicated. Not only was the test procedure a very poor representation of a real world drive cycle but it was very easy for the manufactures to "game" the test.

https://ecomodder.com/forum/showthre...ion-34666.html

So, is the WLTP an accurate reflection of real world fuel consumption?

To answer this question, I have compared actual measured real world fuel consumption for some small engine capacity cars ( all less than 1.25 lit bar the 1.5 lit Mazda 2) to the official combined fuel consumption from the WLTP test.

This data can be found in the chart below.



The last column in the table shows the percentage difference between measured real world fuel consumption - as extracted from https://www.spritmonitor.de/en/ - and the WLTP combined test results.

It is evident that there is good correlation in the fuel consumption data with the difference being less than 5% for the majority of the vehicles.

At this moment in time, the data would suggest that the official WLTP fuel consumption is a good indicator of real world fuel consumption for most small capacity vehicles on the market.

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Old 02-22-2020, 10:08 AM   #2 (permalink)
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The WLTP data can be found at this site

https://carfueldata.vehicle-certific...used-cars.aspx
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Old 02-22-2020, 01:03 PM   #3 (permalink)
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Is this also going to be used for emission testing. Seems like the Diesels from several manufacturers have been scamming the tests. VW got caught and there have been rumors about several others.
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Old 02-22-2020, 01:05 PM   #4 (permalink)
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Quote:
Originally Posted by cr45 View Post
The WLTP data can be found at this site

https://carfueldata.vehicle-certific...used-cars.aspx
Starting from 2001 apparently. I guess my 1998 avensis is ancient.
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Old 02-22-2020, 01:44 PM   #5 (permalink)
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Quote:
Originally Posted by me and my metro View Post
Is this also going to be used for emission testing. Seems like the Diesels from several manufacturers have been scamming the tests. VW got caught and there have been rumors about several others.
I think just about every manufacturer has tried to cheat the test and has been caught since the 1980s.
But with VW they really made an example out of them for some reason.
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Old 02-22-2020, 02:29 PM   #6 (permalink)
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Quote:
Originally Posted by me and my metro View Post
Is this also going to be used for emission testing. Seems like the Diesels from several manufacturers have been scamming the tests. VW got caught and there have been rumors about several others.
It is the old test - NEDC - that the manufacturers were scamming. In the case of the VAG group, their diesels could detect when they were being tested on a chassis dyno compared to driven on the road.

From April 2020 in Europe all new cars fuel consumption and CO2 data will be based on the new WLTP test procedure, which is still carried out on chassis dynos.

One advantage of the new test is that the average speed is now 28.9 mph vs
21 mph for the old NEDC.

The test is also now 14.4 miles in length compared to 6.8 miles for the NEDC.

One problem with the old test was that a manufacturer could bring out a very basic version of a new model of car and the aero data and mass of that vehicle could be used for subsequent testing of related models even though these models are less aerodynamic - bigger tyres, alloy wheels, body kit, larger radiator intakes etc - and are considerably heavier.

Now all versions of a model have to be tested individually even if there is only a small difference in design such as wider wheels.


Some more info here

https://www.parkers.co.uk/what-is/wl...est-procedure/

The pollutants part of the test will be carried out on the open road.

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