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Discussion Starter · #1 ·
The WLTP and it predecessors NEDC and the various EPA test cycles are intended to model average driving behaviour. Their primary purpose is to estimate the emissions of ICE vehicles, on which various taxes are levied. Their secondary purpose is to estimate the average fuel/energy consumption as a cost guide for consumers.

The key word here is "average". The WLTP test cycle is heavily weighted towards urban & suburban driving, with only a small proportion of highway driving (briefly up to 130kph = 81mph), but the overall average speed excluding stops is only 33mph. This may well be an accurate representation of the average use of the average car, and indeed it may give a valid estimate of the average energy consumption of an EV in average day-to-day use. However, that figure is of little interest to an EV owner, as the energy costs are so small. In terms of range, it doesn't really matter whether you need to charge your car every 8 days or every 7 days in average pottering-about or short commute usage.

The only times that range is an issue for an EV owner are, by definition, not average drives. They will be long trips on highways/motorways, at sustained high speeds, with some lower-speed driving at each end of the trip and for eg congestion en route.

What the EV industry needs is a new standard test cycle, designed to measure the RANGE of an EV in "journey" mode. Measured data of kW-hr per mile at various steady speeds would be a start; but these will be optimistic compared with "real" driving conditions and the losses associated with varying speeds.

Perhaps JLR/Merc/Audi/Porsche should get together and start the process of developing a European industry standard?
 

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DougTheMac said:
The WLTP and it predecessors NEDC and the various EPA test cycles are intended to model average driving behaviour. Their primary purpose is to estimate the emissions of ICE vehicles, on which various taxes are levied. Their secondary purpose is to estimate the average fuel/energy consumption as a cost guide for consumers.

The key word here is "average". The WLTP test cycle is heavily weighted towards urban & suburban driving, with only a small proportion of highway driving (briefly up to 130kph = 81mph), but the overall average speed excluding stops is only 33mph. This may well be an accurate representation of the average use of the average car, and indeed it may give a valid estimate of the average energy consumption of an EV in average day-to-day use. However, that figure is of little interest to an EV owner, as the energy costs are so small. In terms of range, it doesn't really matter whether you need to charge your car every 8 days or every 7 days in average pottering-about or short commute usage.

The only times that range is an issue for an EV owner are, by definition, not average drives. They will be long trips on highways/motorways, at sustained high speeds, with some lower-speed driving at each end of the trip and for eg congestion en route.

What the EV industry needs is a new standard test cycle, designed to measure the RANGE of an EV in "journey" mode. Measured data of kW-hr per mile at various steady speeds would be a start; but these will be optimistic compared with "real" driving conditions and the losses associated with varying speeds.

Perhaps JLR/Merc/Audi/Porsche should get together and start the process of developing a European industry standard?
That's quite a lot of assumptions and generalizations you are making on behalf of all EV owners. As such, you make your opinion as irrelevant as ( in your personal view) WLTP.

I believe range is of importance (not all EV owners charge at home), as is energy efficiency (energy is not cheap for all EV owners) and charging speed for example.

The WLTP method is certainly far from perfect and better testmethods are indeed needed but as long as we don't have a good alternative, it's a very relevant test.
 

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We can also share our data within this forum :
Yesterday I drove from Paris to Deauville (220 km x2 ) and back using only the motorways 50 KW DC chargers.
My car is a SE with 20" wheels and the speed was mostly 130/140 and I did not use the clim.
Consumption was just below 27KWh/100km.
I stopped twice for 35 minutes to charge 25KWh each time.
 

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emgf said:
Yes but no clim
Clim uses more kwh/km the lower the speed is because its constant pr hour. At 130-40 at french mid October temperatures it consumes very little energy.
 

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I agree that quoted economy (or not) figures are pretty meaningless. What gets quoted in the mags by the reviewers is also pretty poor.

I ride a Motorcycle (Triumph Trophy SE). The maker quotes up to 64mpg (UK Gallons). One review I read said 54mpg yet on long trips I get up to 70mpg and even riding around town and shortish distances I get 64-66mpg.
It is mostly down to riding/driving style. Journalists seem to be very heavy on the right foot/right hand.

Then you notice the terrain more with an EV. Go one way along a road and get 'x' mpg. You will a different mpg value for the return trip unless the road is perfectly flat and there is no wind.
 

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DougTheMac said:
The WLTP and it predecessors NEDC and the various EPA test cycles are intended to model average driving behaviour. Their primary purpose is to estimate the emissions of ICE vehicles, on which various taxes are levied. Their secondary purpose is to estimate the average fuel/energy consumption as a cost guide for consumers.

The key word here is "average". The WLTP test cycle is heavily weighted towards urban & suburban driving, with only a small proportion of highway driving (briefly up to 130kph = 81mph), but the overall average speed excluding stops is only 33mph. This may well be an accurate representation of the average use of the average car, and indeed it may give a valid estimate of the average energy consumption of an EV in average day-to-day use. However, that figure is of little interest to an EV owner, as the energy costs are so small. In terms of range, it doesn't really matter whether you need to charge your car every 8 days or every 7 days in average pottering-about or short commute usage.

The only times that range is an issue for an EV owner are, by definition, not average drives. They will be long trips on highways/motorways, at sustained high speeds, with some lower-speed driving at each end of the trip and for eg congestion en route.

What the EV industry needs is a new standard test cycle, designed to measure the RANGE of an EV in "journey" mode. Measured data of kW-hr per mile at various steady speeds would be a start; but these will be optimistic compared with "real" driving conditions and the losses associated with varying speeds.

Perhaps JLR/Merc/Audi/Porsche should get together and start the process of developing a European industry standard?
Of course WLTP is important. It sould make it possible to compare consumption (= +/- range) between cars (standardized test).
It sould give a possible real world estimate of range under standard conditions.
Unfortunately Jaguar is apparently not able to live the dream (WLTP)..

Question is: will you be able to drive 80%, 90% or 99% of your trips without charging stops. I am (or was) hoping for 400km as it is way below the stated WLTP. Only small fraction of highway.

See also wltpfacts.eu
 

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Discussion Starter · #10 ·
Bart said:
Of course WLTP is important. It sould make it possible to compare consumption (= +/- range) between cars (standardized test).
It sould give a possible real world estimate of range under standard conditions.
Unfortunately Jaguar is apparently not able to live the dream (WLTP)..

See also wltpfacts.eu
It's not that "Jaguar is not able to live the dream (WLTP)". Assuming Jaguar has not fraudulently tested the I-Pace, we must assume that an I-Pace "driven" (by a computer on a dynamometer) through the WLTP test can achieve 292 miles of range (and presumably 100% to 0% charge). The problem is that a human driver of an I-Pace is unlikely to drive in the way WLTP defines. It's not Jaguar's "fault" that the real world range is so much less than WLTP; the "fault" is either the driver's (for not driving in conformity with WLTP) or the WLTP test (for being unrealistic). Exactly the same argument applies to ICE engines and fuel consumption - no-one actually achieves the WLTP fuel consumption figures in real life.

The "unrealistic" aspect of WLTP is even more emphasised by the limited accelerations in the profile rather than just the limited speeds, especially when applied to a performance EV such as I-Pace or Tesla. The maximum 0-30mph (50kph) acceleration in WLTP is 15 seconds. I suspect most I-Pace drivers would find it extremely difficult to drive so gently.

I believe Jaguar IS at fault in its marketing, where the WLTP range is widely publicised with little warning that it is unrealistic. (Compare with the Zoe, where Renault openly give guidance about "real world" ranges).

But I re-state my case: WLTP is NOT a useful means of estimating REAL WORLD range ON A LONG JOURNEY. The average speed of WLTP is 46.5kph = 29mph. It therefore takes 10 hr to exhaust the battery - and 290 miles in 10hr is certainly not my idea of how to do a journey.

WLTP has its place and its uses, but primarily for ICEs. Testing EVs with this cycle does NOT give a useful estimate of LONG TRIP RANGE, which is what (I believe) most users are most worried about. We need a more relevant test.

And in the meantime, you (not we - don't have mine yet!) all need to enjoy driving a high-performance luxury car and try not to obsess about why you can't drive 292 miles with a heavy right foot - about which, more anon...
 

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DougTheMac said:
Bart said:
Of course WLTP is important. It sould make it possible to compare consumption (= +/- range) between cars (standardized test).
It sould give a possible real world estimate of range under standard conditions.
Unfortunately Jaguar is apparently not able to live the dream (WLTP)..

See also wltpfacts.eu
It's not that "Jaguar is not able to live the dream (WLTP)". Assuming Jaguar has not fraudulently tested the I-Pace, we must assume that an I-Pace "driven" (by a computer on a dynamometer) through the WLTP test can achieve 292 miles of range (and presumably 100% to 0% charge). The problem is that a human driver of an I-Pace is unlikely to drive in the way WLTP defines. It's not Jaguar's "fault" that the real world range is so much less than WLTP; the "fault" is either the driver's (for not driving in conformity with WLTP) or the WLTP test (for being unrealistic). Exactly the same argument applies to ICE engines and fuel consumption - no-one actually achieves the WLTP fuel consumption figures in real life.

The "unrealistic" aspect of WLTP is even more emphasised by the limited accelerations in the profile rather than just the limited speeds, especially when applied to a performance EV such as I-Pace or Tesla. The maximum 0-30mph (50kph) acceleration in WLTP is 15 seconds. I suspect most I-Pace drivers would find it extremely difficult to drive so gently.

I believe Jaguar IS at fault in its marketing, where the WLTP range is widely publicised with little warning that it is unrealistic. (Compare with the Zoe, where Renault openly give guidance about "real world" ranges).

But I re-state my case: WLTP is NOT a useful means of estimating REAL WORLD range ON A LONG JOURNEY. The average speed of WLTP is 46.5kph = 29mph. It therefore takes 10 hr to exhaust the battery - and 290 miles in 10hr is certainly not my idea of how to do a journey.

WLTP has its place and its uses, but primarily for ICEs. Testing EVs with this cycle does NOT give a useful estimate of LONG TRIP RANGE, which is what (I believe) most users are most worried about. We need a more relevant test.

And in the meantime, you (not we - don't have mine yet!) all need to enjoy driving a high-performance luxury car and try not to obsess about why you can't drive 292 miles with a heavy right foot - about which, more anon...
Very well said!
And lets see how Merc's & Audi's do against WLTP in real life
 

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To put in a word for Jaguar, right from the outset at the reveal in Feb in Solihull they said 220-240 mile range if "driven like a Jag" They where actively discounting the nearly 300miles idea.
 

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DougTheMac said:
Bart said:
Of course WLTP is important. It sould make it possible to compare consumption (= +/- range) between cars (standardized test).
It sould give a possible real world estimate of range under standard conditions.
Unfortunately Jaguar is apparently not able to live the dream (WLTP)..

See also wltpfacts.eu
It's not that "Jaguar is not able to live the dream (WLTP)". Assuming Jaguar has not fraudulently tested the I-Pace, we must assume that an I-Pace "driven" (by a computer on a dynamometer) through the WLTP test can achieve 292 miles of range (and presumably 100% to 0% charge). The problem is that a human driver of an I-Pace is unlikely to drive in the way WLTP defines. It's not Jaguar's "fault" that the real world range is so much less than WLTP; the "fault" is either the driver's (for not driving in conformity with WLTP) or the WLTP test (for being unrealistic). Exactly the same argument applies to ICE engines and fuel consumption - no-one actually achieves the WLTP fuel consumption figures in real life.

The "unrealistic" aspect of WLTP is even more emphasised by the limited accelerations in the profile rather than just the limited speeds, especially when applied to a performance EV such as I-Pace or Tesla. The maximum 0-30mph (50kph) acceleration in WLTP is 15 seconds. I suspect most I-Pace drivers would find it extremely difficult to drive so gently.

I believe Jaguar IS at fault in its marketing, where the WLTP range is widely publicised with little warning that it is unrealistic. (Compare with the Zoe, where Renault openly give guidance about "real world" ranges).

But I re-state my case: WLTP is NOT a useful means of estimating REAL WORLD range ON A LONG JOURNEY. The average speed of WLTP is 46.5kph = 29mph. It therefore takes 10 hr to exhaust the battery - and 290 miles in 10hr is certainly not my idea of how to do a journey.

WLTP has its place and its uses, but primarily for ICEs. Testing EVs with this cycle does NOT give a useful estimate of LONG TRIP RANGE, which is what (I believe) most users are most worried about. We need a more relevant test.

And in the meantime, you (not we - don't have mine yet!) all need to enjoy driving a high-performance luxury car and try not to obsess about why you can't drive 292 miles with a heavy right foot - about which, more anon...
The test cycle is driven on a Chassis Dynamometer (rolling road) by a person not a robot (although robots are capable of doing the same). The "driver" simply follows a speed profile that is presented on a computer screen. There are maximum and minimum limits for the profile that the "driver" has to stay between. A good "driver" is able to use these limits to achieve slight improvements in efficiency.

The best way to see what the car will do for your own personal journeys is to get Jaguar to loan you a test car for a day or two and test it the way you would drive it.

However, in saying this, if you are coming from an ICE car to a BEV, there is a different style of driving to be learned if you want to achieve high mileage between charges.

Oh, and Jaguar state the WLTP range but also make it clear that most drivers can expect to get around 240 miles range from a full charge. This will be different in winter than in summer as well, with longer range in summer.
 

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Chewy said:
The test cycle is driven on a Chassis Dynamometer (rolling road) by a person not a robot (although robots are capable of doing the same). The "driver" simply follows a speed profile that is presented on a computer screen. There are maximum and minimum limits for the profile that the "driver" has to stay between. A good "driver" is able to use these limits to achieve slight improvements in efficiency.
How do they take aerodynamics into account while the car is on the chassis dynamometer? Is that a calculated value that then introduces more rolling resistance?
 

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I've heard from a reliable source that the Audi e-tron will come in at around 160 miles real world range. I leave it to you to a) consider the veracity of this, b) work out if £70k+ is good value for this and c) would this work for you in day to day driving.

As to Audi/VW/Porsche/Mercedes/BMW formulating their own European test cycle, I doubt that the rest of the world outside Germany would believe their figures, considering recent history when it comes to testing standards. I certainly wouldn't.
 

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Snoerd said:
Chewy said:
The test cycle is driven on a Chassis Dynamometer (rolling road) by a person not a robot (although robots are capable of doing the same). The "driver" simply follows a speed profile that is presented on a computer screen. There are maximum and minimum limits for the profile that the "driver" has to stay between. A good "driver" is able to use these limits to achieve slight improvements in efficiency.
How do they take aerodynamics into account while the car is on the chassis dynamometer? Is that a calculated value that then introduces more rolling resistance?
There is a procedure they use to determine the force a car sees on the road....

On a straight and flat stretch of road the car is accelerated to 160 kph then put into neutral and allowed to coast down to a stop. In this way, car rolling resistance, wind force etc will decelerate the car. Accurate speed measurement and timing is used to record the "coast down". This is repeated in both directions on the track and an average is taken of the times. The profile of the coastdown is then put into the Chassis Dyno Control System Software and it works out a set of Terms that describe the coastdown.

The Chassis Dynamometer itself will have an inertia (mass equivalent) and its own friction losses. These are measured over the same roller speed range and accounted for when simulating the vehicle loads.

Once the software has the "coastdown data" from the vehicle the car is putonto the Chassis Dynamometer and the control system runs in speed control mode and accelerates the car up to the same 160kph then forces the car to follow the same speed profile on the Chasssis Dynamometer that was seen on the road. During this process the forces seen on the Chassis Dyno load cell monitoring system are recorded with the speed. From the force/speed data the Control System software calculates a set of terms that describe the force profile seen on Chassis Dynamometer, This is of the form..

Force = A + B.v + C.v2, where v = vehicle speed.

The Control system software works out the constants A, B and C.

So when we now run the car on the Chassis Dynamometer, the final calculation used is of the form...

force = A + B.v + C.v2 + M dv/dt, where

M = vehicle mass
dv/dt = acceleration.

Gradient can also be added to the final calculation, but The older Test Cycles for emissions do not use gradient.

This gives a very accurate representation of the forces the car would see on a road when running on a Chassis Dynamometer.

I will try and post up some graph plots if I get time.
 

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Chewy said:
The test cycle is driven on a Chassis Dynamometer (rolling road) by a person not a robot (although robots are capable of doing the same). The "driver" simply follows a speed profile that is presented on a computer screen. There are maximum and minimum limits for the profile that the "driver" has to stay between. A good "driver" is able to use these limits to achieve slight improvements in efficiency.

The best way to see what the car will do for your own personal journeys is to get Jaguar to loan you a test car for a day or two and test it the way you would drive it.

However, in saying this, if you are coming from an ICE car to a BEV, there is a different style of driving to be learned if you want to achieve high mileage between charges.

Oh, and Jaguar state the WLTP range but also make it clear that most drivers can expect to get around 240 miles range from a full charge. This will be different in winter than in summer as well, with longer range in summer.
I though it was with NEDC and for WLTP they changed that with real road test driving ?
 

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Tophe74 said:
Si only EPA does real driving wich would explain the better accuracy for all cars (EV and IC)E).
In France WLTP tests include real driving done in Mortefontaine national car test center ( I was told a few weeks ago when testing my I-Pace)
 
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