Fuel economy. I now think my Phev is a lemon.

[Trex]

Yes you read that title right.

I have been away for awhile and trying to catch up on some of the posts and have been reading figures thrown out there like 40mpg (7.06L/100k) at 70mph. :shock:

Out on the highway here the best I can do is 8.0L/100k at 110kph (roughly the same speed). in normal mode.

Or is the grid charge being included in these figures here folks. Talk about apples and oranges.

How I test my fuel consumption and I do it all the time:

1. Empty the grid charge first even if that includes highway. Takes that grid charge straight out of the question.
2. Reset either manual or auto fuel economy computer or both.
3. Take measurements from there on.

Now I know people are going to say "but I want to save it for ............. " fill in your own words here but there is a charge button for refilling if required which is what I do. (1/2 charge in 1/2 an hour).

I find I cannot take accurate measurements while ever the grid charge is in my Phev . Again how are we ever going to compare figures if we do not have a level playing field?. I can hear you saying "ok but I will press save and then reset the fuel computer" but I found out nearly 18 months ago (never touch the save button now) even then the SOC can drift which can affect my results. Or I forgot to note my measurement before using some more of the grid charge.

Anyway enough of my rant. :lol:

Regards Trex.

 

[gwatpe]

I find I cannot take subjective measurements while ever the grid charge is in my Phev

I think you mean "objective measurements".

Objective measurement is the repetition of a unit amount that maintains its size, within an allowable range of error, no matter which instrument, intended to measure the variable of interest, is used and no matter who or what relevant person or thing is measured.

The battery makes the measurements "Subjective" as it is an unknown variable.

We are certainly lacking tools to objectively measure economy without going to extreme lengths to define driving test conditions.

My first PHEV had a low capacity problem with the battery, and driving with the same style, my replacement PHEV, uses 1L/100km less petrol consumption on average. I am for, "what ever makes the battery maintain its capacity". If cycling the battery more decreases the capacity faster over time, to save a bit of petrol, may end up costing an increased petrol consumption and early battery replacement later on. I hope the battery in my PHEV lasts the life of the car. Presently 97.8%SOH by the computer after 39000km, so am expecting lots more years.

Just wish I had the same telemetry and logging on my PHEV, like I have made for my robotic vacuum cleaner.

The voltage is in red, and the current in and out of the battery is in green + and - amps about the graph centre. Only a NiMH battery, but a LiIon is coming, and checking the operation will be a first step.

 

[Trex]

I find I cannot take subjective measurements while ever the grid charge is in my Phev

I think you mean "objective measurements".

Objective measurement is the repetition of a unit amount that maintains its size, within an allowable range of error, no matter which instrument, intended to measure the variable of interest, is used and no matter who or what relevant person or thing is measured.

The battery makes the measurements "Subjective" as it is an unknown variable.

We are certainly lacking tools to objectively measure economy without going to extreme lengths to define driving test conditions.

:lol: :lol: just fixed it and then read your post. Accurate is the word I meant.

I find the fuel computer accurate and we all have one.

 

[Trex]

gwapte,

I have to learn to press that preview button more and proof read. Just read where you have added more to your post which is what I do ie press submit then edit.

Anyhow. You know how I check my battery (wheels to the road) and it is holding up well but it is early days.

For fuel consumption comparisons I think the Phevs own fuel computer is what we should use but we have to make sure we are not muddying the waters with that grid charge and that is so easy to do in my opinion.

Regards Trex.

 

[gwatpe]

MMC started this problem with the quoted 1.9L/100km. I get better than this sometimes. Does not really prove anything.

My PHEV has averaged out in 39000km to 7.6L/100km. This has included between 25 & 30000km of driving, including paved and dirt roads and without any available recharging. I do expect this average to drop slowly as my driving needs change to include more EV only.

PS does any forum member know at what point the PHEV stops counting litres in the L/100km equation.

 

[Trex]

MMC started this problem with the quoted 1.9L/100km. I get better than this sometimes. Does not really prove anything.

Forgot about the old 1.9L/100k. :lol: Did not think anyone took notice of that? I never did. But it could be a reason.

I just want a way to compare apples with apples.

But the way I am doing it I can even compare cars that are not plug-in and even other hybrids like my old Prius.

I know the grid charge has not biased my measurements but if I started to include them my fuel economy figures would look even better especially on shorter trips and that is the point of why I do not.

Regards Trex.

 

[anko]

MMC started this problem with the quoted 1.9L/100km. I get better than this sometimes. Does not really prove anything.

I don't think they started anything. It is totally according to the books (at least in Europe). The book says: To calculate Plug-In economy, you first drive whatever the electric range is on electricity and then 25 km on petrol as a hybrid vehicle. Then You calculate average consumption of the total distance.

In our case:

( 52 km x 0.0 l / 100 km + 25 km x 5.8 l / 100 km) / 77 km = 1.9 l/100 km.

So, the number is impacted by two figures: EV range and hybride economy. When the battery is increase, plug-in economy increases as well. Totally makes sense.
Of course both values are taken from the brochure, not from real live. But this happens with any car, so, the number is not more meaningless (not less meaningful?) than with any other car.

 

[Trex]

MMC started this problem with the quoted 1.9L/100km. I get better than this sometimes. Does not really prove anything.

I don't think they started anything. It is totally according to the books (at least in Europe). The book says: To calculate Plug-In economy, you first drive whatever the electric range is on electricity and then 25 km on petrol as a hybrid vehicle. Then You calculate average consumption of the total distance.

In our case:

( 52 km x 0.0 l / 100 km + 25 km x 5.8 l / 100 km) / 77 km = 1.9 l/100 km.

So, the number is impacted by two figures: EV range and hybride economy. When the battery is increase, plug-in economy increases as well. Totally makes sense.
Of course both values are taken from the brochure, not from real live. But this happens with any car, so, the number is not more meaningless (not less meaningful?) than with any other car.

:lol: I just remembered a car magazine beat that that figure driving around Canberra but only by holding up traffic. :lol:

 

[Ozukus]

I have been away for awhile and trying to catch up on some of the posts and have been reading figures thrown out there like 40mpg (7.06L/100k) at 70mph. :shock:

Out on the highway here the best I can do is 8.0L/100k at 110kph (roughly the same speed). in normal mode.

Trex,

I think you may find that in a lot of cases, not all, that people are actually quoting a mixed journey. By example I can get 43MPG on a 60 mile motorway commute on a depleted battery, however 3 of those miles are urban and at least 5 miles would be in sub 40 mile speed due to traffic. You may be talking a constant 70mile, non traffic impacted journey, at which point I'd say I'd probably get closer to 37MPG based on a recent situation I had, that was closer to an all motorway drive.

Driving experience and obtained mileage is based on personal circumstances and conditions, and therefore it's hard to compare one person to another, as its not in a controlled environment.

 

[maby]

I'm going to try some slightly more scientific tests over the next few weeks, but my current figures are based purely on the car's fuel consumption meter. We've had it for just over a year now and done about 13,000 miles. The balance of those miles is strongly skewed towards motorway speed and petrol driven - each week we do between 150 and 200 miles of motorway and dual carriageway at an average of probably 65mph and perhaps 20 miles of suburban roads on EV at an average of about 25mph. My lifetime fuel consumption on the MMCS is currently showing about 46mpg.

 

[anko]

PS does any forum member know at what point the PHEV stops counting litres in the L/100km equation.

I think it is the same als with mpg: 99.9 :mrgreen:

 

[gwatpe]

PS does any forum member know at what point the PHEV stops counting litres in the L/100km equation.

I think it is the same as with mpg: 99.9 ...

The 99.9 is purely a mpg display problem, as other display modes are not affected.

I am asking "what is the biggest Litres number" that the internal car computer can use in calcs before it becomes overflow, or scrolls back to zero, like an old car odometer.

 

[Trex]

I have been away for awhile and trying to catch up on some of the posts and have been reading figures thrown out there like 40mpg (7.06L/100k) at 70mph. :shock:

Out on the highway here the best I can do is 8.0L/100k at 110kph (roughly the same speed). in normal mode.

Trex,

I think you may find that in a lot of cases, not all, that people are actually quoting a mixed journey. By example I can get 43MPG on a 60 mile motorway commute on a depleted battery, however 3 of those miles are urban and at least 5 miles would be in sub 40 mile speed due to traffic. You may be talking a constant 70mile, non traffic impacted journey, at which point I'd say I'd probably get closer to 37MPG based on a recent situation I had, that was closer to an all motorway drive.

Driving experience and obtained mileage is based on personal circumstances and conditions, and therefore it's hard to compare one person to another, as its not in a controlled environment.

Ozukus,

You may right that they are quoting mixed journeys. I wish they would state that. Or maybe they are including grid charge which I also wish they would state. Just throwing figures out there makes it hard to compare which I and maybe others do. Which I think makes sense on a specific car forum. We compare and learn from each other.

Thanks for your example. Very concise including telling me key points like the depleted battery. Makes it easy to compare.

For mine it was exactly what I said and you know how I measure (normal mode, no grid charge). Behind in the background because it is a hybrid I get up to speed (110kph gps) press acc, press reset on fuel computer (when petrol engine starts or stops) let the Phev do its ev,charge cycle a few times and measure at the same point of the cycle as before. Easy. :lol: That looks more complicated than it really is but I think it is accurate.

Comparing your figures with mine shows our cars are similar and that's what I want to know .

But maybe both our Phevs are lemons? :lol: :lol:

 

[Trex]

I'm going to try some slightly more scientific tests over the next few weeks, but my current figures are based purely on the car's fuel consumption meter. We've had it for just over a year now and done about 13,000 miles. The balance of those miles is strongly skewed towards motorway speed and petrol driven - each week we do between 150 and 200 miles of motorway and dual carriageway at an average of probably 65mph and perhaps 20 miles of suburban roads on EV at an average of about 25mph. My lifetime fuel consumption on the MMCS is currently showing about 46mpg.

I really look forward to reading those tests and I myself love doing said tests and according to my figures have saved fuel by doing it.

Regards Trex.

 

[anko]

PS does any forum member know at what point the PHEV stops counting litres in the L/100km equation.

I think it is the same as with mpg: 99.9 ...

The 99.9 is purely a mpg display problem, as other display modes are not affected.

I am asking "what is the biggest Litres number" that the internal car computer can use in calcs before it becomes overflow, or scrolls back to zero, like an old car odometer.

Too bad you left out the :mrgreen: when you quoted me. Now it looks as if I was NOT making a joke

But if you want to take it seriously, how do you know that 99.9 is only an issue for MPG and not for displaying l/100 km? Have you ever seen a higher number? As it is a display issue, as you said so yourself, why would it not apply to l/100 km?

 

[PolishPilot]

On Polish motorways the speed limit is 140 km/h.
With empty battery I can hardly get below 10 l/100km at this speed.
By strong wind I burned recently 10.5 l/100km.

Nevertheless, my overall average over the 24.000 km since new stays by 5.8l/100km.

I wouldn't call it "lemon" for a 2t, AWD SUV.

 

[PeterGalbavy]

PS does any forum member know at what point the PHEV stops counting litres in the L/100km equation.

I think it is the same as with mpg: 99.9 ...

The 99.9 is purely a mpg display problem, as other display modes are not affected.

In km/l mode the display is still restricted to 99.9 max - while the units are higher and so 99.9km/l is about 230mpg the display is still this format and goes to --.- above that.

 

[anko]

With empty battery I can hardly get below 10 l/100km at this speed.

At 140 km/h, I would think SOC wouldn't really matter? Come to think of it, at any speed it shouldn't matter.

Unless you keep it above 50% or even higher. Then I would expect MPG to worsen.

 

[maby]

I'm going to try some slightly more scientific tests over the next few weeks, but my current figures are based purely on the car's fuel consumption meter. We've had it for just over a year now and done about 13,000 miles. The balance of those miles is strongly skewed towards motorway speed and petrol driven - each week we do between 150 and 200 miles of motorway and dual carriageway at an average of probably 65mph and perhaps 20 miles of suburban roads on EV at an average of about 25mph. My lifetime fuel consumption on the MMCS is currently showing about 46mpg.

I really look forward to reading those tests and I myself love doing said tests and according to my figures have saved fuel by doing it.

Regards Trex.

I ran the first pair of tests last night and have just written to anko with the results - they were his suggestion and I want to get his comments before publishing them to a wider audience.

 

[maby]

OK - a bit of background - anko and I have had a long running disagreement over the best way to use the car on long runs. I have always taken the view that if I'm driving a hundred miles, then at least seventy of them are going to be driven on petrol so I may as well drive on Save with a full battery until I'm twenty or thirty miles from my destination and use the charge up on the end of the run. That way, I know that I'll have plenty of charge available in case I need an extra boost for high acceleration or hill climbing.

Anko has long argued that this will be less efficient than letting the battery run down early since the car is less able to dump excess power into a full battery. His belief, which makes theoretical sense, is that if the battery is allowed to run flat, then the car will go into a cycle of running in parallel hybrid for a few miles during which time it will also build up some charge in the battery and it will then switch to EV mode to use up that charge. This should allow the engine to run at its most efficient point and produce a better overall fuel consumption. Trouble is that, while it sounds OK in theory, nobody has ever tested it as far as we could tell. Following discussion with anko, I ran a first test yesterday...

I ran the test yesterday night and the consumption figures for the two patterns of usage seem to be so close that I suspect that any difference is lost in the background noise.

I left our house with a fully charged battery and selected Save as soon as I started. Ambient temperature was 11 degrees and stayed at that for the entire trip which lasted about two hours. In order to ensure that the figures were comparable, I drove for about ten miles to make sure the car was properly heated up before I started taking measurements. The first 70-odd miles of the trip was motorway driving and traffic was moderate - I never had to stop and was driving at between 50mph and 60mph all the time.

After getting the engine well warmed up, I cleared the automatic fuel consumption gauge and drove at just under 60mph for 30 miles. Most of this was on cruise control, so minimal throttle variations. I never had to slow down below 50mph and only briefly exceeded 60mph to overtake once or twice. Fuel consumption soon settled at about 44mpg and then fluctuated between 42mpg and 46mpg. At the 30 mile mark, it was reading 44.3mpg.

At 30 miles, I deselected Save and ran the battery flat. I was still driving at around 60mph and the real EV range was a bit more than I expected - just over 20 miles. This did impact slightly on the second stage of the test.

When the battery ran out and the engine started, I gave it a couple of minutes to stabilise, then reset the automatic fuel consumption gauge. The car began to alternate between EV and Parallel Hybrid as we would expect. The fuel consumption gauge took a lot longer to settle as we would expect. It initially swung between about 25mpg and about 60mpg, gradually settling towards 44 mpg though it was still fluctuating a bit more than it did towards the end of the first stage of the test.

Because the battery had given me more EV range than I had expected, I only had about 20 miles of motorway left at the start of the second stage of the test. As I left the motorway, the fuel consumption was showing 43.2mpg - slightly worse than the figure produced running on a full battery. It was still swinging around by something like 2mpg, so I would not consider that to be a 100% accurate figure.

I didn't reset the fuel consumption gauge after I left the motorway and did another 10 miles approximately on urban roads at lower speeds. The fuel consumption did improve over this time and I arrived at my destination with it showing about 49mpg.

So, on the basis of that test, I don't see any evidence that running on a full battery makes a measurable difference to fuel consumption. It is an artificial test since almost everyone is going to be doing a mixture of speeds - I may have a go at testing over the full weekend at some point in the future.