ThudnBlundr
Posts: 736
Joined: Mon Mar 12, 2018 2:18 am
Location: Yorkshire end of M1, UK

Re: What fuel consumption can I expect on 50mile run on motorway?

Mon Mar 22, 2021 6:15 am

I quite agree it might be more socially acceptable to refrain from using an ICE in a built-up area, but that's not my point. No one has produced any figures proving it's more economical. Just a simple "it must be true" doesn't really cut it in scientific circles. I'm not saying it's untrue, merely unproven.
2015 GX4hs since 03/18
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mellobob
Posts: 164
Joined: Mon Jun 11, 2018 5:33 pm
Location: British Columbia, Canada

Re: What fuel consumption can I expect on 50mile run on motorway?

Mon Mar 22, 2021 8:50 am

I may be late for the party around this discussion ... but I travel about once a month to a nearby community 100km away. We live in the mountains and the road is a bit hilly, certainly not flat. I travel, usually with the cruise on, at a steady 105 km/hr.

What I try to do is to use the PHEV default mode when in the built up area around my home and then when in the "big city". On the hwy I use SAVE mode. I try my best to use all the battery power before I get back to my house.

My usage is a predictable 6.5 liters per 100 km on the round trip. Now, that figure will go up a fair bit if it's cold! Like 7 or 8 l/100, depending on just how cold.

jpalfrey
Posts: 7
Joined: Mon Mar 15, 2021 2:42 am

Re: What fuel consumption can I expect on 50mile run on motorway?

Tue Mar 23, 2021 3:13 am

Thanks all, this is great discussion.

For me I know my commute will involve ICE usage, there's no getting away from it with EV range of 15-25 miles.

So I understand the philosophy of letting the car work itself out, I get that, hundreds of hours of calibration and programming and testing in all conditions will have gone in to the car, however it has to adapt to a multitude of condition and in-puts.

Anyway the discussion on "charge" mode and parallel is all good stuff, all comments welcome.

The lockup clutch in parallel mode intrigues me if I'm honest as at highway speeds this is where ICE is in all likelihood more efficient, and direct mechanical drive is also the most efficient use of ICE too (for propulsion).

However a question I have is, which may be the charge vs save discussion, ICE is more thermally efficient with moderate load, so l'll guess it's ensuring the most efficient use of the ICE when it's running.

Also when people quote mpg, are you quoting what is shown on the dash for the trip? Or calculated miles per gallon when not in EV mode for example when the engine is running?

The reason I ask is trip mpg obviously doesn't take in to account the charge spent in the battery from the plug. I'm currently paying 15p/KwH (no night rate or solar etc) so the usable charge could be 10kWh of the 12kWh battery, so £1.50 in electricity. If I get 15 miles from this then I'm at 10p per mile. I'm aware I may need to switch supplier and get a better night rate and charge the car at night to improve this. Anyway you see what I'm getting at here.

I guess it's a difficult one as even the NEDC/WLTP authorities haven't worked it out either with ludicrous MPG figures from running most of the cycle with "free" electricity. Silly really, if thought about you could work out the energy in 1 litre of fuel and we know electrical usage and charge efficency and work the whole thing out.

kpetrov
Posts: 88
Joined: Thu Oct 29, 2020 8:59 am

Re: What fuel consumption can I expect on 50mile run on motorway?

Tue Mar 23, 2021 5:58 am

ThudnBlundr,
What kind of scientific proof you may need? It is basic knowledge the ICE is more efficient on the highway than town, even more efficient when mechanically coupled with the wheels (which occur over the speed of 65km/h only) and electric propulsion is much more efficient in stop and go traffic compared to an ICE and when we include and losses from AC - DC conversions is getting even worse.
Which of those statements you refute? If you agree with them no further proof is needed.

Jpalfrey, exactly why I refrain to mention numbers. Consumption in our vehicles may vary significantly.
If we are going to talk CHARGE vs. SAVE what is the understanding of the average Joe? Just because of the words a lot of folks think that they are saving during SAVE and spending because of CHARGING.
Both modes are very similar SAVE is like intermittent CHARGE and suits most of the drivers cause it's press it and forget it.
I prefer CHARGE on the highway when going further out of battery range, cause I have more control over battery SoC and prefer my ICE to start less frequently. And like usual aiming to arrive with empty battery.
2018 Outlander PHEV (Canadian)

jpalfrey
Posts: 7
Joined: Mon Mar 15, 2021 2:42 am

Re: What fuel consumption can I expect on 50mile run on motorway?

Tue Mar 23, 2021 8:26 am

Thanks kpetrov.

Ideally what I need to know I think is what kind of mpg the outlander PHEV will do without any charge. I did see a useful video from a chap in Australia on this.

I'm aware of how ICE efficiency works, I have a Jaguar XK8 4.0V8 and a Passat 2.0 TDi and it's all about loads. The Jag will do 155mph and the passat 130mph, however the Passat efficiency drops off badly above 70mph, whereas the Jaguar drop off isn't as much. For example drive really gently both cars on motorway 60mph, Jag can return 28mpg say, same trip and speed the Passat 60mpg, but say 80mph the passat would drop to ~ 45mpg but the Jag ~ 24mpg. I know they are petrol and diesel and 2.0 turbo vs 4.0 n/a but the same applies in the outlander.

You have a pair of EV motors and a 2.0 ICE. Two different powertrains and prepulsion systems, and the joy is they are on one vehicle and switch between the two, I just want to gain an insight on how to get the best out of the two and what efficiency to expect from each powertrain.

Personally, if I owned one (for my own knowledge only) I'd like to understand how drive speed effects efficiency, with ICE usage only on low SOC (flat battery).

For example do 30 miles on motorway @50mph and fill the tank to calc mpg
Then do same journey in similar conditions @60mph and fill the tank...
Then same again @ 70mph.

All with low SOC, this would then give real world data on fuel consumption for the ICE side of the car as we know the EV range is done to death. Sorry for all the q's, just my inquisitive mind.

Ideally I'd like to rent one for a week or two and test it myself.

ThudnBlundr
Posts: 736
Joined: Mon Mar 12, 2018 2:18 am
Location: Yorkshire end of M1, UK

Re: What fuel consumption can I expect on 50mile run on motorway?

Tue Mar 23, 2021 10:47 am

kpetrov wrote:
Tue Mar 23, 2021 5:58 am
ThudnBlundr,
What kind of scientific proof you may need? It is basic knowledge the ICE is more efficient on the highway than town, even more efficient when mechanically coupled with the wheels (which occur over the speed of 65km/h only) and electric propulsion is much more efficient in stop and go traffic compared to an ICE and when we include and losses from AC - DC conversions is getting even worse.
Which of those statements you refute? If you agree with them no further proof is needed.
And still no proof! For proof we need to see actual figures, not theories. How do you know the ICE is more efficient in parallel mode on the highway to series mode around town? Any figures? What are the actual losses in Series and Parallel modes? Any figures? And it certainly isn't basic knowledge that an EV with an ICE is more efficient on a highway than in town - you're confusing the PHEV (an EV with regen and ICE optimisation) with a car driven solely by an ICE geared to the wheels. So you are proposing theories as fact - however plausible they may seem, you have nothing to back up those theories. Of course, if you do have any figures whatsoever to back up your claims, I'd be happy to be proved wrong.
2015 GX4hs since 03/18
2015 Renault Zoe R240 owner since 11/17

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ThudnBlundr
Posts: 736
Joined: Mon Mar 12, 2018 2:18 am
Location: Yorkshire end of M1, UK

Re: What fuel consumption can I expect on 50mile run on motorway?

Tue Mar 23, 2021 11:06 am

@jpalfrey

Don't get too hung up on whether to use CHRG or SAVE on a journey. The PHEV has to get its energy mainly from the ICE, and it does this by running in what is effectively CHRG. In SAVE or when the battery is empty, it will run till the range has gone up a bit and then runs in EV till the range has dropped back. Tests have shown that it is very slightly more efficient to run in CHRG and fill the battery to ~60% and then turn it off than to simply leave it in 'D', but the difference is tiny. But pressing SAVE or CHRG merely changes when the ICE produces the energy, and has very little effect on how much energy is required for getting from A to B. That charge/discharge loop is known as the "Hysteresis Loop". Also the PHEV tries to maintain the battery at ~30% when it show empty, so that there is always something in reserve when you ask for more power than the ICE can provide. You can get it to go below that, but you can enter the dreaded "Turtle Mode"

The ICE in Parallel mode is geared quite highly, so when Parallel mode does kick in (and the ICE is therefore geared to the wheels), the only thing the PHEV can do to maintain efficiency is to vary the throttle opening. This means it can produce more power than is required to drive the car which is siphoned off via the generator into the battery. But at low speeds, the surfeit of power will be small as the ICE is revving relatively slowly. So you may well find that there is a "sweet spot" in the speed range where the ICE can be most efficient while having a sufficient surfeit of power to charge the battery quickly.

I find it is quite sensitive to variations in speed around 70mph. If I set it to an indicated 72mph (70mph actual) on a long journey (>2 hours), it is noticeably worse that when set to an indicated 70mph. In the former I'd get ~35mpg (UK), whereas I'd hope to near 40mpg at 68mph.

TBH I've not really looked at shorter journeys where the battery will have more of an effect.
2015 GX4hs since 03/18
2015 Renault Zoe R240 owner since 11/17

You may have speed, but I have momentum...Image

jpalfrey
Posts: 7
Joined: Mon Mar 15, 2021 2:42 am

Re: What fuel consumption can I expect on 50mile run on motorway?

Wed Mar 24, 2021 1:48 am

Thanks ThudnBlundr, that's some great info. It's kind of what I assumed how the system worked but great to hear it from someone with experience.

I did assume the best use of the ICE is to mechanically drive the wheels as to generate electricity to drive the motors is simply additional power conversion losses in to the system.

But yes I'd assume there is some fantastic calculation that shows there's an optimal load for the ICE to have and the throttle is adjusted and load from the generator in order to charge the battery to make use of the spare capacity. I'd imagine that is standard "hybrid or D" mode as why wouldn't you?

So here's a question I saw a video of someone testing 0-60 and it was noisy with the ICE running flat out at max revs. I imagine terribly inefficient but is there a point on the throttle that enables this mode? I've heard of an equivalent to a "kickdown" switch on the throttle pedal that would automatically do this?

Or is it simply battery SOC related? Example: If the driver requested full power for acceleration out of a junction up to say 40mph (I say this specifically so the engine has no option to drive the wheels) and the engine hasn't been used (cold) with a 50%+ battery what would happen? Is the PHEV EV all the time at low speeds with good SOC or does the ICE "top up" the power when full power is requested?

greendwarf
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Re: What fuel consumption can I expect on 50mile run on motorway?

Wed Mar 24, 2021 2:17 am

In the "old days" - well 2014, when this all kicked-off - there was a lot of discussion, user testing, technical & scientific evidence about this issue. As I remember there were graphs to demonstrate where the semi-mythical sweet spot is.

If readers want to plough through 7 years of mainly inconsequential posts to find it, good luck but, apart from curiosity, in the end the consensus of the last 7 years of real world use, is that the variable factors are too large to show a definitive benefit of a particular strategy of for us to all use. Most of us work out what suits our personal driving pattern by trial and error - all part of the fun. 8-)

littlescrote
Posts: 235
Joined: Fri Jul 26, 2019 3:52 am

Re: What fuel consumption can I expect on 50mile run on motorway?

Wed Mar 24, 2021 5:19 am

Regardless of the arguments around total efficiency over the whole journey what clearly makes sense to do from a local environmental point of view is to use just EV mode in any urban environment. To do that when you have an urban section at the end of your journey which is beyond the battery range can be achieved in one of 2 ways as to Just leave it in normal mode where the battery will all be used up from the beginning of the journey will mean that there is nothing left at the end and the ICE will have to run to give the battery its usual charge/discharge hysteresis cycle.

1) Save - You work out how much charge you need at the end of the journey and press the Charge button when you reach that level
2) Charge - You press the Charge button at a suitable point in the journey that will build up enough charge for when you need it

Whatever the differences in efficiency, I'd suggest that option 1 is far more intuitive and simple.

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