Author Topic: WLTP fuel figures and CVT  (Read 2337 times)

John Ratsey

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Re: WLTP fuel figures and CVT
« Reply #15 on: January 01, 2020, 04:56:59 PM »
A few points to add:

1. I had a CVT Mk 3 Jazz in 2015-16 and averaged 57.8 mpg (fuel into tank) over 5300 miles. This was mainly longer journeys at 50 to 60 mpg. A visit to and around Scotland averaged 62.8 mpg over nearly 1500 miles. However, it was a challenge to keep the vehicle running in the efficient Atkinson cycle mode as there was a tendency to substantially increase the revs when only a little more power was asked for (this behaviour was one reason for trading the vehicle in for my HR-V). I can well understand why the WLTP test hit the mpg claims because of the vehicle's tendency to go into a less efficient operating mode at each change in road conditions. I was under the imprssion that Honda tweaked the behaviour when the Mk 3 was refreshed but maybe I'm wrong.
2. I agree that the CVT is less efficient than a conventional mechanical gearbox. Usually this is offset by the software being able to keep the engine running in its most efficient operating range. However, a careful driver who knows what this operating range is can operate a manual gearbox to give the optimum mpg (eg the Land's End - John O-Groats trip involved someone from the factory driving a manual gearbox Mk. 3).
3. I would hope that Honda would use a battery pack larger than 1 kWh in the Mk 4 Jazz. Otherwise the little battery will have a hard life and the hybrid system will struggle to give much benefit in other than simple stop-start-accelerate-brake urban driving conditions.
4. Let's not overestimate the weight penalty carried by a PHEV. Assuming 40 miles battery range at 4 miles/kWh indicates the need for a 10kWh battery. For guidance, the 13kWh Tesla Powerwall domestic battery weighs about 130 kg. However, an automative battery pack will need better thermal and power management (the Powerwall is designed for a sustained 5kW output).
5. Visit Gridwatch https://gridwatch.co.uk/ to see how wind power contributes to the UK generating capacity. I've seen it peak at around 12 GW. However, it is an unreliable source as shown by the attached graphic which I captured on Christmas day (the wind is light blue). Unless there's investment in some massive (multi-GW x multi-day) storage, I think we need to bite the bullet and invest in more nuclear if we are going to have a reliable source of electricity.
6. The sensible solution is to cut back on travel. Closer proximity of homes and work places would be a good start plus road charging to discourage Amazon and the like from moving truckloads of stuff up and down the country.

jazzaro

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Re: WLTP fuel figures and CVT
« Reply #16 on: January 01, 2020, 06:49:54 PM »
The WLTP figures for the CR-V show an overall fuel consumption of 40.9 mpg for the hybrid as against 38.7 for the 1.5L turbo.  So the hybrid gain is only 2.3%.  We'll see later this year how the new Jazz compares.
According to Spritmonitor, 2019 CRVs fuel consumption is 42,8 mpg for i-mmd and 38.9mpg for the 1.5t, a 10%.

jazzaro

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Re: WLTP fuel figures and CVT
« Reply #17 on: January 01, 2020, 09:42:34 PM »
1. I had a CVT Mk 3 Jazz in 2015-16 and averaged 57.8 mpg (fuel into tank) over 5300 miles. 
Mine is 46,3mpg, manual, 35500miles.
Quote
3. I would hope that Honda would use a battery pack larger than 1 kWh in the Mk 4 Jazz. Otherwise the little battery will have a hard life and the hybrid system will struggle to give much benefit in other than simple stop-start-accelerate-brake urban driving conditions.
CR-V and Accord have a 1,3kwh lithium ion battery pack, the Insight has a 1,2 kwh, Jazz Hybrid hardly will have a bigger pack. Toyota HSDs have similar capacities (Yaris 0,9kwh); using the electric part only for efficiency purpose, a bigger pack would be unuseful.
« Last Edit: January 01, 2020, 09:56:46 PM by jazzaro »

peteo48

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Re: WLTP fuel figures and CVT
« Reply #18 on: January 01, 2020, 10:08:45 PM »
Car ownership has got to fall and an interesting thing is that young adults are tending to shun car ownership. When my kids came of age they couldn't wait to get a driving licence, but not so much these days. Young Millennials and Generation Z are public transport minded. Their lifestyle, and the preponderance of private hire taxis and "Ubers" makes it more convenient and good economic sense not to own a car. When I started to drive our town (pop 6,000) had one taxi. It was only available when the owner's garage/petrol station was open (not on a Sunday), unless you booked it in advance. Since most people did not have a phone back then, you had to visit the garage to make a booking. Hardly convenient.

Spot on about the younger generation. A number of factors are kicking in not least the shear cost of getting on the road and we are talking about generation rent here. They are much happier to use taxis and don't have the misguided cost hang ups that some of the older generation have. Put 2 people in a taxi from my house to Warrington town centre and it's cheaper than the bus. The increasing use of social media has been quoted as a factor as well.

Downsizer

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Re: WLTP fuel figures and CVT
« Reply #19 on: January 01, 2020, 10:09:53 PM »
The WLTP figures for the CR-V show an overall fuel consumption of 40.9 mpg for the hybrid as against 38.7 for the 1.5L turbo.  So the hybrid gain is only 2.3%.  We'll see later this year how the new Jazz compares.
According to Spritmonitor, 2019 CRVs fuel consumption is 42,8 mpg for i-mmd and 38.9mpg for the 1.5t, a 10%.
Yes - senior moment, my arithmetic was wrong!  The WLTP figures I quoted represent a 5.6% improvement for the hybrid S model CR-V.

Jocko

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Re: WLTP fuel figures and CVT
« Reply #20 on: January 01, 2020, 10:37:52 PM »
Spot on about the younger generation. A number of factors are kicking in not least the shear cost of getting on the road and we are talking about generation rent here. They are much happier to use taxis and don't have the misguided cost hang ups that some of the older generation have. Put 2 people in a taxi from my house to Warrington town centre and it's cheaper than the bus. The increasing use of social media has been quoted as a factor as well.
My grandsons don't drive, despite their dad being a motor mechanic. They are happy with trains, buses and taxis.
I had a mate who didn't need a car to get to work. They used a taxi to do the shopping (before supermarkets delivered to your door), and every summer hired a brand new car to go on holiday. He was quids in. He liked a pint and a short walk to the pub meant no risk of getting breathalysed.
I really miss my car when I don't have it (like after surgery).

jazzaro

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Re: WLTP fuel figures and CVT
« Reply #21 on: January 01, 2020, 11:11:00 PM »

4. Let's not overestimate the weight penalty carried by a PHEV. Assuming 40 miles battery range at 4 miles/kWh indicates the need for a 10kWh battery. For guidance, the 13kWh Tesla Powerwall domestic battery weighs about 130 kg. However, an automative battery pack will need better thermal and power management (the Powerwall is designed for a sustained 5kW output).

Just a question: which is the  power of a standard home  electric supply in UK? 3-5kw?

Kenneve

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Re: WLTP fuel figures and CVT
« Reply #22 on: January 02, 2020, 09:30:31 AM »
The main supplier fuse in my (UK) house is labelled as 60 amps (although the fusebox itself is rated at 100 amps) which gives a maximum power available of 15 Kw
Individual sockets are rated at 3 Kw, so any plug in type charger would be limited to this value,
It would be possible to install a larger capacity charger, wired directly to your distribution board, but you would still need to take account of other loads within the house ie heating, cooking etc.

If you look at the Gridwatch website, on a cold midweek winters day, you will see that we are, on occasion, already perilously close to maximum grid capacity. I just wonder what will happen, when millions of cars are plugged in for charging?

culzean

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Re: WLTP fuel figures and CVT
« Reply #23 on: January 02, 2020, 09:31:45 AM »
Here is a tale of premature PHEV battery degradation from a guy in Western Australia, it is well known that hot climates kill batteries.

https://www.speakev.com/threads/phev-battery-degradation-and-warranty.124746/

His battery is 27% lower on capacity than it should be,  which is like Honda saying 'sorry, the original 41 litre petrol tank on your jazz is now only 29 litres, but it is not covered by our warranty until it shrinks to 25 litres... sorry for any inconvenience'.
« Last Edit: January 02, 2020, 10:36:22 AM by culzean »
Some people will only consider you an expert if they agree with your point of view or advice,  when you give them advice they don't like they consider you an idiot

Jocko

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Re: WLTP fuel figures and CVT
« Reply #24 on: January 02, 2020, 09:55:21 AM »
What it doesn't say is whether the battery has been treated correctly during the life of the vehicle. This is maybe one of the vehicles where the owner never plugs it in and has been running round with a substantially flattened battery in high temperatures.

culzean

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Re: WLTP fuel figures and CVT
« Reply #25 on: January 02, 2020, 10:08:18 AM »
It is now becoming apparent ( well battery engineers knew it all along but bEV car makers never let on ) that keeping Lithium batteries fully charged damages them, they are stored for maximum shelf life at about 45% charge - keeping them above that figure shortens their life.  it also damages them to fully discharge them,  which is why BEV batteries have an algorithm to keep them in the 30% to 80% zone when new and increasing the envelope as they go through more charge / discharge cycles and  age to maintain range. Also fast charging damages them, through heat and the cells can become unbalanced, that is why many Leaf owners were shocked when the battery control would not let them do a fast charge at motorway services and were stuck there for 3hours+ on a slower charge ( some motorway services now fine people for staying too long ( over 30 minutes sometimes ), wonder if that includes waiting while the car charges up ? )
Some people will only consider you an expert if they agree with your point of view or advice,  when you give them advice they don't like they consider you an idiot

peteo48

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Re: WLTP fuel figures and CVT
« Reply #26 on: January 02, 2020, 10:39:01 AM »
Battery management does seem to be very important. My mate has an early 2014 24 kwh Nissan Leaf. He does most of his charging at home and more or less sticks to the 20% to 80% state of charge which does him for most of his journeys. He does a handful of rapid charges a year when out and about (when he can find a working one that is!!) and will charge to 100% if he needs it.

The car is now not far of 6 years old and he has a 92% State of Health. Total mileage on the car is about 50,000.

madasafish

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Re: WLTP fuel figures and CVT
« Reply #27 on: January 03, 2020, 03:40:04 PM »
An electric car should be white goods.
Any special attention needed is a nogo..

culzean

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Re: WLTP fuel figures and CVT
« Reply #28 on: January 03, 2020, 03:56:24 PM »
An electric car should be white goods.
Any special attention needed is a nogo..


In an ideal world yes,  but batteries are complicated chemical things that unlike a washing machine cannot be left empty or too full for any length of time.  Unlike a washing machine you cannot fill a battery too fast, Frequent rapid charging seems to be a no-no as the battery can get all confused and lose capacity.  Maybe one day .........
Some people will only consider you an expert if they agree with your point of view or advice,  when you give them advice they don't like they consider you an idiot

peteo48

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Re: WLTP fuel figures and CVT
« Reply #29 on: January 04, 2020, 11:03:25 AM »
An electric car should be white goods.
Any special attention needed is a nogo..

I think that it is more or less where we need to get to if we want mass adoption sooner rather than later.

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