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Author Topic: Best ever MPG  (Read 11723 times)
spaces
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« Reply #15 on: August 31, 2015, 01:59:23 PM »

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Yes, diesel has nasty emissions but then so has petrol (and EVs, effectively burning coal, gas and nuke)

I didn't realise my Leaf was fussy about where its electrons came from. I was under the impression it also worked just as well with ones generated by solar and wind ?.

8k miles in my leaf will be about 1850 kWh so on 100% coal (which is not really representative of the uk or any national grid) that would be 1850kg of carbon. I usually charge overnight even though I don't use E7 and grid carbon quite often reduces below 350g/kWh.

And a good job it isn't... but I didn't say it was, just reminding people that behind the 'zero emission' cr@p which government, car salesmen and fashionable greenies spout, the facts are that most - by quite a long way - of the energy to power an electric vehicle is from coal, gas and nuclear. As Bodidly points out, the energy needed to repeatedly accelerate a tonne and a half of car plus occupants is considerably more than our energy needs for heating and lighting, TVs, freezers, computers and the rest.

Looking ahead, I see EV sales taking off since they're so cheap to fuel and maintain compared with the modern car. But their energy-greed means the grid will have to increase the amount of renewables feeding it at a greater rate than the growth in the use of EVs, just to stand still regarding the renewable proportion of energy. There's a possibility that over the next ten years, large numbers of EVs hitting the roads means there's a possibility of having to increase coal/gas/nuke input more than the rate of renewable energy expansion. Just because they're marginally better than what we've had up to now doesn't make them good for the planet, in any conceivable way.

What is needed is a form of personal transport which is reasonably swift, comfortable and protects us from the elements. Riding around in over a tonne of stuff is just crazy, whether it's powered by batteries charged by the grid or an ICE. Something which averages 250mpg or equivalent should be our immediate goal, rather than buying into the belief that somehow we're being environmentally responsible by buying an EV.

There is one big upside to the EV in that coupled with a smart grid, there is the potential for grid energy storage in the batteries of all the EVs.


This at the top of the page,

"navitron -Renewable Energy and Sustainability Forum"

Any mpg is to many gallons.

I take it you're assuming fossil fuels, here? And as I've pointed out on more than one occasion, the 'affection' for nuclear power which is exhibited on here at times surprises me, given it's about as sustainable as trying to fry sausages on a burning oil well head.


All the while so many raise their hands in horror at the use of burning fossil fuels to move us around in personal transport, aircraft not only escape this mass moral condemnation but are more effective at creating global warming and toxins per gallon. Airmiles go up and up with no apparent constraint - yet only 7% of the population uses air travel, at the moment. I think we should be looking at this a little more critically.

https://germanwatch.org/en/2849
« Last Edit: August 31, 2015, 02:28:11 PM by spaces » Logged

Simplicity, the ultimate refinement
dan_b
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« Reply #16 on: August 31, 2015, 04:22:55 PM »

Crikey I wish I hadn't bothered posting now.
I have to work. I'm a contract worker so I can't move closer as then my wife couldn't cycle to work and I'd have to take the kids out of their school so I have to commute. Public transport takes 2 hours each way so I drive.  I am actively trying to improve my MPG which surely is a good thing.
What else would you have me do? How many people get over 70MPG? From a 12 year old car?

I'm off to switch on the central heating and waste my ImmerSUN heated hot water.  
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« Reply #17 on: August 31, 2015, 05:19:31 PM »

Come on chaps
dan_b is trying hard. There are millions out there even the offspring of illustrious moderators such as Biff  who dont even try to do the right thing within the constraints of our current first world society. Don't dismiss the good in pursuit of the excellent. We used to have an "applaud" and "smite" facility (sadly misused by a number of Trolls so was disabled). I for one applaud dan_b's efforts.
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« Reply #18 on: August 31, 2015, 05:32:11 PM »

Sorry Dan

You are doing better than most. I can't throw stones as my truck is only managing 25 mpg Cry
Supposed to do 38 combined but this figure is seeming like a fantasy dreamt up but the manufacturer. Best I have done to date is 30 mpg on a run.

To further the subject should we be worrying about MPG or CO2 emissions? Maybe a combination of the two?

I used to brag about an old Citroen that did 50 mpg but it had have an additive added to the fuel to get through the emissions test.

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« Reply #19 on: August 31, 2015, 06:58:51 PM »

Yes, Dan. I certainly applaud your efforts,
                              I have cut down my annual mileage drastically. I used to always have a car as well as a van and my wife would have her car as well, but when I bought the Vitara, I had a trailer mind to act as a pretty big van and the jeep then double us as a very comfortable car. It is working out pretty good so far. Mrs Biff,s Rio is there to do the big miles,which it can do effortlessly and economically but 55mpg is quite a way off 70mpg.
                                                                   Biff
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« Reply #20 on: September 01, 2015, 01:35:53 PM »

I can't see how you could be doing much better regarding transport, Dan - an older (to most - to me it's relatively new!), reliable, lightweight, smallish-engined, reliable and simple vehicle - and your partner cycles. And with the potential to run the Audi on used plant oils, with some mods, for someone down the ownership chain when diesel once again heads towards 7 a gallon - or heads to double that.

The commute highlights endemic UK problems - the over-centralised nature of England's employment with a lack of affordable housing close to it and the poor functionality of public transport for commuting. We've arranged our economy so motoring taxes contribute way more than they should to our economy, so government is reluctant to cut consumption of the motor car. See how government is bribing us to buy more new cars all the time, not least EVs.

Over-regulation of exhaust emissions has rendered the diesel engine in cars effectively dying for most in Europe, which is perhaps no bad thing. It's quite likely that plenty of goods vehicles will have petrol as their fuel, too. A lot of its clever design elements have passed over to the Otto motor anyway - effectively the modern ICE is a mix of the two technologies, and there is plenty of improvement to come. I imagine syntheised methane will be the fuel of the future, allowing higher compression ratios and more efficiency as well as cleaner exhausts. But where will all the diesel fuel go? And why aren't the exhausts of petrol engines de-sooted also? - they produce less than the diesel but there's still plenty of it.
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« Reply #21 on: September 01, 2015, 01:57:02 PM »

The next generation of "Skyactiv" petrol engines from Mazda will feature diesel-like compression ignition - ie. their compression ratios will be up to 18:1 and won't require a spark plug to ignite the fuel-air mix.  That really would be deeply impressive from a technological stand point, and should improve petrol economy and emissions further still.

Just been eyeing up a couple of 2nd hand BMW i3s.  Can't manage the finance payments though.
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« Reply #22 on: September 01, 2015, 07:20:32 PM »

Dan, what are your driving techniques to achieve this. I do my best also but wonder if I can improve further.
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TheFairway
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« Reply #23 on: September 01, 2015, 08:44:49 PM »

I shall ride a 5 mile round trip along the riverside path to the pub for Sunday lunch today. That will involve a pleasant roast dinner and 4 pints of ale. It's only 10miles to the gallon, but it does improve my quality of life and does little harm to the environment.  Grin
The void between cycling and best performing vehicles wrt CO2 emissions is not as wide as you may think. I believe that cycling is far from being emission free. However I cannot argue about the health benefits, however simply being alive is hardly sustainable so one must draw the line somewhere.
« Last Edit: September 02, 2015, 08:04:35 AM by TheFairway » Logged
dan_b
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« Reply #24 on: September 01, 2015, 09:09:19 PM »

I've been doing a lot more concentrating on the driving conditions and traffic levels, and then giving myself lots of room so if traffic slows ahead, I can use the space to slow down on engine braking rather than using brakes - engine braking engages fuel cut-off mode so you waste less in deceleration.

I've been sticking quite firmly to not exceeding 55mph on the motorway.

I've been short-shifting when accelerating - accelerate at around 90% throttle, but only rev to about 2000RPM before changing gear - this keeps RPM lower and keeps the engine closer to its peak torque, which should be more efficient.

Where appropriate, I've either been coasting downhill (engage clutch) to pick up a bit of speed for an uphill section following, OR, I've been coming off throttle completely and using engine braking to maintain speed and engage fuel cut-off mode.

I've also been doing manual stop-start when in traffic. A bit annoying as in my car that means the stereo gets switched off when you do it, but it's better than idling the engine going nowhere!

I've tried doing pulse & glide, but it's a hateful way to drive, so I stopped doing that.

I don't do really excessive things like drafting HGVs - that can improve MPG by 30%, but it's extremely dangerous! I also don't do ignition-off coasting like some hypermilers do - you lose your hydraulics for brakes/steering.

I also upped the pressure in my tyes a bit.

Dan, what are your driving techniques to achieve this. I do my best also but wonder if I can improve further.
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« Reply #25 on: September 01, 2015, 10:04:40 PM »

Thanks, I do most of those except the 55mph one and stop start. And the dangerous ones ;-)

Is fuel cut off mode just when fuel stops being injected into the engine? Do all cars have this or is it specific to your car? I thought if the engine is turning over there must be some fuel being passed.

Stop start - I've been wondering what the minimum wait time for this should be, and whether there's much point depending on the vehicle's age.
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« Reply #26 on: September 01, 2015, 10:12:50 PM »

Pretty much all modern cars with computer-controlled ignition management will run some sort of fuel cut-off when you're off the throttle and slowing down on engine braking - I think it would be safe to assume they all do these days.  Yes, the ECU shuts off all fuel injection in those situations to save fuel (which couldn't be done on mechanical fuel injection, or, even older, carburettors!).   Of course what a lot of people do when driving is maintain such a short space behind that they can't allow themselves any coasting distance at all and just mash the brakes/accelerator all the time, rather than allowing the space, and the coast, to soak up some of the space.  Also a lot of people will de-clutch at the same time as braking, so they don't engage fuel cut-off at all.

With stop-start - it's important to only do it when the engine is warm (ie past an indicated 70C on the dash), as below this, pretty much all engines will run with an enriched fuel injection mode, which lasts quite a while after the engine has started running, and then you're not saving anything at all.  But once it's warm, if you're stopped for more than 10 secs or so, it's probably worth doing.  Cars with bigger engines and more cylinders will benefit more than smaller ones as they consume more fuel at tick-over.
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« Reply #27 on: September 01, 2015, 11:46:08 PM »

Dan, the maker of your car was fitting carbs which cut the fuel on the over-run back in the 80s, injection systems used through the 80s did the same. Plenty of medium-large cars (particularly German ones) will give the same or even better fuel economy at 70 as 55, in my experience. Tyre quality and size makes a big difference, too. Cheap tyres aren't just lethal when you need them most, but they generally waste fuel constantly as well as wearing faster. Wider, lower profile (than needed) rubber also wastes fuel, but can be tempermental in the wet or on poorer surfaces. The BMW i3 has amazingly skinny, tall tyres - more so even than a 2cv.

Stopping an engine for less than a minute can actually use more fuel as the alternator (a pretty inefficient thing) replaces the battery energy used to turn the starter motor, which uses a lot of electricity. Unless you've a large petrol engined thing, which probably uses as much fuel at tickover as an HGV.

With today's often over-powerful cars, brake lights always seem to be on. An average family car now is roughly twice as powerful as those in the 80s and overweight too - so unnecessary rapid braking and acceleration should be a crime! It's not just extra fuel pollution, but the pollution from tyres and brakes too.

My father's Octavia estate returns the best economy (67-74mpg) if you aim to be doing 65-ish when it's level - it's a 1.9TDi. I'd say some of this is due in part to having more momentum to carry you over crests and up hills without having to use as much extra fuel as if you were going slowly. Reading the road ahead is everything, it's surprising how little fuel you can use even when travelling briskly, if you use gravity to your benefit. I'm always disappointed when single turns into dual carriageway at the bottom of a long hill - it may be good for people who would otherwise soot up the inside of their engines through over-cautious driving, but otherwise it's a monumental waste of fuel as people accelerate from 40mph to motorway speeds, up a long drag. Roads should be planned a little more like the London Tube, where stations are at the top of a rise.
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« Reply #28 on: September 02, 2015, 10:18:45 AM »

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Reading the road ahead is everything

I agree, and to a certain extent knowing the road as well, my MG ZTT recently let me down after 125k miles of fault free motoring, but even a big heavy car like that managed an average 44MPG on Cornish back roads, it could do nearly 50 on a motorway run.

I had to replace it and bought a nissan 2.2 X-Trail off my brother (price was right and my need was high), he complained that he could only get 30MPG out of it on the motorway, i am getting 36-38 on Cornish backroads & 40 on the motorway, the key i find is knowing the road, staying off the brakes (unless you need to) and staying smooth, knowing the roads means that i can coast down to the correct speed for a corner and use hills to my advantage, i dont know why squeezing as much out of a gallon as is possible makes me happy, but it does.

The Nissan though is a short term thing to get my through a moment of need, i suspect i will get rid of it next year and go for an octavia or something similar that can really boost my MPG back to something in excess of what i got out of the MG whilst being large enough to drag my fishing kit to awkward fishing marks that are generally in the back of beyond.

The coasting thing is interesting though (i also do it naturally now) and it was interesting to find out that on the MG (and i guess all rover 75 models) the fuel cut off kicked in if you was coasting and the revs were above 1600, so i used to change down when necessary to get the revs above 1600

I applaud your conservative method of driving, driving is a necessary evil, i could cut down my mileage as i work from home and dont need to really leave the house much, but that would ruin my enjoyment of life as i love to tuck myself away on rocky outcrops and hidden river marks and take in the countryside, i wont be cutting down on that but i will always try to minimise my footprint though careful driving.
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gravelld
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« Reply #29 on: September 02, 2015, 10:46:50 AM »

Thanks.
Of course what a lot of people do when driving is maintain such a short space behind that they can't allow themselves any coasting distance at all and just mash the brakes/accelerator all the time, rather than allowing the space, and the coast, to soak up some of the space.  Also a lot of people will de-clutch at the same time as braking, so they don't engage fuel cut-off at all.
Yes. So the clutch is engaged i.e. not pressed to do this? I don't understand why someone would de clutch. I might have my terminology mixed up.

If there's no-one behind, I've also learnt the places where you can allow engine braking to slow you down so minimal braking is required for a junction. Can get a little tedious though Cheesy

With stop-start - it's important to only do it when the engine is warm (ie past an indicated 70C on the dash), as below this, pretty much all engines will run with an enriched fuel injection mode, which lasts quite a while after the engine has started running, and then you're not saving anything at all.  But once it's warm, if you're stopped for more than 10 secs or so, it's probably worth doing.  Cars with bigger engines and more cylinders will benefit more than smaller ones as they consume more fuel at tick-over.
My car (mark 4 golf) hits 90C in about five minutes from cold and then stays there. Not sure if that tells you anything.
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