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Randomly wondering today after reading this (didn't know it was a thing): could a "hypermiler" get better MPG than a self-driving car programmed to do the same? One for the driving gods on here...
If every car was self driving and interconnected, then I suspect it could, as they could safely drive close enough to really make us of the slipstream effect.
As that isn't the case, then I don't think so, as a self driving vehicle likely wouldn't be programmed to sit right up the arse of a lorry and take the risk that involved, like bored dad in his Volvo would.
As with all things, it would depend on the sophistication of the coding and accuracy of the sensors, systems and actuators connected to it. In theory, if the car were coded to combine weather, traffic and topological route data to the on-board sensors, then yes, it would likely beat an experienced hypermiler, especially if the code were built with reinforcement learning included.
It's all common sense really. Nothing too harsh; anticipation - gasp!
Even my first car (Citroen GSA) had a pretty crude indicator lamp pair that went amber/red if you were too heavy with the accelerator.
Is hypermiling electric cars a thing, or does regenerative braking make driving style less of a factor (with the exception of cruising speed)
a self driving vehicle likely wouldn’t be programmed to sit right up the arse of a lorry and take the risk that involved
This was my first thought too 😅
Thinking bigger, a massive interconnected road network of self driving cars could be (and probably will be) designed to have the entire system run as ecologically as possible. In some cases that would have some cars driving much faster than others, to create space or whatever, and others slower. I'm waffling but there are big possibilities with a truly connected car network. The 'brain' would be thinking 1 hour ahead for your journey. You could be in London but it has already planned exactly where and how you slot in to each moving car that you'll interface with at the exact time in P'boro 1.5h later
broad thinking of course - but very interesting for a future that we won't see but future generations will!
Randomly wondering today after reading this (didn’t know it was a thing): could a “hypermiler” get better MPG than a self-driving car programmed to do the same? One for the driving gods on here…
I suppose it depends if the self driving car lets a car gain momentum downhill for free speed up the next or burn and coast. Not even sure if this would help on an electric car with regen braking anyway.
If it would be smart enough to drop speed approaching traffic lights on red, hopefully to not stop completely.
I guess if it was linked to the infrastructure, it'd know exactly the time to arrive at a junction, roundabout, whatever.
I don't think there would be any point in traffic lights etc if the automation was smart enough.
taking pushbike traffic into account obvs!
I always thought that when I get to design "my" electric car it would feature freewheeling as a real operational function. I used to love having a manual car that I could simply knock out of gear at the crest of a rise and freewheel down the other side. Obviously that's err frowned upon and there's a thought that a well configured EV could effectively do this but also control the speed better and harvest any excess momentum.
Unfortunately real efficiency doesn't seem to be a priority and we're looking at enormous electric SUVs as the norm.
I used to love having a manual car that I could simply knock out of gear at the crest of a rise and freewheel down the other side.
It uses zero fuel on an IC engine to roll downhill in gear above a pre determined number of revs. Every car with fuel injection (every car since the nineties) will cut fuel on overrun. Except I suppose those mapped to pop on overrun.
If you run down the hill in neutral, fuel will be injected to keep the engine running.
There was a study with autonomous lorries in Germany that found they could save 40% on the fuel in the second lorry of a convoy as it could safely follow the lead lorry in the wake zone. The lead lorry also saved 5% or so due to a weird effect that the drivers use in NASCAR where two cars bumper-to-bumper can eactually go faster than a solo car. I think any further lorries used around 50% less fuel than regular.
So yes, an autonomous vehicle can drive more economically than a human operated one uncertain circumstances.
Is hypermiling electric cars a thing, or does regenerative braking make driving style less of a factor (with the exception of cruising speed)
Yes, see plenty of electric cars being driven carefully so as to conserve their range. Even Tesla's with their massive batteries are driven like it. Probably a different skillset so as to maximise regen as well as smoothness.
I thought DSG boxes went into neutral on downhills ?
I thought DSG boxes went into neutral on downhills ?
Not heard that and can't see why it would. Happy to be corrected.
Not really thought about it much but wouldn't you have issues running out of vacuum for the brake booster and HVAC systems?
I thought DSG boxes went into neutral on downhills ?
They don't. I have one. That would be dangerous.
Mine does, however, go into neutral pulling away from a standstill sometimes. Quoted 1600 quid to repair and the car is only worth 3k so I can live with it...
jamesoz
It uses zero fuel on an IC engine to roll downhill in gear above a pre determined number of revs. Every car with fuel injection (every car since the nineties) will cut fuel on overrun. Except I suppose those mapped to pop on overrun.
If you run down the hill in neutral, fuel will be injected to keep the engine running.
There's a hill on the M4 Lndn>Oxfd where I could knock it out of gear at the top at 70mph and coast for about 2 miles without gaining or losing more than 5mph. If I just let off I would have to get back on the gas far far earlier. The not using fuel vs tickover coasting isn't a linear equation because to not use any fuel the engine is braking which is th eopposite of the effect required. To simulate the energy neutral you'd have to at least neutralise the friction in the engine which would prob be using more fuel than tickover.
G
bob_summers
I thought DSG boxes went into neutral on downhills ?
Not sure about DSG boxes but the PDK unit on my Porsche goes into a form of neutral when off the throttle .
So you can be doing any speed and off the throttle and the revs are at tickover
There’s a hill on the M4 Lndn>Oxfd where I could knock it out of gear at the top at 70mph and coast for about 2 miles without gaining or losing more than 5mph. If I just let off I would have to get back on the gas far far earlier. The not using fuel vs tickover coasting isn’t a linear equation because to not use any fuel the engine is braking which is th eopposite of the effect required. To simulate the energy neutral you’d have to at least neutralise the friction in the engine which would prob be using more fuel than tickover
I guess you'd have to be bored and measure it
I know my work van rolls downhill better with 6 gears than either of our cars in 5th.
I think SAABs had freewheels. Quite hard on brakes back then.
Is hypermiling electric cars a thing
Yes, but the results are less dramatic and you have to do it differently. It requires an understanding of the engine, same as petrol or diesel.
I thought DSG boxes went into neutral on downhills ?
No, at least mine didn't. I had a Fiesta with a CVT that did this, it's really weird to drive at first.
There was a study with autonomous lorries in Germany that found they could save 40% on the fuel in the second lorry of a convoy as it could safely follow the lead lorry in the wake zone.
Yes, that was when they were all linked together so that if the front lorry braked they all braked at the same time. This is much better than having radar-sensing brakes like autonomous cars do, because they all have a reaction time and need a stopping distance. The trucks weren't actually autonomous, they were a collective.
It uses zero fuel on an IC engine to roll downhill in gear above a pre determined number of revs.
True but the friction will slow you down more - so it only works over a certain gradient.
The ‘brain’ would be thinking 1 hour ahead for your journey. You could be in London but it has already planned exactly where and how you slot in to each moving car that you’ll interface with at the exact time in P’boro 1.5h later
This is how air traffic control works. One day it'll work for every car on the road. It'll look scary as hell though as you'll bomb through junctions at full speed slotting through the gaps in the cross traffic!
[I]I always thought that when I get to design “my” electric car it would feature freewheeling as a real operational function[/I]
This was (probably still is) a feature in some HGVs, I think Volvo? Automatic models would drop into neutral on gentle descents if engine braking wasn't needed but of course they are intelligent enough to engage a gear when needed for control.
True but the friction will slow you down more – so it only works over a certain gradient
Surely we'd have seen the SAAB freewheel become more mainstream if it was worth doing?
They don’t. I have one. That would be dangerous
They do. I had one. I’m still alive.
This was the newer 7 speed dsg in a golf, with eco mode selected. I used it rarely as the rev matching when you pressed the throttle was slightly jerky and became annoying.
Regarding the electric car comment, I once had to drive an EV from Nottingham to Sheffield with 35mi range showing. Thanks to the trucks I followed I made it back with 5mi to spare!
I thought DSG boxes went into neutral on downhills ?
As above, my Superb does it but only in eco mode. Lift off the throttle and the revs drop to ~800 and there is no engine braking.
My kodiaq does this. The old one used to do it in eco mode only but the 2001 model I now have does it in normal mode in some situations as well as eco.
Learn something new every day
I've been working on this for getting on 10 years, getting cars to hypermile automatically.
It's really really hard and gives me a headache.
Do we go to neutral on this hill? Or do we switch the engine off as well. Or do we just roll down in gear with fuel cut? Or do we use the energy to recharge the battery (12/48/400V). Or do we leave the engine running to charge the batteries?
How long is the hill, how fast is the car going, how much does it accelerate (or decelerate) when we activate each mode? How charged are all the batteries, how much charge can the batteries take right now, how much vacuum capacity do we have right now for braking? What's the status of the climate and cooling systems? Do we have any corners or traffic nearby that might interfere?
https://www.mbscottsdale.com/blog/what-is-mercedes-benz-sailing-function/
Lots of autobox cars do this these days. My Renault Kadjar diesel does - it has an EDC (twin clutch) 7 speed box. Mrs C's Merc with 9 speed slushbox does it too. Both have to be in Eco mode - which the Renault stays in, in the Merc we have to push the switch every time we start the engine. Works well in both.
Or do we switch the engine off as well.
Certainly hope not...you lose all power to everything which would result in a more dramatic attempt to steer and brake your car in an emergency...
Certainly hope not…
Errr, do you really think an auto manufacturer would put an engine shutdown while driving into a strategy if you were going to lose power to everything?
Really?
You could be in London but it has already planned exactly where and how you slot in to each moving car that you’ll interface with at the exact time in P’boro 1.5h later
If these So Called Smart Cars are so clever, why do think they'll be taking me to ****ing Peterborough when I live in Bristol? Maybe the boffins can stop examining gender neutral wasps for a minute and explain that one.
D Fivethousand
Tunbridge Wells
Yes, I'm pretty sure that is how it works - you stop the engine you lose power steering and servo-assist braking. That results in a very heavy steering wheel so takes more effort/time to turn and the brakes (normally after the first stamp) then become much stiffer and heavier and result in much more effort to operate and therefore stop.
Unless of course there is now technology which cuts off the engine but keeps the power going to components/features in a car - I'm not sure it does but I don't have any experience of the fancier engines in fancy cars, so based on the cars I've driven when I've tried to move them without turning the engine on.
I would guess that a car on its own (ie limited to data it can aquire itself, and its own computer) could not beat a dedicated expert human hypermiler, especially on familiar roads.
But a connected car could. Knowing the traffic light sequence and adjusting speed to reach it at green. Or even telling the lights it is coming so it can turn green if nobody else is around.
Getting real time communication from the car in front would allow safe tailgating.
Route selection based not just on distance and speed limits but also on congestion and hills and junctions.
Yes, I’m pretty sure that is how it works
Audi have had it in certain markets for nearly 3 years, BMW and Merc for 2, Volvo for 1. Think KIA, VW, Hyundai, Renault and a couple of others will have it or have already launched in the last year.
The tech has been around for about 10 years using 12V batteries, but the number of stops you could safely have is relatively small (2 or 3, then a loooooong wait to recharge the battery), so no one has done it outside of a few test cars. Adding 48V mild hybrid batteries into the mix means it's now easy to do multiple stops (dozens) safely.
All the key systems are supported by the 48V power supply, and as soon as there is the slightest interruption to smooth rolling (braking, aggressive steering, accelerator input), you can restart the engine in a fraction of a second.
When we had the last fuel crisis (more than 20 years ago) and fuel was in short supply, I had a 60 mile round commute and a 2.5l V6 petrol. My god, did I do hypermiling and cycling to work so I had enough fuel. Out of gear on hills, and tucking safely behind HGV's on the motorway. I've never seen such a good mpg.
jamesoz
Full MemberI thought DSG boxes went into neutral on downhills ?
Not heard that and can’t see why it would. Happy to be corrected.
Yes they do, when in Eco mode. Mines a DQ250 on an '18 plate Octavia.
I was quite surprised to find it actually does save quite a bit of fuel, this car does seem to have quite a bit of engine braking for whatever reason.
Many dsg's (and probably other 'auto' boxes) have a feature where it goes to neutral when you lift off the gas. I couldn't get on with it and found my mpg was worse.
As for regen braking being more efficient? Nope. The losses (kinetic and otherwise) in the conversion back to electric means that the energy you have put into the car to get up to speed will never be gained back to a worthy extent. Lifting early and anticipating is far more efficient.
However, regen has its place as a speed controller for maintaining speed when descending for example.
Also has safety benefits for example if you had a seizure and lifted off the pedals then the car would come to a stop.
Doesn't one of the electric cars (Leaf?) have a zoned throttle where the top of the travel is brake/regen the centre is neutral (coast) and only when you push past this it goes to the increase thrust area?
I always thought it was the next step and was pleased to hear someone try it. I haven't tried it so cannot comment on if it works as I believe it should
Re. the DSG going into neutral - I asked because AFAIK the 7 speed on the VW T6.1 does it, and doesn't have driving modes, so I suppose it's always on.
So with the ACC set to 70, cresting a hill and going down the other side - it must dab the brakes to keep the speed at 70? Sounds all kinds of weird, I've got a 6.1 on the way too...
I always thought that when I get to design “my” electric car it would feature freewheeling as a real operational function
Turn the regen feature off and it does this. You still get regen braking but inly when you touch the brake pedal. Doesn't save much because you modulate the throttle to slow down how you need to slow down in any given situation. It just changes which pedal you press to get what you want.
Doesn’t one of the electric cars (Leaf?) have a zoned throttle where the top of the travel is brake/regen the centre is neutral (coast) and only when you push past this it goes to the increase thrust area?
They all do this, even my 2006 Prius.
So with the ACC set to 70, cresting a hill and going down the other side – it must dab the brakes to keep the speed at 70?
No, the DSG will work with the ECU based ACC (ooh, acronyms...) tend to do engine braking/coasting to keep the speed at or below that selected (usually to about 2-3mph). if the car needs to quickly drop the speed by 10 or 20mph it will use the brakes.
Warning, Anorak content ahead:
My (Hybrid) car does the same but blends the CVT gearing to provide engine braking and Regen function of the hybrid system to hold the speed steady when going down hills when using the adaptive cruise control. In normal driving you can occasionally feel a slight "step" in the braking when it switches from regen only brakes to add the "proper" brakes as well. Toyota Hybrids work best when you effectively hypermile them by accelerating gently using the battery motor and engine together, then once up to speed releasing the throttle pedal than gently depressing slightly to get the full EV mode to kick in to maintain the speed. Its not high performance but its not slow either and actually quite fun/engaging to do as the MPG/Regen displays effectively turn this all into a game to achieve the best efficiency as it gives you an effiency score at the end of every journey.
Hybrids are really a transient tech unless fully synthetic carbon neutral fuels become viable (they're much more likely to be used for aircraft as Jet engines are very very good and no-one has yet come up with an commercially viable working electric alternative). I think we'll mostly be driving EV's by 2035.
My last two DSG's freewheeled when you selected Eco mode.
Re. the DSG going into neutral – I asked because AFAIK the 7 speed on the VW T6.1 does it, and doesn’t have driving modes, so I suppose it’s always on.
So with the ACC set to 70, cresting a hill and going down the other side – it must dab the brakes to keep the speed at 70? Sounds all kinds of weird, I’ve got a 6.1 on the way too…
My T5 DSG used to rev the crap out of itself when it went down a steep hill with the cruise control on. Used to have to dab the accelerator or the break for it to go down a gear to sort itself out.
The article mentions one little game I like to play - seeing how high I can get the range. On long motorway journeys every so often I add the distance travelled to the range left to see what the total is. Now and then I've got it up to around 900 miles. If I could maintain that for a whole tank of fuel I'd be a happy man! Needless to say I don't get bothered by people wanting a race.
Old 2-stroke Saabs had a freewheel to stop you running the engine without injecting fuel, as that would have run it dry of oil as well.
Now and then I’ve got it up to around 900 miles.
For some reason driving up to Preston from Cardiff returned the highest MPG I saw in the Passat, on one occasion 65mpg - and that's with the cruise set at 70. That gave me a range+distance figure of something like 1,050 miles.
Managed to get 55.9mpg indicated out of my 320d last night London to Poole with 5 up and fully loaded with clothes and food for the weekend, without using Eco mode.
I thought that was ok tbh.
That gave me a range+distance figure of something like 1,050 miles.
Mine's a Passat too. Must try harder.
Blimey, I'm definitely doing something wrong as I seem to be below 50mpg constantly in my 1.6hdi puggy Partner...right, I need to try much harder!
Blimey, I’m definitely doing something wrong as I seem to be below 50mpg constantly in my 1.6hdi puggy Partner…right, I need to try much harder!
Probably the shape of it. Vans aren't great.
My work Ford Connect, reasonably loaded I get 50mpg most of the time or 60mpg if I really try. That does mean running with the trucks, which I hate. So I'll do the speed limit and get around 50-53 mpg depending how much town work I do.
If there's a headwind, mpg suffers.
Eco mode is just horrible and makes a day behind the wheel very fatiguing, the 1.5? TD has precious little low down grunt as it is. It just feels like it's broken, unless it's empty of tools.
If every car was self driving and interconnected, then I suspect it could, as they could safely drive close enough to really make us of the slipstream effect.
As that isn’t the case, then I don’t think so, as a self driving vehicle likely wouldn’t be programmed to sit right up the arse of a lorry and take the risk that involved, like bored dad in his Volvo would.
They can indeed do this, it's known as Platooning. There have been some live-road trials already.
Must try harder.
Heh. Didn't do anything apart from set off at the right time to avoid traffic and put the cruise control on 70.
It wasn't that good on every trip, just that particular road. 60mpg was fairly common on a motorway trip. I'm happy to see 50 in the Merc though.
We deal with a few truck dealers at work. Some of the tech in modern trucks is very clever. The iDrive Volvo has autonomous cruise which also looks at the topographical map do it knows when it has an incline coming up and sets speed and revs according to the load. As it approaches the crest of the hill is does the same and coasts with regen down the other side. The operators are talking marginal gains but the total gains in a fleet of 100’s of trucks is mega bucks. Some drivers hate it as it removes them from the equation. Volvo dealer also has a full time trainer to teach drivers how to get the best out of the trucks economy.
Anecdotally I have noticed many more people driving well below the motorway speed limit lately, presumably to try and save fuel. I did smile at one I saw last week doing 55 mph or so, but with a double bike roof rack….with no bikes on it.
@jamesoz
I think the only Saabs with freewheel were the 93 and early 95 and 96, with a two-stroke engine.
Wikipedia page on Saab 93
I understand that the freewheel was to stop the engine seizing on the overrun (when you lifted you foot off the accelerator, but the car was still moving), like on a long downhill.
Being an early two-stroke, there was no separate oil lubrication system: it relied on the oil mixed in with the petrol for lubrication. If your foot was not on the accelerator, the engine wasn't taking in any petrol/oil mixture, so it wasn't getting any lubrication. Soon the oil film between moving parts would gradually get pushed out, and you would be left with metal rubbing on metal. That sort of thing tends to weld itself together, which is bad.
I'm sure someone who knows more about this will be along soon, but understand that best practice for two-stroke motorbike and scooter riders back in the day was: always pull the clutch in on the overrun. Also, always ride with two fingers over the clutch lever: if the engine seized and you were 'really' quick, you could pull the clutch in before the seized engine and back wheel caused a crash.
I believe that some commuter two-stroke scooters have a freewheel. Dimly remember something about some modern two-stroke engines have a separate oil pump, too. It doses the correct amount of oil into the petrol for two-stroke, and also pumps oil around the parts that need lubrication.
I drove a friend's Saab 96 with a freewheel. Could see how it might use less fuel with plenty of practice, but I didn't get beyond the stage of it feeling very strange.
Edit: just saw that this was covered by gofasterstripes. Oh well...
I learned it just the other day myself and your reply is much more insightful than mine