In built up areas drivers spend more time accelerating than driving at a steady speed. So the efficiency of a given speed matters less than the energy it takes to repeatedly accelerate up to a higher speed.
What if I tell you that noise pollution is a type of pollution? A lot of car noise is tyre noise which is proportional to speed. Also, tyre and brake particules are a type of pollution. They are created mostly from accelerating and braking.
You need close to three times (2.78) the energy for accelerating to 50 instead of 30.
If you have to brake, that energy gets converted to heat.
Rinse and repeat. Especially in urban areas where there’s alot of acceleration/deceleration - or just acceleration with different algebraic signs - more speed means more fuel per distance.
There are several graphs floating around showing the fuel consumption at 30 compared to 50 with different gears. It depends on your car and the gear used if 30 uses more fuel than 50. If your car uses more fuel for slower speeds and for such a common speed as 30, the manufacturer is an idiot. There are so many 30 zones in Europe that it really is not an argument against them that a car manufacturer can’t build proper cars.
And since we are also switching to electric cars, that problem will go away in the next decade or two.
If your car uses more fuel for slower speeds and for such a common speed as 30, the manufacturer is an idiot.
Or the manufacturer just optimized the engine and the gearbox to be more efficent at a certain speed.
In the end the consumption is tied to the rpm of the engine, if you need to stay on high rpm to go to 30 km/h on a lower gear because the gear ratios are optimized thinking to a certain set of speeds (50, 70, 90 and 130 km/h which are the most common in EU), you will end with a higher consumption.
That’s exactly what I wanted to say: 30 is one of the most common speeds in the EU. They are not new and have been around since the 70s/80s. Cities are pushing for 30 as a default speed. You have thousands and thousands of kilometres of residential streets with T30. If you do not optimize for that as a manufacturer, you shouldn’t build cars.
That’s exactly what I wanted to say: 30 is one of the most common speeds in the EU. They are not new and have been around since the 70s/80s.
As far as I know, the city speed limit is 50 km/h for a very long time. In the 199x, when I got my driver license it was it, the push for the 30 km/h limit is a relatively new thing, maybe last 5 years. Not to say that before there where not some 30 km/h zones in cities, but the default in every urban center (small or big) is/was 50.
Cities are pushing for 30 as a default speed.
Now yes, but is a relatively recent thing, and only for big cities.
You have thousands and thousands of kilometres of residential streets with T30. If you do not optimize for that as a manufacturer, you shouldn’t build cars.
Italy currently has an estimated total 2700 km of 30 km/h residential streets. My city alone (Milan) has about 58.0000 km of streets (only residential streets, the total is way higher).
Maybe manufacturer are not that dumb if they do not optimize the engine for the equivalent of the (less then) 5% of the streets of just one city in a state.
And I suppose that other states are in a somewhat similar situation.
Data on this is based on highway driving. Not city driving. Acceleration to 50 and then breaking again will be much less efficient than just driving a in 30
My car legitimately takes less fuel at 90 than 30. It’s the whole accelerating to 90 part that takes significantly more fuel, but steady state, 90 is more efficient than 30.
This is all because of how internal combustion engines and transmissions with distinct gear ratios work. Even if you’re not moving, you’re going to use some amount of fuel to keep the engine running, right? The engine has a bunch of internal friction that needs to be overcome. That bare minimum is more significant at low speeds. And then to raise the engine speed, you’ll have to add a bit more fuel. When you shift up a gear, the engine speed goes down - and up to some speed, this is so significant that it affects fuel economy. Then once you get to higher speeds, the energy required to overcome wind resistance is the most important bit and that has a quadratic growth.
CVTs eliminate these sharp rises and drops in fuel consumption since they have no gears, but they have their own issues and even they don’t get rid of the baseline fuel consumption to keep the engine running. EVs eliminate all this nonsense altogether, which is one of the reasons why an EV is significantly more efficient in the city while an ICE is significantly more efficient on the highway (the other reasons are lack of idle and, of course, regen braking).
If you don’t want the issues of CVTs (which are essentially none if you lease a car and don’t give a fuck about it beyond the 3-5 years you use it and also aren’t an enthusiast), modern 8 and 9 speed transmissions are better than older transmissions here. They have more different speeds where the engine is in an optimal RPM range. You still don’t want to go TOO slow (think about it - fuel consumption of a car idling at standstill is essentially infinity liters per 100 km because you’re dividing X amount of liters by zero kilometers - as you approach zero speed, you approach infinite fuel consumption).
Realistically, the optimal speed for fuel economy with an internal combustion engine and no hybridization tech is probably somewhere between 40-80 km/h. The exact number depends on a bunch of factors.
@kokesh at this point you could save some face and not comment any more. You are presenting yourself as an uniformed fool who doesn’t recognise reality.
Um, no not really. The gearbox only exists because the engine can only go so fast. The tyres can spin way faster than the engine. For example, you could take your foot entirely off the throttle and still drive 70 in sixth gear while the engine essentially idles. On the other side of the spectrum, the slowest the car can go, while having full contact with the gearbox would be 8 kmh, give or take. So, in the middle of the spectrum you could drive about 30kmh with 3rd gear fully clutched in and the engine on idle. Slower is also possible, naturally. Most cities choose 30 kilometres an hour because that’s when road deaths sharply increase. The reason for this is complex, but one of the main reasons is the field of view. The faster a car goes, the smaller your field of vision becomes. You can clearly see the pavement on your side, the other side of the road, and even some of the pavement of the opposite side. When driving 50, however, you can basically only see your own pavement and some of the opposite road. When doing 130 you can essentially only see your own lane well, with rudimentary details in the other adjacent lanes.
The gearbox only exists because the engine can only go so fast.
Oversimplified. The transmission exists because engines are optimally efficient at specific RPM ranges and the transmission works to keep the engine in those ranges. It/you (auto vs stick) will also downshift to provide more power at the cost of efficiency if hard acceleration is required.
When doing 130 you can essentially only see your own lane well, with rudimentary details in the other adjacent lanes
If you can’t see adjacent lanes, then you’re not scanning properly. This is called tunnel vision and where I live you’ll fail a road test for it. You’d also fail for going 130km/h.
Your error is thinking about “fuel”. It is the stated goal of the EU to push electronic cars and it totally doesn’t matter if some legacy technology is not working perfectly on safe roads.
I think the biggest and most important impact of this is safety actually. Survival chances from a 30km/h crash are significantly higher than at 50km/h. Crashes also simply happen much less because of a shorter stopping distance. Another thing is that at 30km/h you have much lower noise levels which is imo a public health issue that is very much undervalued. Also wear on the road surface decreases which makes for longer periods of time without construction.
One of the considerations was cars getting bigger and heavier, making changes for bad accidents with pedestrians and cyclists higher. To compensate, speed is brought down to even things out. That push for large SUVs has some downsides.
How is that more ecologically friendly? Driving 30kmh takes more fuel! And the cars will be running for longer time.
In built up areas drivers spend more time accelerating than driving at a steady speed. So the efficiency of a given speed matters less than the energy it takes to repeatedly accelerate up to a higher speed.
What if I tell you that noise pollution is a type of pollution? A lot of car noise is tyre noise which is proportional to speed. Also, tyre and brake particules are a type of pollution. They are created mostly from accelerating and braking.
It does not. It would violate simple physics.
Technically it does. Engines are usually less optimized for driving 30 compared to 50, which causes them to use more fuel for the same distance.
But a slightly higher fuel consumption is easily offset by reduced noise and increased safety (for everyone).
You need close to three times (2.78) the energy for accelerating to 50 instead of 30.
If you have to brake, that energy gets converted to heat.
Rinse and repeat.
Especially in urban areas where there’s alot of acceleration/deceleration - or just acceleration with different algebraic signs - more speed means more fuel per distance.
There are several graphs floating around showing the fuel consumption at 30 compared to 50 with different gears. It depends on your car and the gear used if 30 uses more fuel than 50. If your car uses more fuel for slower speeds and for such a common speed as 30, the manufacturer is an idiot. There are so many 30 zones in Europe that it really is not an argument against them that a car manufacturer can’t build proper cars.
And since we are also switching to electric cars, that problem will go away in the next decade or two.
Or the manufacturer just optimized the engine and the gearbox to be more efficent at a certain speed.
In the end the consumption is tied to the rpm of the engine, if you need to stay on high rpm to go to 30 km/h on a lower gear because the gear ratios are optimized thinking to a certain set of speeds (50, 70, 90 and 130 km/h which are the most common in EU), you will end with a higher consumption.
That’s exactly what I wanted to say: 30 is one of the most common speeds in the EU. They are not new and have been around since the 70s/80s. Cities are pushing for 30 as a default speed. You have thousands and thousands of kilometres of residential streets with T30. If you do not optimize for that as a manufacturer, you shouldn’t build cars.
As far as I know, the city speed limit is 50 km/h for a very long time. In the 199x, when I got my driver license it was it, the push for the 30 km/h limit is a relatively new thing, maybe last 5 years. Not to say that before there where not some 30 km/h zones in cities, but the default in every urban center (small or big) is/was 50.
Now yes, but is a relatively recent thing, and only for big cities.
Italy currently has an estimated total 2700 km of 30 km/h residential streets. My city alone (Milan) has about 58.0000 km of streets (only residential streets, the total is way higher).
Maybe manufacturer are not that dumb if they do not optimize the engine for the equivalent of the (less then) 5% of the streets of just one city in a state.
And I suppose that other states are in a somewhat similar situation.
My car is either lugging along in 2nd gear or doing like 3500 rpm in first at 30 kph, so mine wouldn’t be any quieter.
At that speed, most of the noise comes from the tyres. Slower = quieter.
Not with my exhaust
Username checks out
That’s just not correct
Which part? Can you be more specific as to what you mean?
Data on this is based on highway driving. Not city driving. Acceleration to 50 and then breaking again will be much less efficient than just driving a in 30
deleted by creator
Well, fuel consumption depends on the way you shift gears as well. But yes, it general it’s less.
My car legitimately takes less fuel at 90 than 30. It’s the whole accelerating to 90 part that takes significantly more fuel, but steady state, 90 is more efficient than 30.
This is all because of how internal combustion engines and transmissions with distinct gear ratios work. Even if you’re not moving, you’re going to use some amount of fuel to keep the engine running, right? The engine has a bunch of internal friction that needs to be overcome. That bare minimum is more significant at low speeds. And then to raise the engine speed, you’ll have to add a bit more fuel. When you shift up a gear, the engine speed goes down - and up to some speed, this is so significant that it affects fuel economy. Then once you get to higher speeds, the energy required to overcome wind resistance is the most important bit and that has a quadratic growth.
CVTs eliminate these sharp rises and drops in fuel consumption since they have no gears, but they have their own issues and even they don’t get rid of the baseline fuel consumption to keep the engine running. EVs eliminate all this nonsense altogether, which is one of the reasons why an EV is significantly more efficient in the city while an ICE is significantly more efficient on the highway (the other reasons are lack of idle and, of course, regen braking).
If you don’t want the issues of CVTs (which are essentially none if you lease a car and don’t give a fuck about it beyond the 3-5 years you use it and also aren’t an enthusiast), modern 8 and 9 speed transmissions are better than older transmissions here. They have more different speeds where the engine is in an optimal RPM range. You still don’t want to go TOO slow (think about it - fuel consumption of a car idling at standstill is essentially infinity liters per 100 km because you’re dividing X amount of liters by zero kilometers - as you approach zero speed, you approach infinite fuel consumption).
Realistically, the optimal speed for fuel economy with an internal combustion engine and no hybridization tech is probably somewhere between 40-80 km/h. The exact number depends on a bunch of factors.
Ok, I would have to drive in lower gear. That means using more power, higher RPM. Hence higher consumption.
@kokesh at this point you could save some face and not comment any more. You are presenting yourself as an uniformed fool who doesn’t recognise reality.
Um, no not really. The gearbox only exists because the engine can only go so fast. The tyres can spin way faster than the engine. For example, you could take your foot entirely off the throttle and still drive 70 in sixth gear while the engine essentially idles. On the other side of the spectrum, the slowest the car can go, while having full contact with the gearbox would be 8 kmh, give or take. So, in the middle of the spectrum you could drive about 30kmh with 3rd gear fully clutched in and the engine on idle. Slower is also possible, naturally. Most cities choose 30 kilometres an hour because that’s when road deaths sharply increase. The reason for this is complex, but one of the main reasons is the field of view. The faster a car goes, the smaller your field of vision becomes. You can clearly see the pavement on your side, the other side of the road, and even some of the pavement of the opposite side. When driving 50, however, you can basically only see your own pavement and some of the opposite road. When doing 130 you can essentially only see your own lane well, with rudimentary details in the other adjacent lanes.
Oversimplified. The transmission exists because engines are optimally efficient at specific RPM ranges and the transmission works to keep the engine in those ranges. It/you (auto vs stick) will also downshift to provide more power at the cost of efficiency if hard acceleration is required.
If you can’t see adjacent lanes, then you’re not scanning properly. This is called tunnel vision and where I live you’ll fail a road test for it. You’d also fail for going 130km/h.
@kokesh you’ve not thought this through, have you? 😆
Your error is thinking about “fuel”. It is the stated goal of the EU to push electronic cars and it totally doesn’t matter if some legacy technology is not working perfectly on safe roads.
I think the biggest and most important impact of this is safety actually. Survival chances from a 30km/h crash are significantly higher than at 50km/h. Crashes also simply happen much less because of a shorter stopping distance. Another thing is that at 30km/h you have much lower noise levels which is imo a public health issue that is very much undervalued. Also wear on the road surface decreases which makes for longer periods of time without construction.
One of the considerations was cars getting bigger and heavier, making changes for bad accidents with pedestrians and cyclists higher. To compensate, speed is brought down to even things out. That push for large SUVs has some downsides.
Legacy technology :D