Is engine downsizing pointless?
Discussion
I've had my first decent run out in my 330d this week, drove up from Nottingham to just past Doncaster to see my girlfriend and go to Meadowhall+Ikea for bits for our house, before driving back this morning. Fairly average traffic throughout, bit heavier this morning obviously. Done about 180 miles total.
Averaged 50mpg in that time and I wasn't particularly trying to drive economically, after I came off the A1 the other day I absolutely spanked it for a good 8-10 miles. Mine's xDrive as well which takes a good few MPG off. That's a bit better than my old Mk8 Fiesta ST which was half the engine size and actually ran as a 1.0 2 pot when cruising. It's not too far off what my mum manages in a run in her 1.0 hybrid Puma and she drives everywhere 10 under and never leaves eco mode.
So, what's the point of engine downsizing again?
Averaged 50mpg in that time and I wasn't particularly trying to drive economically, after I came off the A1 the other day I absolutely spanked it for a good 8-10 miles. Mine's xDrive as well which takes a good few MPG off. That's a bit better than my old Mk8 Fiesta ST which was half the engine size and actually ran as a 1.0 2 pot when cruising. It's not too far off what my mum manages in a run in her 1.0 hybrid Puma and she drives everywhere 10 under and never leaves eco mode.
So, what's the point of engine downsizing again?
‘Spanking’ a diesel causes a rise in combustion temperatures to produce more power for acceleration, and therefore an increase in the production of NOx.
I if you covered those miles at a lower speed and drove sedately not only would CO2 per mile significantly decrease but you would probably halve the amount of NOx that was produced.
Massive over consumption of diesel in the UK, exacerbated by aggressive driving style, is the main reason behind all of the clean air zones and reduced speed limits multiplying like rabbits.
I if you covered those miles at a lower speed and drove sedately not only would CO2 per mile significantly decrease but you would probably halve the amount of NOx that was produced.
Massive over consumption of diesel in the UK, exacerbated by aggressive driving style, is the main reason behind all of the clean air zones and reduced speed limits multiplying like rabbits.
I guess the same could be asked in the opposite direction, why go bigger?
My daily diesel Ceed Estate is a 1.6, but it will cruise comfortably and quietly all day and pulls well. I get up to 60mpg on a motorway at 65mph, maybe low 50's at closer to 80mph.
It isn't a rocket ship of course and your 330 would be quite quick I would imagine, but if we are talking motorway driving, acceleration, even between gears, becomes kind of irrelevant.
My daily diesel Ceed Estate is a 1.6, but it will cruise comfortably and quietly all day and pulls well. I get up to 60mpg on a motorway at 65mph, maybe low 50's at closer to 80mph.
It isn't a rocket ship of course and your 330 would be quite quick I would imagine, but if we are talking motorway driving, acceleration, even between gears, becomes kind of irrelevant.
GT9 said:
‘Spanking’ a diesel causes a rise in combustion temperatures to produce more power for acceleration, and therefore an increase in the production of NOx.
I if you covered those miles at a lower speed and drove sedately not only would CO2 per mile significantly decrease but you would probably halve the amount of NOx that was produced.
Massive over consumption of diesel in the UK, exacerbated by aggressive driving style, is the main reason behind all of the clean air zones and reduced speed limits multiplying like rabbits.
What has any of this to do with engine downsizing? Oh wait, you just wanted to find another thread in which to spout your anti-ICE mantra. I get it now.I if you covered those miles at a lower speed and drove sedately not only would CO2 per mile significantly decrease but you would probably halve the amount of NOx that was produced.
Massive over consumption of diesel in the UK, exacerbated by aggressive driving style, is the main reason behind all of the clean air zones and reduced speed limits multiplying like rabbits.
GT9 said:
‘Spanking’ a diesel causes a rise in combustion temperatures to produce more power for acceleration, and therefore an increase in the production of NOx.
I if you covered those miles at a lower speed and drove sedately not only would CO2 per mile significantly decrease but you would probably halve the amount of NOx that was produced.
Massive over consumption of diesel in the UK, exacerbated by aggressive driving style, is the main reason behind all of the clean air zones and reduced speed limits multiplying like rabbits.
The fun police have arrived...chances are in a number of cases we are paying for the car and fuel let people use it how they want within the legal requirements set out and agreed to. I if you covered those miles at a lower speed and drove sedately not only would CO2 per mile significantly decrease but you would probably halve the amount of NOx that was produced.
Massive over consumption of diesel in the UK, exacerbated by aggressive driving style, is the main reason behind all of the clean air zones and reduced speed limits multiplying like rabbits.
Next you will be complaining if someone downshifts to do an overtake on A road because some throbber is doing 40 in an NSL or to build up speed on a sliproad.
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I have only ever downsized in engine terms once from 2 litre to 1.8. But it did come from diesel to petrol. I do think engine downsizing in general does not always deliver the hypothetical gains envisaged.
LunarOne said:
GT9 said:
‘Spanking’ a diesel causes a rise in combustion temperatures to produce more power for acceleration, and therefore an increase in the production of NOx.
I if you covered those miles at a lower speed and drove sedately not only would CO2 per mile significantly decrease but you would probably halve the amount of NOx that was produced.
Massive over consumption of diesel in the UK, exacerbated by aggressive driving style, is the main reason behind all of the clean air zones and reduced speed limits multiplying like rabbits.
What has any of this to do with engine downsizing? Oh wait, you just wanted to find another thread in which to spout your anti-ICE mantra. I get it now.I if you covered those miles at a lower speed and drove sedately not only would CO2 per mile significantly decrease but you would probably halve the amount of NOx that was produced.
Massive over consumption of diesel in the UK, exacerbated by aggressive driving style, is the main reason behind all of the clean air zones and reduced speed limits multiplying like rabbits.
Diesel is not the right fuel for cars, it never has been.
It should be used for moving heavy goods, ships, boats, etc. where engine design and load characteristics are far better suited to each other.
Intermittent high power bursts are exactly the wrong application.
The purpose of downsizing a petrol engine is to try to bring the thermal efficiency of the petrol cycle closer to what a diesel can achieve.
The good news is that spanking a modern petrol engine doesn't increase its NOx output.
So it has everything to do with downsizing AND using the right fuel for the job.
As an above poster has stated, it helps to compare similar vehicles and fuel types.
A 3.0 Diesel BMW on a primary motorway journey should be compared to a 2.0 Diesel BMW for fairness. Having not driven either, my brain would assume given the same road and the same driving standard, the 2.0 diesel BMW at reasonably maintained speed would have some measurable increase in fuel efficiency over the larger engine.
The reduction in engine size as what I think GT9 is implying is not necessarily for your MPG to sky rocket, but for your emissions to diminish for the good of the planet, the environment, and our precious breathable air which we so vitally rely upon.
I love larger engine cars, I still hold a dream of a V8, but I know that the cost in fuel, emissions (via tax) and maintenance is significantly higher than a 2.0 turbo with the regulated exhausts.
Ethically and Morally we should all downsize as a very minimum, and drastically make the switch from Diesel.
As an individual you can define your own line in there, I would imagine it depends much on financial status and your family status!
I'm making the most of what I can and hopefully joining the 3.0 Inline 6 club this month, but I know it wont last forever!
As a note - I currently drive a Leon Cupra 68 plate, FWD 290 version. I drove to the local airport which is approximately 35 minutes away and averaged 43mpg, not Significantly less than your Diesel
Edit: Spelling
A 3.0 Diesel BMW on a primary motorway journey should be compared to a 2.0 Diesel BMW for fairness. Having not driven either, my brain would assume given the same road and the same driving standard, the 2.0 diesel BMW at reasonably maintained speed would have some measurable increase in fuel efficiency over the larger engine.
The reduction in engine size as what I think GT9 is implying is not necessarily for your MPG to sky rocket, but for your emissions to diminish for the good of the planet, the environment, and our precious breathable air which we so vitally rely upon.
I love larger engine cars, I still hold a dream of a V8, but I know that the cost in fuel, emissions (via tax) and maintenance is significantly higher than a 2.0 turbo with the regulated exhausts.
Ethically and Morally we should all downsize as a very minimum, and drastically make the switch from Diesel.
As an individual you can define your own line in there, I would imagine it depends much on financial status and your family status!
I'm making the most of what I can and hopefully joining the 3.0 Inline 6 club this month, but I know it wont last forever!
As a note - I currently drive a Leon Cupra 68 plate, FWD 290 version. I drove to the local airport which is approximately 35 minutes away and averaged 43mpg, not Significantly less than your Diesel
Edit: Spelling
Downsizing reduces frictional loss within the engine. Believe that is mostly due to piston ring area.
Also smaller engines tend to be more economical at lower loads, where they occupy a more efficient zone of the BSFC map.
5.0L V8 capable of 26mpg under cruise, will eat through petrol when stuck stationary in traffic as so often happens in UK.
Also smaller engines tend to be more economical at lower loads, where they occupy a more efficient zone of the BSFC map.
5.0L V8 capable of 26mpg under cruise, will eat through petrol when stuck stationary in traffic as so often happens in UK.
Ninja59 said:
The fun police have arrived...chances are in a number of cases we are paying for the car and fuel let people use it how they want within the legal requirements set out and agreed to.
Next you will be complaining if someone downshifts to do an overtake on A road because some throbber is doing 40 in an NSL or to build up speed on a sliproad.
I have only ever downsized in engine terms once from 2 litre to 1.8. But it did come from diesel to petrol. I do think engine downsizing in general does not always deliver the hypothetical gains envisaged.
CO2 aside, you can have fun in a petrol car without exacerbating the harmful emissions. Next you will be complaining if someone downshifts to do an overtake on A road because some throbber is doing 40 in an NSL or to build up speed on a sliproad.
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I have only ever downsized in engine terms once from 2 litre to 1.8. But it did come from diesel to petrol. I do think engine downsizing in general does not always deliver the hypothetical gains envisaged.
Downsizing is a useful step in the right direction, but only if you change to petrol as well.
Diesel has zero future for cars apart from the legacy fleet already on the road.
Most fuel consumption is determined by,
Otherwise it's pretty much "same speed, same car, same fuel consumption".
- Vehicle gross weight - relevant during acceleration, and
- Vehicle aerodynamics/ wind resistance - relevant during motorway cruising.
Otherwise it's pretty much "same speed, same car, same fuel consumption".
axel1990chp said:
I love larger engine cars, I still hold a dream of a V8, but I know that the cost in fuel, emissions (via tax) and maintenance is significantly higher than a 2.0 turbo with the regulated exhausts.
Sorry, but this line got me. With the current tax system, beyond year 1 (where it is CO2 based), you pay the same for a BMW 3 series with a couple of options bringing it to £40k as for driving something worth double or triple (if not more) and probably does 15MPG less. Maintenace if selected correctly for certain cars with V8s in generally included for 5 to 7 years even for some of the more prestige brands.
Which just leaves fuel really (granted not a small cost considered).
GT9 said:
CO2 aside, you can have fun in a petrol car without exacerbating the harmful emissions.
Downsizing is a useful step in the right direction, but only if you change to petrol as well.
Diesel has zero future for cars apart from the legacy fleet already on the road.
But there is a time and place to make sensible progress, including where necessary downshifting and using the revs. I don't want to get crushed by an HGV because someone tries to merge at 40mph on to a motorway for fear of "emissions" and steady driving significantly below the speed limit where conditions allow you to do the posted limit.Downsizing is a useful step in the right direction, but only if you change to petrol as well.
Diesel has zero future for cars apart from the legacy fleet already on the road.
Edited by Ninja59 on Friday 14th July 12:14
GT9 said:
CO2 aside, you can have fun in a petrol car without exacerbating the harmful emissions.
Downsizing is a useful step in the right direction, but only if you change to petrol as well.
Diesel has zero future for cars apart from the legacy fleet already on the road.
Recently changed my lease car from 120ps 1.5L Diesel to 200ps 1.5L Petrol. The new car is a class smaller and lighter too.Downsizing is a useful step in the right direction, but only if you change to petrol as well.
Diesel has zero future for cars apart from the legacy fleet already on the road.
Driving under the same conditions (as dictated by traffic), fuel consumption (and CO2 emissions) has increased from 51 to 35mpg. That's a penalty of 46%. Hoping we can coax the new petrol closer to 40mpg.
Petrols are just marvellous for the environment and your pocket, aren't they?
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