Hope for London or pie in the sky?

[Grandad]

http://www.cyclingweekly.co.uk/news/latest-news/christian-wolmar-mayor-put-cycling-heart-london-transport-plans-136576

[Bonefishblues]

Too late for the chaos that was London this am due to Kings Cross tube being closed. A 3 mile walk was enjoyable in itself, but I was slightly envious of the Brompton riders, I must admit

[drossall]

I was at KX as usual this morning, and didn't even notice the closure. I'm a Dahon rider, not a Brompton, not that that makes any difference

There are plans for the area, though I'm not well up on the latest.

[Bonefishblues]

I was at KX as usual this morning, and didn't even notice the closure. I'm a Dahon rider, not a Brompton, not that that makes any difference

There are plans for the area, though I'm not well up on the latest.

A bit like the old Cleese-Barker-Corbett sketch is London eh?

I'm a Dahon rider so I look down on Brompton riders etc

[drossall]

Other way around. I couldn't afford/justify a Brompton.

Though the range of gears on my Dahon is a compensation when getting up the hill to Angel.

[Bonefishblues]

Oh I dunno, there are Dahons and there are Dahons: http://dahon.com/mainnav/foldingbikes/s ... _sl-3.html

[MrsHJ]

Anyone wishing to take part in the consultation for the London cycle superhighway can do so here:

https://consultations.tfl.gov.uk/cycling/eastwest

[sirmy]

I was in London on Monday, first time in years, to see Kate Bush(totally stunning BTW) and I found I was having difficulty breathing while walking so how people ride down there beats me. Maybe you adapt to the lack of oxygen in the same way Sherpas have

[Bonefishblues]

I was in London on Monday, first time in years, to see Kate Bush(totally stunning BTW) and I found I was having difficulty breathing while walking so how people ride down there beats me. Maybe you adapt to the lack of oxygen in the same way Sherpas have

It has been particularly bad this week. Diesel vehicles are big contributors. This can't come too soon: http://www.bbc.co.uk/news/uk-england-london-28540259

[MikeF]

If Labour and Tory are competing to put in better cycling facilities this surely has to be good for cycling? Also I think the previous Labour administration had plans which Boris built on. I don't cycle in London so I can't really comment on how good they are, but certainly there has been a large increase in cycling, perhaps more than anywhere else in the country.

[MikeF]

I was in London on Monday, first time in years, to see Kate Bush(totally stunning BTW) and I found I was having difficulty breathing while walking so how people ride down there beats me. Maybe you adapt to the lack of oxygen in the same way Sherpas have

It has been particularly bad this week. Diesel vehicles are big contributors. This can't come too soon: http://www.bbc.co.uk/news/uk-england-london-28540259

Oh yes petrol has green pumps therefore good, but diesel black pumps therefore bad.

I suspect the real reason for the charge is the loss of tax revenue that results in the use of diesel fuel. Both fuels pollute but I happen to find that it's fumes from petrol engines that can make my chest tighten not diesel fumes even though they are unpleasant.

[Bonefishblues]

I was in London on Monday, first time in years, to see Kate Bush(totally stunning BTW) and I found I was having difficulty breathing while walking so how people ride down there beats me. Maybe you adapt to the lack of oxygen in the same way Sherpas have

It has been particularly bad this week. Diesel vehicles are big contributors. This can't come too soon: http://www.bbc.co.uk/news/uk-england-london-28540259

Oh yes petrol has green pumps therefore good, but diesel black pumps therefore bad.
I suspect the real reason for the charge is the loss of tax revenue that results in the use of diesel fuel. Both fuels pollute but I happen to find that it's fumes from petrol engines that can make my chest tighten not diesel fumes even though they are unpleasant.

I have no idea what the motivation is, but not particularly useful to get into that, or respond to "black pump bad green pump good" with rolleyes, which wasn't a point I was making.

Diesel is, by and large, an unsuitable fuel for use in urban areas such as London. Many journeys are short. Engines do not warm, the Euro 5/6 emissions gubbins does not warm sufficiently to do its job (and cars break down as a result, and are often as consumptive as their petrol equivalents - but that's another discussion) so carcinogenic particulates are put into the atmosphere in significant quantities. The results can be seen, felt and indeed tasted in conditions such as last week's.

Petrol isn't as bad. Note the careful phrasing of that sentence.

[MikeF]

Diesel is, by and large, an unsuitable fuel for use in urban areas such as London. Many journeys are short. Engines do not warm, the Euro 5/6 emissions gubbins does not warm sufficiently to do its job (and cars break down as a result, and are often as consumptive as their petrol equivalents - but that's another discussion) so carcinogenic particulates are put into the atmosphere in significant quantities. The results can be seen, felt and indeed tasted in conditions such as last week's.

Petrol isn't as bad. Note the careful phrasing of that sentence.

As I said petrol is far worse as far as I'm concerned. Petrol engines warm up slowly and this is when most of the pollution is produced.

A diesel engine works by compressing a cylinder (or more for a turbo) full of air to a high temperature to ignite the injected fuel. If this temperature is insufficient it won't run - simple as that - there's nothing else to ignite the fuel. This means the combustion chamber is hot from the time the engine starts - it has to be.

A petrol engine works by igniting an explosive mixture of petrol vapour and air. The combustion chamber temperature is unimportant (within limits) for this to occur. Therefore a petrol engine can run with a cool combustion chamber, which also means there tends to be incomplete combustion as well, resulting in a whole range of emissions. The combustion chamber can therefore warm much slower especially if idling. Before catalytic converters were universal, it was noticeable that petrol engine exhausts would show water vapour condensate for longer periods of time than diesel counterparts as the exhaust gases are cooler.

Idling of petrol engines can also result in incomplete combustion, because there is insufficient air intake - hence one need for catalytic converters for them - whereas idling diesel engines can result in effectively complete combustion because there is excess air.

However both diesel and petrol engines pollute, and there's little point in arguing (or taxing) one over the other. Vehicles powered by either kill cyclists pedestrians and other road users, so which do is not that relevant.

If politicians want to fight over the who has the best cycling plans then that seems good news.

[Bonefishblues]

I don't agree with several of the points you make, I'm afraid.

Both engines are dirty until up to full operating temperature. Just because a diesel runs doesn't mean it's up to its optimum temperature for full combustion.

The converse is the case v-a-v warm-up cycle for the two engine types.
Petrol engines warm more quickly than diesel due to their lower thermal efficiency (25-30% vs 40%) which yields more "spare" energy as heat to warm block, coolant, oil & cat. Diesels warm more slowly for this reason, and also because their block and cooling system is necessarily more massive.

I cannot understand the point about an idling petrol engine not having sufficient air for complete combustion. They can get plenty of oxygen for combustion, as can diesels.
If that were the case how could car engines without significant ram air effect (which most road engine installations don't have) possibly operate at say 5K revs when their oxygen needs are massively greater?

Catalytic converters are there because no engine converts all its fuel into energy. A hot cat. is a very effective way of removing unburnt hydrocarbons and other potentially harmful emissions. A hot DPF is an effective way of burning particulates. Note each must be hot to work properly (or at all in the case of the DPF). That's why I made the specific point about the effect of diesel engines, with their longer warm-up cycle and non-functioning DPFs in urban areas.

It's also the case that the development of diesels seems to have reached a plateau, with manufacturers now turning back to petrol/hybrids/electric in the search for lower emissions to meet ever-tighter Regulations.

Where we do agree is that notwithstanding technical development of both types, both are polluting!