The evil diesel

[Mandrake]

Nobody to my knowledge has seriously questioned a petrol engine's real life emissions. There does seem to be a concerted effort by parties with an axe to grind against diesel powered vehicles. I would be willing to bet that a petrol engine chucks out more nasties than it's supposed to especially when it's cold and the cat isn't up to working temperature. At least on a diesel the DPF works regardless of the engine temperature.

Yes a petrol engine will chuck out quite a bit more HC and CO when the cat is cold than when it is hot. Especially when started completely from cold because the mixture will be enriched, which means enough HC to smell on some cars... If the engine is already hot from recent driving and only the cat has to warm up the situation is not as bad as it will not be running at a rich mixture.

But you're forgetting that Diesel's also have a catalytic converter which also doesn't do squat when it's cold. Diesel cats are only 2 way not 3 way, (since they're running lean burn most of the time) so it converts CO and O2 to CO2 and HC to CO2 and water.

So when a Diesel cat is cold it produces a lot more CO, which is pretty noxious stuff in confined spaces of course...and under acceleration will produce more HC when the cat is cold, and because a Diesel engine is more efficient and produces less waste heat through the exhaust, it's more difficult to heat the cat up quickly than a petrol...

The 3 way cat in a petrol car is more capable - as well as what the Diesel cat can do it can also convert NOx back to Nitrogen and Oxygen, which is one reason why the NOx on petrol engines is so low, as well as the fact that they don't produce nearly as much to begin with as they don't run lean like Diesel.

The DPF might work all the time, but it's only there to catch soot particles that properly running petrol engines (GDI excepted) don't produce in the first place.

[Gibbo2286]

If you take a close look at the operation of catalytic converters you will find that they are, for normal everyday motoring, a useless expensive add-on, they never get up to optimum working temperature.

Like the DPF they need to be very hot to work efficiently and town driving. commuting doesn't do it.

[EDC5]

If you take a close look at the operation of catalytic converters you will find that they are, for normal everyday motoring, a useless expensive add-on, they never get up to optimum working temperature.

Like the DPF they need to be very hot to work efficiently and town driving. commuting doesn't do it.

Is this true of the SCR / Adblue systems too?

[doctle]

So we should get electric cars? both Ireland and the UK would have to more than double their electric generation output just to power electric cars. This would skew the renewable power all countries are supposed to produce and it really isn't going to happen. I think the car manufacturers can make cleaner diesels and they will, as well as cleaner petrols. Otherwise I will have to get a C5 only mine will have a Sinclair badge on it

[Michel]

I will happily drive my 18-40mpg petrol Ford Focus until it is prised from my cold, dead hands.

[GiveMeABreak]

Like the DPF they need to be very hot to work efficiently and town driving. commuting doesn't do it.

The PSA DPF system works 'out the box' in ALL conditions Gibbo, all the time. It is only the regeneration cycle that needs the exhaust gasses to be at the correct temperature - hence the additive for assistance and sufficient time for the cycle. But the DPF will always do it's job - until the car will ultimately stop operating at some point where it is too blocked.

The additive particulate filter has been fitted on all PSA Group vehicles since 2009 – two years before it was made obligatory by the Euro 5 standard. It is effective in all the operating conditions of a vehicle:
Start-up
Warm or cold
In cities and on motorways
Even when the filter is full

https://www.groupe-psa.com/en/newsroom/ ... te-filter/

The newer SCR system utilising AdBlue reduces NOx by 90% and CO2 by 2-4% (PSA) and is combined with the DPF.

[Peter.N.]

I think electric cars will be the future, much of Scandinavia already have a large proportion of them but most of their electricity is hydro, in Norway anyway, they have charging points on lamposts. Orkney generates more renewable energy that it can use and exports it to the mainland.

Quite a number of people with EV's charge them from their own solar panels and the Tesla 'Power wall' will store 12kw or more for overnight use. I concede that if everyone went electric overnight the grid wouldn't support it but there is a system in development for power to be drawn from your car to support the grid at times of high demand.

They are actually producing hydrogen with some of the surplus energy on Orkney, although fuel cell vehicles are not the most efficient way of using electricity.

They are now producing electric vehicles with a range in excess of 200 miles, batteries and vehicles are improving all the time and the price is also falling.

Peter

[Mandrake]

If you take a close look at the operation of catalytic converters you will find that they are, for normal everyday motoring, a useless expensive add-on, they never get up to optimum working temperature.

That's far too broad a statement to be substantiated. It depends highly on the design of the cat(s) in an individual car.

Back in the days when there was one big cat under the centre console in the main exhaust feed, (like my Xantia V6) yeah, it would take a while to come up to temperature while driving in stop start traffic. Once it did though it would stay hot enough (there is a range of a few hundred degrees over which it will work) to keep working unless you stop and idle for a long time or turn the engine off.

But modern petrol engines usually have "pre-cats" as well. Look at the ES9J4S V6 used in the C5 - nearly 15 years old now and it has them. Two small cats that are mounted pretty much right off the exhaust headers on the engine on each V6 bank before the headers even combine, then one large cat on the main exhaust pipe for additional processing.

These pre-cats will heat up extremely quickly due to their location and stay hot and working effectively even if the engine is just idling. So what you say about cats being useless for "everyday motoring" is not true at all for any car with pre-cats directly on the exhaust headers.

One wrinkle to this situation though is cars with stop/start systems... I can't see any way that cats can be kept properly hot in a stop/start system where the engine is stopped at every junction, but I've always been against stop/start systems as basically a method for the manufacturer to game the NEDC MPG rating (by drastically improving the MPG over the "stopped" part of the cycle, which is a significant portion of the test) whilst actually being detrimental to total emissions released (due to constant starts and cooling cats) and longevity of engine parts... (worn starter anyone ?)

[Paul-R]

But you're forgetting that Diesel's also have a catalytic converter which also doesn't do squat when it's cold.

I didn't forget about them. I recognise that they also wouldn't work when cold, that's why I said the DPF works when cold.

So when a Diesel cat is cold it produces a lot more CO, which is pretty noxious stuff in confined spaces of course...

As a diesel engine is an oxygen rich engine it will always produce less than a petrol engine with its throttled inlet. So technically probably correct but in comparison to petrol engine waaaay less.

The 3 way cat in a petrol car is more capable - as well as what the Diesel cat can do it can also convert NOx back to Nitrogen and Oxygen, which is one reason why the NOx on petrol engines is so low, as well as the fact that they don't produce nearly as much to begin with as they don't run lean like Diesel.

The latest SCR catalysts on the diesel engines also reduce NOx. Current maximum levels for Euro6 are much reduced and are now down to twice as much as a petrol engine.

The DPF might work all the time, but it's only there to catch soot particles that properly running petrol engines (GDI excepted) don't produce in the first place.

But get caught they are. And that's surely the point? I also think petrol engine particulate emission will come under investigation as smaller and smaller particles come under the microscope.

In addition I remember reading a couple of decades ago that whilst diesel engines may produce more particulates than a petrol engine when new, they remain pretty constant over the lifetime of the engine. A petrol engine will produce more as it ages giving a less favourable comparison when whole life emissions are compared. And there's no DPF to catch those particulates!

[doctle]

I think electric cars will be the future, much of Scandinavia already have a large proportion of them but most of their electricity is hydro, in Norway anyway, they have charging points on lamposts. Orkney generates more renewable energy that it can use and exports it to the mainland.

Quite a number of people with EV's charge them from their own solar panels and the Tesla 'Power wall' will store 12kw or more for overnight use. I concede that if everyone went electric overnight the grid wouldn't support it but there is a system in development for power to be drawn from your car to support the grid at times of high demand.

They are actually producing hydrogen with some of the surplus energy on Orkney, although fuel cell vehicles are not the most efficient way of using electricity.

They are now producing electric vehicles with a range in excess of 200 miles, batteries and vehicles are improving all the time and the price is also falling.

Peter

I'm not sure the Powerwall on it's own would do much good. I have been looking into this and I'd need 2 producing 12kw each for 2-3 cars. I'm on roughly the same latitude as Manchester so not a huge amount of sun, many, many solar panels needed or Tesla roof tiles @ €50,000.00 +. Add the two Powerwalls, permission to to add a changeover switch with the electric company various other bits and pieces of work I reckon €70,000.00 + before I'd even bought an electric car. Oh an the Irish government loves VAT @ 23%. Both the UK and Ireland have big mad plans to ban all internal combustion engines quite soon, 2030 I think the Irish government has suggested.

[Homer]

It's politicians who got us here because they are always looking for a quick fix rather than looking long term.

They forced petrols to have catalytic converters despite the evidence saying that lean burn engines could do the job better and with less CO2. Cats pushed up CO2 so they pushed us to diesel. Now they want another quick fix and a gain they are using a stick rather than a carrot to achieve it.

If you are looking for a large 2nd hand car then there isn't a lot of choice, it's diesel or buy new.

I've driven some of the newer petrols and they are great but I don't have twenty-odd grand kicking around so I have to take what people were buying two or three years ago so it will be another diesel, and maybe in two years time I will have to take the (electric) bus if I want to go into town. Or I just won't go into any big cities, that would suit me fine.

[Gibbo2286]

For the big cities Homer it's a money thing, if they really thought the diesel was so evil they would ban it altogether not let it continue to be evil for a price.

[doctle]

Alcohol kills more people in Ireland than everything else, disease, motor crashes, illness etc all caused by booze, it's the only drug that's NOT banned, go figure as our American cousins say

[Mandrake]

For the big cities Homer it's a money thing, if they really thought the diesel was so evil they would ban it altogether not let it continue to be evil for a price.

Not really. It's just part of the stick side of the carrot and stick that is being used to encourage people to EV's. Make a Diesel more expensive to run in a heavily polluted area like London and it will encourage people to use something else. Money talks.

The alternative is to forcibly take Diesel cars out of people's hands - that's not what you want surely ? There will be people who still want to or must drive a Diesel - their costs will go up, but in the short term they won't be forced to stop using it. But they will certainly be encouraged, and some may be encouraged to switch to public transport instead as congestion is as much of a problem as pollution.

The fact that they are focusing on heavily polluted areas like London first does actually show they are doing it for health and pollution reasons in my opinion, not the reverse.

[Gibbo2286]

I've always been a bit of a cynic Simon, more so as I've aged, I think it all started listening to the BBC 'wireless' when I was very young.

I recall an interview post war of Herbert Morrison who was supply minister during the war, in answer to a question he said that if he saw a shortage of a certain product on the horizon, eggs for example, he would put out a news story that eggs were bad for your health, so as to cut the demand.

Post war he was the guy who nationalised most of British industry and he openly stated that it was not to modernise or better manage those industries it was simply to have them in the government's grasp.

He was by the Peter Mandelson's granddad.