Mazda - Compression Ignition Petrol Engine

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#1861680 10-Sep-2017 09:12

By "silly" NOx emission rules - I presume you mean silly in that they've enabled both the manufacturers to cheat - as in VW, and the consumer to cheat, as in the case of disabling EGR and/or re-mapping ECUs to improve performance and fuel economy.

Reducing NOx isn't a silly idea - except perhaps in a rural area where that pollution isn't a major issue.

The "Atkinson Cycle" petrol engine (so called - actually not a true atkinson cycle but achieves the efficiency benefits with less mechanical complexity) is very efficient but not great power : weight ratio. As used in Prius etc, low maximum engine power can be compensated for (somewhat) by boosting performance using the electric motors.

Mazda's extremely high compression petrol engines (as well as current direct "stratified" injection high compression or forced induction petrol engines) have an inherent problem that they produce very fine nano particulates. (Unlike indirect port or throttle-body fuel injection) The full long-term health impact of exposure to these is unknown, but these do go straight through the lungs into the bloodstream, there's growing evidence that they may be extremely harmful, IIRC to meet future Euro emission standards, direct injected petrol cars will require a DPF system like diesels.

cadman

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#1861854 10-Sep-2017 14:15

TwoSeven: I think there is a long way to go before EVs become comercially viable at the consumer level.

Primarily, I dont think people will start buying them outside of... businesses (which can recover costs)

Just on this point... businesses only "recover" expenses at the applicable marginal tax rate which is currently 28% for limited liability companies. However, they still pay the bulk of expense from their profit. A business with lower expenses (such as purchasing vehicles with lower costs of ownership) will be able to charge less and make the same nett profit as the one with higher expenses.

cadman

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#1861856 10-Sep-2017 14:20

frankv:

ICEs are at best about 40% efficient (at WOT) in turning potential energy in fuel into kinetic energy. That's mainly because they have to pump air through the engine to burn the fuel, and pumping air uses energy

It's more about the fact that more than half the heat produced leaves the engine in the exhaust gases or through the cooling system.

mudguard

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#1861858 10-Sep-2017 14:31

Aredwood:

Also diesel engines are inherently more efficient. But it would suit as a "range extender" engine for an electric car. And in really cold climates, the heat from the engine could be recovered to heat the cabin and keep batteries warm. Which would mean a theoretical efficiency close to 100% as virtually all energy present in the fuel will be getting used for useful tasks.

I thought diesels were so efficient sometimes they can cause issues in cold climates? A friend who lives in Central Otago has installed an electric heater into his Skoda to heat the cabin, as the motor doesn't generate enough surplus heat on cold mornings. I was looking into newer Skoda's awhile ago and I'm sure they have the heater as an optional extra.

Aredwood

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#1861919 10-Sep-2017 18:12

@Fred99 I mean that NOx emissions rules are silly from the point of view, that complying with them makes a car use more fuel. And more fuel usage means higher carbon emissions. So on one hand, you have car owners wanting better fuel economy and governments along with various environmental groups wanting lower carbon emissions.

Then you have NOx reduction systems that cause a massive increase in carbon emissions. And even worse is that there are alot of diesel engines with EGR systems fitted for NOx reduction. Yet they don't have particulate filters fitted as the rules at the time didn't require particulate filters. These diesels have way higher particulate emissions compared to diesels that don't have any emissions control systems whatsoever.

Almost guaranteed the need for particulate filters on petrol cars will be due to them doing lots of tricks to reduce NOx emissions. EGR being the main one.

I see the goal of reducing carbon emissions being the most important one. If NOx emissions need to be higher as part of achieving the goal of lower carbon emissions, then so be it.

MikeAqua

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#1862360 11-Sep-2017 14:30

The long term trends of lithium (carbonate) pricing are interesting.

Eventually when the price is high enough lithium can just be extracted from the ocean, so there is no real supply constraint but the price will have to get higher.

The more I read about the lithium market, the more it seems to behave like the oil market.

Good (2016) article here

Mike

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wellygary

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#1862373 11-Sep-2017 14:56

MikeAqua:

The long term trends of lithium (carbonate) pricing are interesting.

Eventually when the price is high enough lithium can just be extracted from the ocean, so there is no real supply constraint but the price will have to get higher.

The more I read about the lithium market, the more it seems to behave like the oil market.

Good (2016) article here

But at the same time battery prices continued to tumble,

http://www.utilitydive.com/news/why-surging-lithium-prices-havent-stopped-cost-declines-for-battery-energy/433657/

Lithium is only 5-10% of the cost of a final battery, so with commoditisation and major mass production stripping out costs of the other components, a rising Lithium price still seems unlikely to derail the EV industry.......

MikeAqua

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#1862382 11-Sep-2017 15:07

wellygary:

MikeAqua:

The long term trends of lithium (carbonate) pricing are interesting.

Eventually when the price is high enough lithium can just be extracted from the ocean, so there is no real supply constraint but the price will have to get higher.

The more I read about the lithium market, the more it seems to behave like the oil market.

Good (2016) article here

But at the same time battery prices continued to tumble,

http://www.utilitydive.com/news/why-surging-lithium-prices-havent-stopped-cost-declines-for-battery-energy/433657/

Lithium is only 5-10% of the cost of a final battery, so with commoditisation and major mass production stripping out costs of the other components, a rising Lithium price still seems unlikely to derail the EV industry.......

I wasn't meaning to imply that it would derail the industry. But the geo-political similarities to oil are amusing, perhaps ironic

Mike

TwoSeven

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#1862465 11-Sep-2017 17:45

Personally I dont see pure battery vehicles being able to deliver on the expectations any time soon. I like them as a concept and the creativity they introduce but I think there is a little way to go yet.

I also dont think current battery technology will be the long term - go forwards technology.

In R&D there is a term called ‘Disruptive innovation’. Its basically where a new technology comes along unexpectedly and changes the way everyone works. Facebook to the internet, sms to the mobile phone, aeroplanes to the car etc.

I dont see the current or next generation EVs as being disruptive.

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Fred99

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#1862470 11-Sep-2017 17:57

Aredwood:

@Fred99 I mean that NOx emissions rules are silly from the point of view, that complying with them makes a car use more fuel. And more fuel usage means higher carbon emissions. So on one hand, you have car owners wanting better fuel economy and governments along with various environmental groups wanting lower carbon emissions.

Then you have NOx reduction systems that cause a massive increase in carbon emissions. And even worse is that there are alot of diesel engines with EGR systems fitted for NOx reduction. Yet they don't have particulate filters fitted as the rules at the time didn't require particulate filters. These diesels have way higher particulate emissions compared to diesels that don't have any emissions control systems whatsoever.

Almost guaranteed the need for particulate filters on petrol cars will be due to them doing lots of tricks to reduce NOx emissions. EGR being the main one.

I see the goal of reducing carbon emissions being the most important one. If NOx emissions need to be higher as part of achieving the goal of lower carbon emissions, then so be it.

Yeah / nah.

NOx is primarily a local problem, health effects cause the premature death of tens of thousands of people per year - there's also acid rain etc.

CO2 a global problem.

EGR isn't the cause of nano-particulates in direct injected (stratified injection) petrol engines. It's incomplete combustion at the edges of the "explosion" which is centred in the combustion chamber where the fuel is injected - surrounded by compressed air. It's how they work to reduce fuel use by running less that a stoichiometric ratio (very lean) by having a stratified charge of fuel air mixture - rather than a homogenous charge as with carbs or port fuel injection. It causes other issues too - some of the very fine soot either blows back past the intake valve - or is recirculated through EGR, and builds up in the intake ports. Can be a serious issue as the intake ports eventually need to be cleaned out - taking the manifold off a V6 for example and cleaning out the ports using soda or walnut shell flour grit blasting is an expensive job. This less of a problem with conventional fuel injected petrol engines with EGR, as the ports get continuously "washed" by the fuel:air mix.

Basically all of these modern direct injected petrol engines are close to being Compression Ignition anyway. I think current Mazda Skyactiv run about 14:1 compression ratio. Audi/VW use lower compression ratio but usually forced induction. Combustion chamber pressures are such that the fuel air mix would ignite without a spark, precise injection timing coincxiding with a spark makes sure it happens at the right time. If they (Mazda) can get even more precise with injection (and with higher compression ratio again), then they can dispense with the spark. It's then not just "like a diesel". It is a diesel.

Aredwood

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#1862567 12-Sep-2017 00:01

The big issue with EGR is because it is used to lower combustion temps. Lower combustion temps mean more particulates produced, and it means that exhaust gas temps are not high enough for remaining particulates to self burn up, and it also causes issues with getting catalytic converters hot enough to function properly. And the final kicker is lower efficiency - as you get less heat for a given amount of fuel.

Lower exhaust gas temps also mean that if a particulate filter is fitted, it both blocks up quicker. Due to higher amounts of particulates that it needs to filter out. And it often won't get hot enough to self regenerate, So the ECU has to sense when the filter is beginning to block up, and carry out a regeneration cycle. Which consists of injecting extra fuel during the exhaust stroke, to manually increase exhaust temps enough to regenerate the particulate filter. This fuel used for regeneration doesn't contribute to powering the car. But it is still extra carbon emissions. And extra expense to the owner due to unnecessary extra fuel usage.

There are also homogeneous charge compression engines, which completely premix the fuel instead of using stratified air /fuel mixtures. My understanding is that Mazda Skyaciv X uses HCCI combined with a spark plug. So it can either do full HCCI, or bring cylinder pressures close to triggering compression ignition, and then use the spark plug to start combustion, with the resultant increase in cylinder pressure then starts the compression ignition. But the big disadvantages with HCCI are higher unburnt hydrocarbon emissions which will mean higher particulate emissions.

Ironicly systems like Volkswagen FSI are designed to get lots of stratified combustion happening. FSI was designed to keep the rich part of the mixture near the centre of the combustion chamber. So the air at the edges will help insulate the mixture, giving cleaner combustion by reducing the amount of unburnt hydrocarbons and particulates at the edges of the combustion chamber.

My understanding is that Volkswagen no longer make FSI engines as they had high NOx emissions. Also other manufactures like Honda no longer make their VTEC-E engines. Or other engine technologies that were designed to give better fuel economy by running lean air fuel ratios during light load cruising.

Either way, In my opinion, chasing reductions in NOX emissions is still silly due to the increase in carbon emissions. You can still have particulate filters on engines with high NOX emissions, so no problems there.

Also NOX emissions cause OH radicals to form in the atmosphere. These OH radicals react with Methane, removing it from the atmosphere. Considering that Methane is a major green house gas (much larger global warming potential than CO2). Most studies say that emissions from shipping due to their high NOx emissions actually cause a net reduction in global warming. Due to the NOx getting rid of methane.

Now consider that NZ has really high methane emissions due to farming. If anything we should be emitting more NOx to help get rid of that methane. And enjoy lower carbon emissions as well. And the nitrates formed by the NOx emissions (acid rain). When they reach the ground, they are a fertilizer to plants. Which in turn means the plants grow faster, removing even more CO2 from the air.

I get that high NOX concentrations in a small area are bad. But very few areas of NZ have that issue. (unlike alot of other countries). And the NOX levels in those few areas in NZ will reduce in time as electric cars become more popular. So even more reason to grab the available CO2 reductions. Especially for things like shipping and long distance trucking. Where practical electric replacements are unlikely to appear for a long time.

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#1862570 12-Sep-2017 05:48

^^^^ an interesting read. It seems like a lot of the regulations are in order to pick the low hanging fruit.

"lets target NOx emissions as it is easy and we'll look good!"

Sidestep

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#1862624 12-Sep-2017 08:27

dickytim:

^^^^ an interesting read. It seems like a lot of the regulations are in order to pick the low hanging fruit.

"lets target NOx emissions as it is easy and we'll look good!"

Nitrogen oxides are a major component of 'smog'

I've lived in cities overseas where an inversion layer meant a layer of smog - grey brown haze – covered them all day. That stuff's toxic, and very visible.

NZ's a long, thin country lying perpendicular to the prevailing wind, and without large areas of dense population – smog's never going to be anything other than a temporary issue here.

Because our market's too small to develop complex emissions reduction systems just for us, the NZTA accepts emissions standards from the USA, Japan and Europe as a proxy.
They aren't specifically designed for New Zealand. If they were NOx would likely be lower on the list.

frankv

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#1862690 12-Sep-2017 10:16

dickytim:

^^^^ an interesting read. It seems like a lot of the regulations are in order to pick the low hanging fruit.

"lets target NOx emissions as it is easy and we'll look good!"

I think it's more like "lets target NOx emissions as it is possible and not too expensive and a good thing to do"

It makes sense to pick the low hanging fruit if you can.

MikeAqua

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#1862713 12-Sep-2017 10:54

Sidestep:

dickytim:

^^^^ an interesting read. It seems like a lot of the regulations are in order to pick the low hanging fruit.

"lets target NOx emissions as it is easy and we'll look good!"

Nitrogen oxides are a major component of 'smog'

I've lived in cities overseas where an inversion layer meant a layer of smog - grey brown haze – covered them all day. That stuff's toxic, and very visible.

NZ's a long, thin country lying perpendicular to the prevailing wind, and without large areas of dense population – smog's never going to be anything other than a temporary issue here.

Because our market's too small to develop complex emissions reduction systems just for us, the NZTA accepts emissions standards from the USA, Japan and Europe as a proxy.
They aren't specifically designed for New Zealand. If they were NOx would likely be lower on the list.

It seem to me that the solution to local pollution is local regulation - e.g. emission standards for cars that may enter a particular city.

Mike

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