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Peter_XX
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EquiNOx. Isn't that a cool name for a diesel car?
@DJ_D Sorry to say, it is not that easy. Flame speed is definitely an issue with HCCE and PCCI. It is almost like a detonation. It is much, much worse than diesel if you look at pressure rate for cylinder pressure. You would hear this car blocks away. Thus, something must be done to abate combustion noise. You can have low NOx if air excess is high. Yes! HCCI/PCCI can run much leaner than GDI. However, this is not the full story. You have to reduce excess air at full torque (and close to full torque) and then NOx will rise sky-high (any joke about that is on me…). Try to imagine running excess air at 2:1 ratio at full load with high compression ratio and fast combustion. No engine structure in the world could handle such cylinder pressure. It would be much, much higher than for diesel. If you limit cylinder pressure to reasonable levels, power and torque would be a joke and you would have to do a lot of “anti-downsizing” This would ruin fuel economy. Recall research carried out by Huyndai/Delphi. They certainly had to deal with high cylinder pressure and you can find comments from me on that as well in the past on this forum. Furthermore, if you are just marginally on the lean side, TWC will not work. So, in essence, you would have sky-high NOx at high load but conventional aftertreatment would not work. Even if this problem would not be too bad in a conventional test cycle, RDE would kill such an engine. You could imagine replacing excess air with EGR, perhaps gradually, but this is not easy to control. Toyota tried this many years ago with homogenous lean-burn (long before GDI) but the result was not very good. I have tested such cars myself in the laboratory. Needless to say, NOx was much higher than from TWC cars. You could adopt similar aftertreatment as for diesel (NOx-trap + SCR) but it comes at a cost and you would still struggle in off-cycle conditions. In summary, there are a lot of issues to explain. Perhaps Mazda has cracked a couple of the nuts but we have no idea about how they did it.
Sadly, this article does not really say anything about the technology other than using lean burn and a supercharger. I have not read the SAE Paper, I have to admit. They also speak about increasing compression ratio to 18:1 in an older article at GCC. Both increasing CR and using excess air (via supercharging) is beneficial for efficiency. This we also know from diesel engines, i.e. nothing fundamentally new when it comes to thermodynamics. The interesting part is how they control combustion and in particular, knocking and flame speed. This is the Achilles’ heel for gasoline engines but pose no problem for diesels. The main disadvantage of lean burn is the difficulty to control NOx via exhaust aftertreatment. This we also know from experience on diesel engines and, in fact, also on gasoline engines. It was a significant problem on early GDI engines that all operated under lean-burn conditions. Mercedes are one of the few manufacturers who still pursue lean burn on some of their gasoline engines, albeit to my knowledge not on all markets. In summary, this article raises more questions than it answers. If anybody has well-founded technical insights into Mazda’s technology, I am all ears.
The whole idea with mild hybrids is to have a lightweight electrical system, i.e. small motors and batteries. Thus the electric range will be limited to parking garages and similar operation. If you want long electric range, you chose a PHEV. For a mild hybrid, does it matter if the range is, let’s say, 1 or 2 km? Most of the driving will be covered by the combustion engine anyway and the substitution with electricity would be minimal, if we had a plug-in option, which normally is not the case. It does not make much sense either. Battery capacity will be determined by other parameters such as sufficient size for regenerative braking, acceleration, auxiliaries and the requirement for power. Batteries should be kept as small as possible, not only for weight reasons but also to limit incremental cost. If the electric drive system is too heavy, fuel consumption will be significantly penalized in hybrid drive mode. We can clearly see that for PHEVs, where we also have a “conventional” HEV to compare with. The main objective with a mild hybrid is to reduce fuel consumption. If you want to substitute fuel with electricity, there are other (and better) options. I acknowledge that MAHLE, with the limitations of a 48V electric system, seem to have taken this concept to a higher level than before. However, others will follow and challenge. In a few years, this will become the mainstream technology in vehicles. It will provide almost similar fuel economy as a full hybrids but at a fraction of the cost and weight penalty.
Low emissions? Euro V? Hey, come on... Euro VI is the standard since 2013.
Range? Well, perhaps 1500 km with a big fuel tank.
@ai_vin Propane fumigation would have even bigger problems with NOx than diesel engines. This is why we do not see such engines on the road anymore. You simply have to meet the emission limits to sell a vehicle. Propane is best used under stoichiometric conditions where you can use aftertreatment three-way catalyst (TWC). Engine-out emissions are higher than for diesel also in this case but TWC is more efficient aftertreatment than SCR, so we end up with lower tailpipe NOx. Propane and gasoline are roughly equal in this respect. Recall that a gasoline engine also has higher engine-out emissions than a diesel engine. The drawback of stoichiometric combustion is lower efficiency.
The irony here is that heavy-duty vehicles actually are extremely clean compared to light-duty vehicles. A big truck can have lower emissions per kilometer than a small car and if we look at weight-specific emissions, the difference can be monumental. Here, I specifically refer to “actual” on-road (RDE) emission levels of NOx. It may sound strange, since similar SCR technology is used in both cases. I do not have time to elaborate on this at the moment but I can perhaps explain this in a later post. We also know that some Euro 6 light-duty (diesel) vehicles are also clean. Perhaps not fully down to the level of the best gasoline cars but still far below the on-road limit in RDE testing. As pointed out by Carl, a lot of DEF (Adblue in Europe) must be used, particularly so for some heavy-duty vehicles. For reducing NOx, we have three major technologies: EGR (here I would like to include both high-pressure and low-pressure EGR but internal EGR could also be considered), NOx-storage catalyst (NSC or LNT, which you prefer) and SCR. Surprisingly, many “clean” heavy-duty vehicles do not use ANY kind of EGR and LNT is not used in any case to my knowledge. The technology that has enabled this trend is significant improvements in SCR-technology for heavy-duty vehicles during the last couple of years. We are talking about NOx conversion rate of up to 99%. By combining with EGR and LNT, a reduction of NOx by a factor of 10 compared to current Euro VI is not impossible to envision for heavy-duty vehicles. The actual implementation depends on emission regulation (potential Euro VII). It is more difficult to get similar improvements on light-duty vehicles but it will gradually come. Recall that very few cars still have both high-pressure and low-pressure EGR. Some have LNT, some have SCR but very few have both. Carl mentioned BMW but there are a few additional examples. There are also several technologies in the pipeline for increasing SCR efficiency significantly; perhaps not to the level on heavy-duty vehicles but much better than we have today. By reducing engine-out NOx and “after LNT” NOx, the “burden” on the SCR system will actually decrease. Thus, the practical solution of a relatively small Adblue tank and refill only during maintenance can still be obtained. Regarding technology, I do not have any doubt about that very low NOx emissions can be obtained. In addition, it will not cost a fortune. Perhaps the incremental cost will still be too high for the smallest cars but it will not be a show-stopper for medium and larger cars. Recall that some cars already have this technology. Regarding other emissions compounds of health hazard, diesel car are already much better than gasoline cars but this is a discussion we can leave for the moment. The actual “problem” we face today is that some manufacturers have not respected the intention of the regulation, i.e. to give low emissions under all operating conditions. To be honest to the car manufacturers (if one can be than under the circumstances?...), some operating conditions have not been regulated by the legislators, so they could be considered as grey zones. This is the target for the coming RDE regulation. Ironically, Euro 6 cars from the VW group are quite good when it comes to NOx; at least, in comparison to many other car manufacturers. We know they cheated in Euro 5, and in the USA, but this does not concern cars sold today. Finally, we should not underestimate public opinion. This alone can – and will – for sure have a tremendous impact on sales. If people do not want diesel cars, interest from car manufacturers will diminish and development will be stopped.
An electric truck can only transport... batteries.
Well, sd, I understand why you are not employed by the industry. Your idea would be less efficient than the one used by Volvo. Try to figure out why and post your thoughts on this site. Try to find the errors in your own arguments. If you wish, I can help you.
No HarveyD, NOx is not harmful in low concentrations. NO and nitrates/nitrites have very important functions in the body. Without NO, a man could not make love to a woman. That explains all, doesn’t it? Even the lung itself produces NO (exhaled) and at increased levels for some lung diseases. How could inhaling NO in low concentrations be harmful? Although NO2 is more harmful than NO, there is still a threshold level and below this level, no impact is found. NOx is not a poison. This is in stark contrast to toxic emissions, such as e.g. PAH and particles, where no threshold level is found. We should concentrate on such emissions! Of course, we need to lower ambient concentrations for NO2 under the (current) limits in areas with exceedances but there is no rationale for going further than necessary. With measures taken to limit emissions from new vehicles, this will happen nevertheless in a couple of years, simply due to that older polluting vehicles will be scrapped.
All laboratory test cycles include a cold start. It has been so since the 1970's. Thus, a cold start is always part of the test results. The relative impact varies between the different test cycles. In fact, the ”old” European NEDC test cycle is actually one of the toughest (that I know of) in this respect. This furthermore aggravated by the “slow” city driving after start. The impact in the US FTP test is roughly less than half of that in NEDC, since the driving distance per cold start is more than twice as long in FTP. The impact of the cold start will be somewhat less in the new WLTP cycle than in the NEDC cycle. WLTP is based on logging of huge fleets of cars around the world and should be representative of normal driving. The cycle is based on the latest and best knowledge we have on how cars are used in real traffic. Still, this is not sufficient to regulate emissions under all driving conditions and this is why the on-road testing is now introduced in the RDE legislation in Europe. I have not studied how Emission Analytics do but according to the new European RDE testing, a cold start should be included. Unfortunately, there are a number of organizations and companies out there who conduct testing and their results may not always be representative of “real-world” driving. They often highlight some specific driving condition. It is not uncommon that on-road tests are only conducted with warm engines; primary to save time and cost. All-in-all, consumers get misinformed by all the headlines such tests may create. Note that “cold start” usually is defined as a start with cold engine at ~25°C. Cold starts at lower ambient temperatures increase emissions much more than at 25°C. EU regulates this for CO and HC from gasoline cars at -7°C, albeit that the limits are much higher than in the standard test. Cold start emissions of CO and HC are considered much lower from diesel cars and thus, they do not have to be tested. This is based on comprehensive knowledge on results in cold starts in the past. The main problem for cold starts is unregulated emissions that pose health hazard for humans. Gasoline cars are much more affected than diesel cars in this respect (therefore, we want to regulate HC at cold starts). The difference in relative levels can be in the range of 10-100. NOx is generally not a problem during cold starts, since the engine-out NOx is lower (due to lower NO formation) than in a hot start, unless the manufacturer “cheats” in some way. Stopping the engine via conventional start/stop systems or in a hybrid drive is not necessarily “bad” for emissions. This is of particular relevance to consider for engines with low exhaust temperature, such as e.g. lean-burn gasoline engines and diesel engines. At idle, the exhaust temperature might be lower than catalyst light-off temperature and leaving the engine on idle will cool down the catalyst. Stopping the engine gives much lower heat loss and thus, higher catalyst efficiency. You have perhaps noted that there have been several articles on mild/micro hybrid diesel cars that reduce NOx emissions compared to conventional diesel cars on this site. Synergies via hybrid systems can be identified not only regarding higher catalyst temperature but this will be another topic.
@Arnold YES! Electronics always behave as if it was under water. Even under the ice, sometimes. What gives most problems with modern cars? The electrical system! Of course! The more you have, the worse. I know it is contradictory to mention this, since we need hybrid drives in the future on all our cars, but when they introduce this on all their models at once, the queues at the workshops will become long. Now, Audi may have to face similar problems with the electronics that Mercedes and BMW had a couple of years ago. Recall that Mercedes had an electric brake system on their E-class? Failure rate was almost 100%. Of course, the system reverted to the safe and sound electromechanical system in case of failure in the electrical system. For the model after, Mercedes skipped the electric brake system. About all your other comments... Why do you bother to post such crap?
After 3 years, all electric and electronic systems will start to break down; one after the other. :)
They will change the alternator from 12V to 48V and most likely only a few accessories will utilize 48V, most will remain with 12V. Furthermore, this concern only newly introduced vehicles; presumably many old vehicles will remain in production with 12V system for many years to come. I agree with mahonj that this is not a big deal and that it is just good marketing.
Natural gas is cleaner than E85 and gasoline; at least at the dealer’s office. After a while, its catalyst deteriorates and methane emissions will increase. Most of the HC is methane. Could we live with that? Well, methane is not harmful to human health. We produce it ourselves. However, methane contributes to climate change. The fact that methane contains less carbon per energy equivalent than gasoline is negated by methane emissions that have higher GWP than carbon dioxide. The outcome is about similar to gasoline over the lifetime of the car. However, climate change is not global. It does not happen in the USA, as we have heard your president say.
Well, ethanol is definitely not a “clean-burning” fuel. It has its issues - many issues BTW. Apparently some of you did not bother to read the report I posted as a comment to an earlier article. Shortly, emissions of PAH – note that many of these compounds are carcinogenic – are much, much higher than from gasoline during cold starts at low ambient temperatures. Considering that PAH emissions are the main cause of cancer from vehicle exhaust – much more so than benzene – ethanol proponents should keep this in mind. Solve this problem first, and then push for a large-scale introduction. Fuel and engine must be co-developed. This has not happened (yet) for E85, for blends or for pure ethanol (E100). Fuel switching is not necessary the solution to all our problems. By the end of the day, most alternative fuels can only displace a small part of the fuel pool in the foreseeable future. There are simply not enough natural resources available. Thus, we have to solve the problems of emissions from gasoline and diesel fuels. And we are, in fact, a long way on this route already. http://www.ecotraffic.se/media/5771/25.__2008__emissions_from_bi-_and_flexifuel_cars.pdf
@SJC Diesel engines with DPF are far below the PM limit for real-world (RDE) limits. This is not by a small margin; we are talking about levels at least 90% lower than the current limit. PM (and PN) is mainly a problem for gasoline cars. Recall that the PN limit has been set 10x higher for gasoline cars in the EU but it will now be reduced to the same level as for diesel cars. This is why mass production of GPFs starts this autumn. This is for Europe, of course; not for the USA, where EPA do not bother about small particles. At least some diesel cars meet the RDE limits for NOx by considerable margin. NEDC/WLTP limit is 0.08 g/km and RDE stage 1 limit is 0.168 g/km and stage 2 is 0.12 g/km. One of the “best” diesel cars on the market is the new Mercedes E220. It has NOx emissions, on average in various RDE driving patterns, at ~0.04 g/km. This is about 75% lower than stage 1. Of course it is possible to have low NOx also from a diesel car.
@Trees This article is about a gasoline engine. Why do you bring up E85 in this context? Please stick to the topic if you want to comment on the article. I will do that in my comments below. In my view, this is definitely a high-risk project. If it was low-risk, Renault, or any other car manufacturer for that matter, would do the homework themselves without telling anybody and simply start production as quick as they could, if the project was a success. Ideas like this one has been around for quite some time. It looks like a diesel engine, it walks like a diesel engine and it quacks like a diesel engine, albeit it is still not quite a diesel engine. In any case, they need most of the “internal” engine features and exhaust aftertreatment to reduce emissions. These are, e.g., high lambda, EGR (various kinds, presumably also internal EGR), particle filter, NOx storage catalyst and SCR. As for a diesel engine. The Euro 6d emission limit might seem as a great challenge but recall that you simply need to fulfil this limit if you want to sell new cars. Both conventional gasoline and diesel cars will fulfil this regulation. A more progressive approach would be to aim at something we think could be enforced by Euro 7. After all, it will take such a long time to reach production anyway that you would have to think about further emission reductions by then. One should also recall that there have been several research programs aiming at 55 % efficiency for diesel engines in the past but none of these features (including thermal barrier coatings) has yet reached production status. Reaching efficiencies in the 50-55 % range is not easy. I acknowledge that they try!
Of course this would happen any day. Now, all other manufacturers have to follow. Except in the USA, of course, where nanoparticles is not a problem. Please wake up EPA! BTW admin, this news article should be put in the main section, due to its importance.
Think about this: Diesel passenger vehicles (cars, pickup trucks and SUVs) continued to outnumber hybrid vehicles in all states except California, Massachusetts and the District of Columbia.
@Juan The diesel engine is the most efficient heat engine. In the last 100 years, nobody has invented a more efficient engine. Have you tried? If you did, I would probably not be impressed by your proposal. If we want to preserve resources and minimize climate change, we should, instead, increase our efforts to further develop diesel engines for lower emissions and higher efficiency. Logical! In combination with mild hybridization, both emissions and efficiency can be improved at a reasonable marginal cost.
The big potential for reducing NOx by hybridization is in improving aftertreatment efficiency, which this study has not addressed. The 9% cut in NOx is just engine-out NOx. This explains the big difference compared to the Continental article, as mentioned by “dursun”. For once, you should also try to think like a car manufacturer. If you can meet Euro 6 limits in the new WLTP cycle and, in addition, also in the (coming) real-driving test cycle (RDE) for on-board measurements, what is then the motivation for further reduction of NOx? Our emission standards do not demand more. Customers will not pay more for a car that has even lower emissions. The authors indicate that they can meet those limits even with simplification of the exhaust aftertreatment. This will cut costs. Technical measures not implemented can then be postponed until Euro 7, whenever this standard will come. Finally, the incremental cost for 48 V hybrids is relatively moderate (compared to full hybrids). If this hybridization can cut costs in aftertreatment and other areas, it is a further improvement of the cost-effectiveness. For once, I can also agree with Engineer-Poet. Mild hybrids have greater potential to replace conventional cars on short-term horizon than PHEVs. The incremental cost is prohibitive for the latter category.