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Mercedes-Benz OM 654q 4-cylinder diesel complies with Stage 2 RDE, certified to Euro 6d

The Mercedes-Benz OM 654q four-cylinder diesel from the modern OM 654 engine family already complies with the Stage 2 RDE (Real Driving Emissions) standard which does not come into force until 2020, and is certified to Euro 6d.


With its near-engine installation, the emission control system has low heat losses and thus very favorable operating conditions in the vast majority of operating situations. Further measures include:

  • High and low-pressure exhaust gas recirculation including cooling;

  • a diesel oxidation catalytic converter (DOC) to avoid the emission of carbon monoxide (CO) and unburned hydrocarbons (HC);

  • a particulate filter for capturing soot particles with combined SCR catalyst function (sDPF);

  • an SCR catalytic converter (selective catalytic reduction) for reducing nitrogen oxides. For this purpose, ammonia in the form of the carrier AdBlue is mixed in with the exhaust gases and conditioned before entering the sDPF, an additional underfloor catalyst (SCR) with ammonia slip catalyst coating (ASC).

NOx emissions demonstrator. The NOx emissions demonstrator from Mercedes-Benz Diesel Car Development shows how efficiently the emission control technology works. The vehicle corresponds 100% to the series production configuration in terms of the engine and emission control system as well as the control unit software.


The additional sensors and visualization options are intended to provide an experience of the emission performance on the road in a host of driving situations.

For illustrative purposes, here are six different journeys driven in a Mercedes-Benz A 220 d (combined fuel consumption 4.5-4.3 l/100 km; combined CO2 emissions 118-114 g/km):

  • Country road in the vicinity of Stuttgart

  • Country road with climb to the Swabian Alb

  • Full acceleration

  • Mountain road (Feldberg Pass) with/without passengers

  • Mountain road (Feldberg Pass) including cool-down of the engine during descent

  • Stuttgart city center

Mercedes-Benz started an engine initiative in 2016, which includes the all-new four-cylinder diesel engines (OM 654 and OM 654q) as well as straight-six diesels (OM 656). On this basis, which is associated with investments of around €3 billion, a whole host of Mercedes-Benz diesel models, from the A-Class to the GLS, already comply with the Euro 6d standard.



Well, this was quite expected and in the pipeline... Modern diesel cars are now at a development state when emission levels approach zero (see more information below).

The article does not say it explicitly but I suppose the DOC also has NOx storage capacity. Another interesting technology with similar potential as this catalyst would be a passive NOx adsorber (PNA). I kind of like the simplicity of this concept over the quite complicated control of a conventional NOx storage catalyst. Rumors say, however, that the PNA technology is not quite ready for production yet.

Another technology under discussion is to have a second urea injection before the last SCR catalyst. This could allow fine-tuning of the urea injection in a way that the large urea nozzle before DFP/SCR may not quite achieve. I reckon that "overdosing" of urea at this stage is also an option but I suppose that the two-stage injection would be more precise and waste less urea, while at the same time would give lower NOx. Mercedes does not use this but perhaps it is something for the future.

Consider the link below and one of the conclusions from ADAC in the study:
"It found that a Mercedes C-Class 220d powered by a 2.0-litre turbocharged diesel engine emitted no traceable NOx."


Some explanation about ADAC and their testing from the article above:
ADAC, which is similar to the AA in the UK but tests hundreds of vehicle every year at its laboratory in Landsberg on the outskirts of Munich, tested a range of diesel and petrol cars to compare the amount of harmful emissions produced during normal driving on the road.

The Lurking Jerk

I'm hopeful, given this news, but the 'anti diesel' mindset has become firmly entrenched. I predict many will greet this news by continuing to insist that diesel be phased out.


Replacing a device like an internal combustion engined driven car is difficult for those who have adopted its use as a way of life; however, if you know something is detrimental to your health and your children's health and there are better alternatives, why would you not give up the status quo and change? Makes no sense to keep supporting devices that are shortening your life.


@The Lurking Jerk
First, I do not think that a lot of people read this site. Second, I think the diesel reputation is now on such a rock bottom line, that there is not likely any hope for a change here. Note that cities like Paris will ban diesel cars no matter how clean they are. Third, yes I agree with you and I am afraid that many will start shouting out for phase-out even more vigorously than before; just as a response to information like this article. People are not always rational.


Why would anyone expect AVs to reduce fuel consumption ?
They might reduce car ownership, but, as long as they are used by one person at a time, there is no reason to expect lower VMD and hence lower CO2.
If you were able to use them for ride sharing, it would help, especially if you could get 4 - 6 people into each one.
If you went to EVs, this would help, especially if the source is renewable or nuclear. But it could just as easily be human driven EVs.
Also, if ways are found to improve the economy of AVs. they could probably be applied to human powered EVs as well.


sorry, wrong thread.


I might have been a little sarcastic in some of my previous comments, so let me elaborate a little on "real" emission levels.

There is, of course, nothing as a zero-emission vehicle of this kind. To state that, you would need better NOx instrumentation than what is available today for on-board measurements and you would also need to measure background concentrations simultaneously; potentially correcting for the background level. We do not have any traces of NOx emissions as second-by-second graphs in this case but it is likely that there are at least some spikes of NOx at levels above the detection limit of the instrument. However, these bursts are very short and if there is a small offset of the zero calibration (or small zero drift between calibration and test run), this (negative) offset could cancel out the mentioned spikes, yielding zero emissions as a result. The only firm conclusion we can make is that this car, and a couple of others, have very, very low NOx emissions. I would also like to conclude that one should not try to distinguish between cars when the emission level is below 20 mg/km. Any difference between cars at this level might be just due to measurement scatter. Nevertheless, cheers to Mercedes! At least they are among the better of the best ones.

Finally, some additional sarcasm: Results like these are probably the worst possible catastrophe for environmentalist organizations. Their whole rationale for activism is based on that diesel cars are high emitters from hell. If there is no devil (in the detail... er... case) anymore, what will they fight against in the future? Presumably, they will just ignore data like these and continue on as if nothing happened. If car manufacturers drop diesel development and pull diesel cars from the market, they have eventually won this case. If so, I have to acknowledge their success.


True Lies? Apart from that, maintenance on a diesel is more expensive and occurs more often than on an electric drive train. Emissions neutrality is claimed but not proven. I've driven ICEs for 60 years and EVs for shortly 3 years. I'll never, ever again call an ICE POV my own. For those remaining adamant to the ICE culture, I wish you the best of luck; I've struck mine.

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