Diesel breakthrough at Bosch: your questions answered

Bosch has made a decisive breakthrough in diesel technology. Even today, a Golf-class compact car equipped with Bosch diesel technology can achieve average NOx readings as low as 13 milligrams per kilometer in RDE cycles. That is approximately one-tenth of the prescribed limit that will apply after 2020. What makes this so exciting is that Bosch engineers achieved these results simply by refining existing technologies. There is no need for any additional components that would increase cost. “We are pushing the boundaries of what is technically feasible. Equipped with the latest Bosch technology, diesel vehicles will be classed as low-emission vehicles and yet remain affordable,” says the Bosch CEO Dr. Volkmar Denner.

The announcement of this technology at the Bosch annual press conference, and further details of the technology, can be found here. The following article answers the questions that have arisen in conversations with journalists.

When will the diesel technology be available for customers to buy?
The new Bosch diesel powertrain is largely based on components that are available in the market or close to going into production. Effective immediately, therefore, it is available to customers for incorporation into production projects. Parts of the technology already feature in new production vehicles, where they are already producing excellent results. In Bosch’s view, the technology presented in test vehicles can be standard equipment within two to three years – in the time up to then, diesel vehicles will gradually come closer to the 13 milligram mark for NOx emissions in the RDE cycle. Bosch has already actively contributed many insights to its 300 RDE projects with automakers, and will keep them informed of any new progress.

You call it a breakthrough, but then say the parts are close to going into production. Isn’t that a contradiction?
The Bosch diesel technology is based on components already in use or about to be used in production vehicles. The decisive advance is based on an intelligent combination of engine optimization and exhaust-gas treatment. There is no need for additional components that would make the powertrain more expensive. As a matter of principle, however, the vehicle concept must be compatible with either Euro 6d temp or Euro 6d, which means, for example, that it must have an SCR AdBlue system on board. The technology will make diesel vehicles low emitters, preserve their CO2 advantage, and keep them affordable, even in the compact class.

If Bosch is mainly making use of existing hardware, why are we only seeing this technology now, instead of some years ago?
It was especially the new kind of RDE tests that speeded up progress. But for such tests to become reality, a new technology was needed that was capable of measuring vehicles’ emissions in road traffic. A reliable portable emissions measurement system (PEMS) for passenger cars has only been available since 2013. And only since then have we had a detailed picture of where we have to focus our engineering work and what driving situations are especially challenging. The road tests served as a catalyst for development.

What does this technology mean for urban air quality?
To find this out, Bosch asked an independent engineering firm to carry out a precise analysis. It looked at air quality at Neckartor in Stuttgart, a notorious air-pollution black spot. The results of the data analysis are clear: if all diesel vehicles were equipped with the latest Bosch exhaust technology, their share of local pollution would be negligible, and they would remain well within the limits set by the EU, even at Neckartor.

Can the new Bosch diesel technology be retrofitted?
It should be remembered that the success of the Bosch demonstration vehicle was only possible after combining various features in a complete package. In this respect, it makes little sense to retrofit individual components. As a matter of principle, for example, the vehicle concept must be compatible with either Euro 6d temp or Euro 6d, which means, for example, that it must have an SCR AdBlue system on board.

What distinguishes the new diesel technology?
To date, two factors have hindered the reduction of NOx emissions in diesel vehicles. The first of these is driving style. The technological solution developed by Bosch is a highly responsive air-flow management system for the engine. A dynamic driving style demands an equally dynamic recirculation of exhaust gases. This can be achieved with the use of a turbocharger that reacts more quickly than conventional turbochargers. Thanks to a combination of high- and low-pressure exhaust-gas recirculation, the air-flow management system becomes even more flexible. This means drivers can drive off at speed without a spike in emissions. Equally important is the influence of temperature. To ensure optimum NOx conversion, the exhaust gases must be hotter than 200 degrees Celsius. In urban driving, vehicles frequently fail to reach this temperature. Bosch has therefore opted for a sophisticated thermal management system for the diesel engine. This actively regulates the exhaust-gas temperature, thereby ensuring that the exhaust system stays hot enough to function within a stable temperature range and that emissions remain at a low level.

Hasn’t the technology come too late to prevent driving bans?
Staying within air pollution limits at black spots such as Neckartor calls for a raft of measures – they include reduced vehicle emissions equally as much as measures to keep traffic flowing steadily. All these have to be exploited to avoid driving bans. As far as diesel is concerned, normal fleet renewal alone will cause NOx pollution to fall further. Following our breakthrough, we are convinced that in the future, no one will be able to impose a blanket ban on diesel in cities – it will keep its place in urban traffic, too, whether for tradespeople or commuters.

Is this complex technology also affordable in compact vehicles?
Bosch assumes that the cost of the powertrain will be roughly comparable with a modern diesel powertrain equipped with an SCR AdBlue system. Significantly, the new diesel powertrain was premiered in a compact vehicle. Bosch believes the broad mass of vehicles using the new diesel technology will have a displacement of up to 1.6 liters. This includes the compact class. The system can of course be upscaled for larger vehicle classes such as SUVs.

How will AdBlue consumption be affected?
In the trial vehicle, AdBlue consumption is roughly 1.5 liters per 1,000 kilometers, even with sporty driving.

How will fuel consumption be affected?
The aim of our engineering work was to preserve diesel technology’s CO2 advantage, and thus its lower consumption values compared with gasoline technology. We succeeded in that. The Bosch trial vehicle does not consume any more fuel than a comparable diesel vehicle.

How much engineering effort went into the new diesel technology?
Over the past few years, roughly 100 engineers have been involved in work on the new technology. The total cost ran into eight figures.