29th April 2018

Could Bosch’s remarkable breakthrough put diesel back on the table?

Two and a half years ago, diesel emissions spiralled into the news and dominated not just motoring and consumer columns but also main headlines1. Since then, various cities across Europe and the UK have mooted plans to ban certain diesel vehicles from their streets. The media has regularly featured stories over the popular fuel’s contribution to poor public health, the NHS and BBC for example reporting that “air pollution ‘kills 40,000 a year’ in the UK”2. Additionally, increased promotion of hybrid, plugin and electric car adoption by wide-ranging voices has played a role in diesel car sales falling3 by nearly 40% in March 2018.

Aside from small-scale dabbling such as Audi’s e-diesel4, it has certainly increasingly looked from all perspectives that, despite remaining the most suitable fuel for long-distance motorists and those living in remote places, diesel is vilified and will be wiped out as soon as humanly possible.

Engineering firm and car parts manufacturer, Bosch, clearly still believes in diesel’s viability, though. Legislation currently limits cars to emitting up to 168mg/km NOx, a ceiling that will lower to 120mg by 2020 under the real-world driving tests being introduced..

Working with a completely refurbished VW Golf engine, made more generic for perception reasons, Bosch has developed ground-breaking advanced fuel injection, intelligent temperature management and enhanced air management technology systems5 that it says can slash diesel NOx emissions6 by an incredible 90%, the test car outputting just 13mg/km.

Driving a car enthusiastically with no real effort at light throttle use typically increases NOx emissions because vehicles aren’t able to manage airflow efficiently enough. The airflow management system unveiled by Bosch is highly responsive largely thanks to incorporating a turbocharger specifically optimised for the principles of real driving emissions (RDE).

Temperature is also intrinsic to the level of NOx produced and Bosch’s sophisticated thermal management system for diesel engines actively regulates the heat of exhaust gases, maintaining their sufficiency and stability. It seems that exhaust gas recirculation (EGR) valves, which have long proved the bane of many motorists’ lives due to failures or knock-on problems, have largely neither been positioned nor configured optimally across a wide swathe of manufacturers. Moving the EGR valve, diesel particulate filter (DPF) and/or selective catalytic reduction (SCR) hardware closer to the engine definitely makes sense, begging the question over why nobody thought of it sooner.

“There’s a future for diesel. Today, we want to put a stop, once and for all, to the debate about the demise of diesel technology”, Bosch’s CEO Volkmar Denner stated boldly at the firm’s press conference.

Bosch says that this trio of innovative technologies won’t make typical diesel engines more expensive and won’t involve additional components8, which probably sounds too good to be true from Joe Public’s perspective.

The news may appreciably come as a sting to owners of diesels who have recently made the decision to sell or scrap theirs in exchange for a petrol, hybrid or electric model. Bosch’s somewhat ironic announcement, although laudable in theory, creates confusion that flies in the face of the government and automotive industry latterly urging people and businesses to go ultra-low or at least choose petrol. If the technology could be retrofitted to existing diesel cars, it might have had the potential to revive diesel as an attractive fuel, but it’s mechanically not possible9.

As far as new diesel cars go, Bosch highlights that the technology is based on existing components and can be used immediately. OEMs, however, plan new models and life cycle improvements years ahead in many cases, so they’re unlikely to make knee-jerk recalls or other moves to fit the new systems to their current or forthcoming models.

There are already so many acronyms and technologies for motorists to get their heads around, such as DPF, EGR, SCR and AdBlue urea injections for starters. Then there’s the transition from NEDC to WLTP/RDE2 emissions and fuel economy testing, plus the diesel supplement10 that has recently seen diesel company car tax increase by 1%. Little wonder that many will be feeling confused and will perhaps end their diesel days as soon as possible anyway.

Fleets can’t often make spur of the moment decisions, either, and increasing numbers of organisations have made the decision to transition as many of their vehicles as possible to petrol, hybrid, plug-in and electric as expediently as they can. U-turns probably don’t seem palatable at this stage.

With a growing number of OEMs dropping diesel from select models or entire ranges, from the Skoda Fabia11 and Toyota Auris12 to all FCA13 and Suzuki14 cars, it’ll be interesting to see if Bosch’s admittedly amazing-sounding technology will be too little, too late, or things could swing back in diesel’s favour.


1. https://www.theguardian.com/business/2015/sep/25/vw-emissions-scandal-seven-days
2. https://www.nhs.uk/news/heart-and-lungs/air-pollution-kills-40000-a-year-in-the-uk-says-report/
3. https://www.ft.com/content/70131c46-38b6-11e8-8eee-e06bde01c544
4. http://www.trakglobalgroup.com/diesel-makes-something-of-a-comeback-in-the-race-to-develop-viable-and-alternative-fuels/
5. https://www.airqualitynews.com/2018/04/26/bosch-claims-to-have-solved-diesel-nox-emissions/
6. http://www.alphr.com/cars/1009202/bosch-diesel-nox-emissions
7. https://www.cnet.com/roadshow/news/bosch-diesel-emissions-technology-fix/
8. https://www.driving.co.uk/news/new-nox-emissions-tech-bosch-save-diesel-engine/
9. http://www.autoexpress.co.uk/car-news/103331/new-bosch-tech-drastically-cuts-diesel-nox-emissions
10. https://www.gov.uk/government/publications/income-tax-cars-appropriate-percentage-increasing-the-diesel-supplement/income-tax-cars-appropriate-percentage-increasing-the-diesel-supplement
11. https://www.fleetnews.co.uk/news/manufacturer-news/2018/02/08/skoda-drops-diesel-engines-in-updated-fabia-supermini-range
12. https://www.autocar.co.uk/car-news/new-cars/toyota-auris-diesel-ditched-due-low-sales
13. http://www.evo.co.uk/fiat/20843/fca-to-call-it-quits-on-diesel-by-2022
14. https://www.carkeys.co.uk/news/suzuki-removes-diesel-from-uk-range