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A typical piezo-electric high pressure multi-port injector in a modern 4 valve cylinder head. © Robert Bosch GmbH

Volkswagen Group meltdown… or is it hype?

By Andrew Marsh, 06.10.15
Posted in: Public | Technology Trends

The global media can’t believe its luck. A famously cash rich vehicle manufacturer pushing to become the biggest in the world nearly three years ahead of their own plan, caught red handed by the USA Environmental Protection Agency bending the rules. Forget the facts, rush in and join the feeding frenzy.

Lets take a look at vehicle emissions.

No, they are not perfect. The test is performed to a drive cycle that has a series of accelerations, steady cruises and decelerations – and looks nothing like a real driver on a real road. However this system has brought tail pipe emissions down in huge steps since the days of looking at emissions from the tail pipe with no equipment beyond a nose and eyes. Most of the global emission tests are either based on the European system or the USA system, or a hybrid of both.

Passenger car diesel engine emissions progress from 1993 to 2014. © Johnson Matthey PLC

If we imagine the whole possible load and speed conditions that an engine can operate at, the emission test (EU or USA) looks at about 20% of the total area, and all of it at lower speeds as well as lighter loads. Once the vehicle is above these speed / load conditions it can emit anything.

But, the emission control system has to work all the time, and it has to survive use at higher speeds and loads in order to emit correctly under test conditions. Excess fuelling for example will accelerate erosion of the catalytic converter wash coat or even cause the ceramic substrate to collapse, both of which require repair.

A vehicle is tested according to it’s kerb weight and the aerodynamic drag, which can be calculated or measured. All of these factors are carefully considered right at the conception of a new vehicle, because if a vehicle is but 1kg over the target weigh the on-cost in meeting the next level of ‘intertia class’ can be significant. This also applies to the aerodynamic drag factor as well – we can see that aerodynamics and weight are key points in powertrain emission control strategy.

During the emission test special tyres are used on the rolling road because even though the drums are 2m in diameter they still load the tyres abnormally. So the tyres are usually well worn to reduce tread deflection and pressurised to the maximum permitted to reduce side wall deflection – all to ensure no blow outs during the test. From the time the vehicle starts the tail pipe emissions are collected – typically 90% of the measured result is collected in the first 10% of the test.

Crucially CO2 is not a measured type approval (‘legal’) test. It uses the same drive cycle, the same emission measurement equipment, but is not limited. Many European governments based vehicle taxation policy on tail pipe CO2 emissions with the resulting chaos.

The push to reduce CO and hydrocarbon emissions forces diesel fuel injection pressure upwards, which can lead to increased particulate formation but will cause more NOx to form. There are exhaust treatment systems for particulates, for hydrocarbons and CO. However there is no easy fox for NOx – it requires the addition of urea to help form the much healthier NO2, which is an entire additional system.

What did VWG do?

Some years ago diesel engines were seen as a demonstrably more efficient solution for internal combustion engines in that they used a base fuel that could be found more readily than gasoline and so had better long term security. In addition diesel engines back in the 1990s has 10% to 20% fuel economy advantage, so it was a policy win-win.  There were two key developments for passenger cars which followed the commercial vehicle engine technology – higher direct injection pressures and variable turbine geometry turbochargers.

The market was transformed. Old passenger car diesel engines were given a new lease of life and customers like the immense – insane – flat torque curves.

Volkswagen Group (VWG) chose to not go with the Fiat Auto / Bosch common rail diesel fuel injection system, instead investing with Bosch in camshaft operated high pressure unit injector ‘Pumpe Duse’ or PD system. Volkswagen Group used the technology widely, but not one other vehicle manufacturer followed. The crowning glory was raking the in-line 2.5l 5 cylinder engine, removing one cylinder and producing the 2l PD twin cam EA188 diesel engine as the first successor to the 1.9l single cam engine.

In 2005 VWG did a U-turn. The then new 16v twin overhead cam diesel engine – EA189 – featured a common rail diesel injection system, timed to meet the impending European Euro V emission regulations. It was a huge admission. The investment in PD was written off, and from that point on all VWG diesel engine upgrades and new diesel engines featured common rail injection. Crucially the next highest volume engine was 1.6l, based on EA189. Even more importantly, the engine family had to cope with Euro VI which was still under discussion as well as the massive tightening of ruls in the USA – again at that point still under discussion.

Given a new engine family takes around 2 years to develop a feature strategy to enable it to survive in the market for at least 10 years, and takes a further 5 years to go from first ideas to a developed validated production engine, this U turn was done in mid programme. The question – was the combustion chamber design not quite right from the beginning? Was the U-turn done too quickly?

The get out of jail card

Most vehicles are only driven by one pair of wheels. Anti-lock brake systems (ABS) and electronic stability control systems (ESC) rely on measuring the speeds of all four wheels – so when the vehicle senses two wheels are not moving and two are, it needs to decide to enable or disable ABS / ESC. Failure to do this can result in the engine power being reduced – not exactly what’s needed during an emission test.

It seems VWG used this routine set up in the software architecture by the engine fuel system and engine management control module manufacturer, in this case Bosch, to access and emission test specific calibration map. This an engine with a flawed combustion process was able to meet Euro V, Euro VI and USA emission tests and yet give customers all the performance they wanted.

Crucially in the last week of September 2015, the German Federal government stated neither Daimler (Mercedes-Benz, Smart) nor BMW Group (BMW, Mini) had used such a technique.

What next?

Governments around the world are deeply annoyed about this. The implication is that a commercial company can get around legally binding tests with intellect, whilst leaving their customers somewhat bewildered. There are several things that will happen:

  • Share trading in VWG will make the usual suspects fabulously wealthy.
  • VWG will survive, but it won’t achieve the largest vehicle manufacturer in the world status by 2018 – perhaps more like 2025.
  • The push of a single emission test standard which has been in development for a decade already, will increase.
  • The idea of doing a test and submitting one’s own results on the understanding that if caught there are severe penalties – the USA system – will be revised.
  • The European network of government agencies who inspect legally binding performance parameters as part of the whole vehicle type approval process, will be tightened.
  • The push for Euro VII and even tougher USA standards will get offset, and all of the above settles.
  • Euro V EA189 engines will be fixed by a software update, and only for the heavier vehicle applications (ie, those with marginal emission results).
  • Euro VI EA189 engines are likely to gain a retro fit urea injection system along with a software update.
  • USA EA189 engines…. who knows?

VWG executive board debated the situation for 7 hours on 30th September 2015. They undertook to roll out notification to owners affected by the issue throughout October 2015, which would then detail how they will deal with the immediate issue. The UK government have already stated that no owner of an existing VWG diesel engine powered vehicle will have the CO2 tax banding altered, which affects vehicle excise duty (tax0 as well as company car user tax.



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