What is thermal window?
Now that I understand NOx emissions and EGR, what is a “thermal window”?
What is EGR?
OK, now I understand what NOx is, but what is EGR?
We have recently highlighted several of the latest court rulings, all of which have gone categorically against the car manufacturers who have been behind the diesel emissions scandal. These judgments have had references to technical topics such as NOx emissions, EGR valves, and not least the thermal window, soå so that we can understand judgments better, and not least what they mean for appeals, we have created a small series of articles that look at what these "things" is really about.
In the previous article we wrote about NOx emissions, and in this article we will look at EGR, which stands for Exhaust Gas Recirculation, an English expression that can be translated as exhaust gas recirculation. EGR in a diesel engine is, in other words, a system that brings a controlled proportion of the exhaust back to the engine valves' air intake for å reduce the combustion temperature and thus the production of nitrogen oxides (NOx).
How EGR works, in brief
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The EGR system has a valve that åopens and closes a channel between the exhaust manifold and the valve's air intake at the command of an electronic engine control unit.
- An exhaust manifold is an important part of the engine's exhaust system, which collects exhaust gases from the cylinders and directs them to the catalytic converter. It acts as the first path for exhaust gases from the engine, and is crucial for å ensure efficient engine operation. The exhaust manifold consists of a series of pipes and connects the engine's combustion chamber with the exhaust system.
- The engine control unit is a relatively simple computer (everything is relative!) that controls the engine. It is often called "ECU", which is an abbreviation for the English term Electronic Control Unit, i.e. electronic control unit.
- When exhaust gases are mixed with fresh air, the oxygen content is reduced and the combustion temperature drops, which inhibits the formation of NOx gases.
- Modern systems often have an EGR cooler that actively lowers the temperature of the recycled gases for additional effect.
The EGR system's management is based on parameters such as engine speed, load, body temperature and connected exhaust gas purification systems. The system is a critical component for å reduce harmful emissions, which in turn ensure cleaner air, reduce negative effects on milieuø and health, and that the engine can be certified within strict emission requirements.
Unfortunately, this means that the EGR SYSTEM ALSOÅ CAN BE USED FOR Å CHEAT. It can be programmed to å not used e.g. when the engine is cold, but also to å work extra well under test conditions, when emissions må is kept below a certain level. AND THIS IS EXACTLY WHAT WAS DONE!
Why EGR is used in diesel engines
As we saw; in the previous article in the series, diesel burns at higher temperatures than gasoline and therefore has a stronger tendency to å produce NOx than petrol engines. EGR is an effective, relatively inexpensive and compact method; reduce NOx. Preventing NOx development can be combined with after-treatment that converts the remaining nitrogen oxides into harmless gas, and with particle filters that reduce the emissions of harmful nanoparticles. Together, these measures can ensure that the engine meets strict emission requirements, the so-called Euro standards.
Typical problems with EGR
As quite a few of Bilklager's members and other diesel car owners have experienced, errors in the EGR system can result in everything from sluggish performance to reduced diesel bills to expensive workshop visits:
- Build-up of soot and carbon deposits in the valve and channels causing the valve to seize or leak.
- The EGR cooler can clog or corrode.
- Error onå electric actuators or position sensors.
The result is error codes, uneven idling, reduced power, ø increased fuel consumption and, in the worst case, engine damage or failure, which became much more widespread and occurred much more often after the diesel cars were "improved" or "upgraded" after the emissions scandals became known.
It goes without saying that when engines were designed for optimum performance, economy and longevity, where software was an important part of this... and polluted WAY more than what was legal... soå be reprogrammed so that everything is radically changed, then this affects both the performance, economy and lifespan! NORWEGIAN AUTHORITIES, NAF, AND OTHERS HAVE STILL STANDINGLY DENIED THAT THIS MAY BE THE CASE, DESPITE COMPLAINTS FROM CAR OWNERS, EVIDENCE OFHerring; HØYERE BILLS, AND THE LOGIC OF THE CHANGES:
- «The upgrades» which was carried out for å getting cars in accordance with test requirements or adapt aftertreatment strategies changed the operating profile of the EGR system.
- Some upgrades allowed EGR use in certain operating areas or changed the temperature and / or timing logic for when the EGR system should be active, which could lead to faster soot deposition and clogging in valves and coolers on; cars that were actually designed for a different calibration.
- Some measures also included; physical changes such as exhaust cleaning, replacement of EGR skirts, or new valves in addition to software update, because pure software change alone could not solve mechanical poisoning or clogging.
Quite radical!
When manufacturers also required diesel particulate filters (DPF), aftertreatment systems (known as SCR, or AdBlue colloquially) and the EGR system to function more consistently in real-world driving, EGR components were subjected to more frequent or more demanding loads than they were designed for in practice, and failures that were previously less frequent occurred.
In other words, for å reduce NOx emissions if the EGR systems are rebuilt from ensure optimal performance only under certain conditions, including test conditions in a workshop hall, to å do it continuously and in daily use, under all possible driving conditions, from arctic cold to sweltering heat, from crisp air to torrential rain, and from city driving to top speed driving; autobahn.
AND ALL THIS WASN'T LIKELY TO LEAD TO PROBLEMS?
Introduction of the thermal window
We will explain more about the thermal window in the next article, but that was allå in this connection that the Volkswagen Group found that it was best å take a shortcut, or, for å say it onå another way ... they chose å replace an illegal solution (the original cheating mechanism) but a new illegal solution (the thermal window).
It was practically impossible å make the cars with EA189 engine in legal condition. They therefore chose å make it so that they released legal amounts of pollution when the temperature was above 15 degrees Celcius and below 33 degrees Celcius. Then it released legal amounts... which of course caused the EGR mechanism to subject the engine to a lot of wear and tear. And OUTSIDE the thermal window ... just as bad as before. Anyway, more about this in the next article.
Practical consequences for car owners
Typical results of the "upgrade" was increased fuel consumption, reduced performance, or requirements for a workshop visit for cleaning and / or replacement of EGR parts. Often combined with the engine light and other warnings lighting up the dashboard like a Christmas tree. Although the "upgrades" was usually done free of charge, in very few cases this was not the case when it came to the following repairs and the costs of additional maintenance, because not talk about it being impossible å restore the car's original performance. In addition, the waiting time for repairs was often long, and many car owners found that they had to manage without a car for shorter or longer periods.
If the car owner believed that the frequent workshop visits and the greatly increased bills had to do with the so-called improvement; did, they were met with a cold shoulder. Møller and other workshops largely denied that the improvement had anything to do with the problems å do. As the workshops are mostly staffed by mechanics, må there must have been many Møller employees walking around with a sick lump in their stomachs... it is difficult å imagine that THEY did not know that they were once again misleading the customers. It was terribly expensive for many å own a modified car.
A bunch of good advice
It is very important for owners of the affected cars å follow the manufacturer's service intervals to the letter. At the slightest sign of problems that can he with the EGR system å do, have a workshop check and, if necessary, clean the EGR duct and valve. If possible, avoid sustained short trips with a cold engine, since DPF regeneration and the EGR function are then inhibited. We are close with å use the recommended fuel grade, and watch out for that there is AdBlue on the tank if the car has this SCR system installed, and reacts quickly to engine lights or erratic engine behavior.
In other words, quick trips to the nursery and back in the freezing cold, it's just å forget. Drive far, driving; up the engine temperature, use more diesel.
But, in addition, why endure all these disadvantages and negative consequences without å claim compensation for them? SIGN UP PÅ IN THE DIESELGATE CASE THAT IS RELEVANT TO YOU! It's free å join, and you do it here: www.bilklager.no
If you thought you bought a world-class car, but are left with what the individual could find for; å call a crap car ... why on earth should YOU be the one to take all the burden with this, when the EU court has DECIDED that it is the car manufacturers' fault and that YOU have the right to compensation?
Join and get cleaned up the madness. Together we are strong!
Other Stories
What is NOx?
Nice to hear about all the judgments, but tell me, what exactly is this thermal EGR-NOx stuff?
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