Strange the problem hit the headlines in the fall of 2013. The pulleys and belts of the distributor heads of car engines started to break exceptionally often in one area, the Oulu region.
The reason was a riddle, and there was talk of mystery dust. It accumulated in the engine compartment and seemed to cause damage to important parts.
The phenomenon was given the name “Oulu disease”. At least dozens of cars were broken down, among other things Helsingin sanomat newspaper.
Now the culprit is confirmed. It was a modest slag particle that was found in the slag of the Outokumpu ferrochrome factory. The slag was used to reinforce the asphalt, which is hard under the studded tires. Research bulletin published on Tuesday.
The broken gears and timing belts in question use valves that precisely time the gas changes in the engine.
Damage to this so-called distributor head usually breaks the engine. If the timing of the rapidly moving parts goes wrong, the valves can hit the pistons moving in the cylinders.
Researchers at the University of Oulu estimate that 25–50 cars in the Oulu region were damaged each year. Engine repair costs have ranged from 2,500 euros to up to 15,000 euros.
The total repair costs over ten years have been perhaps five million euros, although the figures are imprecise. The researchers have received the information from car repair shops. However, the figures give an idea of what it may have cost to fix the traces of the mystery dust.
Money understandably wanted to find out the cause of the “Oulu disease” reliably.
The decisive turning point was the undercover police work of mineralogists from the Geological Survey (GTK) and mechanical engineers from the University of Oulu. The Finnish Environmental Center Syke, Lapland University of Applied Sciences and Metropolia University of Applied Sciences from the capital region participated in it.
In the end, the meeting of two disciplines, mechanical engineering and mineralogy, helped the most.
“The project had genuine interdisciplinarity. We worked together, not just exchanged results. And it was possible to call a colleague in the evening as well, not just during office hours,” say GTK’s specialists Mika Räisänen and Akseli Torppa.
Räisänen’s field is aggregates, street dust and circular economy, Torpa’s process mineralogy. University of Oulu researchers Perttu Niskanen, Jonne Untinen and Karoliina Jokinen on the other hand, they work in the automotive and construction machinery engineering research group.
Decisive the research began to be planned in 2017. Already years earlier, several groups had been looking for the cause of the defects from many directions.
Immediately it was assumed that the mystery dust was originally slag from the Outokumpu ferrochrome factory, which was used in asphalt in the Oulu area. The slag is used as the base material for the asphalt pavement, which strengthens the coating to withstand studded tires better. The crushed stone is supplied by Destia and the roads are maintained by the Norwegian Railway Agency.
The impact of this crush is being studied by Lapland University of Applied Sciences and Aalto University. The researchers already took samples in 2013 and did laboratory tests in 2014. His report they published in 2015.
However, the investigation cleared the crumb of the charge.
“The toothed belts probably break due to the combined effect of corrosion and the abrasive dust that accumulates and develops there in the engine compartment”, guessed the team from Aalto University.
The team also stated that engine damage also occurred elsewhere than in the Oulu region, contrary to what was reported in the media. It took the attention away from the slag-reinforced asphalt.
Assumption, that the problem would be the same everywhere, however, was soon disproved.
A study commissioned by Helkama-Auto oy and carried out by Metropolia University of Applied Sciences was published on the Jakopää problem. Skoda and Ford engines were included in the investigation. With both brands, the distribution head problems were concentrated in the Oulu region.
Automotive companies usually publish defect statistics reluctantly. From the point of view of companies, the reason is that the public easily interprets statistics and statements negatively.
The researchers soon learned from people in the industry that other engines have the same geographical difference. Rumors circulating at the beginning about the breakdown of a certain group’s cars were refuted.
That so we had to think about why the engines only broke down in the Oulu area.
According to one theory, the cause is road salt. The road salt in the northern regions is different from the one used in the south. Lapland University of Applied Sciences investigate the effect of salt in a fume cupboard. The researchers found the salt’s corrosive effect too small to explain the damage.
In the discussions, acidic sulfate soils were also presented as a possible culprit. That assumption was also rejected, because there are similar lands elsewhere than in the Oulu region.
Corundum, i.e. crystalline aluminum oxide, which is a hard and scratchy substance, also haunted the discussions for a while.
The assumption fell apart when mineralogists joined the study. They said that chemically, corundum is aluminum oxide, but not all aluminum oxide is corundum.
In the engine compartment of the car, only “ordinary” oxide is present, because particles of aluminum oxide and aluminum are released from numerous aluminum parts of the car. It doesn’t eat much of the gear. Corundi got the perfect alibi.
“The cause of the timing belt problem must first of all be a local factor.”
Now GTK’s mineralogists and mechanical engineers from the University of Oulu tackled the problem. They ruled out chemical reactions right from the start.
“The cause of the timing belt problem must first of all be a local factor. Secondly, it causes severe mechanical wear on the distributor head gears, because they show clear signs of wear,” says Räisänen.
The researchers collected data on different types of dust inside and outside the engine compartments of cars. Previous brief reports focused too much on the dust from the housings that protect the distribution head of cars.
“According to our understanding, an extensive collection of samples and a campaign to analyze dust from different sources have been necessary. For example, if you only study so-called red dust, there will be a lot of mistakes, because studying red dust requires an understanding of all dust sources,” says Räisänen.
The share of red iron oxide dust, i.e. rust, of all the dust in the distribution head box was over 80 percent in the Oulu region, less than ten percent in the capital region.
Iron oxide dust is produced when metal wears away. Red dust is therefore the result of wear and not the cause. So the consuming dust had to come from somewhere else.
Observations in addition to collection, experiments with special test dusts were needed. They contained the same aggregates as asphalt in the Oulu region, i.e. ferrochrome slag, granodiorite, mica slate and mafic vulcanite.
The researchers modeled the operation of the distributor head in a test cabinet, where the gears and toothed belts rotate as in the engine. Untinen designed the test equipment. Mineralogists prepared the test dusts at GTK Mintec’s test factory in Outokumpu.
The test cabinet replicated the engine in a simple way that allowed wear to be accurately measured. Besides, testing with real car engines would have become impossibly expensive.
In each test, the simulator was run for about one hundred hours. During the test period, dust was added five times. The gears were weighed before and after the test. The difference in weight measured wear.
“Recycled materials, mineral-based by-products and other new materials need to be studied more.”
Exam were important and instructive to non-scientists in two ways.
First of all, assumptions and theories must be confirmed by experiments, even if they seem obvious. Second, experiments usually also bring surprising information.
The experiments in Oulu confirmed the early guess that the main factor is a slag particle that ended up on the asphalt from the ferrochrome factory. The result was beyond all reasonable doubt, as is the design of an Anglo-Saxon detective story.
Finally, the researchers were able to reveal the culprit to the players in the automotive industry, such as Agatha Christien Hercule Poirot familiar to the public from the works in the hall of the mansion.
The surprise was the intensity of the wear of the engine parts, which was 20-30 times compared to normal. That’s a huge difference. According to the researchers, even double the rate of wear compared to usual would have been a lot.
Results the meaning extends widely. The world’s steel industry produces 180–270 million tons of slag per year, he estimates US Geological Survey (USGS).
Information about the slag particle abrasiveness i.e. due to the consuming effect, the rules of the industry will probably be changed. It increases international interest in the properties of slag dusts.
It is good to remember that slag is an excellent material in many places. In use, you just have to make sure that particles are prevented from coming off and migrating to the wrong place.
The study of the “Oulu disease” is also related to the recycling economy. The reuse of materials must be increased, but at the same time new science must also be created.
“Recycled materials, mineral-based by-products and other new materials need to be researched more,” say Torppa and Jokinen.
Another question is the possible effects of slag particles on health. This topic is still waiting for its researchers. The slag also contains small particles that can penetrate the lungs.