www.bbc.co.uk/news/business-36589106
It found the problem is worst among the Euro 5 category of cars, which became mandatory in 2011.
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Yes this is in the regs.
You can adjust the pollution controls below a certain temp (Im guessing 18C?) to protect components in the engine. Not sure why this is news, or shouldn't be surprising to the authors of this report!
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Do they mean that diesels in colder climates create more pollution.I understand that engines have to work harder the colder it is.
Take the emission test in cold climates and give a true figure.Or both in warm and cold and take the average.
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It means the engines turn off the routines that reduce CO2 emissions when temperatures are below 18oC to protect the engine. They also do this when it is too warm.
So for most of the time in the UK, a diesel car is more polluting than official figures.
I understand taxation will be introduced to deter people buying diesels. Labour were wrong to promote them to reduce CO2 emissions because they ignored NOx and particulates.
Last edited by: rtj70 on Wed 22 Jun 16 at 22:51
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The only way to reduce CO2 is to use less fuel. The 'routines' that are turned off result in lower fuel consumption and less CO2. That is why they do it. What you get more of is NOx.
The principal means of reducing pollutant emission is exhaust gas recirculation, which reduces engine efficiency.
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How does an engine know what the outside air temperature is?
Surely only by the temperature of the air being drawn into the intake?
So isn't that why engines control the air temperature by drawing it past the exhaust manifold in cold weather?
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Good point and I think that is the nub of the story. The manufacturers are doing it when they don't need to, instead of at say -10C.
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>> How does an engine know what the outside air temperature is?
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I would be surprised if the engine ECU did not use the ambient sensor that is used for the dashboard readout.
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>> How does an engine know what the outside air temperature is?
You know what was meant. The ECU for the engine will know the temperature - it has to. Therefore how the engine is controlled takes into account the ambient air temperature.
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>> How does an engine know what the outside air temperature is?
Engines know everything they need to know if they are working properly.
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>> Engines know everything they need to know if they are working properly.
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Exactly my point. There is a decades-old mechanism for monitoring the air temperature and heating it if necessary.
It may be sensed by a hot wire, some more sophisticated electronic sensor, or a good old bimetal strip on a flap.
So the outside air temperature doesn't matter - the combustion chamber surely gets air at the temperature it needs?
(My original question was rhetorical - why do I have to explain that? :))
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Do modern injected engines still heat the intake air?
IIRC one reason it was done in past was to prevent ice forming in the carburetor.
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My Datsun Bluebird had a manual flap in the air intake, to be set to the summer position at temperatures above 15C. Not many early morning starts above that in the UK. I agree it was an anti carb icing device, the flash point of petrol is low enough not to need warm air to burn.
Last edited by: Old Navy on Sat 25 Jun 16 at 21:30
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Can any one explain, (because don't know) where the 18C is measured for a diesel engine? The intake air starts off at ambient temperature, is heated when compressed by the turbocharger, cooled by the intercooler, mixed with exhaust gasses in the EGR, and then enters the cylinders, (engine). As far as I am aware the MAF only measures the air mass entering the engine. The intake air is certainly not at ambient temperature when it arrives at the cylinders.
Last edited by: Old Navy on Sat 25 Jun 16 at 22:11
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>> Can any one explain, (because don't know) where the 18C is measured for a diesel
>> engine?
I don't know, but I guess it will be ambient with the electronics taking account of downstream consequences.
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>>My Datsun Bluebird had a manual flap in the air intake, to be set to the summer position at temperatures above 15C.
Brought back some fond mammaries there ON, of the many, many times I was called out to tune a car, to find that the main problem was the air intake flap was still in the winter position - on a hot summers day (remember those!)
Same probs in the winter of course, with ice in the venturi ... Happy Daze!
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Diesels more polluting below 18C, research suggest - PR
