So what do we think of diesels now?
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In aviation diesel is still perfect as it can run on kerosene that is cheap and available everywhere. Avgas has become exotic in many parts of the world including the military's.
However I'm still not sure if the perfect aviation diesel engine already exists? Not sure about modified car engines. My choice would be nothing that needs battery power to keep going.
For private car use I see diesel engines dying. They have been used for the wrong concept: Instead of making them maximum efficient (that would have been the logical choice) they went the maximum vehicle size plus maximum horsepower/torque route. Not being as clean as advertised will kill them now. You can see the sales numbers erode already.
However I'm still not sure if the perfect aviation diesel engine already exists? Not sure about modified car engines. My choice would be nothing that needs battery power to keep going.
For private car use I see diesel engines dying. They have been used for the wrong concept: Instead of making them maximum efficient (that would have been the logical choice) they went the maximum vehicle size plus maximum horsepower/torque route. Not being as clean as advertised will kill them now. You can see the sales numbers erode already.
I fly a 172 with a CD155 engine in a large group. It is a well equiped aircraft and was expensive to acquire, so the hourly costs are not cheap. It is quite heavy and performance low down is nothing special. It requires lengthy warm up and cool down periods. Power setting is done by setting a percentage, so you have to look down and consciously check it. This takes a bit of getting used to as the throttle movement makes setting exact percentages not very intuitive. We run it on car diesel, which is a lot cheaper and with the lower fuel burn the fuel cost to the group is much lower.
I fly a 172 with a CD155 engine in a large group. It is a well equiped aircraft and was expensive to acquire, so the hourly costs are not cheap. It is quite heavy and performance low down is nothing special. It requires lengthy warm up and cool down periods. Power setting is done by setting a percentage, so you have to look down and consciously check it. This takes a bit of getting used to as the throttle movement makes setting exact percentages not very intuitive. We run it on car diesel, which is a lot cheaper and with the lower fuel burn the fuel cost to the group is much lower.
However I'm still not sure if the perfect aviation diesel engine already exists? Not sure about modified car engines. My choice would be nothing that needs battery power to keep going.
http://gazaile2.free.fr/img/imgFini/moteur/diesel.jpg
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The downside of mechanical injection is reduced efficiency (compared to common rail diesels) and lower power to weight ratio.
Last edited by Mechta; 17th Apr 2017 at 16:58.
That's reducing the facts to the essential, @Mechta, thanks!
Now I agree that it is desirable, at the very least, to have the engine(s) operative without any dependency on the aircraft electrical system. Still, every petrol engine requires sparks so some kind of electricity is required; yet some meet this requirement. The Rotax 912 family at least, and I think a good many US engines too, those that run from magneto's. Thinking along the lines of the 912, why couldn't a fadec get electrical power from a completely separate circuit, with its own generator coils? Does it require a lot of power, perhaps?
Now I agree that it is desirable, at the very least, to have the engine(s) operative without any dependency on the aircraft electrical system. Still, every petrol engine requires sparks so some kind of electricity is required; yet some meet this requirement. The Rotax 912 family at least, and I think a good many US engines too, those that run from magneto's. Thinking along the lines of the 912, why couldn't a fadec get electrical power from a completely separate circuit, with its own generator coils? Does it require a lot of power, perhaps?
I despair when I see a group of people who on the face of it should be intelligent spout such strong opinions on things they know next to nothing. How are we ever going to make any progress or fix our problems if any solutions are immediately dismissed as lies by people who not only know very little but also lack the intellectual curiosity to follow the scientific method to back their claims.
Why now should we believe anything we're told?
My guess? The anti-Diesel thing is another fad like Vegans or the latest diet.
Course it is. It's just the basis of an excuse for the government to put even more tax on diesel fuel and collect more revenue from diesel lorry and train operators.
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David King, the former chief scientific adviser has admitted it was wrong to cut fuel duty on diesel vehicles after being hoodwinked by the car industry.
He said the government at the time wanted to encourage more people to drive diesel cars because they were said to emit less carbon dioxide than petrol vehicles. He said he was aware of warnings that diesel vehicles produced more toxic nitrogen dioxide, but he and the government had wrongly assumed this could be controlled by new technology and European regulations.
“I was in very close contact with the industry that was producing these catalyst trap systems and I was convinced that they could manage the problem,” he said. “What we know now, from the Department for Transport emission results from very extensive tests of vehicles, is that a large number of diesel-driven vehicles on the road in London are emitting more than 12 times the Euro 6 limit.”
Asked whether he was misled by the car industry, King cited the Volkswagen emissions scandal. “They [VW] were designing into the engine of vehicles a system that would in effect produce a very good result on the test bed and then deteriorate when it was on the road,” he said.
But King said all diesel car manufacturers “are managing a system whereby the test bed produces the results they want”.
Of course, this justification will carry no weight for those who deny the overwhelming evidence that our emissions of CO2 are destabilising the climate. Such people tend to fall into either the "It is difficult to get a man to understand something, when his salary depends upon his not understanding it!" camp, or are conspiracy theorists. Either way, no new evidence will ever induce them to change their minds, unlike David King!
He said the government at the time wanted to encourage more people to drive diesel cars because they were said to emit less carbon dioxide than petrol vehicles. He said he was aware of warnings that diesel vehicles produced more toxic nitrogen dioxide, but he and the government had wrongly assumed this could be controlled by new technology and European regulations.
“I was in very close contact with the industry that was producing these catalyst trap systems and I was convinced that they could manage the problem,” he said. “What we know now, from the Department for Transport emission results from very extensive tests of vehicles, is that a large number of diesel-driven vehicles on the road in London are emitting more than 12 times the Euro 6 limit.”
Asked whether he was misled by the car industry, King cited the Volkswagen emissions scandal. “They [VW] were designing into the engine of vehicles a system that would in effect produce a very good result on the test bed and then deteriorate when it was on the road,” he said.
But King said all diesel car manufacturers “are managing a system whereby the test bed produces the results they want”.
Of course, this justification will carry no weight for those who deny the overwhelming evidence that our emissions of CO2 are destabilising the climate. Such people tend to fall into either the "It is difficult to get a man to understand something, when his salary depends upon his not understanding it!" camp, or are conspiracy theorists. Either way, no new evidence will ever induce them to change their minds, unlike David King!
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I own a BMW 3 litre diesel car. The inside of the exhaust tailpipes are as clean as a whistle, bare metal, after almost 100k miles and 11 years. On the other hand, the tailpipe of my other cars (petrol engines) have sooty deposits. In view of the recent bad publicity about diesels I sometimes feel slightly guilty about keeping it, but if I sell it someone else will get the benefit; it's a long way from scrap condition. It's also the most economical on fuel. So it's staying.
All this concentration about CO2 emissions, rather than 'de-stabilising the climate', people forget that CO2 is broken down by vegetation and thus contributes to the ecology (grow more vegetation and more CO2 will be absorbed) whereas if you compare the CO emisions of diesel and petrol cars there is a vast difference because diesel engines only emit tiny amounts of CO compared to petrol engines. It's commonly know that if you run a petrol engine in (say) a garage with the door closed, you will die of CO poisoning, but do the same with a diesel engine and you might get a headache, but that's all.
On the issue of particulates, these are emitted by both diesel and petrol cars with diesel cars producing them at the same (low) level throughout the life of the car due to the 'particulate trap' fitted to the exhaust, however with petrol engines, the amount starts off low with a new cars and steadily increases over the life of the car ending up far exceeding the amount emitted by diesel engines.
By the way, the sooty deposits in the tailpipe of petrol cars are due to the unleaded petrol being used nowadays; leaded petrol, although more harmful in the long run, was 'cleaner' in terms of soot deposits. The same goes for spark plugs; once upon a time a sooty spark plug indicated the mixture was too rich whereas a 'normal' mixture was a brownish deposit on the electrodes or even clean electrodes; nowadays the 'norm' is to have sooty spark plugs.
On the issue of particulates, these are emitted by both diesel and petrol cars with diesel cars producing them at the same (low) level throughout the life of the car due to the 'particulate trap' fitted to the exhaust, however with petrol engines, the amount starts off low with a new cars and steadily increases over the life of the car ending up far exceeding the amount emitted by diesel engines.
By the way, the sooty deposits in the tailpipe of petrol cars are due to the unleaded petrol being used nowadays; leaded petrol, although more harmful in the long run, was 'cleaner' in terms of soot deposits. The same goes for spark plugs; once upon a time a sooty spark plug indicated the mixture was too rich whereas a 'normal' mixture was a brownish deposit on the electrodes or even clean electrodes; nowadays the 'norm' is to have sooty spark plugs.
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I despair when I see a group of people who on the face of it should be intelligent spout such strong opinions on things they know next to nothing. How are we ever going to make any progress or fix our problems if any solutions are immediately dismissed as lies by people who not only know very little but also lack the intellectual curiosity to follow the scientific method to back their claims.
I was told that to burn a gallon of petrol produces about three quarters gallon of water, which is pretty harmless stuff. What does the other 25% consist of and what is the genuine comparison with diesel?
Is there an honest, genuine organisation devoted to finding the truth, or are they all employed to produce a result that will satisfy someone's financial interest?
Or are the answers to these questions so bloody obvious they don't need asking?
All the time people making various claims are relying on the results for their own salaries, no one is going to trust anything or anybody.
The same krap is going to happen with electric motors, what cost in emissions will there be if power stations are used to recharge, manufacture batteries, build the new infrastructure?
There's no such thing as a free lunch.
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So how does the non scientific general public user find out the real truth?
I was told that to burn a gallon of petrol produces about three quarters gallon of water, which is pretty harmless stuff. What does the other 25% consist of and what is the genuine comparison with diesel?
Is there an honest, genuine organisation devoted to finding the truth, or are they all employed to produce a result that will satisfy someone's financial interest?
Or are the answers to these questions so bloody obvious they don't need asking?
All the time people making various claims are relying on the results for their own salaries, no one is going to trust anything or anybody.
The same krap is going to happen with electric motors, what cost in emissions will there be if power stations are used to recharge, manufacture batteries, build the new infrastructure?
There's no such thing as a free lunch.
I was told that to burn a gallon of petrol produces about three quarters gallon of water, which is pretty harmless stuff. What does the other 25% consist of and what is the genuine comparison with diesel?
Is there an honest, genuine organisation devoted to finding the truth, or are they all employed to produce a result that will satisfy someone's financial interest?
Or are the answers to these questions so bloody obvious they don't need asking?
All the time people making various claims are relying on the results for their own salaries, no one is going to trust anything or anybody.
The same krap is going to happen with electric motors, what cost in emissions will there be if power stations are used to recharge, manufacture batteries, build the new infrastructure?
There's no such thing as a free lunch.
His answer was that his understanding is that there are economies of scale from recharging because the incremental increase in emissions from the power station are lower than from diesel or petrol. (Even more so if the power isn't supplied by fossil fuels.)
Of course this may not be true, but it was his truthful response in that he isn't paid by anyone to answer the question in any particular way.
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So how does the non scientific general public user find out the real truth?
I was told that to burn a gallon of petrol produces about three quarters gallon of water, which is pretty harmless stuff. What does the other 25% consist of and what is the genuine comparison with diesel?
I was told that to burn a gallon of petrol produces about three quarters gallon of water, which is pretty harmless stuff. What does the other 25% consist of and what is the genuine comparison with diesel?
The products of combustion is fairly basic chemistry as described here: "Carbon dioxide is the principal product of combustion of fossil fuels since carbon accounts for 60–90 percent of the mass of fuels that we burn."
Diesel emits 2.68 kg of CO2 per litre while for petrol it's 2.31 kg - source.
Note that a litre of diesel weighs about 0.87 kg, so it emits more than its own weight in CO2. That's because each atom of its carbon combines with two atoms of oxygen.
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It's commonly know that if you run a petrol engine in (say) a garage with the door closed, you will die of CO poisoning,
At least, not if it has a catalytic convertor working as per its design. It converts CO to CO2 (and to a lesser extent, excess HC to CO2 as well), that's exactly why it's there!
The last MOT emissions result I got, for my year 2000 petrol car gave CO = 0.00 % vol, HC = 5 ppm at fast idle and CO 0.01% vol. at natural idle. I think you'd be alive in the garage for quite some time at that rate. Other methods of doing yourself in are far more efficient!
I certainly agree that modern petrol fuels emit more soot than the old leaded stuff; I have been building and tuning my own engines for over 40 years; I began when performance cars needed 4 and 5 star petrol.
I re-jetted a carburettor equipped motorcycle only last week after making some induction improvements. it now runs far better than standard. A couple of years ago I tuned the mixture on my SU carb equipped modified car after a rebuild (this involved hand modifying mixture needles). To confirm everything was all OK I took it for a rolling road session before we did a long distance touring expedition. The operator was very impressed that according to his highly sophisticated Lambda machine I'd managed to get it stoichimetric by eye, using the spark plug colours. He suggested I richened it up very slightly to improve the power output.
soay, according to your Transport conversion table, Diesel cars produce less CO2 than petrol as follows:
Small car -29%
Large car -48%
Average car -40%
I must say, I was a little confused by the heading:
Vehicle type Kg CO2 per litre
which then goes on to express CO2 in Kg/km
Small car -29%
Large car -48%
Average car -40%
I must say, I was a little confused by the heading:
Vehicle type Kg CO2 per litre
which then goes on to express CO2 in Kg/km
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That's why the government promoted diesel engines over petrol, because it's the CO2 emissions which are changing the climate. Diesel contains more carbon per litre than petrol, but that's compensated for by its better MPG. For example, the diesel engined DA40 consumes only 5.6 usg/hr (of Jet-A1) at an IAS of 116 kts.
