Want to read Slashdot from your mobile device? Point it at m.slashdot.org and keep reading!

 



Forgot your password?
typodupeerror
Check out the new SourceForge HTML5 internet speed test! No Flash necessary and runs on all devices. ×

Comment Re:I thought diesel ran cleaner (Score 1) 201

Expanding isn't "reacting to heat".

What? What do you call it, then? I didn't say it was reacting with heat. Although it does react with oxygen in the presence of heat, to form NOx, that's explicitly not what I was talking about.

But, back to the original point: Diesel engines take in much more atmospheric air than gasoline engines when running at normal loads (highway cruising).

Yes. But they consume no more when wide open. The size of the exhaust is defined primarily by the maximum flow, not the cruising flow. (That defines other design characteristics more.) Diesels tend to have higher peak boost in spite of their typically higher static compression ratios, but they also tend to have significantly lower RPM limits and tend to run less RPMs while cruising.

Of course, all of this has been muddied by the introduction of the direct-injected gasoline engine, and by developments in diesel engine technology. Not only do GDI motors have higher cylinder pressures and thus higher temperatures, but there are also now diesels with [automated] throttles. As well, the recent crop of automatic transmissions with many gear ratios (8 now being common, 9 not being uncommon, and 10 beginning to roll out) and multiple overdrive ratios has led to gasoline engines being used at much lower RPMs...

Comment Re:How the fuck.... (Score 1) 201

Yeah maybe in America. But that is a fantasy land in terms of fuel. This article however is talking about other places in the world.
In Australia for example most heavy busses have switched to running nat gas because it was cheaper. Most taxis and many passenger cars did too though these are being displaced by electric.

all of which makes sense, but what about long-haul trucking? the hauls are really long in oz.

Comment Re:Think outside the container... (Score 1) 201

I can't help but be a little amused at all the people saying cities could never ban Diesel because there's no acceptable alternative.
There is, of course, just not for long-haul trucking.

You could probably switch to turbine-electric and burn... well, whatever you wanted really, but the only thing which would have the same kind of energy density is jet fuel. That would only cost what, an order of magnitude more or something? But the good news, everyone, is that we're all going to be getting higher-grade fuels whether we like it or not. It's not going to be possible to get much better emissions out of internal combustion vehicles without them. The automakers want to see even higher-grade diesel fuel, and higher-octane gasoline.

Of course, if the Trump takes a Dump on CAFE somehow then we might well not get any of this stuff any time soon...

Comment Re:Stupid (Score 1) 201

Natural Gas for trucks.
Electric, Natrual Gas, or Petrol for cars.

Natural gas? So, you're pro-fracking. Cars are more important than clean water. Nothing is good about petrol, either.

Even if it weren't ecologically retarded, natgas is not a viable replacement for diesel. We use diesel for long-haul OTR trucking for many reasons, but not least because of range. You have to make many more refueling stops for gasoline than for diesel, and you have to make even more for natgas.

Now, to be fair, it is possible to make natural gas from an ecologically friendly source — feedlot manure. Currently this is mostly put into holding ponds to sit and stink for a time before being flushed into a waterway. The smart thing to do with it is put it into tanks (or even into glorified ziploc bags such as the ones often used as water tanks now) and let it cook itself, producing methane in the process; it's going to do this anyway, but we can capture it and put it directly into any vehicle with a propane conversion which involves an O2 sensor. You can buy the conversion parts (the PCM, injectors, and fuel rail) straight outta China for around five hundred bucks.

Methane aside, there is also Butanol, a 1:1 replacement for gasoline. BP and DuPont own a company called Butamax which holds the patents for cost-effective commercial production, which were developed partly with our money. GE Energy Ventures owns a company called Gevo which would like to sell it to us, but Butamax sued them to stop production.

As for diesel, the best replacement is "green diesel", which is what you call it when you crack fats (waste or otherwise) in a distillation column such as we currently use for the distillation of crude petroleum. Like biodiesel produced by the transesterification of fats with methanol or ethanol it is a carbon-neutral fuel (assuming you get your conversion heat energy from a carbon-neutral source) but its other properties are more similar to petroleum diesel, like its gel point. It can be blended with 2-10% traditional biodiesel to deliver a fuel which can be used in any diesel engine and, which will actually extend the life of its fuel system with superior lubricity.

The best solution for reducing emissions in locations where it is excessive, assuming we're going to keep driving around like a horde of motorized lemmings, is battery electric. So sad, it only solves the needs of what, is it 80% of the population? Even if were only 50%, that would still be a massive victory.

Comment Re:So much for biodiesel use... (Score 1) 201

Diesel engines used to run without making ANY NOx. However, because of the political need to reduce CO2, they were modified to minimise CO2 regardless of the consequences for NOx.
Totally separately, if you don't have a particulate filter, the particulates are pretty bad.

Well, congratulations, you got that completely and totally wrong. You could not be more wrong if you were trying to be wrong.

First, NOx is produced any time you have combustion in the presence of nitrogen. Diesels produce more NOx than gassers because they have higher combustion temperatures. It's not unusual for someone to turn the fuel up on their diesel just a bit without understanding the consequences and melt a hole right in one of their fancy forged Aluminum pistons. This is why an exhaust gas pyrometer is a mandatory upgrade (if not fitted from the factory) for anyone who wants to increase power in their diesel. You can cook things very easily, mostly pistons and exhaust valves but also turbochargers.

Second, gasoline engines produce just as much soot as diesels. They produce finer soot, which is more dangerous. The class of soot which gasoline engines produce is collectively termed "PM2.5" or particles of 2.5 microns and smaller. This is the smallest common classification of soot particles, and it is by far the most dangerous because these particles are so small that your cilia cannot sweep them out of your lungs. They can only be removed by adhering to sputum which is then expelled by coughing. Diesel catalysts re-burn diesel soot, which is nice big chunky particles of 10 microns or larger, until it too is PM2.5. This makes them look a lot cleaner, but it actually makes them much more hazardous to health.

Diesels with clever injection systems but without catalysts are the most health-friendly internal combustion engines available which run on liquid fuels. The only internal combustion engines which are superior in that regard are propane engines (typically gasoline conversions, and not purpose-built) run on bio-methane, and lubricated with bio-based oil.

Comment Re: What a stupid question (Score 1) 449

Sure, there's always a subpoena (or more likely an NSL), but before it gets to that point Trump will need to have passed some form of legislation to actually get the database off the ground and into reality, and that's going to require a considerable amount of support from Congress, Senates and (almost certainly) the courts, because you just know this would get challenged in multiple jurisdications and head towards the SCOTUS. Or, I suppose, he could maybe try and do it off the books through one of the three letter agencies and a whole bunch of NSLs, in which case the US is absolutely done as "The Land of the Free" and we'll just have to repeal Godwin because the Nazi Germany / Stasi comparisons will be absolutely justified in that eventuality.

Having multiple parties whose co-operation would be useful, if not essential, to making the project viable basically stating up-front they don't support the idea and will almost certainly challenge any data requests through the courts, again likely all the way to SCOTUS, just as Apple recently did with a certain iPhone is quite likely to undermine at least some of that support. If there's one thing you can particularly count on politicians for, and especially so in Trump's case, is not wanting to back a losing horse, so the less likely the project is to succeed the more likely it is to be stillborn, and that's the best way for it to be.

Besides, since we're entirely talking about hypotheticals here, if Twitter were to do a Lavabit how is TheRealDonaldTrump going to get MSM to jump and report any <140 character bit of random thought as front-page news? ;-)

Comment Re:What a stupid question (Score 1) 449

Build the (still hypothetical) database, not so much. Help *populate* it though? Twitter, like all social media companies, undoubtedly has a lot of data on its users, and that data is going to include stuff that would help identify someone as a Muslim, even if it's just "Went to Mosque today..." type tweets. Think about how this (again, hypothetically) might work - voluntary registration first (the most harmless), mandatory registration second (the weaker-willed protestors to add to low-grade watch lists), then a trawl for those that didn't register (the activists and other "red flags" for the high-grade watch lists... and beyond). Care to guess where Twitter et al in the social media/data gathering trade come into that?

It's absolutely the pointy end, and hypothetical as the question might be "No comment" doesn't even come close to the correct answer of a completely unequivocal "Fuck, no!", so kudos to Twitter for being the only company with the balls to do the right thing. Hopefully, they'll still have those balls should they actually have to follow though on that position.

Comment Re:I thought diesel ran cleaner (Score 1) 201

because it's important: exhaust gas volume is proportional to load.

Gasoline engines, yes, Diesel, no. As I posted elsewhere, Diesel engines have something closer to a fixed air intake on each revolution, irrespective of load.

Please read before replying.

Remember that Diesel engines use compression ignition and, without sufficient air, there is insufficient compression to ignite the fuel.

Would you like me to tell you about my AT185. or my OM617.951A?

Submission + - President Obama's $4.2B CS for All K-12 Initiative Pronounced Dead 1

theodp writes: In a late Friday blog post entitled An Update on Computer Science Education and Federal Funding, tech-backed Code.org explains that Congress's passage of a 'continuing resolution' extending the current budget into 2017 spelled the death knell for President Obama's proposed $4B Computer Science For All initiative, which enjoyed support from the likes of Microsoft, Facebook, and Google. So, wait'll next year? Perhaps not. "We don’t have any direct feedback yet about the next administration’s support for K-12 CS," wrote CEO Hadi Partovi and Govt. Affairs VP Cameron Wilson, "other than a promise to expand 'vocational and technical education' as part of Trump’s 100-day plan which was published in late October. I am hopeful that this language may translate into support for funding K-12 computer science at a federal level. However, we should assume that it will not." The nonprofit may have ruffled the new administration's feathers — among the recent WikiLeaks disclosures was correspondence from Code.org's founders advising the Clinton campaign that the issue of K-12 CS education could be used to win Hillary the election.

Comment Re:I thought diesel ran cleaner (Score 2) 201

Typical compression ratio in a Diesel engine is somewhere around 20:1, vs a gasoline engine that's running 10:1 or there about.

So what?

Basically this is displacement/cylinder * compression ratio * RPM * number of intake strokes per revolution.

The compression ratio is a function of the head volume and the cylinder volume. It has nothing to do whatsoever with determining how much air is drawn into the engine, which is defined by speed, bore, stroke, and intake efficiency. It is rather determined by how much air is drawn into the engine, and how much space you have left for air at the end of a compression stroke.

Ever wondered why diesel tail pipes are a lot larger than gasoline ones? This is why, diesels move a lot more air.

Diesel tail pipes are a lot larger than gasoline ones because diesels shit the bed when you have backpressure. It ruins their efficiency and you have to play tricks to get it back. Turbocharging is worth it anyway because it's turbocharging. Now, pay attention to this part, because it's important: exhaust gas volume is proportional to load. Diesels have bigger exhausts because they have more torque. This is also why turbochargers and diesels go together so well. Turbochargers are driven by exhaust gas expansion, which as mentioned, is proportional to load.

If you carve the piston out, you lower the compression ratio, and you increase the amount of air the engine consumes. You in fact have this exactly backwards.

Slashdot Top Deals

A triangle which has an angle of 135 degrees is called an obscene triangle.

Working...