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Comment by blattimwind | Hacker News Reader

> Gasoline engines don't produce all the particulate pollution that diesel engines do

With injection engines this simply isn't true any more.

> made a big mistake by adopting diesel

The small injection turbo diesel engines offered much higher efficiency and thus much lower CO2 emissions (~half) compared to contemporary gasoline engines (they still do). Other parts of the emissions profile (e.g. NOx) have almost exclusively to do with how efficient the engine is run, e.g. gas engines that are close to efficiency to diesel engines will produce similar amounts of NOx.

Broadly speaking, as more aspects of the combustion are externally, forcibly controlled, differences between diesel and gas engines become a lot less.

(The average German car has a 1.6 liter three or four cylinder engine doing something like 4.5l/100km ~ 50 mpg; basically no one is driving big cars with six or eight cylinder engines).

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You're correct when you say that the difference isn't in diesel vs gasoline. But for better or for worse, US regulations (read: California Air Resource Board (CARB) regulations, not federal/EPA regulations) are much more stringent in terms of particulates and NOx, while EU laws focus more on CO2 emissions. California is primarily worried about smog in LA, while Europe is generally much more concerned with maintaining the North Atlantic Current.

As you said, the high efficiency gasoline engines generate more NOx and particulates, but these engines cannot pass a CARB smog test. Most cars have separate US vs EU specs, (or simply aren't available in one market) and the EU specs always have better power and gas milage. For instance, the 1.0L engine in my 2014 Ford Fiesta is rated for 123hp, but the same 1.0L engine in the 2014 EU spec Ford Fiesta gets 140. (EPA vs EU gas milage ratings aren't directly comparable) This is a direct result of the fact that the US version runs at a lower temperature, which necessarily results in lower power and efficiency, but also results in less NOx.

Incidentally, this is a large part of why the US response to the VW emissions scandal was so different than the EU response. The affected VW engines broke EU regulations by a little, but broke CARB regulations by a lot. It's like going 70mph in a 55mph zone vs a 35mph zone.

>Incidentally, this is a large part of why the US response to the VW emissions scandal was so different than the EU response. The affected VW engines broke EU regulations by a little, but broke CARB regulations by a lot.

We had some Dutch friends visiting when the scandal broke. Their BIG concern was the emissions tax they paid to register the car for the road -- whether they would need to pay back-fees, and an increase in tax for future registration.

The biggest mistake in all of this isn't even diesel vs gasoline, it's that the majority of engine and technology advancements have gone into making cars even more ridiculously powerful and oversize. If a fully loaded van can clear a 10% incline alpine pass with a mere 60 kW engine, there is no justification whatsoever to have any more than half that power in a car driving in the city, or pretty much all over the place.

Gasoline vs diesel feels a bit like fructose syrup vs table sugar, it's pretty clear in both the US and Europe that regulations have not kept up enough of a downward slope on emissions to prevent technological advancement from going into grotesque growths like the SUV instead of cleaning up the exhaust and reducing consumption further.

And when the drunk driver of a 10-seat family van plows into you at high speed, do you want your "compact car" to become a "compacted car" with you inside?

Personally, I don't believe my life is quite worth the money I'd have saved by driving a small sedan instead of the larger vehicle I drive.

(If it were, then I daresay my budget would be severely lopsided. Seriously; what kind of idiot would I have to be to spend more than 70% of my net income to car-related expenses?)

A pickup or SUV isn’t needed to stay safe - especially not when all other cars are compact.

This reasoning reminds me of the tragedy of the commons.

This is totally tragedy of the commons reasoning. There exist big cars on the road, so I need a bigger one to protect myself against them. I'm half-surprised that no one is selling civilian-use APCs at this point.

Pfft. I couldn't weave, pass and lanechange through the usual shitty traffic if my vehicle was that unmaneuverable.

Isn't the traffic shitty (and dangerous) precisely because of the occasional people "weaving, passing and lanechanging" like crazy?

When I make a right-hand turn onto the far-right lane of a divided highway with four lanes in my direction, and over the next three blocks, three lanes become right-turn-only (gradually narrowing the road down to one lane) but I need to not make any of those right turns?

You bet I need some fancy footwork to avoid being forcibly detoured. And you bet that once I'm in the correct lane, I make a point of emulating the people far in front of me, by almost-tailgating the person directly in front of me.

In such a tragedy, any one person's most logical action is to obtain as much of the price-controlled commodity as possible, before the price returns to normal.

SUVs are top heavy with high rollover rates and generally worse crash test performance then smaller, better engineered vehicles.

And when the tired driver of a 40-tonner truck careers into your SUV you'll be compacted just as nicely. So where do you draw the line?

The semi-worst-case planning delusion is why we have convoys of 2.5 tonne SUVs doing the school run with two kids each. There doesn't seem to be any way to end the constant vehicle size escalation other than through legislation.

On the contrary. There are several reasons why vehicle size isn't going any further.

SUVs are at the upper limit of what most people are willing to tolerate in terms of unmaneuverability. Too big a vehicle, and you have trouble passing and weaving through the shitty commute traffic.

And if you try, and the vehicle is too slow for what you're doing, you'll probably crash. So it's a balance between being more survivable and being less likely to crash in the first place.

Also, bigger vehicles tend to be more expensive, non-size-related factors held equal.

We can't stop making cars bigger until everybody drives a Marauder https://www.youtube.com/watch?v=cDoRmT0iRic

You find a way to make that hunk-o-junk accelerate as fast as my small SUV can accelerate to get a right turn into a gap in traffic ... and I just might believe you.

This pattern is perpetuating itself with electric vehicles. Because electric is cheaper we have ended up with behemoths from Tesla and Jaguar, even the Renault/Nissan small car is far from small.

Uh really? No I'd love to replace my gas powered Minivan with a pure electric. There is no alternative other than the Model X.

Actually imho the reason why SUVs became popular is that

a) once a few were on the roads, you couldn't see the traffic ahead, unless you were also in an SUV which then allowed you to see through the front and rear windshield of the SUV ahead, and

b) stupid airbag regulations (you couldn't disable the passenger side airbag) meant that mothers couldn't put an infant in the front seat, because if the airbag went off it could crush the baby. Thus SUVs became more popular for use by mothers with children.

Parents can put infants in the front seat of an SUV?

In newer cars you can turn off the passenger side airbag. But there were many years when you couldn't. If an airbag deploys and the infant is in a typical rear facing infant car seat, then the child can be crushed by the force of the airbag.

Regardless of what's technically possible, the fact remains that US standards for particulate emissions and nitrous oxide are quite a bit stricter than European standards. So much so that, as we discovered recently, at least one major European automaker apparently felt the best way to get their diesel cars cleared to sell in the USA was by, in effect, lying.

One of the revelations of the VW scandal is that, when they actually comply with emissions standards, diesel engines are not cost- or efficiency-competitive; one interpretation of the events is the result of a failed overinvestment in a technology that didn't pan out.

https://www.politico.eu/article/europe-looks-to-electric-car...

Kind of reminds of how air-breathing nuclear jets have great performance, but possess other drawbacks. https://upload.wikimedia.org/wikipedia/commons/3/39/Aircraft...

> e.g. gas engines that are close to efficiency to diesel engines will produce similar amounts of NOx.

Your core theoretical claims may be true, but this specific example was not the fact revealed by the emissions scandal. VW had to cheat on NOx emissions numbers to get their diesel engines to match gasoline efficiency and performance.

They didn't have to cheat on NOx. They could have installed a selective catalytic reduction (SCR) system with an end-user refillable urea (AdBlue) tank. Just like all heavy diesel vehicles have had for years now. It would have added maybe $100 in cost to each vehicle.

The SCR system is an after-treatment for exhaust gasses and does not significantly affect fuel economy or performance.

Using my lungs as the yardstick, diesel exhaust is far far worse than petrol.

Direct injection could be a potential problem for gasoline, but not that much in practice.

Well, if you look at a modern gasoline engine the exhaust processing is basically the same as for a diesel engine. Particle filter, NOx cat, AGR etc.

As of the Euro 6c emissions rules, gasoline engines are subject to the same particulate count limits as diesel engines. This has resulted in the addition of particulate filters to certain 2018 model petrol vehicles (BMW, VW) in Europe.

This suggests that prior to Euro 6c, some petrol engines were getting away with higher particulate emissions than would have been allowed for diesels.

In theory.

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