If hybrids did not exist then diesel would have a strong argument if fuel were expensive. But (1) hybrids DO exist and (2) fuel is not going to be expensive for many, many years. And Toyota makes an excellent hybrid.

 

I'm just trying to understand all of this.

So presently, although diesels yield more energy per unit volume and hence higher torque, lower fuel consumption and lower *** levels for less greenhouse effect, diesels produce more NOx which causes smog, and diesels also produce particulate dust which is known to cause cancer in laboratory animals, hence passenger diesels have been phased out or outlawed in the US and Europe.

On the other hand, commercial diesels are still able to use diesel because they are big and expensive and can therefore house the larger size and extra weight of NOx and particulate dust filters, plus the large costs of commercial diesels can more easily absorb the extra cost of diesel filters; furthermore, commercial diesels have a better track record of servicing than private passenger diesels, and finally, commercial diesels produce less pollution per occupant and per unit mass of cargo transported.
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The higher torque is also a result of the high compression ratio needed for compression ignition. With high compression ratio, you need a long connecting rod, and since torque is the rotation force applied multiplied by the distance from the point of rotation to the point of the force, the longer that distance (the connecting rod), the greater the torque.

This is the same reason why long-stroke engines have greater torque.

Large commercial vehicles still use diesels because, historically, that has been the better option (compared to gasoline engines), and because there are not that many other viable options available right now (although there are more and more hybrid transit buses being used, and pure EV buses are being tested).

 

Not entirely sure about that. A high compression ratio can be obtained by using the same head volume and lengthening the stroke OR by keeping the same stroke and just shrinking the head volume.

As for torque, for a given displacement if you increase the stroke you will decrease the diameter of the piston, thus lowering the effect of chamber pressure on the piston top. I seem to recall that this cancels out any benefit from the crank's longer throws.

My understanding is that a diesel is inherently more efficient because (1) slightly more energy in the fuel, (2) a much higher compression ratio and thus a much greater capture of the gas expansion, and (3) the elimination of a throttle plate so the engine is never working against a vacuum. Even at idle, a full air charge gets sucked in for every stroke. If we are trying to move an 80,000 pound vehicle then the diesel process is by far currently the best mechanism for doing so. But I think a major energy savings could be obtained by using regenerative braking, but that implies a gigantic battery pack to soak up all the kinetic energy in an 80,000 pound slowing vehicle.

 

Here is a good comparison form MotorTrend on the a gas Discovery and a diesel Discovery.

http://www.motortrend.com/cars/land-...vilized-beast/

I still stand on my argument that why would you want to pay $80K US dollars for diesel performance that is 2.6 seconds slower, more curb weight, and less towing capacity than the gas model.

It will give credit for the improved fuel economy of 5 MPG, but the argument that the high torque rating will make customers happy makes no sense as its much more sluggish.

 

There's also tank range where a diesel engined car could get over 1000 km on a tank, whereas the petrol version could get 2/3 that. Most LR owners in Europe don't bother with towing but they do travel long distances across the continent. I remember a Top Gear or Fifth Gear segment where an E-class diesel hit over 1000 miles on a tank, although it was running on fumes near the end.

Big Lexus diesels only sell outside the Middle East and North America, places where gas is cheap. In most parts of the world diesel is the preferred SUV and pickup fuel.

 

Not arguing any of what you say. I posted the Land Rover thing as it just goes to show how the US market it is. People will not be willing to pay more for less driving performance (MPG excluded). A 300 HP Lexus RX is a very good performing vehicle, to get the levels of performance via diesel (MPG excluded), the cost is going to be too high.