Land Rover diesel hybrid dreams

In nearly any config. When the cylinders volume goes over a certain size, there will be incomplete burn of the fuel mixture. While measured in microseconds, the flame front will only have so much time before the piston bottoms out.

In overly bored out V8s, the piston top will only have carbon build up only in the center. Suggesting there wasn't enough time during the power stroke to burn all the gas. The excess just gets pushed out during the exhaust stroke. In addition to not burning all the fuel, the fuel that does burn has to do more work pushing a larger piston.

You end up with lower fuel economy and increased hydrocarbon emissions. With a diesel, particulate emissions might increase.

 

Yes, if you need euro 6, then a 3L 6 would likely be more efficient and have better nvh. It would likely have lower pollution before pollution control devices, but afterwards they can make them the same. A straight 6 might have better nvh than a v6, but requires more forward space and is not suitable to fwd cars, The trade off would be that it would be more expensive, but this is in an expensive car. Its just an artifact of where we are in engine design. When you look at the parameters, a 4cyl will have slightly less friction (about 15% than a 6 if same volume and same bore stroke ratio) but have a harder time breathing through the valves. For more efficiency you want a longer stroke (over square) but the 4 is going to want a bigger bore to put larger valves to work. The ability to turn off a bank of cylinders allows lower pumping losses at lower power levels and requires a less lean burn that is also more thermally efficient.

Now if you want a 4wd SUV for ice, snow, mud, gravel on road and want efficiency, an e4wd system with a much bigger battery might help. In that case you could individually drive the front wheels with a 3 motor system. This would shave weight and mechanical complexity, which could be used for the bigger battery. It would also allow you to individually control power to each front wheel, without braking, and run in a more efficient rear wheel drive mode when nothing is slipping (on nice dry streets). In that case you could drop the ice to say a 2L 4cyl diesel, making up for the power missing from the ice by the bigger battery.

 

And all this is before we discuss the 5 cylinder diesel that Land Rover produce. That should keep both of you happy

 

Incomplete burn in a SI engine comes mainly from wall effect (thermal effect, AKA quench) . In fact, the larger the cylinder volume the less incomplete burn ratio of the fuel mixture.

 

We have trade offs between efficiency, nvh, and pollution. If we were running a single diesel cylinder at 60%-75% load, @1800 rpm turbo charged, di, on the miller cycle (late intake valve closing) for long periods of time, you could simply put mounts on it to get rid of the vibration and sound insulation for the noise. It would be the most efficient since it would have the lowest drag, highest thermal efficiency. If we can take more vibration and don't care about the weight, making it even bigger and slower can make it more efficient. That is what they do on ships, huge cyclinders low rpms, di turbo.

But its going in a truck, with large variability of power requirements, cold starts and nvh considerations. This changes the calculations. That single cylinder with low load is going to need to be turning faster for the needed nvh, which will actually make it less efficient than more cylinders. Current state of the art cylinder design has very good efficiency on cylinders that are 0.5L or larger. This will change and numbers will get smaller with technology. In the 1940s the number looked more like 0.7L cylinders, but smaller were often used to have a higher count for nvh. NVH is much worse in 1 or 2 cylinder engines than 3+ cylinder engines. That gets us to some rules of thumb, that may change with technology. Anything 1.5L or bigger should have at least 3 cylinders, bellow that size there are efficiency/nvh trade offs.

Now I am not saying the range rover needs a 3L engine, but if we are designing a 3L diesel turbo engine for it and simply are looking at cylinder count we have choices given the rule of thumb size of 0.5+L of 3x1L, 4x0.75L, 5x0.6L or 6x0.5L. Right away you are going to throw out the 3 cylinder for nvh and perception, given that you won't significantly increase efficiency over the 4 cylinder engine. You can also throw out the 5 also, without cylinder idling technology it also won't be more efficient than the 6 or as smooth. Therefore its 4 against 6. In a 6 cylinder friction is increased about 15%, but rpms can be lower especially on cold starts without the nvh being too high. The real kicker is under cruise control on the highway, the 6 can happily deactivate half its cylinders running the pumping losses of only a 3cylinder 1.5L ice. Unless your driving cycle is very different than most people that will end up being more efficient over the year. When the cylinder deactivation with acceptable nvh happens on a 4cylinder diesel, this may change, but that takes future technology.

 

I know this is possibly a bit of wishful thinking, but the Prius is the smoothest car I've driven after a Mercedes S600 V12.

Sure it doesn't have the power or speed of that car but it accelerates very similar (though tailing off much quicker) and as quiet and smoothly. Obviously the suspension isn't as good either, but for a car costing a fifth the price, it ain't bad.

 

Those ship big engines are 2-stroke. Although Miller cycle could effectively improve efficiency, actual design gives no chance to implement though, given the ports for inlet air...Some manufacturers actuate on enxaust valve closing.
The Miller Cycle and Emissions Reduction

 

Really interesting post, but for us non-techies, what's NVH?

 

Considering the viscosity of their fuel, those ship engines might as well take advantage of 2-strokes.

 

Noise, vibration, and harshness - Wikipedia, the free encyclopedia

 

Just want to point out that the hybrid has a 1.4L engine, not a 1.8, but it sounds like it uses much of the same improvements.

While the Hybrid Jetta has a combined rating of 45mpg, and the diesel 34mpg, the EPA test normally underreports a diesel's fuel economy. Fuelly users of both models are averaging 40mpg.

 

Who cares What Clarkson thinks, yes he is a auto critic, but also a entertainer. Their show is considered a documentary in the US & by the FCC so they can pass any political or social controversy and not make it seem like they are insulting anyone. Do you really think he hates Hybrids? Why should Clarkson truly even care to hate Hybrids? Jeremy Clarkson hates Hybrids like Piers Morgan hates guns; it's all ratings!

Who watches Clarkson's show and where is his largest audience? If you pay close attention he says negative things about certain cars and make a ridiculous comments, initiated by false or presumptive bias; it's funny, entertaining, catchy I love watching his show but I take his reviews about any non euro car very lightly.

 

I will bet Clarkson will say" the Land Rover Hybrid is the best Hybrid Ever made" LOL!