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Old 02-02-2013, 12:00 PM   #96990
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Originally Posted by Timmeh! View Post
well yes, much better durability results.

disagree, the 1.9 TDI motor is not bad at all.

Mazda is doing that to reduce NOx so that they don't have to run urea injection because people don't like having to fill up a urea bottle. in europe diesel compression ratios haven't dropped.

the direct injection is NOT for charge cooling, that would be what water/meth injection is for. the direct injection is so that the injection can be timed to prevent detonation, just like a diesel.

Turbo diesels are torquey, but by "power" i assume you mean horsepower, which is a calculated value only related to torque and RPM.

diesel has more energy per unit volume than gasoline, diesels also extract more power from that fuel because they can run super lean without any detonation (again, ignition timing).

The reason diesel is more expensive is because it gets taxed higher, because the majority of diesel is used by semi trucks who tear up the road (hence higher road use taxes on the fuel)

Europe is full of turbo diesels, and for good reason. pound for pound a diesel engine will be more efficient and go farther on a given amount of fuel.

the reason that diesel's aren't popular here is because back in the 70's GM adapted their normal gas big blocks to run on diesel... the extra force of combustion was destroying bottom ends.

Please do some more research before you just come in here and try to explain engine mechanics to me. as far as carbon monoxide emissions, diesels trounce gasoline engines, making them cleaner (especially once you add urea injection/a catalyzer for the NOx and other particulates)
Europe also doesn't have the same requirements as far as particulate emissions. California drives the Feds to have a much more stringent standard which requires the use of the expensive after treatment systems such as the urea injection.

The injection of liquid fuel does slightly cool the air/ fuel mixture to prevent autoignition, just not to the same extent of water injection/ methanol injection perhaps, but enough to aid in preventing detonation with a lower octane fuel with a higher compression ratio. It was just enough to cool the charge and prevent detonation, rather than having a pre mixed stoichiometric air fuel ratio coming into the cylinder charge.

In 2004 Izuzu had stated exactly what I had said about the liquid fuel injection having a cooling effect on the cylinder charge, of course they were only going from 9.x:1 to 10.x:1 compression as opposed to from 10.5:1 to 12:1 like the Duratec Ti-VCT engine.

It also allows for a stratified charge to lean out the combustion in the bulk of the chamber with only a small fuel rich charge in a dish just below the spark plug. Of course diesel engines have had direct fuel injection for years. It wasn't exactly new even then, although it wasn't economically advantageous to apply to gasoline engines until recently.

Diesels are heavier in order to withstand the additional forces as a result of the elevated compression levels.

I am well aware of the advantage that diesel fuel contains in terms of energy content.

I'm not trying to explain engine mechanics, although I have semi-extensively studied this in university.

Diesels work well for applications where you need to move a lot of weight due to the additional torque and durability, although it is not a good engine for a sporty car.

Diesels don't sell well here in part because of the GM failures, but also a combination of factors such as the additional cost and the fact that when factoring in the additional cost for the car, the fuel and the energy content it seems to make more sense for people here to go with either a downsized gasoline engine, or a gasoline-electric hybrid over a diesel.

Europe is full of turbo diesels due to the tax advantages for the fuel over gasoline. Lower CO2 emissions don't mean much if its that much worse for NOx and particulate matter without the expensive after treatment means it is that much less likely for it to come here due to Californication dictating the federal emissions laws.

It's why that other than in heavy duty pick up trucks, and a few Volkswagens only luxury cars such as BMW or Mercedes are available with diesel engines here in the U.S. as they can more readily absorb the additional cost in the price of the car.

Horsepower is a function of torque and rpm, yes, however a diesel engine generally has difficulty revving over 5000 rpm. Gasoline engines can usually spin faster due to their lighter rotating mass.

It would be nice to have the choice though. I was just highlighting the basic advantages of adapting this technology to a gasoline engine.

If gasoline has an energy density of 34.2 MJ/L (mega joules per liter) and Diesel fuel around 37 MJ/L that's only a difference of around 8.2% more energy per liter of fuel.

A diesel runs at a much leaner air fuel ratio, yes, that's where much of the fuel efficiency advantage comes from, although its terrible on NOx and particulates if you remove the after treatment systems, or use a less stringent version like they have in Europe for ages.

I actually do like diesel engines, and they have their place, however you'd have your work cut out for you to convince the general public and or the politicians in California who attempt to dictate the emissions laws for the country based on their specifications.
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