Why no diesel Prius?

[Christ]

An evaporated water collection system could be put in the exhaust stream to recycle most of it, but then you're getting into a very complex exhaust system, I'd think.

Of course, the heated water could be used to get some of the exhaust energy back, and any exhaust-driven applique before the water tank would help to cool the exhaust before getting to the tank, making turbochargers and the like more common, as they would help cool the exhaust so as to not boil off the water so quickly.

[roflwaffle]

Originally Posted by Christ

In other words, you're not going to see Caterpillar or Detroit or White putting cans of salt water on their trucks come next week, or even next year, ya know?

Heavy duty trucks just go w/ urea aftertreatment if anything. Treating the entire exhaust stream w/ water is far too weight/volume intensive for a road going vehicle, so what manufacturers do is minimize what NOx emissions they can, use a SCR system to capture the rest, and periodically inject the urea solution into the exhaust stream in order to clean it out. Rinse and repeat. Regarding water recovery, the water has to be deionized, so unless that can be done on the truck, contaminants from the exhaust stream will poison the SCR system.

[Christ]

Originally Posted by roflwaffle

Heavy duty trucks just go w/ urea aftertreatment if anything. Treating the entire exhaust stream w/ water is far too weight/volume intensive for a road going vehicle, so what manufacturers do is minimize what NOx emissions they can, use a SCR system to capture the rest, and periodically inject the urea solution into the exhaust stream in order to clean it out. Rinse and repeat. Regarding water recovery, the water has to be deionized, so unless that can be done on the truck, contaminants from the exhaust stream will poison the SCR system.

Further adding to weight and complexity, of course. By the time we got done with a sufficient system, we'd need a bigger engine to haul it all around.

[roflwaffle]

You got it. It just isn't viable to do anything except SCR for aftertreatment.

[Christ]

*At the moment, that is. I'm sure there will, at some point, be a better method, but for now, there isn't.

[123]

I also don't agree with the diesel emissions standards. Its a ok to have a Hummer that gets less then 20mpg but a diesel that gets 50mpg or more is not how does this make any sense? Also Europe seems to have no problem with diesels. Could it have something to do with the fact that all small diesels are made by non American companies and not emission standards?

Originally Posted by rmay635703

Emissions are not really the reason either (I don't really agree with the emissions standards being placed on small diesel or gas vehicles though anyway but for different reasons)

Diesel exhaust can be cleaned to simple water and CO2 using WATER!

This has been known since the 20's and is the reason much of the underground heavy equip is diesel. The exhaust can be cleaned up 100%. My father drove a 100 ton mine car that used this hi tech 55 gallon water pail system.

And if you want to get real snazzy add calcium chloride or magnesium chloride (driveway salt), then the water can't freeze and need not be dumped as it can be recovered by adding more salt periodically and dumping the small amount Calcium Sulphate (fertalizer) and the like into the trash periodically or use it on your lawn.

Too bad auto companies and the government don't issue emissions standards to improve the environment or you might see workable loopholes like the one I mentioned above available.

Apparently cleaning your exhaust with saltwater is good enough for most large ocean vessels but works too well for the auto industry?

Heck you could run a malfunctioning 2 cycle diesel from the 50's and still have clean exhaust using water, which begs the question why not?

[roflwaffle]

The standards are about emissions of particulates, CO, HCs, NOx, and so on (Carbon Dioxide soon). If a 20mpg Hummer can get it under the NOx limit, while a 50mpg diesel can't, then that's that.

[Christ]

Yeah, that doesn't make it right, though. I don't think they measure in emissions per mile, do they? AFAIK (Could be wrong, don't keep up on it) they measure the emissions as a function of time, not distance travelled.

If this were the case, the largest section of cars that got higher mileage would also probably pass emissions, even with higher (per time period) emissions, because the emissions per mile would be less, due to the higher fuel economy.

[roflwaffle]

They do measure emissions in grams/mile, but if a vehicle was large enough it used to be able to get into a relatively favorable emissions bracket, eg a 2003 H3 may have gotten by w/ more pollution in g/mile than a 2003 TDI powered VW. As of 2009 everything up to 10000 GVWR has to conform to the same standards if I'm reading that correctly, so everything is pretty fair. If a small diesel compact can't get below .07g/mile of NOx while a full size diesel Dodge pickup can, then I agree w/ the standards dictating that it shouldn't be sold here.

[Christ]

Originally Posted by roflwaffle

They do measure emissions in grams/mile, but if a vehicle was large enough it used to be able to get into a relatively favorable emissions bracket, eg a 2003 H3 may have gotten by w/ more pollution in g/mile than a 2003 TDI powered VW. As of 2009 everything up to 10000 GVWR has to conform to the same standards if I'm reading that correctly, so everything is pretty fair. If a small diesel compact can't get below .07g/mile of NOx while a full size diesel Dodge pickup can, then I agree w/ the standards dictating that it shouldn't be sold here.

Knowing that changes the game just a little bit, then. I agree that if a smaller car can't match the emissions of a full size truck, there's a problem.

Of course, if a smaller, lighter, more aerodynamic car is making nearly the same HP as a much larger/heavier truck, it will make more particulate emissions because the engine won't be loaded sufficiently to be efficient, and will be burning fuel uselessly. Does that make sense? Seems like taking some of the power away from the car, or chaning the power curve itself to allow for more load at lower RPM, while still allowing the power to be "fun" when the operator requests it is in order?