## Would a diesel-electric hybrid be better mpg than gas-electric hybrid

Given the earlier thread, why not combine diesel with electric motors?
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We can kill three birds with one stone.

 Diesel hybrid concept car also taps the sun Ford says all-wheel-drive Reflex can get 65 mpg
http://www.msnbc.msn.com/id/10788292/

Note that trains have been running diesel over electric for decades.
 I would almost assure that. Though from everything ive read, a detached diesel motor/generator would be more efficent than a parallel drive design, as a detached generator would let the diesel run at peak efficiency constantly rather than constantly changing rpm and efficiency

## Would a diesel-electric hybrid be better mpg than gas-electric hybrid

 Quote by Frostfire I would almost assure that. Though from everything ive read, a detached diesel motor/generator would be more efficent than a parallel drive design, as a detached generator would let the diesel run at peak efficiency constantly rather than constantly changing rpm and efficiency
This is called a series hybrid and is the type of hybrid that most hybrid auto manufacturers are now focusing on.

While a diesel based hybrid may get better fuel economy than a gasoline engine, it doesn't necessarily make it better. Diesel engines generate a lot of pollution, which is why they are not very common in the US for commercial vehicles. Gasoline is a much more cleaner burning fuel which is why its most commonly used. Future series hybrid electric/gas cars will probably use stratified ignition engines, or something close to it, to try and take advantage of the benefits the diesel cycle offers, but still using the clean burning fuel, gasoline.

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 Quote by Topher925 This is called a series hybrid and is the type of hybrid that most hybrid auto manufacturers are now focusing on. While a diesel based hybrid may get better fuel economy than a gasoline engine, it doesn't necessarily make it better. Diesel engines generate a lot of pollution, which is why they are not very common in the US for commercial vehicles.
Ultra-low-sulfur fuels now required in the US contain 15 ppm sulfur, compared to ~500 ppm in the older fuels. Particulate traps used in late-model diesels further reduce emissions. Diesels are very common in commercial, but not private vehicles, primarily because diesels could not meet emission standards. They do now.

Assuming Exxon et al manage to produce biodiesel from algae [$600 million recently invested by Exxon alone], diesel CO2 emissions would be reduced to near zero. Also, biodiesel contains no sulfur. Recognitions: Gold Member Science Advisor  Quote by Topher925 While a diesel based hybrid may get better fuel economy than a gasoline engine, it doesn't necessarily make it better. Diesel engines generate a lot of pollution, which is why they are not very common in the US for commercial vehicles. Gasoline is a much more cleaner burning fuel which is why its most commonly used. Future series hybrid electric/gas cars will probably use stratified ignition engines, or something close to it, to try and take advantage of the benefits the diesel cycle offers, but still using the clean burning fuel, gasoline. Sorry, this is cobblers. Do you have anything to back up the claim that Diesel engines "generate a lot of pollution"? Have you actually even compared a modern gasoline engine with its Diesel counterpart, in terms of brake specific NOx/CO/HC/PM/CO2 emissions, or do you just think "old lorries make smoke, so all Diesel engines must be terrible"?  Quote by brewnog Sorry, this is cobblers. Do you have anything to back up the claim that Diesel engines "generate a lot of pollution"? Have you actually even compared a modern gasoline engine with its Diesel counterpart, in terms of brake specific NOx/CO/HC/PM/CO2 emissions, or do you just think "old lorries make smoke, so all Diesel engines must be terrible"? No it isn't. Yes I do. Yes, and no I don't. A simple google search reveals lots of info about how gasoline is cleaner than diesel....  Most of today’s hybrids and even some conventional gasoline vehicles are considerably cleaner... http://www.hybridcenter.org/hybrid-w...vs-diesel.html  ...it takes about 25% more oil to make a gallon of diesel fuel than a gallon of gasoline, so we should really look at how a vehicle does on fuel efficiency in terms of "oil equivalents."  ...when it comes to smog-forming pollutants and toxic particulate matter, also known as soot, today's diesels are still a lot dirtier than the average gasoline car.  US tailpipe standards for diesel cars, which have historically been weaker than those for gasoline cars, are being updated to force diesel and gasoline vehicles to meet the same set of emissions standards. The tiered structure of the new "Tier 2" standards, however, allows automakers to produce some cars that release two times more soot and smog-forming pollution than the average new vehicle and still meet their targets. Also, until the standards are fully implemented in 2009, existing loopholes allow some cars to pollute even more.  Making a gallon of diesel fuel requires 25% more oil and emits 17% more heat-trapping greenhouse gases than gasoline reformulated with MTBE. Similarly, diesel requires 17% more oil and emits 18% more heat-trapping gases than gasoline reformulated with ethanol. This means that diesel fuel's advantages from its higher per-gallon energy content and better performance on greenhouse gases are partially offset by the impact of diesel's fuel-production process. http://www.grinningplanet.com/2005/0...ne-article.htm  We know from before that passenger cars with diesel engines emit, depending on their condition, about 20 percent less of the greenhouse gas carbon dioxide (CO2) per kilometer than the same car type with gasoline engines. However, besides CO2, the exhaust contains a number of other components such as nitrogen oxide (NOx), carbon monoxide (CO), and particles. With the exception of CO, emissions of these components are generally higher from diesel cars, and lead to lower air quality and negative health effects. http://www.cicero.uio.no/fulltext/index_e.aspx?id=6871 The text book right in front of me, (An Introduction to Combustion, by: S.R. Turns) also supports my claim. While the sulfur content in diesel has decreased, it hasn't changed the fundamental ways diesel engines operate. Unless flame temperatures can be lowered, fuel can be better atomized, or diesel production be made more efficient, I don't see how diesel could ever be cleaner than gasoline. If I'm missing something or don't know of some technological breakthrough that has made this possible please enlighten me.  Quote by Ivan Seeking Assuming Exxon et al manage to produce biodiesel from algae [$600 million recently invested by Exxon alone], diesel CO2 emissions would be reduced to near zero. Also, biodiesel contains no sulfur.
Biodiesel is still far from reality. Even so, diesel engines whether biodiesel or not, still generate pollutants. Yes there is less CO2, but theres also plenty of CO, NOx, HC, etc. But if biodiesel creates less of the pollutants than gasoline, I don't know, I've heard mixed information. Do you have any info on this?

EDIT: Some good info about biodiesel,
 but diesel still has a long way to go to match the emissions performance of the many fuel-efficient conventional and hybrid electric gasoline-powered vehicles on the road today.
http://www.ucsusa.org/clean_vehicles...in_cars_and_li

 Driving a modern, small displacement diesel can be fun. I assume they'd make a fine hybrid animal given their advantages in torque and economy. Of course, pollution is in they eye of the beholder. Europe loves diesel cars and things there are clean, especially Germany. Yes, diesels pollute an order of magnitude more than gasoline. But if you consider the 'problem' of automotive gasoline pollution equivalent to the 'problem' of time dilation at highway speeds (as I do), you should have no moral hangups with a diesel.
 Recognitions: Gold Member Science Advisor Topher925, are you really standing by your link which holds the Tier 2 on-road regulation as being consistent with a modern on-road (Tier 4b, Stage V etc) Diesel engine?

 Quote by ensabah6 Given the earlier thread, why not combine diesel with electric motors?
As already pointed out, trains have been utilizing diesel/electric power for a very long time.

They also have jet turbine/electric systems. Which may not be as practical in a family sedan

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 Quote by Topher925 Biodiesel is still far from reality.
Not true. Biodiesel is in common use now. What is not sustainable is the source - that typically being soy and canola, cotton, and a few other crops. That is why algae-derived fuels are the key. Algae can produce five to ten times the yield per acre-year, or more, compared to any other fuel crop.

 Even so, diesel engines whether biodiesel or not, still generate pollutants. Yes there is less CO2
Not less CO2; I said virtually no CO2. In principle, biodiesel emits no new CO2 - only that absorded from the atmosphere by the fuel source [crop]. It is carbon neutral. No other fuel option can make the same claim, less perhaps ethanol, which has other serious drawbacks and is completely unsustainable. The best option for a sustainable source of ethanol may be...algae.

 .. but theres also plenty of CO, NOx, HC, etc. But if biodiesel creates less of the pollutants than gasoline, I don't know, I've heard mixed information. Do you have any info on this? EDIT: Some good info about biodiesel, http://www.ucsusa.org/clean_vehicles...in_cars_and_li
Note that only the limit of your graph shows the results for pure biodiesel.

Biodiesel is notoriously low in emissions, less NOX emission, which are a bit higher than petrodiesel. Beyond that, the emissions from any particular biodiesel fuel depends on the source of the fuel. Oils low in saturated fats, like oils from algae, produce the cleanest fuels. Being high in saturated fats, soy produces a relatively unclean biodiesel, which is what most studies would have used.

There are two factors to consider regarding the energy content of petrodiesel. First is the amount of energy contained in a gallon of fuel. While this tracks approximately 1:1 with the amount of crude required, we transport ~25% less fuel to the market for a given amount of energy. Beyond the reduced distribution energy costs, diesel engines are more efficient than IC engines.

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 Quote by Topher925 No it isn't. Yes I do. Yes, and no I don't. A simple google search reveals lots of info about how gasoline is cleaner than diesel.... [...] If I'm missing something or don't know of some technological breakthrough that has made this possible please enlighten me.
Topher, after citing this:

 Quote by Cicero article [...]We know from before that passenger cars with diesel engines emit, depending on their condition, about 20 percent less of the greenhouse gas carbon dioxide (CO2) per kilometer than the same car type with gasoline engines. However, besides CO2, the exhaust contains a number of other components such as nitrogen oxide (NOx), carbon monoxide (CO), and particles. With the exception of CO, emissions of these components are generally higher from diesel cars, and lead to lower air quality and negative health effects.
one can see your first blanket answer to the OP's query about gasoline versus diesel pollutants in this engineering forum was incorrect on a per km distance for CO2 and CO. It is known that Bio-diesel burns cleaner than petrol diesel. Brownog also drew your intention to the new Tier 2 bin 5 EPA standards, which reduce particulates to nearly nothing.
 Blog Entries: 2 Recognitions: Gold Member Science Advisor This thread really got way off on a tangent... In response to the OP's question- yes, diesel hybrids (parallel or series) will tend to get better mileage than a gasoline one. This is due to the fact that turbo-diesel engines are generally more efficient than a gasoline engine because of their high compression ratio and turbocharging. Additionally, Diesel has approximately 10% more stored energy per volume than gasoline, adding to a diesel vehicle's MPG rating (but not overall energy efficiency). The reason they aren't widely available is mainly cost. A turbodiesel engine is more expensive than a naturally aspirated gasoline one, which can make a big difference when you're putting a lot of expensive hybrid equipment on a vehicle as well.

No. I'm not familiar with the politics, but only the science of how thermal engines work.

 Not true. Biodiesel is in common use now.
I did not know this. Where is it being used?

 Biodiesel is notoriously low in emissions, less NOx emission, which are a bit higher than petrodiesel.
Yes, but keep in mind that NOx emissions are one of the most harmful emissions created. The idea behind a closed CO2 cycle is appealing but you can't ignore the other harmful products that are generated as well.

 Quote by mheslep Topher, after citing this: one can see your first blanket answer to the OP's query about gasoline versus diesel pollutants in this engineering forum was incorrect on a per km distance for CO2 and CO. It is known that Bio-diesel burns cleaner than petrol diesel. Brownog also drew your intention to the new Tier 2 bin 5 EPA standards, which reduce particulates to nearly nothing.
I'm sorry, I don't understand your logic??? I never stated that diesels produced more CO2 or CO, I merely stated that diesels produce more pollution than their gasoline counterparts, which according to my sources they do. I have seen no information that suggests otherwise.

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 Quote by Topher925 I'm sorry, I don't understand your logic??? I never stated that diesels produced more CO2 or CO,
Meaning what, that neither CO2 nor CO are pollution? In post 3 you made the blanket statement
 Quote by post 3 Diesel engines generate a lot of pollution, which is why they are not very common in the US for commercial vehicles. Gasoline is a much more cleaner burning fuel which is why its most commonly used.
[my highlights]Without attaching a qualification that assertion is incorrect. The truth is the pollution profile, diesel vs gasoline, is mixed for unit of energy delivered. Also, this considers only the gasses at the point where they are exhausted directly from the cylinder. Post processing in the most recent engines might change the mix decidedly in favor of diesel, I dunno.

 I merely stated that diesels produce more pollution than their gasoline counterparts, which according to my sources they do. I have seen no information that suggests otherwise.
Look, I could point to those same sources and naively make the reverse statement because I happened to focus only on CO2 and CO in favor of diesel.

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