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Discussion Starter #1
To me this makes no sense. The electric motor is primarily a stop and go driving thing, with conservation of power from regenerative braking. All good stuff.

And yes a stratified charge, variable valve timing, spark ignition engine is nice. But it is still a spark ignition engine!!! And on the highway, this is want is needed to move.

VW manages 42-46 mpg highway from its 90hp diesel. The Prius has 70hp. Presumably a smaller diesel would be even more efficent. And the VWs are a brick relative to the Prius.

Ultimately, the diesel uses only enough fuel to make exactly the power it needs where a spark ignition always has to inject enough fuel for combustion.

Are diesel/electric hybrids the thing of the future? Were the railways of the 1950's a harbinger of things to come???
 
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Hi DavidNJ:

___Have you ever heard of the Partnership for a New Generation of Vehicles or PNGV for short? It cost the American tax payer ~ 1.5 billion which would have been a great investment if it had worked out but Ford, Chrysler, and GM backed out of the deal along with the Bush administration The Big 2.5 created a nice set of truly mid-sized Diesel Hybrids that could accelerate to 60 in the 10 second range and received between 63 and 70 mpg on the highway IIRC. They were built of some non-std. materials however and who knows what the true cost would have ended up at even with mass-production. The real problem and the one that still kills the diesels of today is the damned Diesel emission issue. It is great on the CO2 side of the equation with an ~ 20% reduction from a std. ICE out of the box but those pesky NOx and PM emissions are tough to knock back so far. HC and CO are relatively under control without the HW so that isnt really the issue but NOx is the Diesel killer and it is really too bad given what they could do for the US overall fuel economy.

___As another source, have you looked into the Honda Accord i-CDTi available in Europe in the not to distant future if it isnt available now? It not only has the performance of a large ICE (Accord Saloon: 0 60 in ~ 9 seconds) but receives the equivalent of ~ 35 - 45 mpg EPA city/highway estimate and it is supposedly cleaner then any Diesel available in Europe. Ford was considering bringing their Diesel equipped European based Focus over recently as well given its relatively good performance with a large increase in fuel economy vs. the 2.3 L PZEV they are currently using

___There is talk of Urea sprays and post NOx adsorbers along with particulate traps for diesel exhaust clean up but none seem to be that far along in their development for practical application. Both Ford and Honda supposedly have the Diesel clatter/shake knocked down to a point they would be more then acceptable in any Luxury automobile here in the states but it all comes back to the pesky diesel emissions issue. Even with LS Diesel, emissions appear to be too problematic for the US and Canada to head towards diesel powered Hybrids at any time soon from my understanding. That and I believe Boschs patented HP Common Rail Injection systems cost ~ the amount of a complete Hybrid drivetrain which might have something to do with the reasons they arent over here already as well?

___Good Luck

___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___[email:4tush2ky][email protected][/email:4tush2ky]
 

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The quest for lower diesel emissions in the US is impeded by the high sulfur content of US diesel fuel (500ppm limit; typical is about 300ppm, although typical in California is about 125ppm). In late 2006, the limit goes down to 15ppm, which should make NOx catalysts and particulate traps possible (sulfur damages these devices).

From a fuel economy standpoint, a diesel hybrid makes a lot more sense than a gasoline hybrid, since a gasoline hybrid basically only meets or slightly betters the fuel economy of a diesel non-hybrid. But don't expect to see a lot of diesel engines offered in passenger cars in the US until the 2007 model year. There are a few from VW and DC, but they only barely meet 45-state Tier II limits for 2004-2006 and do not meet 2004 CARB limits, since they cannot make use of emissions control devices that would depend on diesel fuel with a maximum of 15ppm sulfur.
 
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Hi Tjl:

___I believe Europe is already using < 50 ppm low sulfur diesel (LSD) and they still cannot meet the upcoming CA. emissions/new Fed requirements for road use automobiles? Even when we receive LSD or (ULSD < 15 ppm) here in the states, it wont be a cleaner solution then the SULEVs and PZEV ICEs we have available to us today. IIRC, the latest in diesel emission technology used w/ the European diesels are ULEV like clean (yet still containing some nasty Carcinogens in the PM) but they will never be on par with the SULEVs and PZEV based ICEs or hybrids. I however would love to own the Honda or Ford Diesel in a Focus, Accord, or Civic myself given the predictable performance, great highway fuel economy, and hopefully lower initial costs. Maybe even a .66 - 1.0 L i-CDTi offshoot for my Insight would be even nicer still w/ a guaranteed 100 mpg tank over tank ;)

___Good Luck

___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___[email:1498nnlj][email protected][/email:1498nnlj]
 

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Besides pollution, a major problem of Diesel engines is their high compression ratio, which makes them difficult to start and stop seamlessly like the gas engine of the Prius does. Why not, but some serious engineer work to be done still.
 

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Discussion Starter #6
With the large electric motors in hybrids, starting the diesel shouldn't be that much of a challenge. The stratified charge engine also has pretty high compression.

It is the modern electronics and high pressure fuel systems that allow the engine to fire immediately and consistantly that make this possible. And the big electric motors.

Plus, although it doesn't show you rpm, in electric only mode, isn't the motor only turning 1000-2000 rpm?
 
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With the large electric motors in hybrids, starting the diesel shouldn't be that much of a challenge.
Starting is not a problem. Making it seamless is the problem.
The stratified charge engine also has pretty high compression.
Compression ratio for Diesels is roughly twice that for gas engines.
Plus, although it doesn't show you rpm, in electric only mode, isn't the motor only turning 1000-2000 rpm?
Of course not. There's a maximum speed in the Prius above which the engine must be spinning even in electric mode, because there's a maximum speed the generator must not exceed, but it's above 40 MPH (don't remember exactly). So at low speeds, where starts / stops are most easily noticeable, the engine does stop in electric mode.
 

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Diesel hybrids are definitely on the horizon - especially here in Europe.

Toyota are already developing them (see here).

As are some others...

http://www.benerridge.freeserve.co.uk/imogen.htm

http://www.benerridge.freeserve.co.uk/azure.htm


Expect to see such systems in trucks and buses earlier though, simply because fuel costs are a more significant running cost for these vehicles. Nissan diesel already sells one in Japan, and it uses 50% less fuel in stop start driving.

:)

[Edited to add; my figures are in UK gallons, so divide by ~1.2 to get US]
 

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xcel said:
The real problem and the one that still kills the diesels of today is the damned Diesel emission issue. It is great on the CO2 side of the equation with an ~ 20% reduction from a std. ICE out of the box but those pesky NOx and PM emissions are tough to knock back so far. HC and CO are relatively under control without the HW so that isnt really the issue but NOx is the Diesel killer and it is really too bad given what they could do for the US overall fuel economy.
Actually, the CO2 savings aren't that much...

1 liter of diesel fuel is denser than gasoline, and it's molecules contain more carbon relative to hydrogen. In total 1 liter of (european) diesel produced 2,68 kg CO2, while 1 liter of gasoline emits only 2,32 kg of CO2.

Around here in europe, the average gasoline car uses about 9 l/100 km, while a diesel vehicle gets away with 7 l/100 km.

CO2 - wise, these numbers become ~210 g/km for gasoline and 188 g/km for diesel - only a mere 10% advantage for diesel.

But as you correctly stated, the PM & NOx emissions are very likely the true killer. The equipment needed to control these could easily eat up all the remaining diesel advantage, CO2 wise.

The Prius II is already on-par on CO2 per kilometer with diesel vehicles one or two class(es) smaller than itself.

*but* diesel fuel is much cheaper per liter in most european countries. In those where it isn't, the hybrids sell overproportionally fast, in the european comparison.

However, a diesel engine itself is about 50 kg heavier than a equal performance gasoline engine, and more complex (due to more support systems, like turbo-chargers, common-rail high-pressure systems, exhaust recirculation systems and so on). In effect, a diesel is more costly to produce.

When hybrid production (mainly the batteries) is up on the same volume as diesels, the additional cost of a hybrid drivetrain over a standard gasoline drivetrain will probably be less than the current additional cost of a diesel drivetrain.

Only for heavy-duty applications, like trucks, busses, railway engines, a true diesel hybrid drivetrain would make economical sense. These vehicles operate almost around the clock, and some (busses) in situations were a hybrid really is made for, so that doubled additional cost can be recovered quickly in reduced fuel expenses...

Richard
 
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Diesel is most efficient in part throttle operation. Hybrid is most effective in start/stop and energy capture (downhill, varying speed) operation.

Weight disadvantage? 200 pound heavier E320CDI yields 50% better mileage with increase in performance.

Cost? Hybrids, with second motor, complex electronics, batteries have to exceed diesels. Common rail high pressure fuel system is also in new cars (FSI Audis, VWs, MB 350, 760 and to be announced BMWs). Turbo/supercharging is on may petrol engines. Over time many expensive components (ECUs, knock &O2 sensors, FI) have all been absorbed because of increased performance (power, efficency, emissions).

No, the diesel/hybrid combination will be best.
 

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Also, to shed more light on the original question of why Prius etc use gas and not diesel, I should have pointed out that Japanese motorists are strongly opposed to diesel - you won't find many diesel cars over there! For them, air quality is much more significant than outright fuel economy, due to the very dense urban population and resulting sensitivity to exhaust emissions - so use of diesel is frowned upon.

As Japan is the main market for hybrids (lots of stop-start urban drive-cycles), and since the only two companies currently selling hybrids (Toyota and Honda) are also Japanese, it makes sense that they should sell gas and not diesel cars as the latter would not be very saleable in the home market. Indeed Honda have been so opposed to diesel throughout all their history of being the world's leading engine manufacturer, they've never made a diesel burning engine of their own until just this year.

Once they can convince the Japanese motoring public that they've got the diesel emisions issue licked however, both companies will start making diesel hybrids, and expect 80+mpg with them. :)
 

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I was told by my dealer (after I had placed my order) that the German government is planning to phase out diesel by 2010.
I dont know how true this is but certainly the road tax for diesel is a lot hight than for petrol.
 

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Victor said:
I was told by my dealer (after I had placed my order) that the German government is planning to phase out diesel by 2010.
I'd be surprised at that! They've invested billions in agriculture and infrastructure trying to become the world leaders in biodiesel production. VW have taken this as a long term view as well, as all their new TDis are now built with the capability of running on RME (rape methyl ester - or, biodiesel). Come to think about it, if it weren't for diesel, what would all the trucks run on?

By the way, nice website Victor! 8)
 

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clett said:
Victor said:
I was told by my dealer (after I had placed my order) that the German government is planning to phase out diesel by 2010.
I'd be surprised at that! They've invested billions in agriculture and infrastructure trying to become the world leaders in biodiesel production. VW have taken this as a long term view as well, as all their new TDis are now built with the capability of running on RME (rape methyl ester - or, biodiesel). Come to think about it, if it weren't for diesel, what would all the trucks run on?

By the way, nice website Victor! 8)
Thanks.

I Greece diesel is not available for "private" cars, only lorrys. Maybe that is the plan here as well?

When I gought my Hyundai Santa Fe :oops: I bought the petrol version as it was tax exempt until the end of 2005. If I had got the diesel version version I would have had to pay arount EUR 700/year road tax.

Bio-diesel is widely available its true, and you can get LPG in some places, but I guess as the government gets most motor related tax from petrol, they dont want people to move to another fuel. No subsidy here like you get in the UK -Powershift :?: :x

I will be glad when my Prius gets here and I can dump the Santa Fe!
 
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