Biodiesel - MYTH or FACT?

Reflex · **Joined:** Mon Jan 29, 2007 8:48 pm **Posts:** 567

I just can't figure out why someone would buy a Prius when a Jetta TDI can be had for the same price and is a much nicer car that will get better real world mileage. Guess its not as much of a status symbol or whatever..

dieseldoesit · **Posted:** Wed Feb 20, 2008 4:36 pm

don't fault hybrids too much, I can't wait till they start pairing them with diesel motors.

The most powerful part of the car is the brakes, there is a lot of energy available to be recovered if a 90 % conversion is possible. I think the Prius and other hybrids are limited in the amount of power that they can absorb in the battery pack.

They will need a two stage pack, some ultra capacitors for quick energy discharge and charge, as well as a battery pack (or other) for long term storage.

geordi · **Posted:** Wed Feb 20, 2008 4:43 pm

I believe Toyota is working on the 2-stage idea, but I know for a fact that they are developing (and will be releasing in the next year or so) a diesel hybrid. The question I have not seen a solid answer to yet, is whether it will be a diesel version of whats available now... Or the "Freight Train" design, where the diesel is ONLY used for electrical generation and the wheels are 100% electric drive.

I believe they are working on the generator-only option rather than the current shared-driveline designs, as a steady-state engine can be tuned to be MUCH more efficient than a multi-speed engine like ordinary cars now are.

On the subject of hybrids... My family will be discovering exactly how painful those battery changeouts might be, as we have TWO Mercury Mariners, and we tend to drive about 40k each year... On each of our vehicles. If it becomes an issue, I think the first thing we will look at is the pack and software upgrade that will turn them into longer-range electric cars until the packs are depleted, it's like a $10k upgrade right now... But that includes new batteries, and that is only the current price. We know that price will drop.

dieseldoesit · **Posted:** Wed Feb 20, 2008 4:46 pm

It is amazing at how much life is complicated due to the inability to store large amounts of electricity in small, light, efficient packages.

MOSFET · **Joined:** Sat Feb 25, 2006 11:40 pm **Posts:** 295

Reflex wrote:

I just can't figure out why someone would buy a Prius when a Jetta TDI can be had for the same price and is a much nicer car that will get better real world mileage. Guess its not as much of a status symbol or whatever..

Probably because some states prohibit the sale of diesel cars (e.g., New York and California).

NY prohibited the sale of the Jeep CRD, but you could register a used one if it had over 7,500 miles.

Reflex · **Joined:** Mon Jan 29, 2007 8:48 pm **Posts:** 567

Geordi - Mileage really isn't relevant when it comes to battery hybrids. The reason is that batteries lose capacity over time and to a lesser extent, recharge cycles. If you take a laptop battery out and just let it sit a few years then try to use it, you'll find it can barely hold a charge. Thats why there are all these reports out there of taxicabs that go 400k miles and the batteries are fine, it has nothing to do with the mileage put on the vehicle. Hybrids have been on the market now long enough that we should start seeing some real world results on this, hopefully someone does a study...

Threeweight · **Joined:** Mon May 14, 2007 5:57 pm **Posts:** 679

Reflex wrote:

I just can't figure out why someone would buy a Prius when a Jetta TDI can be had for the same price and is a much nicer car that will get better real world mileage. Guess its not as much of a status symbol or whatever..

From firsthand experience, the TDI doesn't get better real world mileage. Our 2006.5 with an auto tranny has been averaging 42-44 mpg on long highway trips lately. In city mileage it is getting 30-34.

I have two different friends with 2nd generation Prius (Pri? Pri-i?). They get about the same highway mileage (low 40's), but 38-42 in the city.

Factor in the tax breaks for hybrids, and the 50 cents per gallon lower cost of running regular unleaded vs. diesel, and it makes much more economic sense to drive a hybrid (at least if you generally replace cars every 3-5 years).

On the other hand, I agree, the Jetta TDI is a much nicer car than a Prius or a Civic hybrid, and much more fun to drive. We test drove all three before we bought the TDI (from a private party). That is why my wife hated the idea of selling it and getting a hybrid -- the Civic drives like an anemic, plasticy econo-box. The Prius is a lot more pleasant to drive, but the level of luxury is pretty meager compared to the heated seats and sporty handling of the Jetta.

Reflex · **Joined:** Mon Jan 29, 2007 8:48 pm **Posts:** 567

There are dozens of Prius' operated as shuttles around my work HQ. They typically average 34-36mpg, which I just didn't find all that impressive. Most the people I know with TDI's claim at least 40mpg on average, although what mix of city/highway driving that is I don't know. The tax breaks certainly do change the equation to some degree, although with the higher long term maintience I think a TDI would still be a better investment(as well as a better car). But I guess an argument can be made either way...

dieselenthusiast · **Posted:** Wed Feb 20, 2008 8:00 pm

Off Subject, but I miss my CRD :twisted:

I'm really hoping a diesel Wrangler comes out to make me free better

Reflex · **Joined:** Mon Jan 29, 2007 8:48 pm **Posts:** 567

dieselenthusiast wrote:

Off Subject, but I miss my CRD :twisted:

I'm really hoping a diesel Wrangler comes out to make me free better

To my mind a diesel Wrangler makes more sense than a diesel Liberty...

UFO · **Posted:** Wed Feb 20, 2008 10:15 pm

Reflex wrote:

dieselenthusiast wrote:

Off Subject, but I miss my CRD :twisted:

I'm really hoping a diesel Wrangler comes out to make me free better

To my mind a diesel Wrangler makes more sense than a diesel Liberty...

Very much so. The diesel is ideal for real Jeeping.

Threeweight · **Joined:** Mon May 14, 2007 5:57 pm **Posts:** 679

If I had the option of diesel Wrangler Unlimited pushing close to 28-30 mpg highway, my CRD would be gone in a flash. And I love the little guy.

dieselenthusiast · **Posted:** Thu Feb 21, 2008 12:07 am

CDX has been giving hints……………..and test vehicles have been spotted…………..so who knows, maybe by the 2008/2009 year we might get one!
[img]http://www.cumminsforum.com/forum/images/smilies/00000004[1].gif[/img]

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[img]http://www.cumminsforum.com/forum/images/smilies/93C_peelout[1].gif[/img]

retmil46 · **Posted:** Thu Feb 21, 2008 4:34 am

Guys, they already make diesel JK Wranglers - we just can't buy them in this country.

While in TX over the holidays, we were checking things under the hood of my friend's '08 JK Unlimited. The decal for the refrigerant charge weight for the A/C system listed weights for two different engines - the 3.8 V6 and a 2.8 L diesel.

We just need to convince them it's worth their time rigging up the beast to pass emissions, and that we're willing to pony up the money for a diesel option. You'd think with the way our KJ CRD's flew off the lots it would be a no-brainer for them.

On one of the JK forums, one thread took a poll asking people to choose what Chrysler DIDN'T get right on the new JK. 55% of the poll takers selected "no diesel option" as their biggest gripe. 2nd most popular response with 15% was "better fuel economy". Taken together, you could say that basically 70% of the respondents were asking for an oil burner.

retmil46 · **Posted:** Thu Feb 21, 2008 5:20 am

Reflex wrote:

There are dozens of Prius' operated as shuttles around my work HQ. They typically average 34-36mpg, which I just didn't find all that impressive. Most the people I know with TDI's claim at least 40mpg on average, although what mix of city/highway driving that is I don't know. The tax breaks certainly do change the equation to some degree, although with the higher long term maintience I think a TDI would still be a better investment(as well as a better car). But I guess an argument can be made either way...

That mirrors what I've seen and heard as well. I've spoken with several people that considered a Prius when shopping for a new car. Same story each time - while city stop and go driving could kick the average up above 40 mpg, when it came to sustained high speed highway driving it fell flat on it's face and mileage dropped into the mid 30's at best.

No surprise there really. With highway cruising, regen braking is doing absolutely nothing for you. Neither is the auto shutdown and restart feature on the gas engine which shuts it down at traffic stops of more than a few seconds - and truth be told this is where the lion's share of city fuel economy improvement is gained, not thru regen braking as many believe.

Mid 30's highway is also pretty much in line with the fact that the Prius uses the same gas engine as the Toyota Yaris, a smaller economy car rated for high 30's highway - and about 12 grand cheaper.

Over the past couple of years, I've started seeing several reports in the media of hybrid owners who's driving cycle cosisted of mainly highway driving complaining that their real world fuel mileage fell far short of what was advertised, to the point that I was starting to get the feeling that there was a backlash building against the "hybrid hype" as some put it.

KeighJeigh · **Posted:** Thu Feb 21, 2008 11:16 am

Concerning the Prius vs TDI: They are completely different beasts. I would have chosen the TDI (and almost did except for lack of 4x4 which is required for my mountaintop driveway) because I could fill it with BD and get great mileage. My mom almost bought one as well....but after trying out both extensively, she went with the Prius. Why? Because it is far quieter, there is no rattle, the engine stops when not needed, it is full of advanced electronics and it is a ULEV which means very little is actually coming out of the tailpipe - it is clean as hell. The TDI is more about for performance which at 75 she really doesn't care about. So, it was not for "political" reasons (unless you want to claim environmental concern to be "political) it was simply what she wanted to drive and has been immensely happy with it ever since. Her mileage is consistently in the low 40 to mid 40s.
I have been calling for a diesel hybrid for years as it seem like a no-brainer. Algae production and diesel hybrids: A recipe for success. And then go the next step and mess with the charging circuit, specify rechargeable lithium Ion batteries and make it into a plug-in hybrid. Many people are already doing this with their Priuses which means about 35 miles before the engine needs to start. Pretty dang neeto!

Reflex · **Joined:** Mon Jan 29, 2007 8:48 pm **Posts:** 567

Lithium Ion is really bad for transportation uses, thats why its not in current hybrids despite its advantages over nickel metal hydride. For one, if cells get punctured it will erupt into a ball of fire, and there is no easy way around that without adding a ton of internal shielding and weight, which negates its advantages.

I also disagree with the plug in concept for most of the country simply due to how the power is generated, your doing the environment a disservice if your power is generated by coal or gas. That said, in the northwest our situation is unique where most of our power comes from hydro and nuclear(over 70%) so in this region a plug in concept is not a bad idea, provided we have the electric capacity to do so.

The main reason, btw, that diesel hybrids have not caught on is because it would require a different hybrid setup(series hybrid) since starting and stopping a diesel engine is about the worst way to be efficient, diesels run best when hot, letting them cool off reduces their mileage significantly, and would negate most of the savings from a hybrid. That said, there is some hope in the series hybrid concept(ie: electric car with a constantly running low rpm diesel generator).

Threeweight · **Joined:** Mon May 14, 2007 5:57 pm **Posts:** 679

On Prius highway mpg, my friends' experience (and my experience driving them) is that it has a great deal to do with speed and tire selection/tire pressure.

A Prius pushed at 75-80 mph with tires aired to 35 PSI will struggle to hit 35 mpg. A Prius cruising at a mellow 65 mph with tires aired to 44 PSI will hit 40+ (at least that is what the computer says when I drive them). The Jetta TDI has the advantage of being a diesel and being geared taller... ours still returns 40+ mpg at 70-75 mph. Tire pressure seems to make much more difference with these vehicles than our CRD (my guess is because our CRD starts at such a huge disadvantage due to weight, mechanical friction and aerodynamics.

On plug-in hybrids and electricity generated by fossil fuel plants, I'd love to see any evidence that such an arrangement is a net harm to the environment vs. the equivalent in emissions from standard hybrids running the gasoline engines. Even the nastiest coal fired plant pales in comparison to the total pollution generated by the number of car engines required to produce an equivalent amount of energy. It sure would be better if the electricity came from clean sources, but the only anti-plug-in arguments I've seen have lacked any sourcing to back up the claims.

Reflex · **Joined:** Mon Jan 29, 2007 8:48 pm **Posts:** 567

Well I don't have a bunch of sources sitting around on that, but its been brought up many times by reputable environmental organizations in active discussions. The Sierra Club has expressed that concern locally here in the NW, for instance. The problem is that a 'clean coal' plant could concievably do better, but the vast majority of our plants are ancient, some as old as a century, and they definatly are not even close to clean. Burning gasoline in the engine is cleaner since it gets to use a catalytic converter to clean it up, while many of the old coal fired plants have only the retrofits to emissions required by law and that are possible with their plant design.

Once again thats not so much an issue in the NW, but on the eastern seaboard, its a huge issue.

dieselenthusiast · **Posted:** Thu Feb 21, 2008 7:42 pm

http://www.caranddriver.com/reviews/hot ... age-4.html

Biodiesel - MYTH or FACT?

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