VW Jetta GL TDI vs. Toyota Prius in new Popular Mechanics

Re: VW Jetta GL TDI vs. Toyota Prius in new Popular Mechanic

I think that particulates are a health issue for asthma and other pulmonary conditions as well. I think these sorts of problems can be solved though we just need the will. I would still prefer a fuel cell car powered by renewable energy sources, solar, geothermal, tide generators and low head water, wind etc. Keep the oil in the ground.

 

There does appear to be some misconceptions on how modern diesel motors work.

The old fashioned mechanical rotary injection pump worked as described above: depending on pump timing, more power required much more fuel to be "dumped" through the mechanical injectors. That created the cloud of black smoke when accelerating.

At idle is when a diesel is remarkably efficient. It's just an air pump, as there is no throttle blade in the air plenum. A diesel motor at idle runs very lean. For constant speed and constant loads, a mechanical system wasn't too bad.

Most modern diesel motors use some sort of electronic unit injector. Some of these are "fired" by using oil pressure, an electronic solenoid turns the oil pressure on or off, and that moves the plunger to operate the fuel injector. It's easier to control a flow of motor oil at 60psi than a flow of high pressure fuel. The actual diesel fuel is under very high pressure, way over 5,000 psi.

Other unit injectors have a miniature pump/plunger system that is pumped by a lobe on the camshaft. The "base" timing is done with the camshaft and the more precise timing is done with an electronic solenoid valve on the injector itself.

A good example of this is the electronically controlled Cummins ISX HD diesel motor with variable geometry turbocharger. Another example using similar technology is the MAN engine used in European MAN trucks.

Modern LD and HD diesel motors are entirely electronic control. The PCM monitors crank angle, cam angle, ambient temp, motor temp, fuel pressure, load, knock, exhaust, etc etc. The electronics are used to very precisely time the injection of fuel to eliminate most particulates.

Most modern electronic diesel motors also use "pre" injection or "pilot" injection, where a much smaller pulse of fuel is injected before the main pulse of fuel. This has been found to aid in efficiency, reduction in emissions especially NOx, and reduction in that God-awful diesel clatter.

To further reduce NOx, a water-cooled EGR system is used to feed some exhaust gas into the intake manifold. With sulfur-free diesel fuel, a very effective catalytic converter can be used to take care of the rest.

Just like with gasoline cars, you'd still have high emissions if not for very effective catalytic converters.

I personally like diesel motors. The only problem is in the climate I live in, they need to be plugged in all the time.

 

All true. And you're right that I had forgotten about modern high-pressure diesel injection systems.

Nevertheless, the lowest emissions
"modern" diesel automobile engines currently on the US market (mostly VW TDIs) are catagorized as "Federal Tier 1" for emissions purposes. Most barely pass this standard, though manufacturers are gearing up for "Tier 2" compliance in 2007 once low-sulpher diesel is mandated in all states. This is reasonably low, true enough, though still higher than even the fairly lax CARB LEV standards.

However, comparing Federal Tier 1 to CARB SULEV gasoline vehicle standards we can see a 97% reduction in hydrocarbons, a 75% reduction in CO, a 97% reduction in NOx, and a 90% reduction in particulates.

 

Re: VW Jetta GL TDI vs. Toyota Prius in new Popular Mechanic

When you compare VW diesel models sold in North America and those sold in Western Europe, the European models achieve far stricter Euro3 and Euro4 diesel emissions standards.

Due to the sulfur content of North American diesel fuel, the emission control system isn't near as effective. If you ran a European market VW on North American diesel, the Check Engine would turn on and you would ruin the emission control system.

This reminds me of the raging debate we once had over getting the lead out of gasoline. The Fed demanded it, carmakers whined a bit but redesigned the intake valve seats to prevent erosion, and a certain large chemical company claimed lead was GOOD for us.

Ethyl Corp.

This is the same Ethyl Corp that has somehow convinced the Canadian gov that MMT (Methylcyclopentadienyl Manganese Tricarbonyl) is GOOD for us when used as an anti-knock additive. Despite the fact it's banned everywhere else, and every major automobile manufacturer warns about bad effects on the emissions system if you use it.

Just the fact that Canada allows the use of MMT means that Kyoto Compliance is impossible. So it's really hard to move an issue forward when key decision makers appear to have their head stuffed in a yellow-stained snowbank.

 

Re: VW Jetta GL TDI vs. Toyota Prius in new Popular Mechanic

That's great, but if you look (carefully, since the board unformats it) at the following table, you'll see that the euro 3/4 diesel standards are still 2-3x that of the Euro 3/4 gasoline engine standards (except for CO).

I'm glad to see that the particular standards are tightening up quite a bit. Still high (depending on how you define "particulate", but tighter. I suspect they're tight enough that they'll need to start using filters, which should prove interesting.

However, it's also worth noting the CARB SULEV standards met by the Prius:
HC: 0.006 (~1/10x the Euro4 Diesel standard, though that's complicated by the fact that they only have an NOx+HC standard for diesels), CO: 0.6 (1.2x), NOx: 0.01 (<1/25x), Particulates: 0.006 (< 1/4x).

All units are g/km (converted from g/mile for SULEV).

Tier Date CO HC HC+NOx NOx PM
Diesel
Euro 1† 1992.07 2.72 (3.16) -0.97 (1.13) - 0.14 (0.18)
Euro 2, IDI 1996.01 1.0 - 0.7 - 0.08
Euro 2, DI 1996.01a 1.0 - 0.9 - 0.10
Euro 3 2000.01 0.64 - 0.56 0.50 0.05
Euro 4 2005.01 0.50 - 0.30 0.25 0.025

Petrol (Gasoline)
Euro 1 1992.07 2.72 (3.16) - 0.97 (1.13) - -
Euro 2 1996.01 2.2 - 0.5 - -
Euro 3 2000.01 2.30 0.20 - 0.15 -
Euro 4 2005.01 1.0 0.10 - 0.08 -

 

So that may be the real reason rental places in NY won't let you take their cars in Canada.

 

Re: VW Jetta GL TDI vs. Toyota Prius in new Popular Mechanic

Dan:

Hasn't NY state adopted the stricter CA emissions? A few years back my Aunt and Uncle from San Fran visited me, then drove the TransCanada all the way to Vancouver before driving south back to San Fran.

Their Check Engine came on in Alberta and stayed on. Back home, their local Nissan dealer claimed running the Canadian gas damaged the O2 sensors and the catalytic converter.

It was an expensive repair not covered by warranty.

 

Re: VW Jetta GL TDI vs. Toyota Prius in new Popular Mechanic

Yes, they have, along with Masschusetts, Maine, and Vermont.

And 1.5 years from now, the other 45 states will too... which is why VW recently announced that every single diesel vehicle they sell in the United States will have a major emissions upgrade before then. Otherwise, they would be prohibited from selling them.

So expect a price increase and a efficiency decrease. Unfortunately, we likely won't know how much or how little that will be for awhile still. The actual emission rating achieved (ULEV, etc.) hasn't been revealed yet either.

 

Re: VW Jetta GL TDI vs. Toyota Prius in new Popular Mechanic

Ray:

It's important when comparing emissions standards to compare apples to apples. That is, a giant SUV like the Ford Excursion is classified as an LEV. Compared to what, a car or a similar size SUV?

The Europeans are more concerned, at this point, with CO and NOx. True, particulates are bad too. Diesel motors also emit lower CO2, and CO2 emissions may contribute to Global Warming.

Let's compare a European mini like a VW Lupo 3L: it has a tiny 3 cylinder turbodiesel and is rated for 3 liters per 100km, or around 94 mpg imperial gallon. Around 78 MPG U.S. gallon.

Considering how much less fuel it uses, I wonder if the emissions would compare favorably to the Prius? The Prius in Europe is rated for CO2 emissions at 104 g/km. The Lupo is rated 85 g/km CO2 emissions.

http://showrooms.volkswagen.de/vwcms_publi...eset_outer.html

For the climate I live in, a diesel isn't a very practical choice. That said, diesel motors offer some very distinct advantages over gasoline motors. I would love to see Toyota develop a Prius with a small 3 cylinder turbodiesel, as they already offer a small diesel in the European Yaris.

 

Re: VW Jetta GL TDI vs. Toyota Prius in new Popular Mechanic

Lupo doesn't qualify for sales in the United States, since it lacks a number of safety requirements.

Adding them would sour both the efficiency and the price, as well as the acceleration.

 

Re: VW Jetta GL TDI vs. Toyota Prius in new Popular Mechanic

John:

How can VW possibly meet the proposed Federal emissions requirements with sulfur levels where they are right now? That is, around 300 ppm when the fuel will require less than 10 ppm?

VW had a Lupo do a cross-country tour around 4 years ago, and they had to supply it with European diesel. The test drivers were warned under NO circumstances to try to add American diesel fuel, as it would ruin the emission components.

 

Re: VW Jetta GL TDI vs. Toyota Prius in new Popular Mechanic

I don't think VW will meet the requirements until the new fuels are available. Once they are, I think the newer technologies in the latest generation of VW Diesels will bring them in line with regulations.

If anything, the engines should become more efficient (thainks to the new injectors) and somewhat more powerful (injectors here as well).

 

Well, I don't live there anymore, but I had gone to a reunion in Canada, where many of my relatives live in NY. They wanted to rent a car to go to Canada, but couldn't. I was considering flying to NY, then renting a car and drive to Canada, but comparing cost vs. travel time, it didn't make sense, so I didn't even try that route. Then hearing from my relatives, I wouldn't have been able to take that route, and now I see why.

Its kind of sad that a neighboring country that US residents frequently drive to would be damaging their cars.

 

Re: VW Jetta GL TDI vs. Toyota Prius in new Popular Mechanic

Jonny:

In Europe, VW's new PD turbodiesel motors have improved economy, lower emissions, better drivability, etc.

When the PD motors came here last year, the overall MPG went DOWN. VW had to dramatically detune to compensate for the +250 ppm sulfur in our diesel.

The similar pump unit injector in HD trucks has brought improvements to economy, lowed emissions, and improved drivability.

Now if they can only get the sulfur out of our diesel ...

 

Dan:

Tell me about it. I HATE renting cars at airports! It's a complete zoo I swear I'd sooner hitchhike. Argh.

If you think Canuck gasoline is bad for your car, how about Mexican fuel?? Yikes ...

 

Re: VW Jetta GL TDI vs. Toyota Prius in new Popular Mechanic

This is not a chicken or egg issue.

The federal emission requirement will not begin until *AFTER* the low-sulfur requirement is already in effect.

 

Re: VW Jetta GL TDI vs. Toyota Prius in new Popular Mechanic

Just wait till they combine diesel and hybrid. I would guess at 70 miles per gallon could happen.

 

Apples to apples? I can't read German but the Lupo looks like half the car the Prius is.

 

Re: VW Jetta GL TDI vs. Toyota Prius in new Popular Mechanic

They already did, 5 years ago.

Do a search for the "PNGV" prototypes. The most efficient achieved 72 MPG. Unfortunately, every trick in the book was used... including sparing no expense. Like a fuel-cell vehicle, it worked but was far too unrealistic for practical application.