First Drive: 2008 Volkswagen Jetta TDI - Previews

darkscout said:

That's what every on high way truck manufacturer is doing (that I've seen). Cummins and DDC are using dosing, Caterpillar is using their own "CRS" system to elevate exhaust temps.

Is there a scheduled ash removal period? Burned oil creates ash. The ash doesn't burn off in the DPF and accumulates, which means that after time it has to be removed.

It's a nightmare to say the least.

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CAT's CRS (Caterpillar Regeneration System) is a "burner" that sits at the outlet of the low-pressure turbo. It has: A fresh air connection, a compressed air connection, 2 coolant connections, a diesel fuel connection, and a spark plug. It attemps to light a flame, keep it lit under varying engine conditions, and use that flame to provide heat to burn soot in the filter.

I'm skeptical, to say the least. You are correct about Cummins, DDC, and Volvo, they all use a doser/DOC/DPF arrangement. In fact, they all use a Cummins Filtration filter. Volvo uses the Cummins turbo, as well.

Ash removal is on a ~400,000 mile time-table, depending on duty-cycle.

moondawg

MrMopar said:

The new engine will probably monitor back pressure of the exhaust stream to judge when it is time to rejuvenate the particulate filter.

If that be the case, easy mod for higher fuel economy:
Step 1: Cut DPF out of the exhaust
Step 2: Install straight pipe replacement
Step 3: Save on fuel costs, maybe more HP from less back pressure

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You'll definitely get a CEL for that one. I wouldn't be suprised if you get a derate as well. The system will be smart enough to detect a lack of backpressure, even if you leave the sensors in tact.

The sensors will be smart enough to realize backpressure never changes, even if you put a restrictor plate in place of the filter to try and fool the dp sensor.

BMW and Audi have both had phenomenal success with running DPFs in race conditions. They will not be a significant hinderance to performance.

moondawg

READ IT, UNDERSTAND IT BECAUSE THIS IS HOW THE NEXT TDI WILL WORK

The bold text are my additions... Great explanation!

moondawg said:

You won't need it, because the Common Rail system can be made to fire during the exhaust stroke, which does the same thing.

And yes, they will likely be injecting some fuel into the exhaust.

The DPF(Diesel Particulate Filter) systems used to trap soot work by storing all of the little soot particles and burning them off all at once. These systems require ALOT of heat to completely burn the soot. To get this heat, many systems utilize a DOC(Diesel Oxidation Catalyst) to help burn fuel injected into the exhaust stream. In order to help this process along, most systems use some sort of intake or exhaust throttle to provide some extra load on the engine to generat more heat.

So, the process goes generally like this:

1. Measure pressure across the DPF {back pressure sensing in the exhaust, post turbo}, notice that it is getting clogged with soot.

2. Tell engine to go into "generate more heat" mode.

2a. Injection timing can be retarded to increase the catalytic temperatures to reduce the number of burn-off cycles
2b. Secondary injection initiated by the CRI system injects multiple injections of fuel (as reqd to achieve the optimum catalyst temperature) into the exaust stream leaving the cylinder. This results in a rise in exhaust gas temperatures triggering a "Burn-off-cycle"
2c. Cycle continues only as needed to maintain the temperatures and only until the back pressures are reduced to optimum.

3. Once exhast temps are high enough, start injecting fuel.

4. Hot exhaust and fuel hit DOC, get even hotter.

5. Resulting hot gasses burn off soot.

5b. This same process is required when using AdBlue to further scrub NOx. SCR technology requires higher than normal temps in the exhaust stream to maximize the effectiveness of urea injection.

6. Measure pressure across the DPF, notice that filter is clean. Stop process and wait for soot to build up again.

Wash, rinse, repeat.

moondawg

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DB

Waldek Walrus said:

On the other hand, how much is this "hotter" exhaust cycle to burn off the NOx and particulates in the trap going to cost in fuel economy?

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If it's like the Honda about a 3-4% hit to economy.

lbhskier37 said:

I wouldn't think this extra late injection is going to cause a significant increase in fuel consumption. All 2007 heavy trucks are using the same thing to regenerate their particulate filter, and in all the articles I have read, equipment manufactures are claiming fuel consumption is down over 2006 models. This extra injection doesn't happen every cycle, and it doesnt have to be very big, it is basically just sending a big flame out the exhaust port whenever the DPF needs to be regenerated. This technology is in every 2007 onroad diesel engine and has been in the works for years, if VW did their homework this should be pretty mature by spring '08. By then the trucking and equipment industry will have over a year and millions of miles on the stuff.

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Depending on your regeneration duty-cycle, the extra fueling can be a noticable penalty. Most engine makers are using their 2004 base engine for 2007. That means they've had extra time to tune the engines for base engine fuel economy improvements to offset the increased fuel they're using for DPF regeneration. In some cases, they've also offset the penalty for ULSD (about 1%)

And exhaust-cycle injection on the common rail systems does NOT send a flame, just hot fuel. The fuel then "burns" when it hits the DOC.

The trucking industry ALREADY has millions of miles on these systems. In short, they work.

moondawg

Drivbiwire said:

READ IT, UNDERSTAND IT BECAUSE THIS IS HOW THE NEXT TDI WILL WORK

The bold text are my additions... Great explanation!



DB

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thanks. Thanks also for the specific info on the VW system. I can only speak in general terms because they're all MOSTLY the same.

moondawg

Westro said:

Look at the new 6.7L Cummins in the Dodge. They have two pressure sensors before and after the trap. I am guessing that VW will follow along the same lines.

http://www.turbodieselregister.com/forums/showthread.php?t=172361

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It's actually one sensor, a delta-pressure sensor. There are also thermocouples to monitor the temperatures in the DPF and DOC to make sure everything is burning at a controlled rate. (If you burn too fast, the soot burn can run-away and crack the filter substrate. not good)

moondawg

(Edited to change "to fast" to "too fast")

darkscout said:

Originally Posted by MrMopar
I used to work at a Wal-Mart oil change place for 3 years while in college, so I've read some documentation about how the new DPF traps on semi-trucks are going to need full cleaning overhauls on a schedule of something like every 400,000 miles or so. Obviously the trucking industry is not thrilled with yet another expense.

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That's a good explanation you posted about other heavy-duty engines - garbage trucks, etc.

I do have a problem when you took my post, and stitched two unrelated items together into a quote that wasn't in my post. My employment at Wal-Mart was unenjoyable, but paid for college. And that employment had nothing to do with the market information I've read about DPF traps on new heavy-duty trucks. Please don't portray my intellegence in that manner again.

When I visited the International Auto Show in Detroit a couple of weeks ago, I asked a VW rep about the 2008 TDI. He said the Jetta should be available this summer (2007), at the start of the 2008 "model year". Fuel economy he said would be around 50 mpg (US) with the 2.0 L 140 hp cr-tdi engine. I sure hope he's right. He also said that the tdi Rabbit would be somewhat later, but its release date was not yet firm.

bBay said:

When I visited the International Auto Show in Detroit a couple of weeks ago, I asked a VW rep about the 2008 TDI. He said the Jetta should be available this summer (2007), at the start of the 2008 "model year". Fuel economy he said would be around 50 mpg (US) with the 2.0 L 140 hp cr-tdi engine. I sure hope he's right. He also said that the tdi Rabbit would be somewhat later, but its release date was not yet firm.

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I sure hope you are right. I need a car and I'm considering a base Rabbit 2.5......................sheeit...........what to do.

MrMopar said:

I do have a problem when you took my post, and stitched two unrelated items together into a quote that wasn't in my post. My employment at Wal-Mart was unenjoyable, but paid for college. And that employment had nothing to do with the market information I've read about DPF traps on new heavy-duty trucks. Please don't portray my intellegence in that manner again.

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Sorry. long day at work. Some reason I thought you mentioned something about cleaning cycle. I fixed the post.

When I started working here I didn't even know we made on-highway truck engines. Then I just concentrated on my job.

I just got rotated to on-highway marketing. There are things and markets I've never considered before. Especially with stuff like emergency vehicles, stuff *always* has to work.

moondawg said:

Ash removal is on a ~400,000 mile time-table, depending on duty-cycle.

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Given the marketing material I've seen for Cummins and DDC that is *very* optimistic.

I wish our CRS stuff would go to publication so I could post pictures here without fear of losing my job .

I do have to say there's no reason to be skeptical. Anyone going to MidAmerica in Louisville in March should stop on by, we're going to have some kick *ss displays.

Any speculation as to how well the '08 TDI's will tolerate biodiesel?

darkscout said:

Given the marketing material I've seen for Cummins and DDC that is *very* optimistic.

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Ooops. you're right. 400k is the top end of the "estimated" range.

google turned up this: http://www.cleanairfleets.org/documents/EdJohnson.pdf

Which even has a picture of an ash cleaning machine, along with Oil specs, and pretty pictures of DOCs and DPFs!

moondawg

moondawg said:

400k is the top end of the "estimated" range.

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Us engineers, always 'estimating'.

Nice. Grabbed this graph for those asking about each of the On-Highway reductions. I wish I could find one for passenger vehicles.

yeah, notice that on a percentage basis.... the reduction in NOx for the next 3 years is roughly equal to the reduction over the past 13 years.

It's going to get alot harder to chase that last bit of NOx and PM.... at some point it's going to start impacting fuel economy more and more.

moondawg

bBay said:

When I visited the International Auto Show in Detroit a couple of weeks ago, I asked a VW rep about the 2008 TDI. He said the Jetta should be available this summer (2007), at the start of the 2008 "model year". Fuel economy he said would be around 50 mpg (US) with the 2.0 L 140 hp cr-tdi engine. I sure hope he's right. He also said that the tdi Rabbit would be somewhat later, but its release date was not yet firm.

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I'm holding out for a new Passat TDI. I wonder if they'd bump the power for that application in the heavier car? The euro-spec 170hp motor would be nice

The 140 hp engine will do just fine in a Passat. I believe the torque numbers between the 170 and 140 hp engines are nearly identical. In fact even the 105 hp engine will allow a Passat to cruise at extra-legal speeds effortlessly in this country, though it might be a bit peaked with a heavy load and bikes on the roof rack.

moondawg said:

yeah, notice that on a percentage basis.... the reduction in NOx for the next 3 years is roughly equal to the reduction over the past 13 years.

It's going to get alot harder to chase that last bit of NOx and PM.... at some point it's going to start impacting fuel economy more and more.

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That last bit of NOx is pretty darn small compared to what has been removed from emissions already. The low hanging fruit has been picked. I think that's why 99% of rational people say enough is enough, and fault the EPA for setting diesel emissions just a bit too tight in a misguided attempt to reach the impossible zero level.

I personally think the time has come that the EPA really needs to consider other gains that can be made. We're at the tipping point where better returns can come from reducing fuel consumption rather than focusing more tightly on emissions. With emissions as low as they are, the increases in overall emissions will come from more vehicles being driven as the population expands. The decrease in emissions is a downwards curve that is starting to flatten out big time.

My alma mater has a big splash on their web site about the RAM/Cummins 6.7 combination meeting the 2010 truck emissions standards. I wish they swouldn't do that, it just encourages the EPA!!!!

John C

MrMopar said:

That last bit of NOx is pretty darn small compared to what has been removed from emissions already. The low hanging fruit has been picked. I think that's why 99% of rational people say enough is enough, and fault the EPA for setting diesel emissions just a bit too tight in a misguided attempt to reach the impossible zero level.

I personally think the time has come that the EPA really needs to consider other gains that can be made. We're at the tipping point where better returns can come from reducing fuel consumption rather than focusing more tightly on emissions. With emissions as low as they are, the increases in overall emissions will come from more vehicles being driven as the population expands. The decrease in emissions is a downwards curve that is starting to flatten out big time.

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I don't fault the EPA for setting more restrictive emission levels. It is the only way to get automakers to improve emissions. The EPA's mandate is to set emission regulations to what the technology allows. It my mind the EPA has been far too slow to act.

The EPA only regulates what they are allowed too. If you set CO2 has a pollutant, than the EPA can affect mileage. Currently the only body that can mandate fuel economy is the US Congress and they have done nothing for the last 2 decades.

As for the 2008 TDI Jetta, I'm not interest at all. The current Jetta is the size of the last Passat, which is far to large of a vehicle for my needs. If they bring over the Polo TDI they might keep a customer, but nothing in the current lineup interests me.

There is likely nearly as much solids released from tire wear as there is from a well maintained modern diesel

lets see, I guess 8mm tread depth over 60000 miles, 205 mm width, starting diameter approximately 324 mm, density of rubber about .92g/cm^3, and about 60% of the face is rubber, gives me about 1820 grams of rubber, four tires=7280 grams PM, whereas a 100hp engine can emit 1000 grams over 60000 miles at an average speed of 60 mph


Well, that is a lot of rubber, I am surprised myself. I also think that more than 60% of the face is rubber. How them latex allergies treating you, you poor bast*rds? (the royal you, not anyone in particular ). That is not to mention the materials pulverized off of the roads.

That is an absurdly low amount of PM emissions, and I wonder if those are only 10 micron, or if they are also measuring the sub 2.5 micron. i have heard that gassers release a surprising amount of fine PM. Don't get me wrong, I am a tree loving country boy who likes clean air, but wow.





See that? clear over there? That is the original topic of this thread. See how far we have come?


So yeah, the 2.0 TDI CR sounds like a dream. I wish they would apply the tech to a car that looked less like a Camry. Also, I would gladly deal with 90 HP for 60-65 real MPG.

MrMopar said:

That last bit of NOx is pretty darn small compared to what has been removed from emissions already. The low hanging fruit has been picked. I think that's why 99% of rational people say enough is enough, and fault the EPA for setting diesel emissions just a bit too tight in a misguided attempt to reach the impossible zero level...

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I trust our EPA as far as I can throw them all with a broke arm. The emission standards for diesels are impractical at best and the expectation that these low emission cars work RIGHT and RIGHT as consistantly as a gasser are older diesels should be low.

I dont believe the US will be allowed to have cars that get 40 - 75 mpg, there is too much money in congress to allow for this to happen.

That's why we have to use the grey market, and the 25 year loophole. Only four more years until you can legally get a diesel Polo in the US...

The EPA may very well be the only body to influence the car,and got that power through an associative. They are smokestack watchers, and cars have smoke stacks. 75mpg is a moral question; MPG is not an exhaust measurment. There's the con, the confusion. They don't care if your car does 30 and gets 1mpg. The eastern world it is exploden.

I tend to agree: the emissions standards should be the same regardless of fuel: only so many grams per mile. Per vehicle class I should say: a buss that carries 100 people should be allowed more than a passenger car, and big trucks certainly accomplish more work per mile also.

The only difference being, if, on a large scale, overal emissions are reduced by allowing a bit more in one area, then it makes sense to have special limits. For example, let's pretend that a diesel vehicle could somehow run on biodiesel only--as in, it has a sensor that detects biodiesel versus D2, and won't run on bio. [Let's ignore legalities here of what to do if D2 is added--just run with me for a moment. Or think about some magical fuel to be invented tomorrow.] We know that CO2 emissions drop dramatically with bio usage, and it can help American farmers, and it can reduce imported oil. On the large picture, the slight increase in vehicle output NOx may well be balanced by the drop in other emissions. So, this biodiesel-only vehicle ought to have a higher NOx limit, since the overal emissions are better.

Actually, I have to wonder if NOx wouldn't go down also: I mean, what's the extra NOx emissions of the tankers as they cross the ocean? They run some high sulphur fuel IIRC, dunno about their emission control systems. How can the emissions of transport (Middle Eastern oil versus homegrown fuel) be compared, so as to give good comparasions?

Gettin50MPGs said:

I dont believe the US will be allowed to have cars that get 40 - 75 mpg, there is too much money in congress to allow for this to happen.

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We had that car for 7 years. The 2000 Honda Insight was rated at 61/70 mpg. The 2006 was rated at 60/66 mpg. Americans just didn't buy it so it has been discontinued. No secret government hand at work here, just economics.

PlaneCrazy said:

The 140 hp engine will do just fine in a Passat. I believe the torque numbers between the 170 and 140 hp engines are nearly identical. In fact even the 105 hp engine will allow a Passat to cruise at extra-legal speeds effortlessly in this country, though it might be a bit peaked with a heavy load and bikes on the roof rack.

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I drove an '05 Passat TDI wagon at a dealer last year and thought it had good acceleration. But, since when is more power a bad thing? (ask any owner of a new 600hp Viper or Z06 Vette) Regardless of what engine VW puts in there's always the aftermarket for ECU chips and injector nozzles.

How will the emissions be checked going forward? Currently, for example, NY state inspection is just a visual test for smoke on my 2003 Jetta Wagon TDI. No biggie, and will stay that way since tests are not backward compatible. If they actually start testing for 2008 TDI emission limits annually at state inpection, it could be costly to maintain I would assume.

I look forward to EPA viewing CO2 as a pollutant that will be weighed equally in the trade-off with NOx and HC, in terms of overall emissions.

Meanwhile I am having flashbacks to the mid-70s... before the three-way cat and fuel injection/Oxy Sensor feedback were perfected. We suffered a generation (well okay, 1/3 of a generation) of unreliability and poor driveability.

Luckily the tech came along to clean up the gas engine AND improve performance and reliability. I wish I was as hopeful that the tech will come along for the diesel and save us from the wasteful kluge that's been described above (burners, sensors, plumbing, and controls)... however they've been working hard on this stuff for ten years or more, and perhaps this really is the best they can come up with. Until CO2 is weighed equally as a pollutant, at any rate...

Eddy

I'd like to see how much mpg they could wring out of the thing at 120 hp, or even 100. I spend a lot more time cruising than accellerating. I've never felt short of power in my '04 Golf. Overall, I'd rather drive a slow car fast than a fast car slow. So I'm sorry they're taking this approach. Maybe what I really desire is a Polo TDI?