Which is better: DPF or AD Blue?

FormerOwner

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I want to hear from the experts here. I am in the market to buy a TDI next year... I want to know which system is better for a 5-10 year ownership cost.

I'll take any and all opinions... !

Shawn
 

VeeDubTDI

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AdBlue gives you significantly better fuel economy because there is no (or less) post injection to keep the emissions components hot.
 

Fixmy59bug

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Pro to DPF:

You do not have an additional purchase (exhaust fluid). Albeit the exhaust fluid is <$20 every 10k miles or so.

Pro to AdBlue:

Since there is no post combustion injection, the likelyhood of fuel washing past the rings to dilute the oil is greatly lessened. Major plus if you want to run >5% biodiesel.

Con to AdBlue:

If you allow the AdBlue tank to run empty, the vehicle will not start.
 

JSWTDI09

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Your choice is not DPF or AdBlue. All modern diesels will have a DPF. Your choice has to do with how Oxides of Nitrogen are handled. Lighter weight cars can get by with a NOx storage catalyst (Golf and Jetta), while heavier vehicles need (Passat, Mervedes, etc.) require an SCR (Selective Catalytic Reduction) system. SCR systems require a Urea (AdBlue) injection system. There are advantages and disadvantages to both as previously stated. SCR systems do not require post combustion fuel injections, but they do require AdBlue injections.

Have Fun!

Don
 

740GLE

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Pro to AdBlue:

Since there is no post combustion injection, the likelyhood of fuel washing past the rings to dilute the oil is greatly lessened. Major plus if you want to run >5% biodiesel.
As stated before Adblue systems still have DPF so there will still be post combustion ignition, so there is still potential for oil dilution and still held to the same B5 max limit as non adblue systems.

Another Pro for adblue is the egr system and IC set up is better designed and *should* be less prone to issues.

The CEBA and CJAA use very very heavy EGR to keep NOx down, and the NOx catalyst happy.
 

FormerOwner

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Sounds like Ad Blue is for me... I have read about numerous DPF problems with TDI's, and also with the 3/4 ton medium duty diesels (i.e. Cummins in Ram Trucks, Fords, etc.) I'd prefer to keep my vehicle on the road without the horror stories.
 

Fixmy59bug

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As stated before Adblue systems still have DPF so there will still be post combustion ignition, so there is still potential for oil dilution and still held to the same B5 max limit as non adblue systems.
You guys are right about there still being a DPF.

But are you sure the DPF is cleaned using post combustion injection? I thought that was the whole point of the ad blue. The ammonia in the fluid chemically scrubbed the filter and broke down all the soot. And the lack of post combustion injection is what contributed to the better fuel mileage of a heavier car.

I could be wrong, but I am pretty sure that is how the DEF system differed from the light vehicle system.

Of course, despite this, Vw will still only allow < 5% biodiesel usage under warranty. So if you want to run more, it is at your own risk.
 

GoFaster

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The method of soot control and therefore DPF regeneration is independent of the method by which NOx is controlled. For the driver who putters around slowly, it is still occasionally necessary to raise the exhaust temperature (more specifically, the oxidation-catalyst temperature and therefore the DPF temperature) to regenerate the DPF.

The only influence on the DPF will be secondary effects because of the method of de-NOx regeneration used on the car which does not use SCR (and AdBlue).

The de-NOx catalyst is regenerated very frequently (every few minutes - much more frequently than DPF regeneration) by operating the engine with a slightly rich exhaust stream for a few seconds at a time. This is done on the VW's by momentarily increasing the amount of EGR (which reduces the amount of air).

Running a diesel engine in that manner can be expected to produce more soot which the DPF has to capture and eventually regenerate.

Not having to do that ... ought to be better.

The AdBlue system allows the engine to be calibrated more efficiently.
 

740GLE

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You guys are right about there still being a DPF.

But are you sure the DPF is cleaned using post combustion injection? I thought that was the whole point of the ad blue. The ammonia in the fluid chemically scrubbed the filter and broke down all the soot. And the lack of post combustion injection is what contributed to the better fuel mileage of a heavier car.

I could be wrong, but I am pretty sure that is how the DEF system differed from the light vehicle system.

Of course, despite this, Vw will still only allow < 5% biodiesel usage under warranty. So if you want to run more, it is at your own risk.

the urea is injected before the SCR, which is post DPF, so yeah to clean out that DPF you still need active/passive regens of the DPF through post combustion injection

http://forums.tdiclub.com/showpost.php?p=3414844&postcount=669
 
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740GLE

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Sounds like Ad Blue is for me... I have read about numerous DPF problems with TDI's, and also with the 3/4 ton medium duty diesels (i.e. Cummins in Ram Trucks, Fords, etc.) I'd prefer to keep my vehicle on the road without the horror stories.
You'll still have a DPF. And the system the 2012 Passat uses is pretty much the same design as what the 2011 Ford PS and 2011 Dura Max uses.

(cummins still uses a massive NOx trap to meet emissions and has since 2007 when they saw the writting on the wall)

BTW there are many members her who've put on decent number of miles (60-120K) on their 2009 and newer VW's with DPF with out many issues.
 

bluesmoker

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the advantage of ad blue (urea fluid) is that the egr rate can be turned down increasing the engine efficiency, it also reduces the particulate load in the dpf (more egr = more soot)

basically the adblue destroys the NOx post combustion
 

Max Period

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Cummins now uses SCR for their EPA2010 and Euro 4+ heavy duty engines. (The Ram pickup truck is the only exception, the chassic cab version uses SCR)
 

considering a tdi

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I'm in the market for a 2012 TDI jetta sportwagon as long as it doesn't require the use of UREA!!!! I'm not going to be held hostage by that crap!! Any idea if the 2012 Jetts TDI wagons require UREA??? I sure hope not!!
Thanks,
 

compu_85

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Urea is a better emissions system and costs less to run overall :confused: It's not hard to refill the tank every oil change.

-J
 

Derrel H Green

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No Urea for the Golf/Jetta TDIs

I'm in the market for a 2012 TDI jetta sportwagon as long as it doesn't require the use of UREA!!!!
I'm not going to be held hostage by that crap!! Any idea if the 2012 Jetts TDI wagons require UREA???
I sure hope not!!
Thanks,
:)

As far as I can determine, the 2012 Jettas are mechanically the same as was the 2010 I just sold.

No Urea fluid needed. But you'd be better off if VW did use that fluid, as it is
possible for VW to tune the engine for more power when using the ad blue.

That's why the Passat TDIs have a little more power and slightly better F E also. :p

:D

D
 

VeeDubTDI

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Enjoy your intercooler problems and worse fuel economy with the non-urea cars. ;)

Given the choices in VW's lineup, I think the Passat with Urea is the best option at the moment. 45 - 50 mpg without trying and no intercooler malarkey.

Also not sure what you mean by "being held hostage by that stuff." That's like saying you don't want to be held hostage to diesel fuel or engine oil. ;)
 

GoFaster

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I'd take the Passat with the urea system and no intercooler freezing possibility at the moment, too, but it's in a car that's too big for my needs. Let's see what happens with the next Golf in another year or so.
 

turbocharged798

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If the new golf got urea and got close to 50mpg, I would strongly consider it as a replacement for our pre-CR TDIs. It sounds like a good system overall and is probably better on the engine as well.
 

jbright

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I love my '09 Jetta as it is, but if I could have the same car with urea I'd go that route without hesitation.
 

gergg

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It would be interesting to see the mpg's a Golf could get if it were set up like the 2012 Passat.....I too would prefer the new Passat to any other option currently available from VW here in the states.
 

considering a tdi

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Lots of love for the urea based TDI's here. I just don't like the idea of having it freeze up in the cold weather, running out of it and being stranded in "limp mode", and having 1 more thing to add to the car besides diesel fuel and engine oil. I guess that's my take on urea. I can take a little less HP and mileage gains to not have to hassle around with urea if at all possible.
 

VeeDubTDI

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Understood... I've heard a few stories of Sprinters and other vehicles with frozen urea tanks and the PITA such an event causes. Hopefully this won't be an issue on the Passat, but who knows.
 

740GLE

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heat tape and heated tanks are your friend!
 

Drivbiwire

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Urea vs Non-Urea.

Urea Wins.

Urea based systems work the following way:

VW non -Urea system:



Oxidizing catalyst (like older TDI's) is mounted ahead of the DPF, this provides an initial scrub of Soot, HC, CO and reduces the load on the DPF. This is also installed on the VW small vehicle DPF system. The Oxidizing catalyst is a direct pass catalyst which does not require monitoring for restriction (back-pressure), each passage is open ended and exits at the DPF substrate entry point. Higher loads on the motor increase the efficiency of the Oxidizing catalyst, but only to a point hence the need for the DPF.

Any remaining PM, CO and HC is either trapped or burned off as the gasses pass thru the heated substrate of the DPF. Each passage is a dead end channel This forces the PM to accumulate until being burned off in the filter. Gasses are broken down further as they pass thru the filters substrate to the exit passage leading out of the DPF housing. Since the only gasses can pass thru the substrate you have a near perfect filtering of all solid matter.

By the time the gasses exit they have nearly eliminated all PM and resulting gasses. However because of the lean burn of the diesel it is not possible to fully reduce the NOx hence the SCR.

As the remaining gasses enter the SCR urea is injected based on inputs from a NOx sensor at the exit of the SCR system. The SCR pump will inject the fluid as needed to insure the NOx is completely eliminated out the tailpipe.

Audi/MB AdBlue urea system (first module is the Oxidizing catalyst ahead of the DPF).


The result is Soot free exhaust comprised only of CO2, NO and water.

After all the miles we have put on our SCR cars, the tailpipes remain soot free and appear as if the engines have never been started.

If I had a choice, SCR all the way.

The VW system requires not one or two burn-off cycles but three. Each catalyst requires a separate and individually controlled burn-off cycle thus the hit on fuel economy. In contrast an SCR system only requires a single burn-off cycle which is further reduced with the coexistence of the oxidizing catalyst.

Urea in the ML/GL consumes about 1 gallon per 1500 miles. Consumption is a direct result of fuel consumed and average load. Given the 24 city, 31 hwy fuel economy of both vehicles and their weight the cost of the system works out to about $30 per 10,000 miles in urea cost. If you figure that urea costs about 7.5 gallons of diesel fuel at current prices, I suspect that SCR easily saves 7.5 gallons by virtue of eliminating two additional burn-off cycles over the course of 10,000 miles if the VW system were employed.

Another benefit is the requirement of only a high pressure EGR system where VW requires both a high pressure and low pressure system. The low pressure system despite it's soot free introduction of gas results in increased moisture into the intercooler where the charge air and gasses are further cooled for entry into the motor after passing thru the turbo's compressor.
 
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Drivbiwire

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Lots of love for the urea based TDI's here. I just don't like the idea of having it freeze up in the cold weather, running out of it and being stranded in "limp mode", and having 1 more thing to add to the car besides diesel fuel and engine oil. I guess that's my take on urea. I can take a little less HP and mileage gains to not have to hassle around with urea if at all possible.
Not gonna happen.

Urea contains alcohol as an anti-freeze.

ALL urea tanks are heated, and also contain line heating elements.

Given the range of the Urea system, I can't see ANY way possible for you to ever run out.

Keep in mind that a Jetta or Passat sized car will be getting over 2000mpg on the stuff!

All SCR cars have a spare .5 gallon jug in the boot, and Urea is sold at nearly every truck stop meaning you are never out of range even if you did not have your spare bottle.

All cars will give a 1000 mile warning to the driver that the Urea needs topping off.

All cars are required to have sufficient urea to last 10,000 miles in order to allow the car to drive un-serviced between normal servicing intervals.
 

Scott_DeWitt

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DPF is a Diesel Particulate Filter and Ad Blu is a urea based Nitrogen oxide catalyzing system. These are not the same systems.

DPF's have been around for 10+ years. They collect visible diesel particulates in the exhaust and after a certain amount of of time go through a regeneration cycle where the collected crap is burned off, this typically requires highway driving or additional fuel to get the proper temperatures to do the job.

NOX reduction catalyst uses urea (or in some systems extra fuel) combined with a catalyst and nitrogen oxides in diesel exhaust to create nitrogen, carbon dioxide and water.

Most of the larger engines (3.0+ liters) use Diesel Exhaust fluid (Ad Blu is a brand) and the smaller ones tend to use additional fuel to provide the necessary components for the NOX reduction catalyst.

The engine will consume slightly less fuel with the DEF systems as additional fuel is not required in the reduction reaction.

DPF's however will consume more fuel for the regen cycle as well as pumping losses by the DPF itself.
 
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greengeeker

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I agree SCR is a much better solution.
The result is Soot free exhaust comprised only of CO2, NO and water.
I think this was a typo Pete? NO and NO2 are converted to H2O and N2 in SCR catalyst so the exhaust is comprised of CO2, N2, H2O, O2...

I'm not 100% on the specifics of the VW systems but a difference that might play a role is the cal in the ECU. With the DPF system relying solely on the EGR system(s) to reduce the NOx levels and EGR systems only being ~50% effecient, the combustion is optimized to reduce the NOx formation at the expense of PM. This isn't a big deal since DPF's are >90% efficient at reducing PM. In contrast the SCR system relies heavily on the SCR catalyst to remove the majority of the NOx since they are >90% efficient at removing NOx. Because of this, the combustion is optimized to reduce PM instead. The DOC of course plays a pivotal role in both systems but it also removes 20-40% of the PM.
 
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