DPF Cleaning

Originally had this posted in another section, but was recommended to bring it over here. So here it is:

I recently bought a 2009 Q7 TDI. Going through the vehicle and wanting to make sure everything is running as good as can be. I've come across DPF cleaning videos/how-tos, both on and off the vehicle. Seems there's a lot of methods. One of those is using a cleaner you spray directly onto the DPF via a sensor port just upstream from the DPF while in situ. This seems to create a lot of foam and other chemical build-up. Couple questions here:

Is this effective?

Will this harm the SCR or NOx sensor that are downstream of the DPF?

The Audi method is to simply replace the whole thing once ash loading reaches critical point..

Spraying stuff into it wont do jack **** IMHO.. its gotta be taken off, cut open, emptied out, then welded back up.. its whole purpose is to fill up with ash, eventually it gets full and like a fireplace burning up logs, yeh gotta shovel the ash out from time to time.

I'm just deleting mine, it'll pass our emissions here in Colorado fine.

If everything is right on your car, it has software that causes a regen when the DPF gets close to full. If you have a scanner you may be able to force a regen. If not, the manual states that you can cause a regen by keeping 2000 to 2400 rpm for 10 to 15 minutes. This can be done by keeping your car in a lower gear. It is supposed to keep itself clean on its own if everything is OK.

Regens convert the soot to ash, its still in the DPF.. it didnt magically disappear or be allowed to exit the vehicle as particulate matter..

In normal nomenclature, DPF cleaning is the process of removing that ash once the DPF has filled up.. which is something that has to be physically done, at that point it will refuse to do anymore regens in fear of causing the vehicle to catch fire.

nayr said:

The Audi method is to simply replace the whole thing once ash loading reaches critical point..

Spraying stuff into it wont do jack **** IMHO.. its gotta be taken off, cut open, emptied out, then welded back up.. its whole purpose is to fill up with ash, eventually it gets full and like a fireplace burning up logs, yeh gotta shovel the ash out from time to time.

I'm just deleting mine, it'll pass our emissions here in Colorado fine.

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You're going to or you already have? Does this, also, require removal of the SCR?

I did my Golf, my Q7 is at dealer getting some last min warranty work I found it needed when I went to go take the exhaust off, it does remove SCR and disables EGR and Swirl Flaps.. I think the cat is optional, it wont complain if its gone.

nayr said:

Regens convert the soot to ash, its still in the DPF.. it didnt magically disappear or be allowed to exit the vehicle as particulate matter..

In normal nomenclature, DPF cleaning is the process of removing that ash once the DPF has filled up.. which is something that has to be physically done, at that point it will refuse to do anymore regens in fear of causing the vehicle to catch fire.

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The DPF's I have seen have been a monolithic honeycomb that the exhaust must pass through and the soot gets caught on. As the efficiency declines the ECM adds additional fuel to get the internal temps above 700-800C to burn off the soot and turn it into ash. Where does it store the ash and with that in mind what would be the life span of a DPF? A vehicle being used to pull a trailer and creating more soot would have failure rapidly. The DPF on my Q5 looks that it couldn't hold more than 1 gallon of ash if it doesn't get burned off and flushed out the exhaust system. The ash would be harmless to the environment if released out of the back. The failures I have heard of have been either a sensor not reporting correctly causing a melt down or the car is drove to easy and not brought up to highway temps on a regular basis to keep it cleaned out. If these things have a failure rate of less than 50k miles then mine will disappear before I pay for a new one after the warranty. The removal would be less than the cost of a new DPF.

It just clogs up the honeycomb


The Ash coming out the back is just as bad for the environment as the soot, you've already burned off everything but the carbon and released it.. its a particulate filter, literally says it in its name.. releasing a bunch of smaller ash particles would be counteractive to its entire purpose.. the regens happen so it reduces the soot in mass and it can hold more.

Supposedly they last for over 115k miles, thats when Audi recommends you start checking ash loading levels w/VCDS, if its below a certain threshold you keep driving and re-check every 20k miles, once it passes that threshold you dispose of it.. however those intervals were created pre-dieselgate, and the fixes seem to be killing DPF's left and right now days on other vehicles.

Most 'DPF Cleaning' services are designed around diesel fleets.. they rack up millage quickly and their DPFs make ours look cheap.. passenger cars its a wear item, warranty wont cover a full DPF.

Was that on your car? On the Q5 it is just off the turbo beside the firewall. It is not much bigger than a gallon can.

No that was just result of googling DPF cleaning.. Looks like its off a truck.

Ash, a byproduct of oil consumption from normal engine operation, builds up in the filter as it cannot be converted into a gas and pass through the walls of the filter. This increases the pressure before the filter. Warnings are given to the driver before filter restriction causes an issue with drive-ability or damage to the engine or filter develop. Regular filter maintenance is a necessity

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https://en.wikipedia.org/wiki/Diesel_particulate_filter

So what do you think of a DPF delete? Would this then send all the ash/soot to the SCR? Foul up the downstream NOx sensor?

If you do the DPF delete it sends the soot out the tail pipe.. there's no downstream SCR or nox sensor anymore.. DPF & SCR come out together.

when my DPF filter plugs up it's getting a Delete kit with software update totally legal in Ontario, Canada for all that are from here.

nayr said:

If you do the DPF delete it sends the soot out the tail pipe.. there's no downstream SCR or nox sensor anymore.. DPF & SCR come out together.

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Gotcha. So "DPF Delete" means everything after the cat. Am I understanding this correctly?

Maybe I should change the name of this to DPF Cleaning vs Delete. Of the things I've seen and read re: deleting, it's very polar - There's those absolutely for it, and those against. And interestingly there is "logic" of both sides. Any comments are welcome.

I'm all for more power and better fuel efficiency (at least, that's what I've read about doing a DPF delete), but I don't want to roll coal out of my Audi. If I do a delete, is this basically the outcome - putting all that s**t out into the atmosphere? Or is it not as bad as that?

pedroYUL wrote: "I also wonder the efficacy of that Liqui Moly DPF cleaning spray.
Their diesel purge is not bad if you use it straight from the can, rather than dumped in the tank."

Is the diesel purge the stuff you put directly fore of the DPF, through the port?

Delete means no emissions components at all from the turbo to the tailpipe

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apbreaux said:

Is the diesel purge the stuff you put directly fore of the DPF, through the port?

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Diesel Purge is a little can of concentrated product you use to clear impurities in the fuel system/injectors after the fuel filter. You disconnect the hoses from the filter and run your car >2k rpm using only the product from the can.

This has nothing to do with DPF cleaning, but it does work for cleaning injectors IMO.

apbreaux said:

Gotcha. So "DPF Delete" means everything after the cat. Am I understanding this correctly?

Maybe I should change the name of this to DPF Cleaning vs Delete. Of the things I've seen and read re: deleting, it's very polar - There's those absolutely for it, and those against. And interestingly there is "logic" of both sides. Any comments are welcome.

I'm all for more power and better fuel efficiency (at least, that's what I've read about doing a DPF delete), but I don't want to roll coal out of my Audi. If I do a delete, is this basically the outcome - putting all that s**t out into the atmosphere? Or is it not as bad as that?

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Everything after the turbo.. exhaust is straight back to muffler.. costs about $2k for the exhaust + software.

Your Audi wont roll coal w/delete, the tunes are very good and have none of that nonsense.. mebe a quick puff of smoke if you just rail on the throttle but nothing even remotely close to 'Rolling Coal'

The environmental impact on the delete is largely subjective, and depends greatly on where you drive it.. now this is all my opinion, but particulate matter and nox are really only a pollution concern in densely populated areas.. Rural America its virtually a non-issue, you driving down a dirt road is putting more particles into the air than the exhaust.. the NOX coming out the back is going to be fertilizer for the fields within a week or so.. Those are contributors to smog issues, which Rural America dont have issues with.. however tuning/deleting often increases FE dramatically, so one could argue that the CO2 released has been reduced, and that stuff stays in the atmosphere for eons, not hours/days like PM/NOX.

Me I live in a dense Urban Area, but I put on 95% of my millage out in Rural america.. I drive a different car in the city, mostly because its bad on my Diesel to do such short runs, and the delete makes it warm up even slower.

For me, I have no issues to the delete or the people who delete em.. but I do think anyone who rolls coal is a total douche..

apbreaux said:

Gotcha. So "DPF Delete" means everything after the cat. Am I understanding this correctly?

Maybe I should change the name of this to DPF Cleaner vs Delete. Of the things I've seen and read re: deleting, it's very polar - There's those absolutely for it, and those against. And interestingly there is "logic" of both sides. Any comments are welcome.

I'm all for more power and better fuel efficiency (at least, that's what I've read about doing a DPF delete), but I don't want to roll coal out of my Audi. If I do a delete, is this basically the outcome - putting all that s**t out into the atmosphere? Or is it not as bad as that?

Click to expand...

Any recommendations for cleaning sprays to use without removing dpf?
I know ill most likely have to remove dpf but want to take the chance with a spray just incase. Because i cannot be ****d to remove it if im honest. Allready removed sensor off top of dpf so just looking for any reccomendations on a spray.

What do you think of a fuel additive that claims to be a DPF Cleaner?

For example, Lucas Oil makes a "Diesel Deep Clean" product that you add to a full tank of fuel. It seems to get good reviews. Other manufacturers make similar products. These products supposedly increase temperatures in the exhaust allowing more soot particles to burn and exit the system.

Any of you using them?
Are they any good?
Or are they a waste of time and money?

If they were any good, don't you think VW would have dumped a bottle in their customers' tanks instead of doing the expensive warranty replacements?

The reason why they need replacement is because they crack inside. Doesnt matter how much cleaner you shove in there, wont help anything. Also i have never heard of anyone cleaning these DPFs in North America.

You can force a regen if soot is high, but ash is low. Once ash levels get high - you're done. Nothing you put in your tank will help. Like MrCypherr said - more fail for cracking than getting "full". I can tell you that my A7 could not regen properly during normal driving - even at extended high speeds. I had come home from a 400 mile round trip buzzing along at 80+ MPH when the light came on. Soot measured was over 52g and it dropped to 4 I believe after a vcds forced regen. Since it's sitting upstairs in my shop - it's still around the same levels

Wow! That is double where mine usually initiates a regen at (24 or so).

Lightflyer1 said:

Wow! That is double where mine usually initiates a regen at (24 or so).

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I hadn't measured it since I bought the car more than a year prior. I regularly run it hard too. I tend to leave it in manual and drive with the paddle shifters. There was a short period of time where I was trying to see what kind of MPGs I could get, but that was still running 75mph with a 1000' elevation change in the middle of my commute. I never once noticed a regen running... With emissions testing here - I swore I would never get stuck paying for a DPF out of warranty and deleted it shortly after that forced regen @118k miles. I can swap it back in whenever I need!

I don't try for the best economy, I just drive normal. 34 to 36 mpg over the years I have owned it since new (2017 stop sale car). I do monitor regens using VAGDPF though as I want to get the most trouble free usage as I can. As my warranty is still intact till 2028 and 100k more miles, no delete in my future unless VW gives me great trouble. I haven't had the second part of the fix done yet (2b) that may add more to the warranty. Car was recently totaled by a hail storm and the insurance company paid me $18k after buying it back from them. I had the glass fixed but none of the body damage dents. So what ever happens I am ahead on this car. Also dropped full coverage down to liability so more savings there. It is still a very good low mileage car with great fuel economy and can't replace it with anything that will do as well. I own multiple vehicles so I have no worries on transportation. I want to keep VW on the hook as long as possible. It is mostly used for commuting to work and back 35 miles each way. At least for the next year and a half when I will retire.

Damn that sucks to see that ! I bet it sucks watching the car get damaged by hail and there really isnt much you can do!

Just cosmetic. It will buff out!

Still a very usable, dependable vehicle. If there isn't anything you can do you just go with it. I only paid $22k new so the payout and buyback made the sting much less.