cleaning EGR system without removing intake

Discussion in 'Gen 3 Prius Technical Discussion' started by ColoPriusV, Apr 8, 2021.

  1. ColoPriusV

    ColoPriusV Junior Member

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    With all the discussion about the need to completely remove the EGR and intake manifold for cleaning in Gen 3 engines, was wondering whether the PriusChat collective wisdom thinks this type of preventative maintenance could possibly be beneficial or extend the EGR maintenance interval:



    My hypothesis is that turbo engines (and especially turbo diesel) with direct fuel injection suffer many of the same problems with EGR soot plugging up intake systems, so perhaps regular use of some maintenance/cleaning products and techniques designed for those applications could prevent or delay the soot build up in our Gen 3 engines.

    Thanks in advance for your thoughts and comments.
     
  2. bisco

    bisco cookie crumbler

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    i'm no expert, but if it says professional on the label, it must work.
     
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  3. Rocky Mountain Priusman

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    I have 0 expertise or knowledge about this, so it would be great to know if this stuff works, but I worry it will foster the types of spirited and highly polarized discussions you get around other products like fuel additives. Also, if you were spraying it in the intake wouldn't you also need to do some techstream trickery to make sure it actually goes through the EGR system?
     
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  4. Ed Beaty

    Ed Beaty Active Member

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    Only one way to sufficiently test this hypothesis:
    1. Take apart the entire EGR circuit (incl. the intake manifold) as THOUGH you were going to clean it.
    2. Do NOT clean it, but reassemble it (noting any cloggage, of course).
    3. Do the thing with the stuff...
    4. THEN take apart the EGR circuit (again, inspecting it carefully for changes for the better...).
    5. THEN properly clean all of it (as it will, IMO, certainly need it).
    6. Reassemble the EGR circuit.
    7. Congratulate yourself for going on a Fool's Errand™
     
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  5. ChapmanF

    ChapmanF Senior Member

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    I looked up the directions for the stuff. It is made for cleaning the particulate filters on diesels, and the directions are to remove the particulate filter. fill it with the stuff, and let it soak.

    But they do suggest that it does something when used as a "Service Shot" through the intake. Ed's point is well taken that a Prius is probably not going to send much or any of it through the EGR, under idling conditions like what's shown in the video.

    I've been wondering lately how clogged the exhaust heat exchanger under the car ever gets? Not as much gets posted about that. I wonder if taking that pipe off and soaking it in something like this might be of some benefit.
     
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  6. Rocky Mountain Priusman

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    Maybe you could put a potato in the exhaust pipe (to act as a plug) and then remove your EGR pipe and add 50 liters of the stuff until the entire EGR and exhaust system was full of liquid cleaner, then remove the potato, let drain, put EGR pipe back on and fire the car back up?:ROFLMAO: :ROFLMAO::ROFLMAO:

    Obviously I am joking here, because it sounds appealing that you could soak the entire EGR and exhaust system by filling it and draining somehow, but I am sure there are 100 reasons why this wouldn't work.
     
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  7. Ed Beaty

    Ed Beaty Active Member

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    At LEAST 200...
     
  8. ColoPriusV

    ColoPriusV Junior Member

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    Since both the engine and throttle are computer controlled, you'd need to put the car into a mode that forced the engine to run, and the throttle to be activated at a level higher than idle. You would then need manually operate the EGR valve to force it to open briefly while giving a pulse shot of the spray cleaner. Precisely how to do all this is the question - and you'd likely end up with a CEL that would need to be cleared when done.
     
  9. rjparker

    rjparker Senior Member

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    Turbo diesels certainly have their problems with gunk build up but mechanics almost always have to disassemble and clean those systems as well, regardless of marketing claims. With that said, there are engines of a given type with better designs than others. In the case of a Prius, either the gen2 with no egr or the gen4 with a vastly improved egr largely eliminates the issue. Combine oil burning on the early gen3 engines and you have quite a design fail.

    The sprays are unlikely to help a design issue. Plus the basic layout of a non turbo, port injected Prius is quite different than a turbo diesel, offering no direct access to the egr cooler from the air intake. Generally the only thing that gets removed with a spray are your dollars.

    Typical Turbo Diesel EGR and EGR Cooler
    CF5651B3-6C40-4B8D-9FB0-11769A6D2F04.jpeg
     
    #9 rjparker, Apr 11, 2021
    Last edited: Apr 11, 2021
  10. Mendel Leisk

    Mendel Leisk Sunday driver DIY’r

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    Thinking (as an example) of the effort required to clear the EGR cooler when it's out of the car, multiple hour soaks in Oxi-Clean, liberal oven cleaner sprays, pressure washer, wires on drills: there is no way this proposal is going to work, lol.
     
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  11. ChapmanF

    ChapmanF Senior Member

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    Maybe there is something super effective about the DPF cleaner. Not that it would work miracles sprayed haphazardly into the intake, but who knows, maybe soaking in it works better than Oxi-Clean?

    Thinking about it and the exhaust heat exchanger downstairs ... I don't think there even is any access to that for wires on drills, etc. Two catalytic converters in the way ahead of it, a longish pipe section behind it. Soaking in some kind of liquid might be the only option (short of cutting it up, cleaning, welding back together).
     
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  12. ColoPriusV

    ColoPriusV Junior Member

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    I totally agree this would be a futile way to clean a clogged EGR system if used as an alternative cleaning method to the 75-100K mile service interval widely discussed in multiple PriusChat threads. But that's not what I proposed. What I asked was whether such a spray might be effective if used on a more frequent basis, say every 15-20K miles, to prevent carbon build up that leads to the nearly complete EGR blockages and follow-on problems so many have reported.

    Based on claims in the video (and multiple endorsements in viewer comments), the spray treatment appears to be effective in turbo diesel EGR systems that are so plugged they are throwing CEL codes. My theory is that if a similar preventative treatment was used on a regular interval and before ECL codes appeared, it might delay or possibly prevent the inevitable blockage. And if performed frequently enough, it wouldn't need to be so effective that it left a Gen 3 EGR "squeaky clean" as everyone attempts to do when they go to the trouble of disassembling the entire EGR and intake system.
     
    #12 ColoPriusV, Apr 11, 2021
    Last edited: Apr 11, 2021
  13. Ed Beaty

    Ed Beaty Active Member

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    All very reasonable conjecture, but how to ascertain that it works on the Prius? Please review post #4 (wherein you'd have to repeat that process n times, where n is the number that would satisfactorily determine the efficacy of the process.

    Perhaps better to just clean the deuced thing every 50,000 miles, eh?
     
  14. rjparker

    rjparker Senior Member

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    The problem is the Prius egr cooler is between the exhaust pipe and the egr valve meaning the magic aerosol has to make it through the intake, combustion chamber, exhaust valve and then to the intake of the egr cooler. After going through combustion, any cleaner is just another part of the problem. The hardened gasoline carbon deposits at the entrance to the Prius egr cooler are significantly more dense than the fluidized sludge created in a turbo diesel. The Prius cooler is exposed 100% of the time to the exhaust flow while the diesel egr cooler is downstream of the egr valve and does not see exhaust gas when the egr is closed. So the gunk in a turbo diesel is more like axle grease where the carbon in a Prius egr cooler is closer to baked on epoxy than a grease.

    Some correlate the injector and valve cleaning ability of gasoline additives to these unrelated spray cleaners. In the case of gasoline additives, those chemicals are applied continuously prior to combustion through the injectors and intake valves (port injected engine valves). They are effective and are included in any retail gasoline.

    But the biggest issue with gen3 Prius is the engineering. The gen4 design moves the egr cooler downstream of the cat. The cat cleans up the exhaust flow first. The gen4 egr cooler is bigger and less likely to clog. The oil burning issues of gen3 have been resolved in gen4. Which means far less hydrocarbons in the exhaust stream. Better engineering means better results.
     
    #14 rjparker, Apr 11, 2021
    Last edited: Apr 11, 2021
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  15. ChapmanF

    ChapmanF Senior Member

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    It's important not to give the impression that the Gen 3 to Gen 4 change from uncatalyzed to catalyzed EGR was some kind of bug fix slapped on for the discovery that EGR passages could foul.

    There was active engineering research around that period into which of the two forms of EGR was better for managing the combustion process in the cylinders. There were some early results that weren't clearly showing that catalyzed EGR was a better way to run an engine (such as those reported here), and later work that seems to have worked out better ways of optimizing for the catalyzed EGR source and showed improvements in performance (as mentioned, e.g., here).

    One of the differences is that pre-catalyst EGR still contains some stuff that'll burn (NOx, CO, HC). The post-catalyst stuff doesn't. So while both slow down the combustion process in the cylinder, the catalyzed EGR slows it more, among other chemistry-related effects, so calibrations in the ECM have to be tweaked for that. Passing through the catalyst reduces the available pressure, so all the EGR plumbing is upsized for the simple reason that it has to be to carry the necessary flow of lower-pressure gas.

    There's a whole lot that goes into designing and building these things.
     
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  16. Grit

    Grit Senior Member

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    o_O
     
  17. mjoo

    mjoo Senior Member

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    I had thought about doing the potato plug and soaking the entire Exhaust from the EGR cooler down in ammonia. It would definitely remove the soot. But then it could corrode the aluminum parts. Not sure what it would do to the catalytic converter.
     
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