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PD or Common Rail

Discussion in 'A3/S3/Sportback (8P Chassis)' started by centurion, Nov 8, 2007.

  1. centurion
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    centurion 3rd gear's my favourite...

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    [Nov 8, 2007]
    Hi all,

    I've come from a VW/Audi group back ground having owned both Skoda and Seat and when I asked the dealer if the A3 2.0 (140) was a PD or a common rail he said it was a common rail and saying that all face lift diesel A3s were all common rail.
    I know Skoda and Seat still use the PD system on their 2.0 TDi's and according to the Audi website it states that the 170 is "Common rail direct injection with piezo injectors" and that the 140 is "High-pressure pump-injector direct injection" so the 140 is still a PD regardless of face lift or not?

    Is it possible to tell if I've got a PD or common rail from looking in the engine bay or something similar?

    Mind you he also told me it had a DPF fitted which it doesn't.

    Cheers for your help...
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  3. Amchlolor
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    Amchlolor Active Member

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    [Nov 8, 2007]
    140 is definitely PD, regardless of facelift.
    No DPF on UK 140.
    170 is allegedly sort of common rail, type thing, in a roundabout sort of way.
    DPF on the 170 too.
    #2
  4. stevehsv868
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    stevehsv868 Unofficial Audi UK Endurance Test Driver

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    [Nov 8, 2007]
    140 is Pume Duse (unit injector)
    170 is common rail

    all new audi diesels will be common rail

    the PD engine will have a large rocker cover and minimal pipe work

    the common rail will have a rail of high pressure diesel with pipes coming off to each injector.

    with me actually having the PD 140 , I do not rate it , the reliability is terrible , new cylinder head on mine , new turbo on my mums , both items you do not expect to fail at low mileage
    they drink engine oil , which is very expensive

    and the 170 has issues with the transit van mode (engine running rough) and for me the turbo delay spoils the engine.

    i much prefer the old PD 130 and PD 150 , they were bombproof when compared to the PD 140
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  5. Twizzler
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    Twizzler Member

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    [Nov 8, 2007]
    Is the 'transit van mode' the dpf problem encountered by some? I don't recognise this rough running problem in mine, although I have only done 1100 miles in it so far. No dpf warning light seen yet. It runs as sweet as a nut.
    #4
  6. Amchlolor
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    Amchlolor Active Member

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    [Nov 8, 2007]
    Amen to that.
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  7. mfspen
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    mfspen Member

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    [Nov 8, 2007]
    This was discussed here some time ago, and the consensus was that the Audi UK website was wrong.

    The 170 is not common rail, but is a bit of hybrid between Pump Duse and piezoelectric injectors. It still has the camshaft driven mechanical fuel pumps (one per cylinder), but gets piezo rather than solenoid injectors. So, its quieter than PD, but not as smooth as full common rail.

    Here is an excerpt from the World Car Fans news feature (which they got from the Audi AG press release), when the engine first came out, which says :

    "[FONT=Arial, sans-serif]Slotting in alongside the existing 2.0-litre 140PS TDI engine in the A3 and A4 model ranges, the new 170PS unit is the first in the Audi range to combine 'pumpe-duse' or 'pump jet' direct diesel injection with the performance-maximising piezo crystal injector technology from the 2.7-litre V6, 3.0-litre V6 and 4.2-litre V8 TDI engines.[/FONT]"

    (http://www.worldcarfans.com/2060517.004/new-piezo-tdi-engine-for-audi-a3-and-a4)
    #6
  8. stevehsv868
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    stevehsv868 Unofficial Audi UK Endurance Test Driver

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    [Nov 8, 2007]
    The transit van mode is the engine running rough , like an old transit van , it has been encountered by some people on the forum , but not everyone

    the DPF issue is more due to how people use the car , if you drive your car steadily (low revs) over short journeys the DPF will not get enough heat form the exhaust to regenerate , which puts the DPF light on the dash , leave it too long without a decent journey length the second DPF light comes on the dash. and only the dealer can regenerate the DPF

    Basically the DPF stores the diesel soot particulates , until a predefined level then burns them off during regeneration. but if the DPF does not get enough heat from the exhaust , regeneration cannot occur, thats why in the maual it says to drive with moderate revs (over 2,000 rpm) over 40mph for a decent distance , to get DPf to regeneration temperature.

    if you drive like I do (drive it like you stole it approach) , then there should be no issues with regeneration of the DPF filter
    #7
  9. Macduff
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    Macduff Member

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    [Nov 8, 2007]
    170 is also PD but with piezo injectors. VAG 2.0 common rail are coming but not here yet. I believe the current 2.7 and 3.0 V6s are common rail. Not sure about the 4.2
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  10. Twizzler
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    Twizzler Member

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    [Nov 8, 2007]
    Steve,
    Thanks, how does the dealer regenerate the dpf?
    #9
  11. centurion
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    centurion 3rd gear's my favourite...

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    [Nov 8, 2007]
    Cheers, as I thought it was.

    It amazes me that the dealers will tell you any old rubbish just to sell a car.
    #10
  12. stevehsv868
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    stevehsv868 Unofficial Audi UK Endurance Test Driver

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    [Nov 9, 2007]
    Hello I am not sure how the dealer regenerates the DPF , I wouldnt be supprised if they just thrashed the nuts off the car
    #11
  13. stevehsv868
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    stevehsv868 Unofficial Audi UK Endurance Test Driver

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    [Nov 9, 2007]
    The 170 tdi engine is common rail , its been a joint venture between vag group and bosch , to create a common rail system with the high injection pressures of PD (unit injector) and the piezo injectors first seen on the larger diesels such as the 3.0 TDI , the 170 TDI also has not one ECU , but 4 one for each injector , to meter fuel in exact ammounts.

    normal common rail injection pressure 1500 bar (peak)

    VAG ag common rail injection pressure 1850 bar (peak)

    Vag PD Pump Duse unit injector injection pressure 2200 bar
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  14. mfspen
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    mfspen Member

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    [Nov 9, 2007]
    That doesn't agree with the Audi press release in the link above. What they describe is a hybrid - PD mechanical fuel pumps with piezo injectors.

    Whereas, a true CR engine has a single electric fuel pump feeding all cylinders via a common chamber (hence common rail). This gives lower peak pressure, but a constant pressure, so there is more scope for multiple injection pulses each cycle, hence smoother running.

    I would tend to believe a press release from Audi AG, rather than a brochure from those half-wits at Audi UK !
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  15. Amchlolor
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    Amchlolor Active Member

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    [Nov 9, 2007]
    That's all very interesting, but WHY do Audi want to combine the high pressure of PD with common rail?
    I currently see no advantage to it at all
    If there was an advantage,the 170Tdi would be more powerful/quieter/more efficient than it's competitors.
    It isn't though.
    Current 'lower pressure' commonrail engines are better than the 170 in just about every way (BMW is more powerful and quieter, Honda is quieter etc.etc.)
    So I can't see any reason for Audi to boast about their higher pressure units?!?
    Unless anyone can explain?
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  16. mfspen
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    mfspen Member

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    [Nov 9, 2007]
    I think the 170 was just a stop-gap bodge, until the true CR VAG engine was developed.

    The new 2.0 CR in the A4 has been praised in the reviews for being much smoother and more refined than the old 140/170 engines.
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  17. Amchlolor
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    Amchlolor Active Member

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    [Nov 9, 2007]
    But the same argument is there.
    It's no more powerful, efficient or refined than the BMW318D, so where is the advantage of the higher pressure???
    Maybe Audi have been watching Spinal Tap

    "this amp goes up to 11"
    "what advantage does that give you over 10 then?"
    "................................it goes to 11"
    #16
  18. steve184
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    steve184 Active Member

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    [Nov 9, 2007]
    i had a 140. 11,000 miles of ***** stop start rubbish town mileage (worst you can throw at an engine - result: not a single hiccup from that engine it ran flawlessly, reliabilty not an issue.

    I now have a 170 dpf - also ***** town stop start mileage, 3000+ miles, not seen a dpf warning light yet at all, and not experienced any sort of 'tractor noise' just the normal noise a diesel car makes (never gonna be as quiet as a petrol although quieter than petrol at motorway speeds due to less revs!)

    I think you will find you have less probs with the dpf if you have the dsg gearbox as the engine ecu and gearbox 'talk' to each other and when regeneration is needed the dsg alters its shift points a little higher (but not as high as sport mode) this helps to keep the soot in the exhaust low and so it never gets clogged, even with the worst kind of stop start driving.

    Manual seems to be a diff story, it is left to the drivers control to drive the c different every once in a while to maintain the dpf - and if they dont do this or forget then it causes problems.
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  19. mfspen
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    mfspen Member

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    [Nov 9, 2007]
    AFAIK, the new engine in the A4 is conventional CR - that is, it uses an electric fuel pump, and achieves 'standard' pressures.
    #18
  20. stevehsv868
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    stevehsv868 Unofficial Audi UK Endurance Test Driver

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    [Nov 9, 2007]
    The high injection pressures were what made the old PD units so good, the higher pressure leads to better atomisation of the fuel , there fore increased power and efficiency

    at the end of the day a higher injection pressure means more noise

    the old PD units back in the day had more power than the majority of there competiors , but they werent exactly quiet

    But i do agree Audi are getting left behind by the likes of BMW for performance and Honda for noise.
    #19

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