2.0T engine hypermiling subtlies

Discussion in 'Volkswagen' started by Vooch, Oct 24, 2007.

  1. Vooch

    Vooch Well-Known Member

    I've found that my best ratio for MPG - Turbo Boost - Wind Resistance is about 1900 RPM (61 MPH) = 43 MPG

    I've also found that driving below 1800 RPM doesn't increase MPG until I drop to, say 45 MPH.

    anyone else have similar nos. ?
     
  2. johnf514

    johnf514 Zoom? Try Glide!

    Sure do Vooch. While I don't have the "T" in "2.0T" I get my best MPGs around 41-42 MPH. This turns the engine at 1700 RPMs and is good for 55+ MPG.

    Keep that turbo out of boost and you'll see great numbers! :)
     
  3. Vooch

    Vooch Well-Known Member

    why keep it out of boost ? - should the boost help efficiency ?
     
  4. xcel

    xcel PZEV, there's nothing like it :) Staff Member

    Hi Vooch:

    ___Turbo’s have great efficiency and poor FE. Stay out of it and she will reward you. Get into it and your numbers go south in one heck of a hurry.

    ___Good Luck

    ___Wayne
     
  5. Vooch

    Vooch Well-Known Member

    Wayne,

    You said this once before on another thread - can you be more technical ? For what you are telling me is counterintuitive.

    here is how I understand it ( and I most certainly could be wrong) The increased air pressure inside the mixing chamber brought about by using waste gases to drive a intake turbine - allows a leaner mixture to be burned at the same output.

    I'll agree that increased speed = log wind resistence - and most cars tend to max their FE around 40 - 45 MPH (sweet spot of rpm vs. torque vs. wind resistance). This was the case with my '96 Passat Wagon normal Fuel Injection, no-turbo w/ iFCD. I've plotted steady state FE curves based upon 190,000 f experience with that car.

    However, with the 2.0T turbo engine - I've concluded that YES the max FE is indeed at the same 40-45 MPH - thereafter the FE curve drops substantially UNTIL the Turbo Boost comes on.

    So, when I can I drive 40MPH - However, on the HWY I am forced to go above 40MPH and then drive 61 MPH = 1850 - 1900 RPM.


    DO YOU DRIVE ON THE HWY 40 MPH ?
     
  6. xcel

    xcel PZEV, there's nothing like it :) Staff Member

    Hi Vooch:

    ___No, you should be at such a low load at 55 – 60 mph so as to see nothing more then 2 – 3 lb’s max. Anymore is wasting fuel.

    ___Good Luck

    ___Wayne
     
  7. Vooch

    Vooch Well-Known Member

    wayne - thks for the insight. Perhaps on the prior VW's the Turbos had very little boost pressure during the first 100 - 200 rpm, but I've found otherwise on th 2.0T.


    the 2.0T turbo kicks in at 1800 rpm and has a steep boost rate ( nearly vertical ) - according to the specs - I believe I am getting about 7-8 lbs of boost pressure at 1900 rpm - there is a noticeable INCREASE in MPG going from 57 MPH to 61 MPH on iFCD - after 61 MPH the MPG drops.


    thks for the clarification.
     
  8. shifty35

    shifty35 Well-Known Member

    Generally engines must be tuned richer under boost to prevent detonation as cylinder pressures are much higher.

    Also, what you mention about spoolup is correct - it is essentially a positive feedback system, boost should rise rapidly until the wastegate opens and caps it.
     
  9. Vooch

    Vooch Well-Known Member

    Isn't my compression ratio the same in or out of turbo boost ?
     
  10. Blake

    Blake Well-Known Member

    Your engines effective compression ratio is MUCH higher while in boost. Your forcing much more air and fuel into the engine, although take the boost out of the equation and you'll have the same CR.
     
  11. PaleMelanesian

    PaleMelanesian Beat the System Staff Member

    My take:
    Yes, under boost the engine will be more efficient. However, you don't NEED that much power. My car cruises just fine with a non-turbo 1.6L engine. Maybe get into boost for the Pulse part of P&G, but steady-state cruise you want it as low as possible.
     

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