Volkswagen Jetta 1.6 - how many HP - prop calc

Discussion in 'DIY Marinizing' started by sailingmonica, Oct 20, 2009.

  1. sailingmonica
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    sailingmonica Junior Member

    Sorry, my last post was lacking brain matter.

    Yes, CDK, the issue of the wet exhaust was the reason I mentioned removing the turbo. There is more head scratching needed on my part.
     
  2. sailingmonica
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    sailingmonica Junior Member

    What if I remove the turbo and I replace the smaller intake manifold with one from a non-turbo to allow the engine to breathe properly? Then I have no need to reposition the wet exhaust manifold and I still have 70 Hp available to me.

    And does the turbo actually save fuel? I thought, based purely on logic, that if the turbo is giving the engine more power and anything that gives more power uses more fuel, then the turbo burns more, not less.
     
  3. apex1

    apex1 Guest

    Specific consumption Monica! And there the better "aspiration" has a advantage.

    Regards
    Richard
     
  4. marshmat
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    marshmat Senior Member

    A turbocharger's role is to cram more air into the engine than it would be able to take in at ambient pressure, thus allowing it to burn more fuel and produce more power on each stroke.

    Generally speaking, any sort of forced induction device will increase cylinder pressures, which usually has the effect of improving efficiency (reducing specific fuel consumption).

    However, the optimum operating point will also change, so it is quite possible that a turbocharged engine, if run underloaded, may be thirstier than its naturally aspirated twin would be at the same load. (The more sophisticated multi-turbo, variable geometry turbo, variable boost, etc. setups tend to alleviate this drawback.) The only way to know is to compare the 'fuel maps' or 'performance maps' for the engine in both turbo and natural configurations.
     
  5. apex1

    apex1 Guest

    Ja,

    that was the prolonged version.

    Better cooling (the intake vessel) is another point..........
     
  6. baeckmo
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    baeckmo Hydrodynamics

    More important is that the turbo will allow you to tap the power you need at lower rpms, as long as you don't need the max rpm power. This gives you higher propeller efficiency AND lower specific fuel consumption from the engine!

    So, whatever you do, keep the turbo, don't mess things up now!!!!! Better take some time and locate a watercooled exhaust manifold for this engine! They come ready and complete with engine heat exchanger from "Bowman" for example.
     
  7. CDK
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    CDK retired engineer

    The posts from Apex1, PAR and Baeckmo have dealt with that already, but I understand your concern about the physical layout.
    Moving the turbine to the exhaust flange of the manifold takes only 3-4 hours.
    If you replace the manifold and discard the turbine, you need to replace the injection pump as well or have it recalibrated for the reduced air mass.

    I'd rather spend some time moving the turbo charger.
     
  8. sailingmonica
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    sailingmonica Junior Member

    Got the Bowman. Spent the weekend staring at the current layout and thinking.

    I promise to not mess it up. I owe you guys that much.
     
  9. FAST FRED
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    FAST FRED Senior Member

    More important is that the turbo will allow you to tap the power you need at lower rpms, as long as you don't need the max rpm power. This gives you higher propeller efficiency AND lower specific fuel consumption from the engine!

    This is fine as long as the turbo is working , a problem comes in "no wake zones" where the engine might need too basically idle hours on end.

    IF long slow speed transits are required , usually a no turbo engine will have longer service life.Although the fuel burn will be higher .

    FF
     
  10. sailingmonica
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    sailingmonica Junior Member

    Fast Fred, I am a sailboat with 30,000 lbs of displacement and 6 feet draft, able to reach "top speeds" of about 6.2 knots. Sorry if I wasn't clear on that. No wake issues here.

    However, I like the overnight stop idea. May I send you a PM so I can plan for next time I head South?

    Monica
     
  11. sailingmonica
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    sailingmonica Junior Member

    Hydralign propeller

    All right, time has passed, new problems have arised.

    I always wanted a feathering prop, but the cost is well above my paygrade. Just found this on Ebay, seems to be the model for aperture setup, the seller confirmed the forward to stern dimension is only 3 inches. I am contemplating bidding on it. Here is the link

    http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=290497849814

    What do you guys think?
     
    Last edited: Nov 12, 2010
  12. sailingmonica
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    sailingmonica Junior Member

    Hi, guys! Cavitation problem SOLVED!

    After a few years and a few propellers (expensive testing, I tell ya'), all cavitating at 5 knots and over and none allowing the engine to reach its full RPM, we stumbled upon a Hydralign Feathering Propeller on EBay.

    Long story short, I bought it. I then contacted the manufacturer in Australia and asked for the pitch adjustment table; while we were talking I told the guy that I am trying to figure out what the pitch should be. He asked for the usual boat specs and then came back with 18x7. Yeah, right, I thought!

    But I was willing to give it a try, since I already tried everything else. So I set the pitch at, well, 7.9, put the boat in the water and floored the throttle.

    Wow! I got up to 8 knots, no banging noise, RPM going up, engine happy and the boat was barelling down with bow up and the swim platform almost in the water. I even had a wake!

    Then I tried docking, no problems there either. Perfect control.

    So I am happy like a pig in a mud bath right now. Why it works at this pitch, I don't know.
     

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  13. marshmat
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    marshmat Senior Member

  14. sailingmonica
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    sailingmonica Junior Member

    Marshmat, the Hydralign is the only feathering propeller manufacturer I know of (and as I said I found out by mistake while browsing Ebay) that actually makes feathering propellers for apperture setting. Instead of those long hub props you see all over, this one is only 3 inches. See attached for sizing reference only (that's my husband trying to figure out how to adapt the extractor to the new prop).
     

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  15. Tanton37
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    Tanton37 Junior Member

    Sailing monica

    Anyone know how I can get in touch with this poster?
    Thanks
     
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