Volkswagen Jetta 1.6 - how many HP - prop calc

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

  1. CDK
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    CDK retired engineer

    Sailingmonica, if you have doubts about the tacho you can use the rpm-to-sound program and a laptop to check the accuracy. I did the same for my instruments and found it very enlightening.

    The discussion about engine types seems not relevant to me, because both should reach a much higher rpm at full throttle/no load than the figures you posted here.
     
  2. baeckmo
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    baeckmo Hydrodynamics

    Sorry, conflicting info on rotation. Have confirmed from ZF that 2.63 RIGHT HAND is correct! So, back to engine checking.

    With a correct engine setting, you should have a good compromize with a RH 18" * 12", giving ~3600 rpm on the engine.
     
    Last edited: Oct 30, 2009
  3. sailingmonica
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    sailingmonica Junior Member

    CDK, could you please provide more info related to the rpm-to-sound program, such as where would it be available?

    Baeckmo, thank you for checking with ZF, I could see the point you made initially that it would be easy for an amateur to connect the gear box backwards. In all honesty, the very first time and the very first transmission we actually connected backwards, but we learned from the screw-up and knew better next time.

    If I can get my hands on the program mentioned by CDK I will check my rpm's, but can only do that next spring.

    So, I will take your advice and order the 18x12 and see what happends. I can always have the pitch adjusted if need be.

    I would like to thank all of you for your help and patience. None of us can know as much as all of us. Hugs to all of you. Be safe, healthy and happy!

    Monica
     
  4. baeckmo
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    baeckmo Hydrodynamics

    Ok, so you are wrapping her up for winter now? Right now it feels good to be at the warm side of the Gulf stream,lat ~58 deg N...

    Just to cure my curiosity, have you checked the banjo bolt connecting the injection pump to the fuel return line? If correct, it should have a set of tiiiiiny little holes, like 0.4 mm dia. Anything bigger will cause too low pressure in the pump housing. There are two important consequenses:

    1/ The injection timing is controlled directly from the variation in pressure as a function of rotational speed.

    2/ If the housing pressure is too low, the filling of the injection pumping cylinder intself will be reduced, due to cavitation in the inlet slot. This phenomenon "overrides" the centrifugal governor and will reduce both max rpms under load and max no-load rpms.

    Some pumps have nearly externally identical banjo's for inlet and return, guess what has been observed on DIY conversions..............? The inlet is the one with biiiig holes!

    All the best to you, good luck!
     
  5. CDK
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    CDK retired engineer

  6. apex1

    apex1 Guest

  7. sailingmonica
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    sailingmonica Junior Member

    All right, got to admit I changed the pump. When we were down South the old one (the one that came with the engine) started to leak, apparently due to the ethanol in diesel, which causes the gaskets to dry and shrink. So we ordered a replacement from the only place that had one available, namely partsplaceinc.com in Michigan. Of course, it too was a rebuilt.

    We connected the in and out the same way they were connected before. I have good close ups but they exceed the limit for jpeg attachments. I don't know if you can see on the one I attached previously (taken with the cell phone as less pixels), but the fuel inlet is the one at the bottom of the picture going upwards, the one where the hose has mesh inside. The fuel return is the one that goes from the top of pump at the back to the right and has a spare clamp dangling from it. I will look for the big/tiny holes nonetheless, just in case.

    And yes, MONICA is out for the winter. They only haul you out till mid November, but I wouldn't want to do it that late, too darn cold.
     
  8. baeckmo
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    baeckmo Hydrodynamics

    Hear,hear, hear...... Hope I may live to hear the end of this tale!! (And that you care to tell me!)
     
  9. Frosty

    Frosty Previous Member

    A power boat needs to go fast , it needs max HP and a perfect matched prop.

    You don't need that. you need leasurley economy with low noise.

    42 feet,-- 6 knots at 3000 RPM with 53HP. you will be lucky if all your prop changing will get you 1 knot more.

    You are pretty close where you are, I would not set up a cruising yacht for max RPM.
     
  10. sailingmonica
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    sailingmonica Junior Member

    Frosty, I am not looking for speed. I want good docking maneuvrability (which I have now) and I want to be able to take off without spinning before picking some speed. I am concerned that if I have no thrust for take-off I may not be able to fight currents or strong winds on the bow. Any suggestions are welcomed.

    Baeckmo, I will keep you posted. I am not one to turn my back once I got what I wanted.

    CDK, thank you for the info.

    Apex1, will keep in touch.
     
  11. sailingmonica
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    sailingmonica Junior Member

    In the spirit of the promise to keep you updated, and as humbled as I can possibly be, I have to tell you what I did.

    I stumbled upon a 1994 Volkswagen Golf Diesel engine, 1.9, non-computerized, and I bought it. It is turbo, but I will remove that, which should leave me with something like 70 Hp at 4,200 RPM.

    That brings me back to square one. Now, I cannot ask you to go through the exercise of calculating a new propeller for me, because you've done it already on the 1.6 engine. I just wanted to let you know what happened since the last post.

    But, of course, I will welcome any advice.
     
  12. baeckmo
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    baeckmo Hydrodynamics

    Hi again, nice to have a sign of life! But I must oppose here: don't mess with the turbo, let it stay in place!!! You have a far better engine with it than without, even if you won't use all the horses in the herd. It gives you (us?) more freedom to select a propeller that suits the boat.
     
  13. CDK
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    Words of wisdom Baeckmo! The tiny, narrow intake manifold will leave the engine short of breath if the turbocharger is removed.
    But I'm afraid it cannot stay where it is now because the wet exhaust manifold will be in the way. I think Monica has to read the whole Marinizing VW turbo-diesel thread........
     
  14. sailingmonica
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    sailingmonica Junior Member


  15. apex1

    apex1 Guest

    Fully concur! Leave the turbo where it is! As one positive effect it saves a few drops of fuel, even at lower power.

    edit:

    I meant Baeckmos comment! Did not know about Cornelis argument.
     
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