Auto Diesel (Yeah, again, but...)

Discussion in 'Propulsion' started by Filmdaddy, Jul 21, 2005.

  1. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    Those are high performance engines. It has nothing to do with this thread, which deals with standard marine installations. The overlap in the cam is for engines that idle at over 1500RPM. C'mon Filmdaddy, you are grasping at straws to make a point. Read all the instructions. They are for a high flow HEADER SYSTEM. We are talking about EXHAUST MANIFOLDS.
     
  2. Filmdaddy

    Filmdaddy Previous Member

    Headers ARE exhaust manifolds. They work to get the hot gasses out of the cylinder. Check the definitions. And the physics of fluid dynamics work exactly the same no matter what you call the pieces, which is all that Tom Kane said. Why not just admit that he isn't blowing smoke, and that there is some validity to his comments?
     
  3. gonzo
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    gonzo Senior Member

    Because normal use manifolds are a big chamber that is designed to neutralize the cyclical pressure. They work like a muffler. Also, a high performance engine with overlapping cam lobes creates a completely different situation than a normal camshaft. You are still grasping at straws.
     
  4. Filmdaddy

    Filmdaddy Previous Member

    Please refer to my previous comment about your credibility.
     
  5. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    Your comments and personal attacks don't affect my credibility, or the facts. Post an example of any manufacturer of standard manifolds that claims they make water go into the intake valves. Even Hardin Marine says that it may be a problem in a faulty installation, not in a proper one.
     
  6. Filmdaddy

    Filmdaddy Previous Member

    Word for word:

    "Checking For Water Reversion - Reversion, what is it? Is it simply the exhaust pulse flowing backward momentarily during the overlap phase of the camshaft at low cycling rates. During the overlap phase, the piston is pushing out the last of the exhaust gasses and prior to reaching top dead center (TDC) the intake valves and the exhaust valves are still partially open. At high cycling rates the inertia of the incoming intake charge and the outgoing exhaust pulses keep the exhaust flowing in the proper direction. But at low cycling rates, as the piston is pushing out the last of the exhaust gases, the intake valve opens and some of the spent exhaust charge is pushed into the intake manifold. As the piston reaches top dead center and begins the intake stroke the exhaust valve is still not completely closed. As a result, the piston pulls from the intake and exhaust valves simultaneously causing the exhaust gases to flow in a reverse direction. This is normally not a problem until you add water into the exhaust stream. Reversion can be severe enough to seize or stall an engine, add water to the oil, rust the exhaust seals, etc. This effect only happens at idle speeds, but remember that during shut down the engine encounters the greatest chance of reversion."

    This says nothing about 'proper' or 'improper' or even 'faulty' installation. It says that, due to the nature of fluid dynamics and the operation of internal combustion engines, when there is water in an exhaust system, water reversion can occur. Whether you are talking about liquid water or steam, Tom Kane is right.
     
  7. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    No you are not. There isn't the overlap they talk about in a camshaft for normal service.
     
  8. Filmdaddy

    Filmdaddy Previous Member

    Wow. You better write them and educate them.
     
  9. gonzo
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    gonzo Senior Member

    You need to put things in context. Your quote is from a website selling high performance products. Look out the camshaft specs for a standard marine engine.
     
  10. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    GM 5.7 INT open 7ATC close 29ABC EXH opens 37BBC closes 4BTC . As you see there is no overlap afte TDC.
     
  11. Filmdaddy

    Filmdaddy Previous Member

    "... the opening and shutting valves creates waves that carry pulses back and forth which carry moisture back to the valve seats and beyond (wet spark plugs from steam) depending on the cam and manifold design.Just the fact that the exhaust contains moisture is enough for moisture to percolate back into half opened valves and cylinders,rings especially when hot,the heat attracts moisture as it cools on shut down."

    That's what Tom Kane said. Nothing about it always happens. Just that it can.
     
  12. Filmdaddy

    Filmdaddy Previous Member

    This is getting boring. You have staked your claim. You have to protect your position. Fine.
     
  13. woodboat
    Joined: Nov 2003
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    Location: Baltimore MD, USA

    woodboat Senior Member

    Gonzo I think you're missing it. They have actually made your point for you. If one were to take an automotive engine with a high lift large duration racing cam coupled with high performance headers not proper marine manifolds then reversion can happen. If one were to use a proper marine engine with a cam designed to operate from 4000-4400 WOT and proper marine manifolds this reversion does not happen. In the marinization process the engineers have overcome this possibility that could otherwise occur when using an automotive engine. In my defense I was always thinking in terms of a proper marine engine. I knew the pulses were there but never considered a large duration cam in an engine idling @ 1500 rpm with modified wet headers. Manuevering would be difficult at best with one of these.
     
  14. PowerTech
    Joined: Feb 2005
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    Location: FL,Keys

    PowerTech Senior Member

    that can happen with proper manifolds if not instaled properly.like not enough rise or to little of drop in the exhaust or to small of a muffler or allot of bends and to small of exhaust hose it is quite common.Boat builders are retards some times.I doubt the dude that started this thread would sriously instal a V8 car motor into a trawler.that would be nasty as hell.and you would have to buzz the hell out of it to make any horse power.If you have to marinize something your self get your self a industrial diesel out of some sort of piece of equipment.
     

  15. Filmdaddy

    Filmdaddy Previous Member

    But reversion CAN happen, right? Like Ton Kane said? That's the only point I was trying to make, so thanks, woodboat, for the support.
     
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