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Thread: Muffler ?'s Reversion?

  1. #1
    Bryan Rose
    I see some Manufacturers are claiming to eliminate reversion , is this possible and how is it done? by creating more back preassure? Any one have any ideas? One in particular is the Drew Marine Shotguns. I would like to know.............................................. ................
    Bryan

  2. #2
    Dana Marine Products
    The Drew shotgun mufflers have a spring loaded rear stainless plate that will act like a flapper. By having an additional flap plate on the back similar to the external clamp on flappers you can help eliminate back wash up through the transom.

  3. #3
    Bryan Rose
    I was under the impression that reversion occured inside the header or exhaust from the water introduced to cool the exhaust system itself, not from water drawn in from outside the boat at the transom....
    This is why I thought most people who manufacture exhaust like to tout that they introduce the cooling water fartest back as possible, trying to eliminate or at least control it.
    Am I wrong here?
    Bryan

  4. #4
    Senior Member
    Join Date
    Jun 2009
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    10,871
    I was under the impression that reversion occured inside the header or exhaust from the water introduced to cool the exhaust system itself, not from water drawn in from outside the boat at the transom....
    This is why I thought most people who manufacture exhaust like to tout that they introduce the cooling water fartest back as possible, trying to eliminate or at least control it.
    Am I wrong here?
    Bryan
    You are exactly correct. (http://shopping.rexmar.com/Merchant2...-pslrumor-fact) The term reversion is the inverse flow pulses created primarily by large camshafts at idle. It can actually suck water droplets up the inner wall of the riser pipe if the water is introduced into the exhaust stream too close to the manifold outlet (too high) back into the cylinders.
    "Backwash" is when a surge of water flows backwards through the exhaust tip or silencer when the boat comes to a stop.
    They can have the same result (water in the engine) but are not the same thing.

  5. #5
    Senior Member
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    4,169
    Reversion is a function of cam design. Generally long duration or overlap will cause exhaust to be drawn back into the chamber thru the exhaust port. If there is water injected into the exhaust gas, it will go back into the chamber along with the gas. The scavenging effect headers produce help minimize reversion midrange and higher, but there is not enough velocity to prevent it at idle/off idle. That's why Bassett made the T to pevent water injection until rpm is over about 2000 rpm.

  6. #6
    Dana Marine Products
    As Rexone stated, you are exactly right on the reversion issue. Introducing the water as far back in the exhaust system is safe and many times necessary to avoid reversion. On your question regarding mufflers, no muffler is going to help prevent the cam from sucking water back in. A muffler properly equipped can help prevent back wash through the transom. On the flip side, you have to be careful with any exhaust configuration to make sure too much water is not being withheld in the exhaust. This can back up and reversion can occur.

  7. #7
    Bryan Rose
    So when a muffler company claims " eliminates reversion " As does the drew marine site , they are full of Sheeeeaaaaatttttt correct.
    Bryan

  8. #8
    Floored
    you have reversion in the intake and the exhaust so a muffler will not stop what happens ahead of it. you just hope the muffler won't act as a restriction when water is added to the exhaust stream and becomes steam which increases the volume of flowing gasses in the pipes which then pulse in and out, more noticeable at low rpm's with a large cam. If the water is withheld until the exhaust has suficient flow to shorten the pulse length then no water gets into your engine( T-valve, Banderlog valve) If they,the valve, stick open at idle even with no muffler you will suck water. muffler just needs suficient flow and sound cancelling to do the job with minimum hp loss. We aren't running step headers and specific tuned length headers built for our engine combo, we buy a set of cool looking headers, chrome of course, and bolt them on and go and try not to blue them or get a noise ticket. :idea:

  9. #9
    Dana Marine Products
    Any type of water injected headers, Bassett, Rewarder, etc... can have reversion very easy beacuse the water is being introduced so close to the head. Any double wall system that is introducing the water much further back in the system can also have the problem if the ingredients are right. As far as your initial question with regards to advertising a muffler that prevents reversion, I can't provide a direct answer to that scenario other than the muffler helping prevent back wash.

  10. #10
    Bryan Rose
    I do not run OT headers, I run water jacketed Lightning Headers. I do not have reversion now I was just curious about the muffler claims.
    thanks for all the great input. :rollside:
    Bryan

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