Venturi to increase exhaust?

Discussion in 'Engine & Performance' started by Camar068, May 6, 2017.

  1. Camar068

    Camar068 Supporting Member Supporting Member

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    Going to look at the configuration of our sterilizers tomorrow. They use water to pull, up to a 28", vacuum on the steam chamber. The black/white diagram appears to be correct...for what's used on a steam sterilizer at work. I've got Inlet gas at 45° stuck in my brain for some reason. Been a while since I've worked on them.

    All good points.
     
  2. theblindchicken

    theblindchicken Full Access Member

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    @chengny; just finished my final on monday for my fluid mechanics class.

    Some super interesting stuff, by maaan its a lot.


    I feel like as long as you could direct the airflow purely downwind in the exhaust, there would be an improvement. But only if the ambient air was building a higher pressure than the exhaust gases themselves.


    So if you had a scoop set, it probably wouldn't have any effect on the piping until you hit at least highway speeds. Driving around town probably wouldn't do much for it, and more likely hinder the flow.
     
  3. 87ChevyR10

    87ChevyR10 Full Access Member

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    Wasn't this idea explored back in the 70's and 80's? I seem to recall a certain system on these vehicles that everyone wanted to delete. It was usually belt driven, pumped air into the manifolds and such. If only I could remember the name of this system.
     
  4. Honky Kong jr

    Honky Kong jr Super Sarcastic Man

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    That was for emissions at start up. It's called secondary air injection no a days. It pipes in fresh air to the exhaust to clean up tail pipe emissions when the engine is cold......smoke and mirrors for the tree huggers.
     
  5. Camar068

    Camar068 Supporting Member Supporting Member

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  6. Honky Kong jr

    Honky Kong jr Super Sarcastic Man

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    Hey others said it was useless and would work I found that they aren't and do.
     
  7. 87ChevyR10

    87ChevyR10 Full Access Member

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    I was being sarcastic. However, whether the air is being pumped in or venturi'd out, it's still doing the same thing: pushing the exhaust gasses faster through the exhaust system. Why not take that smog pump, reroute the air line near the end of the exhaust and see what happens. At least this way, the scavenging effect would be present no matter how fast you're moving.
     
  8. Georgeb

    Georgeb Full Access Member

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    I think in the end headers, an X-pipe, free flowing mufflers and properly sized pipes do a pretty good job of scavenging. I believe the venturi works because the outlet is near the end of the pipe and open to atmosphere but still very close to the engine since it is installed in the header collector. Would it be true to say that increased back pressure from more pipe length, the accumulation of bends and the addition of mufflers would reduce or eliminate any gains the venturi could provide? I believe time spent on induction and ignition after the above mentioned exhaust system would be more beneficial than trying to create a "vacuum scoop" under the truck where turbulent air flow abounds.
     
  9. Rusty Nail

    Rusty Nail Deo Vindice

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    Right, but the heat, man. Voted no because not enough consideration is given to the exhaust gas temperature, which is really high!
    Wouldn't the incoming cooler, fresh air be stifled by the rapidly expanding, escaping hotter exhaust?


    And what Jerry said.
     
    Last edited: May 20, 2017
  10. 68post

    68post Full Access Member

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    Additional scavenging is done with a merge collector and/or an X-pipe - plus a correct length of pipe of the correct diameter after it. No need for further scavenging.

    The best work is done by headers scavenging the cylinders, unless the rest of the exhaust is built too small and/or restrictive in other means, (mufflers), and keeping the headers from being their most efficient, no more should be needed or would do any good.

    For smallblock powered street vehicles I use 3" collectors into either ; a 3" H-pipe setup and long tapered 3" to 2 1/2" reducers, or the reducers first and 2 1/2" H-pipe setup. Then into 2 1/2" mandrel-bent pipes all the way to the back or at least over the axle. The mufflers need to be as far back as practical, and with at least an approx. 14" pipe afterwards.

    Exhaust gases cool as they travel,(and slow down), and therefore also take up less space within the pipe. Sooo ... tailpipes can actually be a size smaller with no ill effect !

    Just look at any racing exhausts to see what works within that engines operating range, the brightest minds the world has to offer have had decades to reengineer them !
     

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