Whats a waste gate for

Discussion in 'Diesel Engines' started by Frosty, May 28, 2007.

  1. lazeyjack

    lazeyjack Guest

    maybe we start new company Stian?
     
  2. Frosty

    Frosty Previous Member

    I thought you were posting sequential pics for me.

    I was infact refering to compound charging.

    I am of the opinion that a waste gate can be removed on a single turbo engine if you want pressure then why waste it. You have your foot on the gas? Your in charge.

    Unless it is on a generator 300 yds away
     
  3. FAST FRED
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    FAST FRED Senior Member

    Most fun is the truck folks have just "rediscovered " the PRT.

    Power Recovery Turbine, where the exhaust gases go thru a turbine which is geared down and simply adds power to the crank , via a shaft.

    The 3350 air craft engines had 3 of these PRT , rated 150 hp each , back in the 50's.
    They used mechanical 2 speed supercharging and alcohol injection for 1 hp per cubic inch ,for take off rating.

    Whats old is new again,

    ********

    Question , for the new boat I'm looking for a 200rated Hp engine that is Legal (tier 2) yet will operate with out electric?

    I can fix mechanical injection , but not rebuild a computer ECM at sea (or ashore)..

    Prefer no rubber belt driven camshaft too.

    Cummins B-4 seems close.

    FF
     
  4. Frosty

    Frosty Previous Member

    What the hells going on here.

    Sequential is 2 turbos one small one larger. The engine winds up using the smaller first as is more efficient at lower speed untill the bigger one can be brought on.

    The pics are not a sequntial set up?????? look at the circuits you have given me.

    Your just googling stuff and contradicting yourself.


    The tubos are the same size on both pics and drawings and are fed from a common manifold. AND are blowing down a shared manifold.
     
  5. StianM
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    StianM Senior Member

    Shure, what will we do? Just transfere some money for investment to my cayman island bank account. Where can I order cheap tickets to Brazil?

    The only diesels I have noticed has a wastegate is high speed diesels. All the large diesels don't have. The optimal for fuel efficensy is a turbo working with a perfectly matched engine setup running at a high load, but once your going to drive on part load or half load the way to go is wastgate.

    Are you investing in a new engine since you wondering about this?
     
  6. StianM
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    StianM Senior Member

    [​IMG] Read!

    [​IMG] I circled in a nice litle valve for you in black. Once this valve is closed one off the turbos will have no flow.
     
  7. Frosty

    Frosty Previous Member

    Thats a very complcated system now I look at it needing 2 valves in actuall fact to also shut down intake from the non op turbo.

    Bloody Italians.
     
  8. StianM
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    StianM Senior Member

    I don't think the Italians invented it.
    I know it has ben used in some upgrade kitt on some boy racers from japan.

    I would gues it's a invention from UK or Germany since they are some off the countrys with the strongest motorsport tradition. I don't know this, but hust gues.
     
  9. Frosty

    Frosty Previous Member

    Very interesting but remember waste gates. Thats the thing that opens up and expels all the power that youve just built up.

    My engines are reaching 3800 and the turbo boost meters are just out of its needle rest.

    You dont need a gate when the throttle is in your hand.

    Now without coming head to head with Google!!!

    Unless its a generator that MAY run away and the cycles go up to 70 with 270 V and you have to run with your pants round your ankles to shut it down. A waste gate would be real handy in that senario.
     
  10. Steve in SoCal
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    Steve in SoCal Junior Member

    Jack,

    Are you questioning why a waste gate is installed on some engines but not others? On most engines with a waste gate the engine is used in an application where an overload could produce high boost and melt pistons.

    To reduce the chance a waste gate is installed. Compounding and sequential turbos may be used where demand or flow merits the design. One large turbo has more mass to accelerate and needs more heat and pressure to drive it. On an engine that uses high boost from a low RPM to moderate or high RPM the amount of air needed changes greatly from low speed to high. Adding another turbo to increase airflow is the point. Now if the engine is under high boost and at high RPM and for some reason the slows down; overload. The waste gate opens to vent pressure so the engine is not damaged.

    The waste gate is like a water pressure regulator on a building, it is not used to waste pressure but to control maximum pressure. It will bleed off the excess pressure when conditions create over boost.

    Steve
     
  11. marshmat
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    marshmat Senior Member

    Seems there's a few different ideas floating around here as to what a wastegate is and what it does. I'm no expert on marine diesels, but provided the terminology is the same with diesels as gas engines, the following description is reasonably accurate.

    When you slowly open the throttle of a turbocharged engine, the turbocharger speeds up with the increased exhaust flow, which in turn increases the boost pressure created by the turbocharger. At some point the system will come to equilibrium, with the turbocharger using some of the energy left in the hot exhaust gases to compress the intake air flow.

    When you quickly open the throttle, the exhaust pressure builds faster than the turbo can speed up (remember, it has to go from 10,000 to 90,000 rpm in about one second). To allow the engine to rev up normally during this brief time while the turbo climbs to operating speed, the wastegate opens to relieve the exhaust pressure and allow some of the exhaust gases to bypass the turbo. Hence why turbocharged cars have less "turbo lag" when a wastegate is fitted.

    If the boost pressure on the intake side starts to get too high for the engine to operate correctly, the wastegate will open. This vents some of the exhaust gas directly to the exhaust system, bypassing the turbo. Reducing the exhaust flow through the turbocharger causes it to slow down, reducing the pressure on the intake side.

    I have never seen a wastegate fitted to the intake side of a turbo; by definition a wastegate is a device which allows waste exhaust gas to bypass the turbocharger if necessary.
     
  12. Steve in SoCal
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    Steve in SoCal Junior Member

    Matt,

    I don't know if you are referring to my above analogy about water regulators. I used that as an example of how the waste gate regulates boost pressure. I have seen waste gates on both the intake and exhaust side, on diesels the exhaust is controlled by intake pressure or transducer but both rely on inlet boost pressure to control waste gate activation.

    The valve I am familiar with in spark ignition turbo systems is a bypass valve, it allows the engine to accelerate using manifold pressure from the plenum until the boost overcomes atmospheric pressure. This is also used with centrifugal superchargers.

    Steve
     
  13. marshmat
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    marshmat Senior Member

    Ahh, OK Steve. The device you refer to which relieves intake manifold pressure under quick slowdown is what I usually hear referred to as a blow-off valve, bleed valve or relief valve (sometimes also called bypass or diverter valve... this one's got many names depending on exactly where and how it vents the excess pressure) it allows some intake air from the high-pressure side of the intake half of the turbocharger to vent to ambient or back to the compressor intake while the turbo slows back down to idle. This helps keep intake manifold pressure from getting so high as to damage anything, especially the turbine. Not quite the same function or purpose as a wastegate, but fairly similar. Am I referring to the same device as you are here?
     
  14. Steve in SoCal
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    Steve in SoCal Junior Member

    Blow off valves are indeed what you may have though I was talking about. I think we are on the same page.

    Steve
     

  15. Steve in SoCal
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    Steve in SoCal Junior Member

    On reading my own reply I should clear this up. The blow off valve is not what I was thinking about when I first posted. The waste gate will get an overboost signal and dump exhaust to reduce inlet pressure within a few revs of an engine. As Matt said; the by pass or blow off is designed to keep parts from breaking on a high overboost condition. The blow off valve can be the weakest link (hose) on the inlet system!!!

    Steve
     
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