internal wastegate vs external wastegate

Discussion in 'Technical' started by maTTz, Nov 30, 2005.

  1. maTTz

    maTTz 500 Club

    can anyone please tell me the benefits of each?

    i thought i read somewhere that external wastegate means the turbo can spool up quicker (i can't remember exactly why but the impression i had was because the design is more streamlined or something)
  2. maTTz

    maTTz 500 Club

    i raise this because

    graham said this in thread:
    the thread is titled this:

    so it sounds like there could be issues with the turbo size on an upgrade :wacko:

    here is some literature:
    and from autospeed and turbosmart:

    and another quote
  3. Doom

    Doom New Member

    As far as I know

    Externals vent direct to the atmosphere instead of going thru your exhaust so they're much more efficient but they're noisy and not street legal anyway.
  4. Tektrader

    Tektrader Z32 Hoe, service me baby

    Re: As far as I know

    Well they can vent out to the Atmosphere, But usually you plumb them back into the exhaust further down.

    So the noise issue isnt one that is a concern.

    Here are the ones EGG got for me.


    They where only a little more expensive than the HKS actuators. But I have to make a special 5 bolt dump for them now. (I would have had to anyway with the GT28R's)
  5. Doom

    Doom New Member

    Ah ok I think mattz was one step ahead of me but I just learned something

    So back to his orig question whats the benefit of the external one?
  6. Tektrader

    Tektrader Z32 Hoe, service me baby

    Re: Ah ok I think mattz was one step ahead of me but I just learned something

    I can give you two reasons, but there may be more.

    The external gates can have a comparitively huge hole to enable the gas to pass through easier and quicker.

    Also their means of actuation is better and can keep the gate closed to withstand much higher boost pressures.

    The term "Wastegate creep" is where there is more pressure pushing the wastegate open than the old actuator has force to hold it shut.

    If this happens during boost the wategate can actually be forced open by the pressure of boost bypassing the turbine and losing boost pressure.

    External gates pretty much fix this problem and allow full boost right up to when the boost controller says "open".
  7. J4Play

    J4Play New Member


    better boost control. and also better flow dynamics, ie less power robbing viscous turbulence!
  8. maTTz

    maTTz 500 Club


    some of the literature i quoted said:

    A common myth is that in order to run higher boost pressures, you need a larger wastegate. This is incorrect. Larger wastegates are necessary to run low boost levels on large turbos.


    An external wastegate is also ideal for people that fit hybrid turbos with oversize compressors. They tend to experience a lot more backpressure in the exhaust manifold and a bigger wastegate helps in that regard," says Nick.

    Daniel continues, "If a compressor and turbine is matched to achieve good spool-up you generally can't have a hole big enough with an internal wastegate. The external wastegates come in various sizes and can pass a huge volume of exhaust gas. The appropriate sizing of the wastegate is dependant upon how much power you want to make and the size of the turbine. Space can also be a factor."

    "The size of the turbine and the wastegate really go hand in hand," says Nick. "If you've got a big turbo running high boost you might get away with a small wastegate, but if you run it at low boost you'll need a bigger wastegate. People often can't understand that; by running less exhaust gas through the turbine, you need to be able to dump it through the wastegate. The smaller wastegate is the more ideal choice because - by definition - there's less energy being wasted.

    "For a mildly modified streetcar that runs from traffic light to traffic light, it can be good to use a relatively small turbine with a large wastegate - this should give maximum bottom-end and response along with decent flow. But, yes, this approach does waste a lot of energy - there are all sorts of theories and it pays to go through with the appropriate development."

    sorry for repeating, but i think some people could learn from that... i know i did :thumbsup:
  9. dave b

    dave b New Member

    all zeds have external wastegates

    Their just plumbed back into the exhaust cause atmospheric is illegal.
    Also found out that GTS-T skylines have internal waste gates (another reason why zeds are better!)
  10. Dan

    Dan New Member

    All Zeds have _internal_ wastegates
  11. MexiCandu

    MexiCandu Grumpy of the Grampians

    Yep -definitely internal
  12. minivan

    minivan Guinea Pig Test Monkey

    Re: all zeds have external wastegates

    thats not true, internal is cheaper and suited to factory installs.. ive seen my internal wastegates face to face last week
  13. AAD00R

    AAD00R New Member

    Ain't no expert so diagrams help me - AND turbo engineering websites =)


    Image courtesy Garrett

    i would say factory turbos are built with internal wastegates that either vent or are feed back in, until someone wishes to upgrade
    IE factory builds internal for cost reason
    as internal is part of turbo therefore cheaper
    As you can see in the pic above that U shape diaphram moves back allowing venting to flow out following the red arrow in the pic, and this can then be left as is or plumbed back in as per our laws

    Turbo Features
    The Wastegate
    Most automotive turbochargers have a wastegate, which allows the use of a smaller turbocharger to reduce lag while preventing it from spinning too quickly at high engine speeds. The wastegate is a valve that allows the exhaust to bypass the turbine blades. The wastegate senses the boost pressure. If the pressure gets too high, it could be an indicator that the turbine is spinning too quickly, so the wastegate bypasses some of the exhaust around the turbine blades, allowing the blades to slow down.

    There are two types of wastegates. The first one is an internal wastegate. An internal wastegate is a component on the turbo unit itself. The gate is opened via an actuator which is a diaphram type system. Excess exhaust is then fed directly into the exhaust system. We also have what is called an external wastegate, unlike an internal wastegate, it is seperate from the turbo unit and does not require an actuator. Excess exhaust can either be fed into the exhaust system or it can be vented straight out and into the atmosphere. High performance set-ups typically follow the latter alternative. Most stock systems come with an internal wastegate as this set-up is better suited for low boost applications. However most aftermarket systems perform better with an seperate external wastegate assembly making it an ideal choice for those generating boost in the range of 20-30 PSI.


  14. dave b

    dave b New Member

    ok so what are the pipes that come down from my manifold

    and plumb back into my exhaust?
    please correct me if im wrong but are these not external wastegates?
    UAS dump and engine pipe for "stock" turbos
  15. Dan

    Dan New Member

    That is just the design for the dump pipes

    The waste gate is still internal or integral to the turbo. Those dump pipes split the outlet of the exhaust wheel and the waste gate. Supossdly to reduce turbulance and improve flow throught the exhaust wheel.

    An external waste gate is not a part of the casting of the turbo. It a a large canister plumbed into the turbo manifold (in front of the turbo).


  16. maTTz

    maTTz 500 Club


    if your turbo doesn't have an internal wastegate,and you fit external wastegates, then you won't be needing

    split/divorced dump pipes

    correct? :cool:

    so you can just get plain cheap ones that will save you more money

    and the rave that people give in regarding to using split dumps, ie the lack of turbulence, you will have that same effect by using external wastegate

    correct? :cool:
  17. J4Play

    J4Play New Member


    external wastegates make split dump pipes redundant, as there is nothing left to keep split. Dump pipes (when using external gates) only take exhaust gas that goes through the turbine, not around.
  18. maTTz

    maTTz 500 Club


    thats interesting... what if you had a Z with 4 exhaust pipes?

    2 from the wastegate and 2 from the dumps

    is there a way that could be beneficial? in terms of different backpressures for the 2 setups? i guess to be legal all would need cats... is there anything beneficial here? be creative please :cool:
  19. Tektrader

    Tektrader Z32 Hoe, service me baby

    Re: hmm

    Well if you dont plumb the pipes back in basically that is what happens. They are called screamer pipes for good reason.

    If you want a nice blow off vlave type sound nothing beats an unplumbed waste gate.

    The cops will love you as they defect the car at every opportunity :thumbsup:

    Sounds awesome but really loud AND KINDA COOL.:LOL:

    I can just imagine the look on peoples faces in chapel st when the wastegates open WOAHHHH
  20. maTTz

    maTTz 500 Club

    i just read

    some guy had screamers on his rex, rev'd it up near a shop, some people jumped on the floor as if a gun or bomb went off, and there were 4 fat harley bikers that half jumped for cover and were then losing it laughing and giving him the thumbs up

    remember teh adjustable bov that zrated posted a little while back? i wonder if you can get an adjustable wastegate...

    now would that b farking awesome or wot? :)

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