External wastegates?? Worth it?

Thread in 'Technical Questions' started by aaronblue, Oct 13, 2015.

  1. aaronblue

    aaronblue Active Member

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    Hi all I'm currently building a mx5 turbo with a few bits I have around. I have a CT26 turbo from a mr2 turbo and I'm making my own manifold but I was thinking is there a need for an external wastegate? I'm not that knowledgeable of turbos. Any help would be great.
     
  2. Stavros

    Stavros Active Member

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    Isn't a MR2 CT26 a twin scroll twin internal gate turbo?

    If it is, hell no. Build a twin scroll manifold for it tho.
     
  3. aaronblue

    aaronblue Active Member

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    Cheers buddy saves me time and money.
     
  4. Boostd2

    Boostd2 Member

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    Twin internal gate? I don't think i've heard that before, nor has been any turbo running dual internal wastegates, ever.
    The mr2 CT26 is a "Twin Entry" turbo with internal wastegate. It is NOT a true twinscroll turbo, meaning the housing is not fully divided. Just the turbo exhaust entry is divided. many people confuse the terminology and call it a twin scroll tho.
    You could always weld the internal gate shut and run an external wastegate. Should make a bit more power then. And generally speaking the ct26 is no good beyond 15psi or so. It simply cannot hold boost beyond that in the engine's upper rpm range. Beyond that you'd be better off with a SR20 t28bb.

    Good Luck!
     
  5. Stavros

    Stavros Active Member

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    Err, right o. Cool info bro. Don't agree with any of it though tbf.

    Regarding these twin intergal gates you seem to not believe even exists...

    The 3SGTE CT20/CT26 has 2x internal wastegates, and is fully divided, fully twin scroll...

    [​IMG]

    Oh, and a Mitsubishi Evo one...

    [​IMG]

    [​IMG]

    [​IMG]

    Oh yeah, and FC RX7 ones...

    [​IMG]

    Oh yeah, JDM Impreza STi too...

    [​IMG]

    Oh, and plenty of others, like this GT3576...
    [​IMG]

    Shall I carry on? Or have you seen them now?
     
    #5 Stavros, Oct 20, 2015
    Last edited: Oct 20, 2015
  6. Boostd2

    Boostd2 Member

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    Those are all single wastegates, just 2 ports. They all have 1 actuator opening those 2 ports, which is the same as 1 WG. The ports are not the wastegates, the actuator that opens up those ports is the wastegate actuator. Twin wastegates required twin actuators for it to be a true twinscroll setup. You never see that with internally gated turbo's.

    But you were correct on it being a true twinscoll tho, I confused it with a supra ct26 I had years back which was not.
    My bad on that.
    Nice job on the pictures tho!
     
  7. Stavros

    Stavros Active Member

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    Eh?

    It doesn't make any difference how many actuators there are, that's true twin scroll twin gate.

    You never see two actuators as that would be retarded and pointless when they only ever are meant to open at the same time.

    Where the turbine flow is bypassed is a wastegate.
    The hole and the flap, thats a wastegate.
    That's what it means- Waste exhaust gas. And a gate to open and shut to let it through or not.
    And there's two holes and two flaps, thats two wastegates.

    You could have 90000 actuators controlling one internal gate, it's still got one wastegate.
    You could have 90000 wastegates controlled by one actuator, it's still got 90000 wastegates.

    Its true twin scroll, and has one wastegate for each scroll. Fact.
     
  8. Michael7s

    Michael7s Member

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    which is recommended wastegate to buy? quality/price
     
  9. C35Rob

    C35Rob Member

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    Stavros is correct, the CT26 is a proper twin scroll, they're also a bit crap (i've got an mr2 - with a CT20b - as well as my C35) the exhaust housing is really small, as are the wastegate ports. boost creep is a big issue on 3Sgte's running CT series turbos especially once you ditch the cat and fit an exhaust that isn't restictive, it probably won't be as much of an issue on a 1600 mr2, but it's worth porting the wastegate as much as possible when the turbo is off to give yourself a fighting chance.
     
  10. sparky_s13

    sparky_s13 Active Member

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    Facepalm.

    Wastegates are exactly what they say on the tin, gates for the waste gas.

    Also you can get single wastegate twin scroll manifolds, its jus the collector that defines how many wastegates are required.

    Nobody should EVER try to tell Stav about turbos. #Turbogod lol

    And to answer the OP's original question, external wastegate errrrythingggg, even if its just for noise, youll also never get any better boost control with internal gates
     
  11. Boostd2

    Boostd2 Member

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    I understand what your saying and I agree with you 100%. But if the flaps operate as one, meaning they open at the same time for both scrolls, wouldn't it just be 1 wastegate with twin scroll housing? You get me? I said i've never heard anybody or a turbo company calling their units 'twin internally wastegated turbo. That's what's referred to as twin port or twin scroll. The housing up till the gate/port/exit itself is divided but with one wastegate actuator operating on it.

    I think you guys are calling the scroll exits (ports/holes/turbine exit) the wastegate. Which technically speaking is a 'wastegate' too (it wastes the gas), and in that manner you'd then refer to it as twin wastegates because it's divided in two. In your vocabulary then twin scroll and twin wastegate should mean the same thing.
    So why would you call the turbo twin scroll with twin internal wastegate?
    It should be called a twin scroll housing with internal wastegate.


    So in that way the mr2 ct26 is true twin scroll or 'twin entry' as Toyota called it, but not twin internal wastegate. The twin scroll already refers to the fact that the gate/hole/port is divided in two.
     
  12. Stavros

    Stavros Active Member

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    You seem to misunderstand what is called what and why. Or are just trying to be argumentative, I'm not sure.

    The wastegate actuator is called that because it actuates (ie operates) the wastegate. The actuator is NOT part of the wastegate.

    The wastegate is simply the hole with a flap that the exhaust gasses flow through.

    And if there's 2 of them, there's 2 wastegates. It don't matter if it's internal or external.

    And its nothing to do with how many actuators its got, as thats not part of the wastegate, it just actuates it, hence the name.

    An engine powers the wheels, that doesn't mean a car has 1 wheel just because it has one engine...
     
  13. Boostd2

    Boostd2 Member

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    But wouldn't twin scroll/divided housing and twin wastegate mean the same thing to you then?
    so why call the turbo twin scroll twin wastegate. jsut call it twin scroll, or just twin wastegate.
    Your giving the same thing 2 different names.

    an example:

    So hypothetically if you had a twin turbo car, with both turbo's having a twin scroll turbine housing/divided housing with internal wastegate(both operated by single flap), you'd call it quad wastegate then, correct?

    However if on the same car you had the same twin turbo's setup but with 2 external wastegates (again single flap port), one for each turbo, you'd call it twin wastegate setup.

    I think the actuator is definitely part of the wastegate. If the actuator did not get any pressure input it would not open at all and wouldn't bypass/waste any gas past the turbo. It'd be the same as having NO wastegate at all. So the actuator is definitely needed to open the port for what you call the wastegate to flow exhaust gases past the turbo.

    I think we're getting confused on the terminology but mean the same thing. But you are calling the same thing by 2 different names. Like i call where my engine sits the hood, you call it a bonnet.
     
  14. Boostd2

    Boostd2 Member

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    True twinscroll setups will not have the scrolls interfere with each other ever. And if you have a twin scroll manifold, it requires a collector that is seperated in two,plus wastegate('s) Thus requiring 2 wastegates optimally, one for each scroll. True you could get single wastegate twin scroll mani but it wouldn't be called a twin wastegate mani then. Because the pipe would have to merge to fit 1 external wastegate.

    In the way Stavros names it, a twin scroll single wastegate exhaust manifold would have to be called Twin scroll Twin wastegate exhaust manifold, because it has two holes (even though that merge) where exhaust gases can be wasted past the turbine.
    Like this

    [​IMG]

    These single wastegate twin scroll manifolds are not good IMO because they allows pressures in both ports to equalize at the merge for the wastegate before reaching the turbine pretty much making it pointless to go twinscroll in the first place. Like said before, True twinscroll requires 2 wastegates (if external) and if the wastegate is internal if must have the ports/scrolls separated from turbine entry up until the wastegate exit/flapper.
     
    #14 Boostd2, Oct 22, 2015
    Last edited: Oct 22, 2015

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