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Twin Turbo better than Single Turbo?

Discussion in 'V6 Development And Modification' started by Blue-Chip, Nov 8, 2005.

  1. Blue-Chip

    Blue-Chip New Member

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    Is a Twin Turbo set up better than a single turbo set up and why?

    We were just after some input from the forum members as to what their opinions are on this subject as each seems to have its own following.


    Cheers BCT
     
  2. jack.mc

    jack.mc Nothing witty to say :(

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    from what i've heard, a twin turbo setup is useful if you have one small one, and one big one - it lessens lag? I'm not sure on this, so dont quote me...
     
  3. Boonz

    Boonz Donating Member

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    if your going to have a twin turbo setup then why not ahve a turbo...and a supercharger....ive seen it done at CAPA and the results were awesome...
    all they used was a t/04 turbo that ran straight through to the supercharger on top of the block...get the best of both worlds for the same price as a twin tubo setup
     
  4. Shivaga

    Shivaga New Member

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    what your saying there is true. think about it...
    The turbo is run by the exhaust, therefore, the bigger the turbo, the faster the exhaust has gotta go in order for it to spin the rotors. so what some people do, instead of having 2 identical turbo's, have a smaller one, and then a larger one. if this dosnt make sense you can PM me about it all.

    Back to the question, i'd have to say that this (above) twin turbo set-up would be more ideal, aside from having a super!
     
  5. chevy_big_block_bro

    chevy_big_block_bro New Member

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    if yoy have a look at hinterland's post on making a new intake manifold for ecotech, he says he is going to run a turbo with an eaton charger between the turbo and the TB.
    How would this go on a twin turbo setup
    Twin turbo twin supercharger commodore!!!!!
     
  6. Boonz

    Boonz Donating Member

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    no rubber left in like 3 seconds i rekon haha
     
  7. Shivaga

    Shivaga New Member

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    lol, thas about right.
     
  8. Bax

    Bax Projecting

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    Depends how its set up.

    Twins in series - so the smaller starts pushing through until the larger is wound up and then the larger takes over. Or running parralell I guess, two smaller turbo's/ instead of one larger turbo. Improved spool time, better efficiency and same power.

    The latter being easier to setup - Because when you think about running them in series, the first mode of delivery kinda restricts the second. i.e. a small turbo or small blower will have to be bypassed once the larger turbo has reached its power band.

    I'd stick with two smallish turbo's in paralell.
     
  9. Blue-Chip

    Blue-Chip New Member

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    The twin staged setup that works to the best of my knowledge is as follows:

    The main turbo is the small unit that is plumbed to your exhaust manifolds as normal and blows into the intake plenum.
    The dump pipe from the small unit discharges into the exhaust entry of the large unit, the large unit draws air from the air cleaner and then pumps into the entry of the compressor housing of the small unit.
    This type of set up works relatively well and has the best of both worlds,quick spool up and high levels of boost. Ideal for methonal applications.

    Its good to see you guys have lots of different ideas as to set ups. As far as the S/C Turbo combo in my opinion this sounds like an awesome idea using a turbo to blow through a Supercharger providing that the Supercharger isnt an eaton M90, if I was to do somthing along these lines I would use somthing like a Whipple or Autorota with matched male and female screws to prevent leakage.


    Cheers BCT
     
  10. blofly

    blofly Guest

    if you were to run a turbo charger into a supercharger how would you go about intercooling the final charge? I mean after air is compressed by a turbo it is about 80-90degrees sometimes then stuff it into a supercharger and heat it up even more? And what about the cost of the supercharger robbing 15% of the crankshaft horsies?
     
  11. Shivaga

    Shivaga New Member

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    when the larger one is being used, the smaller one just diverts to its wastegate.
     
  12. Cheap6

    Cheap6 New Member

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    My opinion, so open to debate (While I have had personal experience with positive displacement and centrifugal mech. S/C and single turbos, I am definitely not the last word in forced induction):

    Sequential turbos, one large for top end power, one small for fast spool up and low end power - Very difficult to get to work successfully. Even manufacturers, with access to professional engineers and computer modelling have difficulty in making such systems work. eg. Liberty/Legacy
    TT, S6/7 RX-7. The problem lies in switching from one turbo to the other. First, the exhaust gas flow has to be distributed prior to the change over point, robbing the smaller turbo and making it difficult to spin the larger one. It is also difficult to match the flow of both turbos at the change over point, particularly over a wide load range. Not doing so leads to noticeable dips in the power/torque curves.

    Twin turbos in series - used i believe on some diesels, perhaps stationary engines or elsewhere that changes in load are not great. Intercooled between each stage, the idea is to increase efficiency over a single large compression and/or expansion (turbine) stage. I don't think that throttle reponse to changing loads is a priority. Long and complicated pipe runs would make throttle response poor and difficult to fit in a car.

    Using a mechanically driven supercharger and an exhaust gas driven one, sequentially, has been done before, most notably by Lancia in their S4 rally car of the mid-late '80s. I also recall an HKS turbo bolt on turbo set up for
    Toyota 4AG-ZE (factory S/C'd). Both of these used positive displacement (Rootes type), mech. driven S/C, switched out and bypassed when gas flow through the (large) turbo was great enough for it to be efficient. Change over is easier to achieve seamlessly than sequential turbo. as the air flow through the positive displacement S/C is more closely a linear function of engine (blower) speed than gas flow through the whole system and there is no distribution of exhaust gas required.

    Mech. driven centrifugal S/C makes some sense on an engine that is restricted in valve area relative to piston area and therefore limited in high engine speed air flow, such as a two valve per cylinder engine; the S/C works best when the engine works worst (at higher engine speeds). Because the output of a centrifugal s/c is a non linear function of its speed, its performance is dependent on the gear ratio it is driven at. Attempting to provide boost at low engine speed by high gearing and bleeding off the resulting excess boost at higher engine speeds is extremely inefficient. (Although maybe some extra intercooling effect could be achieved by doing so after intercooling through a heat exchanger, like aircraft air conditioning).

    For a street driven car, I think that simple positive displacement s/c, twin parallel or single turbo. are the most practical options. Which is better depends on what is trying to be achieved and how much money is available.

    Positive displacement blowers fit very nicely into the valley of 'V' configuration engines. Airflow and therefore power delivery, is more linearly related to engine speed with a positive displacement s/c. Throttle response is very similar to a N/A engine.

    While there isn't (someone may prove me wrong) enough space to fit twin turbos between the chassis rails and engine of VN-VS Commodores, I would suggest that twin turbos would have advantages in packaging and plumbing over singles on most 'V' engines. VT- may be a different situation, but I have no recent direct experience and I suspect not. I believe that there are still advantages in packaging and plumbing with twin turbos over single in a VN-VS and VT-.

    If the turbos are to be sourced used, perhaps as Jap imports, there is likely to be a much wider range of suitable sizes available for a twin turbo set up over a high flow single. For this reason, twin turbos on a budget turbo RB30 may also make sense. (The issue is less clear cut because of the large (aftermarket) development history for this engine with turbo and wider range of turbos of suitable size available).

    Most street driving is done at low engine loads where boost response is important = adv. for positive displacement blower. At the higher boost levels required to make really big power, blower efficiency falls away so centrifugal compressors, turbo or mech. driven start to look better.

    In theory, twin turbos should have better response than a single, particularly where plumbing runs and gas volumes can be kept smaller with twins, as in a 'V' engine.

    A well set up and sized system of any configuration will outperform a poorly set up system of theoretically higher efficiency.

    Re: power to drive a mech. s/c. The power required to drive a turbocharger is not entirely free either as the turbine impedes the flow of exhaust gas out of the cylinder somewhat. This is less of a problem where the exhaust valve area is already restrictive, as in a two valve per cyl. eng.
     
  13. chrishodge

    chrishodge Guest

    Sorry to be bringing an old thread back from the dead but would uneven back pressure be an issue when using a single turbo setup on the 3800 V6? A while back I was talking with a mechanic and he said he would have opted for a twin turbo over a single due to the uneven back pressure! What are peoples thoughts.
     
  14. burnz

    burnz dah dut dut da dah

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    how much space?
    are we talking vee or inline?
    six one halve dozen or the other all the same!
     
  15. chrishodge

    chrishodge Guest

    talkin V6. Thanks for the answer champ. Cheers
     
  16. Stewart1000

    Stewart1000 work done by ME

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    VL twin turbo. VN5L. old jeep, shit mondeo.
    yeah, i saw a setup in a mag, cant remember what one, it was a turbo running into a super, but i wonder that spin the shupercharger too fast?
     
  17. hinterland

    hinterland commyvt

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    my setups getting closer every day this is day 2
     

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