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Thread: Twin Turbos

  1. #1
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    Twin Turbos

    Hi guys, I have a question regarding twin turbos. I have been learning a lot recently about how turbos work. I now know that sometimes it pays to have two turbos. One can provide instant power (with lighter components) and the other can provide more power higher up the rev range.

    My question is, does this affect the amount of air inlets to the engine? I have noticed on a twin turbo Porsche (928 I think) that their were two air intakes, it almost looked like one for each bank of the engine. I beleive the car had a twin turbo. Was this because it was a twin turbo? Are the turbos configured to work at different rev ranges on different air supplies or are their actually a turbo and air intake for each bank of the engine (seperate?) I would have thought that if the turbos were simply for power at different revs they would run of the same air supply? I haven't had a look at any quad turbo engine bays but would they have four air intakes or just one?

    If any one could shed some light on this it would be much appreciated.

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    Having two turbos doesn't mean its always one turbo for low rpm and one for higher. You can have a set up so both turbos are the same (parallel) or you can have a set up that has one for low rpm and high rpm (sequential). I would think for both systems you'd want a single air intake so that the air going into is balanced, so one bank isn't running at a higher/lower boost than the other.
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    Generally if you have parallel turbos, each turbo would run off the exhaust of the other bank. This means that if for some reason one bank was working harder than the other the great resulting exhaust pressure would spin the other turbo harder to even things out. That should mean you can have two seperate yet equal air intakes.. like on either side of a Porsche 911 turbo for instance.

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    Quote Originally Posted by johnnynumfiv View Post
    Having two turbos doesn't mean its always one turbo for low rpm and one for higher. You can have a set up so both turbos are the same (parallel) or you can have a set up that has one for low rpm and high rpm (sequential). I would think for both systems you'd want a single air intake so that the air going into is balanced, so one bank isn't running at a higher/lower boost than the other.
    this, even if I suspect the damn electronics would equal the situations in various cylinders even if each provided of its own air intake.

    In the old 928 the turbos were working in parallel, as on the last GT-R, as opposed to the previous R34s, for instance.
    Hypothetically, you'd want to have even more turbos for each bank, but it isn't feasible both for mechanical and fluid-dynamics loss and for a complicated (and expensive) layout.

    I don't know if you're into energy plants, but they use multi-stadium turbines, which is somehow a similar idea to turbocharging the engine (very somehow). Given that those turbines are as big as a bus if not more, and keeping on comparing them to a turbo, they can use way more than just two turbos.

    Just to get things right, the turbine does the opposite thing than a turbocharger, that's to say it expands the fluid rather than compressing it, and it's the thing connected to the exhausts.
    It isn't possible to use more than a stadium (which somehow like using more than a turbine) due to the after all low temperatures and pressure levels in the exhausts of an ICE.
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    First of all, there is no indication I have read anywhere that a twin turbo is any better than a single turbo system. My beleif is that use of a single or double intake system depends on how the intake runners are designed. Some cars intake runners or plenums are poorly designed, and this is restrictive enough to require twin intake systems rather than a single intake system.

    An engine with a good single intake system and a single turbo, will produce just as good power as an engine with a twin turbo system. In fact, the single turbo system may be even smoother in power delivery than the twin turbo system, especially for everyday use.

    The idea that a twin turbo system is better than a single turbo system is not entirely true, if you take into account the restrictive nature of the intake runners or plenums, and the intended use of the turbo.

    The major difference I see bewteen a twin turbo and a single turbo is that the twin turbo can still produce more power if such a requirement is a desire of the owner of the car. A twin turbo system tuned at 10 psi will produce the same power as a single turbo system tuned at 10 psi, for the same engine. Better still, a supercharger is even better for daily use but at the sacrifice of some power lost because its turbos are turned by the power of the engine crank.

    Single turbo system---less heat produced in the turbine blower when compared to a twin turbine blower system.

    For example, the VQ35 DE engine of Nissan was designed with single intake systems. The next generation engine called the VQ35HR was designed with a double intake system. Yet, you can install a single turbo or a twin turbo system to the VQ35DE engine, which has a single intake system.

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    what about the variable vane turbo's used nowadays too? like in the 335i and the 911 Turbo.
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    Variable vane turbos should ordinarily create a more powerful vortex or swirl of intake air compared to equal length turbos with less energy, which in theory, should increase the power output delivery of the turbo blower, with less energy and consequently less heat output. The less the energy the blower uses to produce a powerful vortex of air delivered to the intake, the better and more reliable the turbo. Just a thought.
    Last edited by G35COUPE; 09-27-2009 at 05:52 PM.

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    VVG turbos aren't so much about creating more from less so much as creating from less or more without the usual loss of efficiency associated with less moving much.

    Or, if you want an explaination that makes sense, try this.

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    Leon,
    I think you meant to say "stage" not "stadium". We would refer to multi-stage compressors or turbines. I'm going out on a limb and guessing that was some type of mistranslation from Italian.

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    Quote Originally Posted by pimento View Post
    VVG turbos aren't so much about creating more from less so much as creating from less or more without the usual loss of efficiency associated with less moving much.

    Or, if you want an explaination that makes sense, try this.
    I knew what you were trying to say and I stil couldn't follow you.

    I would have just said that since a big turbo gives more boost but a smaller tubo spins up easier then VVG is just trying to get the best of both worlds in a single turbo. I'm wanting a VVG twin turbo setup to try to kill lag completely for my dad's truck, but it's more work that it's apparently worth. Although the VVG tech from semis did make it's way into the 6.7 cummins when it came out and that made a pretty big difference in power delivery.
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    VVGs have been fairly common in diesels for a while now due to the cooler exhaust temps. The 911 turbo was the first I heard of them in a non-limited production petrol car, but I'm not sure that's factual.

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    Quote Originally Posted by G35COUPE View Post
    First of all, there is no indication I have read anywhere that a twin turbo is any better than a single turbo system.
    having switched from a single turbo car to a twin turbo car last year, I can now let you read the first indication that bi-turbo is better. It considerably reduces turbo lag.
    Probably you may want to read also a test of a BMW 335i, which is a car that is more familiar to the country where you live.
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    Thanks for the info guys. From what you have said I understand that you can have two turbos running off the same inlet for power at different RPMS, or alternatively have two turbos working the same RPMs but on each bank of the engine with seperate inlets.

    In this situation, I take it each turbine section would be located at the end of the manifold on each bank.

    I am aware of Porsche putting VVG on their 911 Turbos now. I have driven the Nissan GTR and I can tell you their is no turbo lag. Would be interested if this uses VVG too. Haven't driven the 911 turbo, but from a TV review comparing it to the GTR they claimed the GTR made the 911's turbo lag noticeable.
    Last edited by TheScrutineer; 09-28-2009 at 01:13 AM.

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    Quote Originally Posted by TheScrutineer View Post
    In this situation, I take it each turbine section would be located at the end of the manifold on each bank.
    for your info, I have a single bank 2.2 litre four pot, with twin sequential turbos....
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    Quote Originally Posted by G35COUPE View Post
    First of all, there is no indication I have read anywhere that a twin turbo is any better than a single turbo system.
    may I suggest an engineering book?
    Just think about it, in an ideal world there are no loss and friction, and if with two turbos you can achieve a good response of the engine at low revs with a smaller one, and plenty of power at higher revs with a bigger turbo, what if we could have a dedicated turbo every, don't know, 1.000 revs?
    Every turbo could be designed and dimensioned specifically for its range of revs, without bothering considering what's going on later or before of it.
    It's basically what VVG is all about, changing the geometry so that it can be modified accordingly to all the conditions it has to face, so basically, in a single system, you try to have more of them.
    A clever idea to gain space and efficiency in the real world.

    Quote Originally Posted by culver View Post
    Leon,
    I think you meant to say "stage" not "stadium". We would refer to multi-stage compressors or turbines. I'm going out on a limb and guessing that was some type of mistranslation from Italian.
    Yes, thank you, it was both a mistranslation and a brain fart as it was late and I didn't even check, sorry.
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