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Thread: twincharging prototypes needing constructive critisism (SC14 + turbo)

  1. #1
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    Default twincharging ideas

    i am just throwing a few ideas around here so constructive feedback is good feel free to correct and add to any of my thoughts. Be aware, useless and irrelevant posts with be dealt with

    eventually when i get around to making something twincharged, i will be using a SC14 supercharger (PD type).


    one way valves
    using a one way valve in plumbing of twincharge arrangement would open many avenues for the arrangement of the turbo and SC. however, as far as i can see, they do have their downsides. if you were to use a one - way valve, you would want the following specifications/properties;
    1. minimal restriction to the air flow
    2. reasonably quick to close when air flow direction reverses
    3. self controlled if possible
    4. reasonably light, not too bulky and cheap to obtain/make
    5. shouldnt leak air when closed


    most (if not all) the one way valves i have seen rely on pressure to overcome a spring mechanism to open. now from the 1st specification, the valve is always going to oppose the "normal" flow of air which means there will be a small restriction placed on the air flowing through the valve. using springs with a lower spring rate should overcome this but it will also sacrifice the effectiveness to snap shut when a sudden change in air flow direction occurs (gear changes). comes down to a trade off as usual



    there seems to be 2 common one way valves. One being a flapper style (similar to 1g/7m etc AFM) and another is just conical valve and seat. See pics



    flapper style


    Just by looking at it, it seems that a flapper style one way valve will not be able to resist leaking under at least 10psi of boost. A unit that could however, would most likely be quiet expensive. I see the flaw being in how the flap seals to the housing as it swings. That said, this type of oneway valve should easily be able to made large enough for adaquate flow.


    conical type


    from what I can visualise, making the device open to give the same amount of surface area as a 3” pipe, would be massive! Also the sharp corners of it wouldn’t help at all with flow.

    The other possibility is making one controlled electronically using a 1JZ traction control TB (operated by a motor). Though, i cant see how you could accurately or quickly determine which way the air is flowing through a pipe with an electrical instrument.

    Any other types im missing?

    No? well it seems like one way valves arent the go for achieving a efficient and smooth(ish) twincharge setup….bugger



    The SC14
    Firstly, I want to rule out one possible characteristic of the SC14….. can air flow through it when it is not turning??? I am guessing it can but not 100% sure. Could someone please clarify this? If the air could not flow through it when its off, a twincharge system would be much much simpler to create.


    Anti lag?
    this is another thing I want opinions on. Would arranging the system so the SC is sucking air through the turbo give any benefits in terms of “early” spooling? I think I recall an occasion where I used a vacumm cleaner to extract a bolt from my turbo housing after I accidentally dropped it in (oops )….in the process, the turbo was spinning.

    more air flow through engine = bigger turbo?
    so the SC is added to the system for the single reason providing forced induction down low….but will this create a significant exhaust gas flow increase whereby a rather large turbo can be used without the lag it would usually impose on that type of engine??

    Maybe we can relate this to a “perfect world” scenario. Please enlighten me on how the inefficiencies of an engine and “boost” would alter this. Also for this scenario we’ll assume the pulley ratio of the SC => engine is 1:1

    2000cc engine consumes 1L of air per 1 revolution
    (this gets less as the revs go up?)

    an SC14 displaces 1.4L of air per 1 revolution
    (this gets less as revs go up? )

    so…. Putting an SC14 on a 2000cc engine would make the engine consume 1.4L of air per 1 revolution.

    This would then equate to gas flow of a 2800cc NA engine (1.4 x 2). So then theoretically, a turbo that performs well on a ~3000cc engine (2jz/7m) should perform just as well on a twincharged 2L engine.

    But then ofcourse there is boost. This is created because the engine can not “consume” all the air that is being forced into it. So this means a twincharged 2L engine would not be comparable to a 2.8 – 3.0L engine. does all that shoud right?

    Id also imagine cams profiles have a part to play in this argument…but meh.



    So this is where I shall leave it for now, when I get some feedback on the couple questions/queries I will be able to rule out many of the combinations and start to make some solid plans

    Thanks for the help in advance

    Brett
    Last edited by brett_celicacoupe; 15-09-2010 at 09:05 PM.
    hello

  2. #2
    Estranged Member Chief Engine Builder mullett's Avatar
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    Default Re: twincharging discussion (SC14 + turbo)

    ooooh...ok, here we go again!

    i think there'll be lots of 'just put a turbo on it' in this thread, but hell, I think twincharge is cool

    You'll need valves in the system, to bypass when one thing is flowing more air than the other. I think the simplest system is:

    Intake:turbo:SC:Manifold.

    In which the SC is always running. Now, maybe the turbo will flow more air than the SC can possibly have stuffed through it, but I think this is how the HKS kit did it. On the plus side, the car will always respond the same, just as if it was a bigger motor with a turbo on it. But maybe the SC can't hack it, and it will definitly act as a restriction in the system eventually....

    Slightly more complicated:

    Intake:turbo:Bypass:SC:manifold

    So when the turbo's really boosting, air is diverted around the SC. I guess you could turn it off, or keep it running. But now, when you back off in a hurry and get back on the power (like in a corner), you're opening yourself up to heaps of bizzare things to happen. Odd power delivery, sudden jerks, etc. All the things you don't want So maybe the solution is some sort of electronically controlled valve, which is also linked to a small computer which controls the SC. In this way, you'd have a little control over what was likely to happen when.

    Then there's all the other options, like having the SC before the turbo, etc.

    I think the key to it is going to be a really good valving setup, controlled electronically, so that the car always responds predictably.

    *edit* I tried to rep you for starting this thread...but I hit 'enter' halfway though leaving a message and my computer freaked out. I *think* you got it

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    Default Re: twincharging discussion (SC14 + turbo)

    thanks for the input.

    im really hoping to have those specific questions answered first.though. after that i can start to make a couple rock solid plans


    Quote Originally Posted by mullett
    i think there'll be lots of 'just put a turbo on it' in this thread
    i know how to deal with those people
    hello

  4. #4
    Junior Member Domestic Engineer myne's Avatar
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    Default Re: twincharging discussion (SC14 + turbo)

    There's a guy on here that's got a turbo that blows INTO an SC on his GZE.
    It runs 10psi with the pulley, and up to 23 psi once the turbo kicks in.
    It's really the essence of simplicity.

    Turbo > TB > SC > IC > inlet

    Personally I'd use 2 intercoolers. The stock topmount modded to water to air, and a frontmount just after the turbo. That should retain throttle response as well as sufficiently intercooling.

  5. #5
    Estranged Member Chief Engine Builder mullett's Avatar
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    Default Re: twincharging discussion (SC14 + turbo)

    You'll reduce Lag by a very significant amount, I don't think the SC sucking air through the turbo would help much, but the pressure created by the SC (and hence more air/fuel burnt) would make the turbo spool pretty damn fast. Just as if it was a much bigger engine.

    So, yes, you can run a bigger turbo for sure, and I think you'd have to, or the exhaust wheel would create a massive restriction when it was on full boost...

    I think having the SC running constantly would be the EASIEST, and also easiest to get smooth transitions from, but maybe it's not the best....

    RM.

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    Default Re: twincharging related questions (SC14 + turbo)

    ideally i would like to have the SC controlled so that it can turn off periodically for fuel consumption and SC life reasons.

    so it seems that 'sucking' air through a turbo will acheive nothing significant...any more opinions?
    hello

  7. #7
    Estranged Member Chief Engine Builder mullett's Avatar
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    Default Re: twincharging related questions (SC14 + turbo)

    It'd be pretty easy to keep the electronic clutch, but have it wired to a switch and a bypass valve. So when you turn the SC off, the car just acts like a turbo car, the air bypass' the SC (which isn't spinning) and when you activate the switch, SC runs constantly, and the bypass is closed...

    RM.

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    Junior Member Domestic Engineer myne's Avatar
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    Default Re: twincharging related questions (SC14 + turbo)

    Keep the SC working as it does as stock.
    More than 8" of vacuum and the SC turns off.
    If you leave the throttle where it is on the stock engine, this system will work fine.

  9. #9
    Estranged Member Chief Engine Builder mullett's Avatar
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    Default Re: twincharging related questions (SC14 + turbo)

    Yep, good point, it'd work great.

    Becomes more of an issue if you're running non-stock managment (or you didn't start with an SC car), you'd need a little module to control the SC with. But for sure, if you got it working with a little time delay (like the stock managment has), and a pressure switch etc, it'd work beautifully.

    RM.

  10. #10
    Founding ****** Automotive Encyclopaedia Mos's Avatar
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    Default Re: twincharging related questions (SC14 + turbo)

    Quote Originally Posted by brett_celicacoupe
    one way valves<snip>
    The other possibility is making one controlled electronically using a 1JZ traction control TB (operated by a motor). Though, i cant see how you could accurately or quickly determine which way the air is flowing through a pipe with an electrical instrument.

    Any other types im missing?
    A TRC throttle body already has a motor on it - the large stepper motor that controls the TRC throttle could easily be used to make the that throttle do whatever you want. A controller would need to be made to move it - I have no idea how quickly you could make it move though.

    Another possibility would be a valve like the ones used on the sequential setup on a 2JZ-GTE. There are two throttle style valves on the setup - one in the outlet of the compressor of the second turbo (maybe 1.5"), the other on the outlet of the exhaust turbine (2.25"). They are both throttle plates operated by wastegate type actuators. I would imagine these can snap shut and open rather quickly.
    On the 2JZ-GTE the computer assumes the pressure coming from the second turbo is adequate to open the valves - it doesn't measure it in any way, so a lot of 2JZs have a dip when the valves open because the turbo isn't spinning up fast enough yet. A better way would be to wait until it's known it it's creating enough pressure and airflow but that would introduce more complexities.

    You could also try and fabricate something like what's used as heart valve replacements - a disc, like a throttle, that is hinged off centre, so the flow of blood seals and opens it - there are no springs.

    Quote Originally Posted by brett_celicacoupe
    The SC14
    Firstly, I want to rule out one possible characteristic of the SC14….. can air flow through it when it is not turning??? I am guessing it can but not 100% sure. Could someone please clarify this? If the air could not flow through it when its off, a twincharge system would be much much simpler to create.
    This is a qualified maybe. If you force the rotors to a stop, then air will only flow through it because it's leaking (ie not much air should flow through it at all).
    If you are using a clutch, then the air being sucked through it will cause it to rotate - not great for SC-off efficiency.
    So if you want the SC to act as one of the one way valves you would need to find some way to lock it, but it may still leak air around the rotors.

    Quote Originally Posted by brett_celicacoupe
    Anti lag?
    this is another thing I want opinions on. Would arranging the system so the SC is sucking air through the turbo give any benefits in terms of “early” spooling? I think I recall an occasion where I used a vacumm cleaner to extract a bolt from my turbo housing after I accidentally dropped it in (oops )….in the process, the turbo was spinning.
    You will get a lot more spinning by running exhaust through the turbo than you will by sucking air through the compressor.

    If the SC is sucking air through the turbo, you will be losing some of the efficiency wrt the SC having a free intake.

    There are pros and cons to either method.

    If you create a true sequential setup then you have two independent sources of airflow and boost - one the SC, the other the turbo. They switch when the turbo is exceeding the capabilities of the SC. The advantage to this is that you can run the SC at twice the normal rpm, but turn it off say half way through the engine rev range after the turbo has already spun up and is producing boost. This way you can get more performance out of the SC at low engine revs. Disadvantage is you need valving.

    As others have suggested, running a turbo in front of the SC makes for a very simple setup. The SC14 will happily pump a specific volume of air every revolution. It doesn't care if this air is at atmospheric or at 20psi.

    Quote Originally Posted by brett_celicacoupe
    more air flow through engine = bigger turbo?
    so the SC is added to the system for the single reason providing forced induction down low….but will this create a significant exhaust gas flow increase whereby a rather large turbo can be used without the lag it would usually impose on that type of engine??

    Maybe we can relate this to a “perfect world” scenario. Please enlighten me on how the inefficiencies of an engine and “boost” would alter this. Also for this scenario we’ll assume the pulley ratio of the SC => engine is 1:1
    All depends on how you set it up. In the sequential-double-SC-rpm setup you have a lot more exhaust flow available so you can use a bigger turbo.

    If you run the SC all through the rev range the exhaust flow due to the SC will not be as great so you would need to size the turbo appropriately to achieve what you want.

    Quote Originally Posted by brett_celicacoupe
    2000cc engine consumes 1L of air per 1 revolution
    (this gets less as the revs go up?)
    Multiplied by VE (volumetric efficiency). VE is dependent on rpm and many factors such as ports, runners, cams, etc. It doesn't necessarily go down with revs. Some engines (economy) will be set up to have a high VE at lower rpm, but suck (badly) at high rpm. Other engines have unfavourable VE at low revs, but perform well at high rpm to do better VE. Engines with two cam profiles try to create two VE peaks.

    Quote Originally Posted by brett_celicacoupe
    an SC14 displaces 1.4L of air per 1 revolution
    (this gets less as revs go up? )
    I don't think the volume of pumped air changes much, but the SC heats the air more when spinning faster.

    Quote Originally Posted by brett_celicacoupe
    But then ofcourse there is boost. This is created because the engine can not “consume” all the air that is being forced into it. So this means a twincharged 2L engine would not be comparable to a 2.8 – 3.0L engine. does all that shoud right?
    Boost is always made because the engine can't consume all of the available airflow - whether it's a turbo of SC doesn't matter, the reason is still the same.

    Basically you need to decide which method you wish to use
    A true sequential setup would give higher gains but is more complex. Thoughts?

    Mos.
    Admin, I.T., Founding Member, Toymods Car Club Inc.
    2000 IS200 Sports Luxury 1UZ-FE VVTi, 1991 MX83 Grande 2JZ-GTE (sold)

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    Default Re: twincharging related questions (SC14 + turbo)

    mate,

    those responses are exactly what i was looking for
    really appreciated
    hello

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    Default Re: twincharging related questions (SC14 + turbo)

    okay, so im thinking something along the lines of;
    whether "TB 1." is mechanically driven or electronically is something ill need to look into. if it is mechanically driven, the butterfly will probly have a flat filed into it so that it can never close 100%




    thoughts/opinions?
    hello

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    Default Re: twincharging related questions (SC14 + turbo)

    having a TB before the SC should also help during gear changes.....so the BOV may not be required. also by having this pre-SC TB, at cruising speed you only ever use 10% of the available throttle, therefore the SC would spin freely in almost a vacum?

    another SC14 question; how would they react to the pre-SC TB snapping shut (not 100% though) at say 3000rpm? no issues?

    also..... theoretically, the drag the SC imposes on the engine would be SFA when there is no air pumping through it (ie. pre SC throttle body closed) ???
    hello

  14. #14
    Junior Member Backyard Mechanic Valkyrie's Avatar
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    Default Re: twincharging related questions (SC14 + turbo)

    Hi,
    Good thread!!!

    The set-up I was looking at with my car (TA22-4AGZE) was to use 2 intercoolers mounted at the front of the car, with separate bottom tanks and a common top tank. The drivers side intercooler would be for the supercharger, with the passenger for the turbo.
    I would then have them feed into a common top tank into the inlet manifold.
    I was looking at using 2 RX7 or JZ Supra intercoolers welded together.

    Plenty of cars share separate entry and common exit for the intercooler (GTR for starters)
    The supercharger set-up would be as factory. The TB would remain in the original location (larger 4AGE item most likely).

    The turbo would have a filter on the front, with a blow off valve pre intercooler.

    I would run the blower in the normal manner. ie clutch off at idle, and engaged otherwise.

    I couldn't see to many problems with excess air on gear change.

    My idea and 2c worth.

    Cheers

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    Default Re: twincharging related questions (SC14 + turbo)

    will there ever be a situation where you close the TB before the SC and the air that is going though the bypass pipe where it will force itself through the back of the SC. Or is that why you are saying TB1 would never be fully closed to at least provide some pressure differential at the back of the SC so the turbo air going to the back of the SC isn't an issue?

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