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  1. #1
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    Why Twin Turbo? (from old site)

    I've cleaned this thread up a little to remove the off-topic bits and correct spelling in a couple of places. -D
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    faststcarinschool
    Registered User
    Posts: 6
    (8/22/03 8:49 pm)
    Reply why twin turbo?
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    why is every one so into twin turbos, when one can be set up to run very well? is there an advantage or is it just for the wow factor or just an excuse to spend more money?


    andrewb70
    Registered User
    Posts: 1494
    (8/22/03 9:22 pm)
    Reply
    Re: why twin turbo?
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    I think its mainly the cool factor. The second reason is that its easier to package 2 turbos. With one turbo you have to figure out a may to route the exhaust to a common collector/turbo mounts.

    Andrew
    Project GatTagO



    George
    Registered User
    Posts: 402
    (8/23/03 12:30 am)
    Reply yeah
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    The grand nationals had one turbo and it was under the car. that makes it harder to work on. I think it is probably easier and not much more to do 2 turbos rather than one. The turbos themselves arent that expensive.




    andrewb70
    Registered User
    Posts: 1498
    (8/23/03 5:19 am)
    Reply
    Re: The question is..
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    Actually the GN mounts the turbo on the passanger side, right up top. Very easy to get to.

    Andrew
    Project GatTagO



    XcYZ
    Registered User
    Posts: 578
    (8/23/03 6:12 am)
    Reply
    Re: The question is..
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    Packaging is one reason, but the biggest reason for twins over a single is where the turbo(s) work best in the desired airflow range. A small turbo is quicker to respond, building boost quicker, but lacks the capacity for making big hp at higher rpm. A single larger turbo makes major hp gains at higher rpms but is lazy at lower rpm/airflow rates. So running twins gets you the best of both worlds, a quicker responding setup that works very well a lower rpm and yet makes great max hp at high rpm.
    Scott
    My 69


    KUL FIR CHIK N
    Registered User
    Posts: 7
    (8/25/03 9:18 pm)
    Reply 1 or 2
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    Ask any turbo expert what will work best if you don't care about the wow factor, and he'll tell you to run one. Size for size, the smaller turbo spins up faster, but remember with twins, you only have half the motor working to spin up each turbo. The total rotating mass of two turbos is greater than the rotating mass of one of equal capacity. If you want wow factor, twins are the way to go, and they'll still perform killer. Ever see a t101 or 106? WOW!

    andrewb70
    Registered User
    Posts: 1517
    (8/26/03 6:06 am)
    Reply
    Re: 1 or 2
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    Those big single turbos are awesome looking. I have seen one, not really sure what the technical name for it was, but the thing was the size of a basketball!

    Andrew
    Project GatTagO



    Andy B
    Registered User
    Posts: 17
    (8/26/03 4:47 pm)
    Reply twin turbos
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    On page 37 of Corky Bell’s book Maximum Boost, he claims that “an engine with flow capabilities greater than 300 cfm can benefit from two turbos….. Over 350 cid, twin turbos become a virtual necessity.” The book is not about building a full race turbo engine but more of system suitable for a street application.

    Andy B


    TT 65 Nova
    Registered User
    Posts: 62
    (8/27/03 8:50 pm)
    Reply Re: 1 or 2
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    Quote:
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    Ask any turbo expert what will work best if you don't care about the wow factor, and he'll tell you to run one.
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    Respectfully, I would have to take exceptyion with this. I think this might be the answer you would get, but it would depend on the question that you asked. If you asked "what will make the most horsepower at high rpm", then I think you might be right. However, if you are looking for decent boost over a usable rpm range on the street for a V8 app, the twins are gonna be the way to go.

    Most of the guys running big singles on V8s that I am aware of aren't even getting into boost until about 4k. This is fine if you are launching on a trans brake, right where the boost is just starting to come on, but for daily driving, and playing around on the street, how much of the time are you actually spending from say 4k - 8500?

    This brings up another good point. By tailoring the setup towards working from 2 - 6k with a twin setup, you can generally get away with a way less exotic bottom end and still be relatively safe. Turbos by their nature are semi-easy on parts when you are looking at similar output setups, and it's generally rpm that kills rods, etc. By staying a little understated, and lower rpm, you can have a lot more fun with less money.


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    I knew I shoulda bought a camaro...
    my nova site (in progress)

    DT0
    Registered User
    Posts: 112
    (9/13/03 5:52 pm)
    Reply twin vs single.
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    banks and duttweiler say to run twins on a v8 setup..

    i think they know what they are talking about..

    [d]

    KUL FIR CHIK N
    Registered User
    Posts: 8
    (9/15/03 7:44 pm)
    Reply 1 or 2
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    remember, those who make kits get more for twins than singles. Turbo design has come a long way in recent years, and I'm not talking about a large frame turbo (96-106mm), I'm talking mid frame (76-88mm) for high hp and quick spool on v-8's. I have a friend who has a precision turbo PT88 in his camaro with a 400sb. He has 15psi by 3k rpm, and 20 by 3.5k. This may seem a little higher than the 2k you speak of, but his motor is belting out 1200hp @6500 rpm. You can get a smaller turbine housing and have full boost @ 2k, but at the expense of a little at the top, maybe only 1000. Give the guys @ Precision Turbo a call, I'm not trying to argue, just giving up what little I know. Besides, If I'm wrong I'll need to convince somone to buy my PT88.

    ronracer
    Registered User
    Posts: 181
    (9/21/03 9:38 pm)
    Reply Re: 1 or 2
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    Alright, I couldn't resist....


    He has 15psi by 3k rpm, and 20 by 3.5k. This may seem a little higher than the 2k you speak of, but his motor is belting out 1200hp @6500 rpm. You can get a smaller turbine housing and have full boost @ 2k, but at the expense of a little at the top, maybe only 1000.


    And what if you "HAD TWO" of the smaller turbines? 2000HP!

    Multiple turbos will alway's have more performance advantages over a single. It all boils down to money or the racing rule books.

    Ron
    Ron's Camaro Page

    KUL FIR CHIK N
    Registered User
    Posts: 10
    (9/23/03 7:37 pm)
    Reply 1 or 2
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    Enjoy your twins guys. Ya never got the point......

    camcojb
    Registered User
    Posts: 505
    (9/23/03 8:58 pm)
    Reply Re: 1 or 2
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    Quote:
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    remember, those who make kits get more for twins than singles. Turbo design has come a long way in recent years, and I'm not talking about a large frame turbo (96-106mm), I'm talking mid frame (76-88mm) for high hp and quick spool on v-8's. I have a friend who has a precision turbo PT88 in his camaro with a 400sb. He has 15psi by 3k rpm, and 20 by 3.5k. This may seem a little higher than the 2k you speak of, but his motor is belting out 1200hp @6500 rpm. You can get a smaller turbine housing and have full boost @ 2k, but at the expense of a little at the top, maybe only 1000. Give the guys @ Precision Turbo a call, I'm not trying to argue, just giving up what little I know. Besides, If I'm wrong I'll need to convince somone to buy my PT88.
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    The guys at Precision Turbo talked me out of a single turbo and into twins. This is on a 383 with a goal of 1000 to 1200 HP. The owner helped me and recommended the PT52's.

    Jody
    MY CARS

    ronracer
    Registered User
    Posts: 182
    (9/23/03 10:27 pm)
    Reply Re: 1 or 2
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    Excuse my ignorance, but I guess I missed your point.

    This thread started out about "Why Twin Turbos" then went into "1 or 2".

    Not saying that 1 turbo is bad, (every design has its place) there is just more advantages with multiple turbos if you can afford to lay out the cash.

    On another side note:
    I'm not 100% sure. Correct me if I'm wrong, but I think the Pro 5.0 Drag class changed the rule book from Twins to Singles. The Duttweiler twin turbo powered cars were dominating everything. I would then think they did this to make it more competitive.

    walapus
    Registered User
    Posts: 78
    (10/30/03 3:28 pm)
    Reply twin or single
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    I have friend at Garrett, works in the independant aftermarket division, he's build a 383ci LT1 for his 69 chevelle. He's a very sharp guy with access to any turbo(s) he wants, and what did he build? A single turbo'd setup. I'm not sure why, haven't engaged him the details, but it probably has something to do with the higher efficiency of the bigger turbos amongst other things


    andrewb70
    Registered User
    Posts: 1756
    (10/30/03 5:00 pm)
    Reply
    Re: twin or single
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    How is Dave? I have not seen him post on Chevelles.com on a very long time. He and I talked on the phone a few times. Did he ever get that Chevelle on the road?

    Andrew
    Project GatTagO


    walapus
    Registered User
    Posts: 80
    (10/31/03 1:40 pm)
    Reply you know Dave??
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    I co-op'd under him a few years back! He's good, the chevelle sounds like it got sidetracked in favor of a wife who's now expecting. It sounds like he's really close though

    DT0
    Registered User
    Posts: 123
    (1/29/04 2:12 pm)
    Reply single turbo efficiency..
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    on a v8 setup, [according to corky bell] distributing
    the exhaust pulses into seperate turbo chargers,
    allows for symmetry [prodigal in turbo setups] and
    lowers the amount of wear on a turbo providing
    boost..

    the rpms required for one turbo to provide, say
    30psi [14.7+15.3] would be more extreme, than
    having two seperate turbos provide, individually
    7.65psi each. thus decreasing wear, oil temperatures,
    and spool time.

    this of course, is in consideration for the street..
    given; a lot of the indy cars, maintained high enough
    rpms [and maintenance schedules for that matter]
    to have a single turbo setup..

    the argument shouldnt which is better.. it should be:

    what is best for your application.. ?

    mostly tho, in corky bell's book, 'maximum boost'
    he states, frequently, that a v8 mandates that you
    run a twin [symmetric] setup.. and supports it with
    all sorts of factors.. which if one was really serious
    about running and building turbos, you should really
    buy this book and/or give Mr. Ken Duttweiler a call..

    [d]

    Edited by: DT0 at: 1/29/04 2:22 pm

    GT1guy
    Registered User
    Posts: 138
    (1/29/04 5:39 pm)
    Reply Re: single turbo efficiency..
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    I think Indy cars use a single turbo because of rules. I think if they could run whatever they wanted, you'd see twins, at least on the road/street courses. The big ovals wouldn't matter, being that they run flat out all the time.

    Kevin

    68 Camaro31
    Posts: 26
    (1/29/04 10:29 pm)
    Reply singles...
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    Ive heard on several occassions that single turbos produce more peak power... If you go on to Supra forums you will see that the guys making the large hp numbers are all using large single turbos rather than twins. I had a site i saw before on all of this. if i can find it ill post up the link.

    walapus
    Unregistered User
    (1/30/04 10:46 am)
    Reply what?
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    7.65 psi each? that makes NO sense

    If one turbo is operating at the portion of it's map that is PR=1.5 (7.65psi gauge), and the other is also at 1.5, your manifold wil be at.....(drum roll)....1.5!!!

    It's the airflow that is halved, not the PR added.

    Each turbo will be operating at PR=2.0, but with HALF the engine's total flow rate moving through it, which is why twin turbos are each smaller than the 1 single which would replace it! Smaller turbos *usually* must operate at HIGHER RPMs to acheive the same pressure ratio as their bigger brothers.

    Bigger turbos, on average, are more efficient.

    However, one must also look at the installation.

    A single big turbo is perfect for a Supra (inline), but not always so for a V8. If plumbing gets too long, a lot of energy is wasted (see the other thread about the retarded rear-mount turbo).

    For people on this board, I'd spend less time sweating the last 1-2% gains to be had from single over twin or vice versa. Look at your car, look at your engine bay, vusualize which setup will result in the simplest and most effective routing, then spend a LOT of time pouring through compressor AND turbine maps (turbine matching is incredibly important, and everyone seems to just wing it, no good!). You'll gain so much more from a properly selected twin OR single than you will from a guesstimate of the other. (I'm not sure that last sentence reads quite right, I hope you can tell what I'm trying to say)

    It is also a good idea to have your engine dyno'd without the turbos before matching. VE is probably going to change a fair amount, but its a step up from bench-racing.

    DT0
    Registered User
    Posts: 124
    (1/30/04 2:20 pm)
    Reply Re: what?
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    you are absolutely right. i got lost in the definition for
    efficiency while trying to subtley tie in the issue of wear.

    but.

    in my mind, i would rather spool smaller turbos higher and keep
    my engine rpms low[er]. people say RPMs are free.. i may be
    wrong but i recall inertial loads increase with the square of rpm



    KUL FIR CHIK N
    Unregistered User
    (1/30/04 9:26 pm)
    Reply What?
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    Beautifully stated, Walapus.

    BB69
    Registered User
    Posts: 5
    (2/3/04 12:42 pm)
    Reply Twins
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    Routing the exhaust for twins usually keeps more heat and velocity in the gas, which is better. A single turbo on a V engine requires longer exhaust pipes which lose thermal energy. Twins also offer the possibility of using two different turbos to maximize power over a larger RPM/load range.

    Something else to consider is traction. If your base engine spins the tires, who cares if you have boost down low? All you are going to do is spin them faster and make more smoke. This may very well be a good case for a single.

    My buddy has a Mustang that started out with twins, and now has a single. He makes just as much top end HP with the single. He lost some at the bottom, but the car still spins the tires wildly. The single also makes getting to the engine easier.

    I don't think there is one answer. In my opinion though, if you are adding a turbo, you're going to have plently of power either way, so go for the cool factor

    SHMOOV69
    Registered User
    Posts: 401
    (2/3/04 5:11 pm)
    Reply I'll pipe in
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    Ok, here's my take! None of us are going all out PRO racing with our cars here, just goofing around right? That being said, every last HP will not matter a bit. Because most people out there do not have any idea just how much friggin' power 600 hp is!! Espically with a turbo(s)! Just because some cars have that much power, but it is at a much higher RPM. Turbo cars have an abundance of TQ, well pretty much at any RPM you stab it! (give a second for spool up that is) Believe me, I know, I thought that "oh it's no big deal, lots of car have 600 (true) hp!" Boy was I wrong!! The car is TOTALY different than what I had expected! At ANY speed under 80mph, I can smoke the tires (radials) without down-shifting and with 3.00 gear at 2200 RPM!! So, twins or single?? You will have more power than the car can handle (in most instances) unless you totaly screw up on the turbo size(s). Everyone has thier own opinion though.
    I am stepping down from the soapbox now!
    Jimmy

    perkidelic
    Registered User
    Posts: 419
    (2/3/04 8:26 pm)
    Reply single?
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    Hmmmm, I was actually planning on twins, but after reading this thread I am wondering if a single might not be better for my app. I will have a really lightweight car that it would advantageous to not have so much bottom end torque in. If I can come up with a setup that would not have excessive lag and ramp up too abruptly I may go single. It's worth considering anyway. I gotta get the Maximum Boost book and start learning. Are there any other good books available?

    perk

    SHMOOV69
    Registered User
    Posts: 403
    (2/5/04 10:13 am)
    Reply Book
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    "Turbochargers" by Hugh Macinnes.
    It has a Banks small block on the cover. Pretty good book along with Maximum Boost.
    Jimmy

    BTW- On the boost ramping up quickly, well, once it starts, it pretty much is at max within a very short time. On most at least! Mine is like this....no boost....full throttle.... no-boost.....1psi....2psi....4psi....12psi....OMG!!!! !
    LOL!

    mrmagoo
    Registered User
    Posts: 40
    (2/5/04 9:15 pm)
    Reply good reading
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    I found this site. It has some great reading on turbo systems in general. Then again it might just be this guys .02 of BS. www.grapeaperacing.com


    boodlefoof
    Unregistered User
    (2/5/04 9:50 pm)
    Reply GrapeApe
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    GrapeApe knows his stuff from what I can gather. He used to frequent Camaros.net and was very informed.

    John
    www.geocities.com/boodlefoof

    perkidelic
    Registered User
    Posts: 424
    (2/5/04 10:43 pm)
    Reply Re: GrapeApe
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    Grape Ape I used to love that cartoon! I always forget about that site.

    Since we are in the computer-controlled everything age, it would seem that a computerized boost controller would be able to control how fast the boost ramps up. I'll have to do some research on that.

    Thanks for the info guys
    perk

    todd's hot rods

    mrmagoo
    Registered User
    Posts: 43
    (2/5/04 10:56 pm)
    Reply ?'s
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    What type of car do you have? Engine? What would be a good sized turbo for a SB350 that will be in a 68 camaro. I'd be shooting for about 500 hp. I'd also be running an intercooler and efi. Just for a thought, you can also have a nitrous system on your turbo motor if turbo lag is your problem. Use the nos coming of the line and have it programed to shut down before the motor comes into full boost. Best of both worlds! Near .5 second spool up times!

    walapus
    Unregistered User
    (2/6/04 10:25 am)
    Reply That's achievable
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    500 hp won't require too much boost (depending on your engine combo). You may not even need an intercooler, so you may be able to save some weight and space. Or, you could stick with NOS alone to achieve it.

    Assuming your engine makes 400 hp N/A, you will only need 4-5 psi, and intake temps should come in well under 140F. (Pr = 1.25, Tatm = 80F, eff_comp = 75%)

    If your engine is more like 350 hp, then Pr gets up around 1.4, and an CAC may become necessary. I would say, get a dyno reading, find the components that suit your needs, and do some calcs.