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Thread: 2TG Turbo Upgrade - Advice/help please

  1. #1
    Junior Member Backyard Mechanic scottsta22's Avatar
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    Default 2TG Turbo Upgrade - Advice/help please

    I had the 2TG in my TA22 rebuilt approx 12mths ago, mostly stock with oversize pistons and mild cams the only 'work' done. I was talking to the mechanic that did the rebuild and he suggested a turbo upgrade but said I will have to change the twin Solex's to a single downdraught carbie.

    All up with a custom intercooler he's quoting $1500.00.

    Now I'm not the least bit mechanically minded so I'd appreciate some advice from you 1st gen experts if this is the best way to go.

    Is it going to make a significant difference to the power or is there a better option.

    Thanks in advance & Happy New Year everyone

    Scott.

  2. #2
    Junior Member 1st year Apprentice WeekendWarrior's Avatar
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    Default Re: 2TG Turbo Upgrade - Advice/help please

    it is a good way to go the castlemain rod shop built turbo kits back in the day for the 2tc and it was just a suck through turbo setup with a 40mm weber and a small turbo and running on 12psi it doubled the horsepower.having said that u are not mechanicaly minded thats not a bad price but i think u would better going efi. but saying that ive been experimenting a bit with carby turbos and if setup right they can be quite good. now you can keep the twin carbies but you will have to box them. what you do you make like a plenum chamber that the carbies sit inside that way when the extra pressure from the turbo is coming into the carbies the same pressure will be surrounding the carbies aswell, thats called a blow through setup where there turbo is before the carby. the other setup is the suckthrough or draw through which is the simplest setup. here are some details u looked at when i first started doing this stuff.

    this stuff should give you some understanding to hel make ur decision

    Draw-Through: Generally speaking, there's 2 ways to use a carburetor with a turbo engine...draw-through or blow-through. The draw-through arrangement is where the carb is arranged first and the turbo then sucks air through the carb. This has the benefit that it doesn't require any special carb changes because the carb is just seeing more air flow through it. The main drawbacks are that the fuel-air mix must pass through the turbo. Since fuel is denser than air it will tend to separate in the turbo and puddle up. Don't expect instant off-idle throttle response. The turbo also becomes less efficient because it has to pump this heavier fuel mixture, and it is trying to do it's job after the carb has already caused a pressure drop. You basically have the carb causing a pressure drop and the turbo trying to increase the pressure. The efficiency losses translates into a hotter fuel-air mix in the engine which limits the boost you can run and your power.

    Now here's the confusing part to me. The majority of the people with Carbureted Turbos run them in a draw-through arrangement and they say you get more power that way. Personally I don't agree with that thinking and some of my research has led me to believe otherwise. I tend to believe that the power difference they speak of is related to people not using fuel enrichment in a blow-through setup. I have not tried either so you should make your own decision and there are certainly plenty of engine builders who would argue the point.

    In addition, In a draw-through system it is possible to create an extreme vacuum if the turbo is at boost and you shut the throttle. This vacuum will have a tendency to suck the oil out of the bearings. You will need to use a turbo with a positive seal on the compressor in a draw-through arrangement. Diesel turbos do not have this seal. I think most gasoline cars do have a positive oil seal but with the popularity of fuel injection on the newer cars I'm not positive.

    Blow-Through: In a blow-through arrangement the turbo is going to blow pressurized air through the carb and then into the intake. This presents two problems: First, a carburetor does not understand pressure. Remember, a carburetor supplies fuel by creating a pressure drop across the venturi. If the carb sees a 2 PSI pressure drop across the venturi, it will supply that much fuel whether you are at 0 boost or 15 pounds of boost. This would cause the engine to run very lean at max boost, but it can be fixed with some form of fuel enrichment. The second problem you will encounter is that when you put pressurized air into the carb, it will make the fuel flow in ways that it is not suppose to flow. The pressure will try to crush the fuel float, it's going to want to blow fuel mix out the throttle shaft, or back into the fuel line. Don't be discouraged though these problems have all been overcome with varying degrees of success. The book Turbocharging by Hugh MacInnes covers a lot of the carburetor mods you can implement to have a successful blow-through turbo setup.

    Carb Sealing: The entire carb must be sealed so it does not leak the pressurized air-fuel mix. I've heard that Dellorto carbs have ball bearings and mechanical seals so they may not need further sealing. On other carbs the throttle shaft rides inside a brass bushing, the leaking can be "fixed" by running a hose from the top of the carb where there is more pressure to a fitting that will pressurize the area around the shafts with "clean" air. Note: This method will leak clean air, but not leak the much more dangerous air-fuel mix. In a closed engine compartment, leaking fuel vapor is even more dangerous so please be careful. The metal plugs on the carb could blow out under the increased pressure. Use a punch and put several "dings" around the outside of the plugs to hold them in better. Others have used epoxy on the plugs.

    Some have also set the entire carb inside an airtight box. You will then need to seal the opening for the throttle cable by using a sealed marine cable or a similar "trick".

    Fuel Pressure: You will need to use an electric fuel pump and a boost sensing fuel pressure regulator to increase fuel pressure as boost pressure increases. Remember every pound of boost that comes out of the turbo is another pound of boost that the fuel pump must be able to overcome if it wants to push fuel into the carb. Read the "Fuel System" page for background on a turbo fuel pressure regulator. With a carb, you will not need a high pressure pump and regulator like you do in an EFI application, so a decent quality electric fuel pump and regulator should suffice.

    The fuel floats should be filled with foam so they don't crush under the increased pressure. Some manufacturers sell floats designed to withstand the increased pressure.

    Carburetor Type and Size: In most cases the same sized carburetor is used on a turbo installation. Many people use a side draft or downdraft Weber 40 or Dellorto.

    Fuel Enrichment: Your carburetor does not take into account boost pressure when it supplies fuel to the motor. Because of this you must take certain steps so that it supplies the correct amount of fuel when the turbo is at the maximum boost level.

    What most people seem to do is to jet the carb so that at max boost they have enough fuel. The problem with this method is that the engine will run rich at lower than max boost pressures which is also where most of your driving is done. A better method is to use a carb with a power valve and reference the valve to boost pressure. That requires possibly drilling some holes and running some vacuum lines. Some people have used a 4 barrel carb with vacuum operated secondaries. In this case the secondaries are jetted and plumbed so that they open during boost.

    The other alternative is to use external means that can overcome the inability of the carb to understand boost pressure. These fall into two categories, a "dumb circuit", and a smart controller.

    The first type of circuit uses a pressure sensing switch to open a fuel solenoid. The fuel then sprays into the intake through an orifice. You set the pressure switch at what boost point you want the fuel enrichment to occur. As you can probably guess this system will not properly meter the fuel flow but it is better than nothing

    here are some pics 2 of which are 2tg running a blow through turbo setup with unboxed carbs and malpassi rising rate fuel regulator
    Last edited by WeekendWarrior; 25-10-2007 at 06:49 AM.
    - Project "BILLYGOAT" the ta22 found on the edge of a hill




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  3. #3
    Junior Member Too Much Toyota
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    Default Re: 2TG Turbo Upgrade - Advice/help please

    $1500 is very cheap for a turbo manifold, dump pipe, cooler, intake manifold, carbi and associated engineering work (inc. regraphing ofthe dizzi) ... i'd be guessing it would be a used kit.

    Having inflicted upon myself the carbi+turbo experience, i'd first suggest you look at converting to efi (2tge).

    Given that you've rebuild the engine recently, it will:
    -have the wrong compression ratio (too high)
    -be limited to a small amount of boost
    -have significant timing issues when you do get on boost courtesy of the high CR.

    EFI would allow you to leave the engines as-is and take advantage of the cam and CR. Starting out with EFI would then allow you to consider turbo use at a later date with no change to the induction system apart from larger injectors.

    cheers,
    Charles.
    ------------------------------
    ST185 road barge / MZ11 forest barge / RA65 garage barge

  4. #4
    The Evil Director Backyard Mechanic jfallen's Avatar
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    Default Re: 2TG Turbo Upgrade - Advice/help please

    execellent write up +rep

    To scott, are you un happy with the power output of your 2TG, why the sudden interest in turbocharging it?

    As was mentioned in the above post EFI will solve many headaches, but create a few others. Suck throughs are easy (the sigma turbo carburetor is a good choice here,) but you can't run an intercooler and there is a limit to the amount of boost you can run before it all get way to hot. Blow through setups are complex because of having to seal the carbies up, and if you get it jsut slightly wrong as soon as there is positive pressure generated, the car will cough/stall...

    Personally I love the sound of the NA 2TG sucking through the twin solex's, and while it may not be the most powerful donk in the world it still brings a smile to my face every time I kick mine in the guts.

    Cheers
    Jordan
    Past rides: 86 Hilux, 3x ke55 rollas's (2coupes,) 5th Gen GT4 x2, RA28, TA22 x3, KE10, P610 datto, RT40 corona x3, RT132, MX13

    Currrent: , CA-A22 Celica living life as a Sports Sedan, 2000model ST215W Caldina GT-T manual, RT40 corona.

  5. #5
    Junior Member Backyard Mechanic scottsta22's Avatar
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    Default Re: 2TG Turbo Upgrade - Advice/help please

    Thanks for your replies.

    Judging by the issues involved with a carbi setup it looks like EFI will be the go if I do the turbo conversion.

    To be honest I don't know if turbo is what I really need, The motor is good and sounds great but I just want a bit more power in general so is there another avenue I should be exploring.

    How hard would it be changing to a 3T crank, (if I could get one that is) will that give me more power and if so how much.

    Any suggestions or ideas welcome.

  6. #6
    Junior Member 1st year Apprentice WeekendWarrior's Avatar
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    Default Re: 2TG Turbo Upgrade - Advice/help please

    jfallen has got the right idea an N/A 2tg with twin carbs does sound quite sweet and they rev well to

    cheers have a good new year
    - Project "BILLYGOAT" the ta22 found on the edge of a hill




    BEARCON All your construction needs 67 624580

    THE CELICA SHOP COMING SOON

  7. #7
    Toymods Vice President Chief Engine Builder TheToyman75's Avatar
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    Default Re: 2TG Turbo Upgrade - Advice/help please

    Fitting the 3T crank now will basically require your engine to be rebuilt again as you will need to change the crank and pistons (So head off). As such your pulling it appart a second time meaning new gaskets and bearings (3T bearings and 2T-G bearings can be different)

    The N/A 2/3TG hybrid is a fun engine because you can drive them at their limit and not be doing 200mph. The first thing you have to do is ask the guy who rebuilt your engine what the new compression ratio is. Its probaly 9.8 - 10.4:1 if he has half a clue.

    If your looking for a bang for your buck power increase and more than an extra 20 odd KW I would say Turbo what you have now, but on a budget. A 3TGTE exhaust manifold and turbo will bolt up to your 2TG head. You will need custom oil drain into the sump and oil feed lines but thats no biggie. You can easily fit the 3TGTE oil distribution block to the side of your 2TG and even the 3TGTE thermostat housing all of which you can do without replaicing anything more than your sump gasket and some gasket goo.

    For your intake side locate a 2TG EFI intake plenum and rail, fit some 3TGTE injectors (for low boost - up to 7PSI) or something bigger for medium to high boost. (Don't push it hard if its a high comp turbo package. I'd aim for 8, maybe 10PSI so some 440 or so cc injectors would be nice I think 7MGTE ones would work well - gotta confirm there size tho)

    Then its just your efi Fuel system and aftermarket management and your on the road. Ideally the budget should stretch to afront mount intercooler, given the compression its more required than optional. BUT it will cost you more than $1500 ! YOu wont have a tire frying demon but your looking at a healthy increase in rwkw (Potentially double what you have now) for a minimal investment. Don't get to greedy with the boost and don't scrimp on the management and tune and you will have a reliable and fun package to drive.
    1971 2T-B Celica TA22 ST.
    1973 2T-G Celica TA22, aka "The Unicorn".
    1975 2T-G Celica TA27 GT
    1976 2T-G Celica TA23, aka "The Colonel".
    1985 3F Auto FJ62 Landcruiser
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  8. #8
    Rest in Peace Conversion King ViPeR_NiPPleX's Avatar
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    Default Re: 2TG Turbo Upgrade - Advice/help please

    I'm suprised nobody has mentioned the use of an sc12 or sc14...?

    how 'mild' a cams are you running?

  9. #9
    The Evil Director Backyard Mechanic jfallen's Avatar
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    Default Re: 2TG Turbo Upgrade - Advice/help please

    suck through supercharger set up.

    I like that run a stromburg (or 2) or a Rover V8, sound tuff as nuts.

    Jordan
    Past rides: 86 Hilux, 3x ke55 rollas's (2coupes,) 5th Gen GT4 x2, RA28, TA22 x3, KE10, P610 datto, RT40 corona x3, RT132, MX13

    Currrent: , CA-A22 Celica living life as a Sports Sedan, 2000model ST215W Caldina GT-T manual, RT40 corona.

  10. #10
    Junior Member Backyard Mechanic scottsta22's Avatar
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    Default Re: 2TG Turbo Upgrade - Advice/help please

    Thank for all the help & advice, after much thought & research I have decided to forget the turbo and go with the 2TG/3T hybrid conversion. That way I can keep the solex's and all the work that has gone into the engine bay won't be wasted.

    So anyone know of a 3T going spare in SE QLD.

    Cheers
    Scott

  11. #11
    The Evil Director Backyard Mechanic jfallen's Avatar
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    Default Re: 2TG Turbo Upgrade - Advice/help please

    locate your nearest thrashed/wrecked TE72 (AKA T-18) corolla, shouldn't be too hard.

    yank it out of there. While you're there pull the diff out and sell it to the Sprinter chumps for $300.

    Cheers
    Jordan
    Past rides: 86 Hilux, 3x ke55 rollas's (2coupes,) 5th Gen GT4 x2, RA28, TA22 x3, KE10, P610 datto, RT40 corona x3, RT132, MX13

    Currrent: , CA-A22 Celica living life as a Sports Sedan, 2000model ST215W Caldina GT-T manual, RT40 corona.

  12. #12
    Junior Member Grease Monkey rob20v's Avatar
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    Default Re: 2TG Turbo Upgrade - Advice/help please

    I would only go EFI as I have had a bit to do with a suck through system with a CD Stromberg and it took forever to get the setup right. At least with a programable EFI you can alter fuel and spark anywhere throughout the rev range. Another thing if you use a suck through you need a turbo with carbon seals so you don't suck through oil (most newer turbos from importers are late air only turbos). Weekend warrior summed up the systems pretty well but if I built another turbo I would only go EFI. Good luck with it, would be interested in seeing how it goes as I am running a standard 2TG. Rob.

  13. #13
    Junior Member Backyard Mechanic scottsta22's Avatar
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    Default Re: 2TG Turbo Upgrade - Advice/help please

    Had her dynotuned this week and she goes heaps harder, ran 95rwhp, not a bad result I thought considering. So I may leave it be for the moment until I decide which way to go, just get sick of all the hotted up jap jobs gunning it beside me!!

  14. #14
    Photographer and Backyard Mechanic Rinmax's Avatar
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    Default Re: 2TG Turbo Upgrade - Advice/help please

    They may be hotted up jap jobs, but you have old skool goodness and thats worth more.
    "It's an ingenious solution to a problem that should never have existed in the first place." - JM

    "A Ferrari is a scaled down version of god while a Porsche is a Beetle with mustard up its bottom." - JC

  15. #15
    Junior Member Domestic Engineer Hurricane's Avatar
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    Default Re: 2TG Turbo Upgrade - Advice/help please

    or ya could run a suck throught turbo set up like me? jjust cant use a cooler
    * 84 FJ60 - 37's, 308, 80 series coils/diffs and LS1TT in the makin
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