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Convert to a Carb/Turbo?
Part II, the Blow-Thru Turbo
(Also read Convert to a Carb/Turbo Part I)
The most common request I get through direct e-mail and the Message Board are in regards to converting a non-turbo Buick 3.8 V6 into a Turbo V6. In order to prevent repeating my thoughts on this over and over, I will sum it up here. This just my opinion; I have done not a conversion like this, but I do know what is involved with this engine. I hope it will help others make the right decisions and know what they are doing before investing too much time and money.
This Blow-thru project is an idea I am seriously considering trying. I am sure it won't go as smooth as I am describing, but this is a start. I believe this is a better alternative for adding a turbo to a NA engine, but I would NOT recommend changing a factory Carb/Turbo system over to this. As always, I suggest doing as much research as possible and asking questions on the message board!
DRAW-THRU vs. BLOW-THRU TURBO - First let me explain the difference between the factory, Draw-thru (DT) turbo and a Blow-thru (BT) turbo. The factory DT places the turbocharger between the intake and carburetor. The turbo draws air thru the carb. Carb-->Turbo-->Intake. The BT rearranges this to Turbo-->Carb-->Intake. In this case, air is blown thru the carb.
There are pros and cons to both. These are outlined in Hugh MacInnes book "Turbochargers". I recommend reading this book before committing to adding a turbocharger. The biggest pro to the BT in this application is that most of the components will come from the 1986/87 SFI Intercooled Turbo Regal. Basically it is the 86/87 set up, less the fuel injection. It is the SFI where the complexity and expense of the 86/87 system comes from. Plus there is tremendous aftermarket support for 86/87 TR's.
Will this perform as well as a 86/87 SFI Turbo V6? NO! But it will perform well and for a fraction of the cost. And maybe better than the factory DT.
EXHAUST PLUMBING - The 86/87 SFI/Turbo exhaust is perfect for this application. (Please note that 79 and later heads may be required for these headers.) The driver's side (DS) header is connected to the passenger side (PS) via a crossover, and the turbo is mounted directly on the PS header. Then a Downpipe connects the turbo to the catalytic converter. Here are some pictures from the The Turbo Regal Website photo guide: www.gnttype.org/techarea/pictureguides/downpipes/stockhdrs.html
INTAKE PLUMBING - The beauty of the BT arrangement is that the carburetor and intake manifold can be left in their stock position. Using the 86/87 turbo inlet as a pattern, simply connect an air filter to the turbo. There may or may not be issues with clearance for the fan. (The 86/87 uses an electric fan.) Then the compressor outlet needs to be ducted to the carburetor. "Reclocking" or rotating the housing of the turbo will help. There are aftermarket "Carb Bonnets" available to help adapt the duct work to the carb.
INTERCOOLING - This arrangement will allow an Intercooler to be installed. Again I recommend using 86/87 TR components. Unless a front mount is used, the cooling fan will need to be swapped with an electric unit. Intercooling isn't practical unless your are running more than 10 psi of boost. I would leave it off to begin with, and then add it later if needed.
MISCELLANEOUS - There is more to this than above! This is just a starting point. He are some other issues that will need to be addressed:
QUESTIONS or COMMENTS? Please use the message board!
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