carburated twin turbo sbc

[screaminturbos]

Im looking into doing a twin turbo sbc build however this will be my first attempt with forced induction. It will be kind of a budget build so instead of going for an efi system I plan on using a demon blow through carb. how would the ease of tunability be for this type of system? and also what would be the best intake manifold set up? because I remember reading about plennum size affecting the hp for different rpm ranges but that was for N/A engines. does this change for boosted applications?

-JT

[hotrodf1]

Going blow thru will work just fine. Lots of people do it, just look around at Turbomustangs.com forums and you will see lots of folks doing it, and LOTS of DIY turbo related info / fab tips, etc. I dont' mean to point you there as this site is awesome too, just letting you know about more info. For me, it's about sharing info.

For the carb, The key is in the air bleeds and PVCRs. if you are familiar with tuning these, then a little searching and reading will tell what you need to do to finetune your app. Starting off with a BT carb is a good start as well.

As far as manifolds I can't really say. Bigger runners normally want a higher engine speed or higher displacement to get the velocity up (NA). You're going to be injesting more densely packed air while boosted, so it seems a larger runner would be able to handle that better? Don't know. I do know that most folks find a single plane manifold to work better and tune easier than a dual place, though there has been some success with the RPM Air-Gap I think. Distribution is key when in boost as cylinders a little lean will probably show up quicker than in a NA application.

Water / alky injection is an awesome addition to boosted engines, especially if you don't have room / don't want intercoolers. There's lots of discussion on that topic everywhere of course.

Pay attention to what carb hat you use, how much spacer you put on top, keep vent tube extensions in mind, and make sure you use a boost ref. fuel regulator and plenty of pump.

Good luck!

[screaminturbos]

yea thanks for the info! I was deffinately considering the snow water/methanol injection system aswell as an intercooler which is another consern of mine. would i be better off with 2 smaller individual intercoolers then y pipe them together before the carb or would it be be better to have them merge before 1 larger intercooler? i would think there would be more surface area through 1 large intercooler making for a denser charge but would there be any loss in psi? also going to a lower or higher psi would require adjusting the blow off valve and retuning the carb right? or is there more i would need to do?

[TwinTurboMach1]

You want an open plenum single plane intake or else you will have fuel distribution issues.

you do not need an intercooler, on carbed turbo apps the fuel atomizing dropps the intake charge significantly. Yes you can use one, however most dont.

Fuel pump and fuel system is most important. You basically have two choises and A1000 or a magnafuel pro star 500. You will need a boost referanced pressure regulator, you will need a blow trough modified carb.

Boost adjustments are made with the wastegates, not the blow off valve.
The blowoff only dumps the pressure between shifts, the wastegates change set PSI.

turbomustangs.com is your best bet for info... IF you dont want to go to a mustang site cause your a chevy die hard. thats ok cause they now redirect you to theturboforums.com The new address for turbomustangs.com.

[JUSTANOVA]

Although I dont know much about blow thru turbo setups, or much about turbo setups in general, I have been reading alot at www.theturbofourms.com and for blow thru stuff they regard c&s specialties and csu very highly as far as carbs go. check out that site and you will be able to read and study until your eyes bleed about turbo's.

they also recommend ready the book maximum boost.

http://www.theturboforums.com/smf/in...?topic=51153.0

[Pantera EFI]

The chances of a "carb" turbo system giving the same results as a "port" injected system for a lower cost
may not be possible.
I would be glad to help prove that an EFI system, using some common "used" items may cost less.

A test case : the engine choice, first, which year SBC ?

Lance