Would it be better/easier/more simple to build a twin turbo I6 fed by carbeurators or fuel injection? I've already got a carbed I6, should i just go with that? or would i be better off to source an injected motor and start there? I lean more towards an older motor simply to avoid electronic, vaccuum, wires and hoses mess.


what do you think?
any ideas are appreciated.


Luke.

 

Turbos definitely work better with EFI, but they can be setup to work OK with carbs. What I would do is find an EFI lower manifold and build and build a plenum to go on top of it, then use an aftermarket EFI system from FAST, Speedomotive, etc. to run it. That is my intention when I build my turbo motor about 2 or 3 motors from now.

 

lower manifold is separate from the upper manifold? I've had zero interactions with injected sixes-can you shed some more light?

thanks for the speedy reply!

luke

 

All Ford injected truck engines use a two-part manifold. I am building a setup identicle to what silver streak is doing. I am using 1.5" stainless tubing, tig welded. This stuff is not cheap, and it's not easy to do this. I made a jig for this. I am willing to make and sell these intakes for not much over my cost. I use a reclaimed 5.8 throttle body on mine.

Jared

 

what does each part of the manifold house? (what's in the top/bottom?)

 

Its just two pieces... The lower goes out from the ports and curves 90 degrees upwards to a flange. Then the upper is attached to this and turns the other 90 degrees to end up over the valve cover.

EFI is the expensive way to go. An offy, holley, late-model cast manifolds would be a much cheaper way to go. You'll probably end up with better mileage and maybe more hp with the EFI though.

Carb + intake + manifolds = ~$4-500

Aftermarket EFI = $1000+ (unless you go with something like the megasquirt)

Then you'll need injectors and a boost referenced adjustable fuel pressure regulator, etc...


-=Whittey=-

 

although i've had a teeny bit of experience with computer controlled hotrodding, i am much more trusting of screws, jets, and cables. Also, gas mileage is out the door for sure. I downloaded the clifford catalog again, i assume you have to call for pricing? i'm looking at the 3-1 intake, weber sidedrafts. and a cam, and major engine milling, blueprinting, etc....maybe even cyrogenic freezing. seeing as how i'm still in college, this is all long-term stuff, but i want to get all my ducks in a row so i can have everything ready to roll when the money gets here. (read, i'm 80)

thanks boys!

luke.

 

Well, if you've got a bit of cash there was a tripple weber intake on ebay just the other day. It might be there still. Yah, if you buy from cliffy you have to call for pricing. Also, do all your ordering over the phone. The website is run by a third party and you'll just create a phone call loop ("call the website people" "call cliffys" "call the website people" etc) when they inevitably take 10x as long to ship as it should. Or you can go with other peoples products (iirc noone else makes the tripple weber though).


-=Whittey=-

 

running carbs with turbos get tricky- you have to build a sealed, pressurized box around the carb. I have seen it, and on production cars, to boot. The Maserati Biturbo 3.0 was a twin-turbo v-6 fed by a single large 4BBL. Lots of power, but very peaky. Fun car to drive. You roll away from a light, pin the throttle, and all of a sudden you are doing 360's on the middle of the road. I'd go with injection. Any fp regulator becomes turbo-sensitive simply through the vacuum line. As the pressure increases, the pressure on the diaphragm increases, and so does fuel pressure.

Jared

 

On a standard 4bbl you do not need a box untill you get up over 20psi. I'm not sure about webers, you'd have to check that out.


-=Whittey=-

 

any carb that has an external vent for the bowl. Plus, you need a fuel pump that can take the pressure. If you run 8psi of fuel pressure, and 16 psi of boost, you need a pump capable of 24 psi, and a regulator inside the box, exposed to the turbo pressure. EFI is cheaper and easier.

Jared

 

Even if you have to go with an aftermarket electric fuel pump and regulator you're still going to be cheaper with a carb than EFI. Even if you go above 20psi where you will need a carb box, you can get them off Ebay or even make one yourself for not too much money, certainly less than even injectors would cost.


-=Whittey=-

 

 

You can also run the turbo as a draw through design instead of blowthrough, but it may or may not work well on the street. My cousin has his pulling tractor set up this way and it works very well, but it only has to go 100 yards or so at one time.

Also, you have to pressurize the carb regardless of the boost you run. If you run 15 psi the pressure inside the carb will be higher than atmospheric pressure and very little fuel will flow. The best thing to do is use a carb topper like Paxton includes with its blow through superchargers. It doesn't completely encapsulate the carb, but fits on top like an aircleaner. This way it can still pressurize the bowls, but isn't in the way of fuel lines, throttle linkage, etc.

EFI might be pricey, but multiple carbs is no cheap ordeal either. How much is the 3x1 manifold? $300? Then you need 3 carbs. How much will those cost? The linkage? The knowledge to setup multiple carbs? You should be able to pick up an EFI lower for under $50. A set of 24 lb fuel injectors from a 93-97 LT1 F-body for about the same. It would probably cost around $200 to have a shop fab a plenum for you if you did the design work. You'll need to upgrade the fuel system anyway, so that's a wash. Edelbrock and Holley both offer MPFI systems complete and ready to bolt on starting at under $2k, you should easily be able to do better than that. Holley offers a TBI system that could be used on a 4 barrel intake for under $1500. This system is fully programmable via laptop and will even control the timing if you use a TFI distributor. It's definitely not cheap, but that's the price you pay to play.

 

what would put me over 20 psi?