Vitamin Pepsi Posted April 5, 2014 Report Share Posted April 5, 2014 Has anyone ever done a 4bbl + turbo mod? plus something like this chevy v8 Quote Link to comment
datzenmike Posted April 5, 2014 Report Share Posted April 5, 2014 At 7K a 2.8 liter motor only needs about 350 cubic feet of air per minute. So a 500 cfm 2bbl Holley would be more than enough and simpler than a 4bbl. Quote Link to comment
ggzilla Posted April 5, 2014 Report Share Posted April 5, 2014 That 2-bbl flows more air than a holley 350 4-bbl Quote Link to comment
izzo Posted April 6, 2014 Report Share Posted April 6, 2014 Yes, its been done before. Quote Link to comment
DanielC Posted April 6, 2014 Report Share Posted April 6, 2014 My understanding is that with a turbo, you do not need a big carburetor. The turbo will expose the carburetor to a fairly high vacuum, while the manifold pressure is above atmospheric pressure. I think carb CFM ratings are for either 1.5 or 3 inches of vacuum. If the turbo is providing more vacuum than that at the base of the carb, the carb will flow more air. Quote Link to comment
EricJB Posted April 6, 2014 Report Share Posted April 6, 2014 The chevy is a blow thru set up. Quite a bit has to be done to make it work. When you pressurize the carb like that, it tends to spew fuel out the throttle shafts and empty the bowls. The carb has to be set up for the pressure, and a higher pressure fuel system, with a regulator that increases with the boost. Or you can put the carb in a box and pressurize it. A draw thru set up allows more pressure with less work. Quote Link to comment
Z-train Posted April 6, 2014 Report Share Posted April 6, 2014 A blow thru is ALWAYS Plan B. Quote Link to comment
datzenmike Posted April 6, 2014 Report Share Posted April 6, 2014 Daniel, yes. That's why a 4bbl isn't really needed and just adds complexity. A blow through allows more power for the same boost by increasing the efficiency from using an inter cooler. Quote Link to comment
Driftease Posted April 6, 2014 Report Share Posted April 6, 2014 Draw thru has many disadvantages too low boost capability, water or methanol injection is the only option for cooling the charge, hard starting, sluggish response and very limited mounting locations for the draw thru as the turbo should be mounted slightly higher than the intake plenum and as close as possible volume wise to the intake ports to keep the airspeed up. It is usally easier to make jet changes on a draw thru setup and no other mods need to be done to the carb other than tuning. Personally I favor the blow thru if it has to be carbureted but there is no replacement for fuel injection. Quote Link to comment
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