Common plenum or individual runners???, for gas milage and drivability Options

[Mueller]

for my 2316 it seems that the stock plenum might be reaching it's limits as far as volume goes.....so, I either fabricate a larger common plenum, or go with individual throttle bodies such as TWM or Jenvey*

single plenum would be easiest, but the individual throttle bodies look better (IMG:style_emoticons/default/smile.gif)

has anyone switched from one to the other on the same motor with everything else being the same???



*Jake Raby is the U.S. distributor of these....

[lapuwali]

Somewhat apples and oranges, though. With individual throttles, you need to look at peak flow for each cylinder with that relatively tiny manifold volume providing no real "buffer", so each throttle has to flow enough for that cylinder at peak. While that one cylinder is sucking as hard as it can, the other three are basically idle. With one TB feeding a sufficiently large plenum (at least the combined size of the number of cylinders drawing air at once, or 500cc for a 2.0 four), then the air for one charge is being drawn from the plenum, and the TB only has to flow enough to keep one cylinder full (on a four, 1.5 on a 6, 2 on an 8).

...I'm hand-waving here, not operating off actual theory, but this sounds close to correct. I have NO data, this is me just thinking out loud. I'm sure Jake will pound me into the ground with actual data...

So, if a 28mm venturi works with a pair of dual Webers on the target engine, then a single 28mm TB with a plenum one cylinder in size should also work. Probably upping the size of the plenum and the TB some to account for inertia effects and cam overlap is a good idea, hence the 45mm TB on the 2.0 (which is probably bigger than actually required for flow). Note that many a 2056 is out there making more power than a stock 2.0, and each cylinder is being fed by a 32mm venturi or thereabouts. A 150hp 2270 is using, what, 36mm vents on 44IDFs?