But, TT, it kinda stands to reason that if you have to jet up to get more fuel for the increased amount of air that you are pulling in, it means that you are getting both more fuel and air at a given RPM. More fuel and more air = more bang. More bang = more power.
No, sir. You increase jet sizes to compensate for the loss of choking restriction pulling on the jet orifice and must respond with larger orifices to restore the A/F ratio. Restoring the A/F ratio, does NOT mean making more power.
The amount of fuel drawn through a jet is a function of differential pressure across the jet orifice. You draw more fuel through existing jets via application of choke. Choke deepens the vacuum in the carb throat forcing more fuel to pass through a given orifice size. This makes the air fuel mix richer for cold operation.
The same effect occurs with filter restriction changes. Pods generally have less restriction than the stock air box system, and therefore carb throat vacuum is diminished and less fuel is drawn through a given jet orifice size. To restore the proper air fuel mix ratio, you have to make the jet orifice larger, to allow the same fuel flow at a lower differential pressure.
Pods do not increase output power at idle settings, yet the slow jet orifice size must increase or carb adjustments must be made to "richen" the mix at idle. The same is largely true for midrange setting where pods often require needle jet changes to adjust mixture, but NOT to produce more power. Main jet is increased for similar reasons, loss of throat pressure differential applied to the metering jet orifices.
With a pure pod change, the engine mechanicals have not increased their volumetric efficiency. Only the inlet restriction, or "choking effect". The engine still requires the same ratio of air fuel for a given RPM. Pods won't deliver "more" air unless the engine is modified to require it or you rev it up higher, outside the design parameters for the stock induction. Near and above red line is where the inlet restriction does or can effect quantity of air getting to the engine. (Like breathing through your mouth instead of through your nose). I can believe that because more air (oxygen) is made available for combustion at the high rev end, proportional increases of the main may be higher than the low and mid range increases. But, much of the size increase is due simply to throat pressure change from diminished "choking effect".
Again, I ask for hard test data, instead of conjecture or rationalizing arguments. Bigger jet sizes, does NOT mean more air, or more power. Track times and/or dyno performance curves might, though.
Personally, I think the "pod people", if you'll pardon the expression
, will be surprised at how little performance, if any, they've gained on their street machine, by installing pods.
Cheers,
