Maybe the Bernoulli Principle is being applied or looked at too simply here. We're looking at how the intake area of the airbox is controlling the effect, but isn't the Bernoulli effect more of an issue directly at the carb?...the carb intake throat size, shape of the throat, length of the intake throat to the manifold, etc? Unless the airbox intake size is ridiculously restrictive...and I think it's very aguable that the stock setup is restrictive...it's the carb issues that I mentioned that are the real factors in the Bernoulli Principle. There are always exceptions in certain designs when you consider things like turbos, superchargers, ram-air induction, etc., but otherwise I think most engines with carbs like huge dead air spaces with plenty of air on demand.

 

When they come out with the same bike fuel injected, I will trade mine. Hoping for cast wheels or at least tubeless tires.

David

 

You can already have tubeless...well, at least if you don't have abnormal wheels...cough, cough, motard.

I've been running them for a year...love 'em.

 

Reversion takes place through any carb: the air flows one way through picking up fuel. Then suddenly the intake valve (or reeds on a twostroke) slams shut, all momentum of the airflow can't go anywhere so a certain amount of it reverses back through the carb, picking even more fuel as it does. The more reversion effect the more fuel there will be in the mix when the valve opens again. Anything that reduces this effect, like changes in the airbox system, may require a bigger jet, even though the airflow in cfm through the motor hasn't changed.

we can add Reversion to Choke effect and Mr. Bernoulli to the discussion, LOL

off topic, but. In a normally aspirated engine we'd expect to have atmospheric pressure ~14.7 present at the intake each cycle. In a well designed system (usually the port) the pressure can go above 14.7 when the valve suddenly closes as the momentum of the air stuffs the port. Before the increase in pressure is lost out the way it came, valve timing could/would quickly open the valve and take advantage of it, free supercharging if you will. Now how quickly the extra pressure escapes back can also be function of the airbox system as it can act like a spring to hold things in if the acoustic (not airflow) energy is tuned to do so. Which takes us back to Hemoltz.

 

Obviously, more is at play than pure Bernoulli principle...which is most accurate during steady-state conditions. Besides, wouldn't we be more accurate talking about what's happening in a Carb with a jet if we referred to this as the Venturi Effect? Isn't the Bernoulli principle a law that helps to explain how a Venturi effect is created?

I hate to say I've forgotten which is more correct....but, I'm leaning toward a Venturi being more accurate in this case.

Whatever the terminology, the non-steady-state conditions surely have an effect on the end result air/fuel mixture.

Went on a TOUGH ride today with my 128 main, HMF quiet core slip on, and no snorkle. 20 miles was at an indicated speed of 70 mph. The remainder was a mix of sand, gravel wash, and single-track...much of it so steep that I had to be in 1st gear WOT to make it up. Got 53 mpg. I consider this bike to need suspension work before it needs more climbing power, no matter if it's Venturi or Bernoulli that I've tweaked with my setupQ

 

I think it's like this:
Bernoulli principle, creates the pressure differential that pushes the fuel from the bowl to the venturi.
Venturi principle, accelerates the air speed through the carb.

Ride on
Brewster