It is kind of basic but gives a good idea what is going on.

http://www.youtube.com/watch?v=p95ZN...layer_embedded

 

Very cool link. Is there one for how teenagers think???

 

Wow, I didn't realize that the slides in our carbs were being pulled up due to less pressure on the backside... I thought they were being pushed from higher pressure underneath for some reason. So the reason that the HRC slides open slower is that air cannot escape as quickly because there is one fewer hole...

Such an art... all destroyed by EFI

 

Yes but..... and there usually is a but....lol

The effect of the single lift hole is exponential not linear. What that means is when the slide is fully closed it will move slower as the air is drawn out due to a single hole. As the slide rises and the pressure inside the slide drops it reaches a point where the single hole will have the same flow rate as the two holes.

So the slide moves slower initially then the farther it is open the closer it moves to the same speed as the slide with 2 lift holes.

That is why you use the lift holes (and the slide cut out) to tune the low mid-range

 

I only wish....... that would make my life much easier.....

 

So, and forgive me if this is incorrect as fluid dynamics always do opposite of what I think lol, as the slide opens more, it is less restricted by the size of the hole. The speed of the slide is more limited by the differences in pressure as it opens more...?

 

Yes that is pretty much it. As the pressure drops you are moving less volume of air through the lift holes. So as the pressure drops, the holes size becomes less of a restriction to the flow rate.