CBR RR throttle bodies

[PowerDubs_imp]

Like everything, opinions differ even among knowledgeable people.

To me ideal VE means 100% cyl fill volume, no more no less.

The reality of that is none of us other than privileged lucky few who work in labs know exactly what and when that occurs unless supplied with very expensive equipment. Us mere mortals can simply guess, calculate, deduct.

But as far as the 'engine' being efficient- VE, personally I think of that being the mechanical flow limitation, before manipulation.

Meaning- you can put in more lift and more duration to get rid of a bottleneck, and the engine will naturally want to breath a certain amount of air, at a certain RPM, and make a certain amount of power- effected by the bore, stroke, valves, port angles, butterfly size, etc.

Take that same exact engine though- slot the cam sprockets and without changing a single thing other than when the cams open and close you can increase the overlap since at higher rpm you have less time to fill a cyl with atmo pressure so you use the suction of the exhaust leaving to pull in more fresh mixture.

Time it right and you can catch the edge of the intake wave right when the exhaust valve closes and let it slam in- piling up even more mix for more power- at high RPM, but you will loose power down low.

Myself- I don't call that increasing VE, I call it manipulating VE. The engine itself doesn't flow more naturally- it can have the same poor port design, valve size, single barrel carb, etc. You are just robbing one RPM to pay another. Same can be done with intake runner length, exhaust primary & secondary sizing, collector choice, etc.

I'm sure you know all this- so don't think I am trying to hold a class. Just having conversation for fun and maybe we can suck some new guys into the rabbit hole. Slippery slope.