Will the pressure inside the runners be at atmosphere pressure when the vavle opens again, or is it dependent on engine speed? If it lags behind, can this be solve with cam timing to better fill the runner before it opens again?

Thanks
Jeremy

 

you are getting into wave pulse tunings which is very interesting. If you can decrease the amount of times the intake charge reflects off the valve the better, see LS1. My understanding is that this is accomplished my decreased cylinder burn time and optimum inertia supercharging effect.

 

I'm talking in N/A terms, if anyone was wondering. I know wave pulses have a big play in this, but I was asking on just a general front. Bcuz if the intake is stacked with air ready to fill the cylinder, then you are "packing" the cylinder with as much air as possible. But, if it only happens at low engine speeds, then there issomething to be gained if it doesnt happen at higher engine speeds.

 

95grandsport just explained it to you, you missed the point. You're trying to generalize somthing thats so much more complicated than you realize.

You have to understand that a wave pulse that has been deflected and not yet on its journey back to the cylinder is at less than atmospheric since; the wave front is pushing pressure away and what is left? vacuum (sort of, or shall we call it less than atmospheric pressure) What can be done to combat this? re-read 95's post and do some research on it. A lightbulb will pop on.

In true reality though, variable valve timing coupled with variable runner length and vomuletric capacity to keep velocity up are the only way to do anything about this. However the project to even come up with a concept let along build a working model with that many parts and have it work for 5 - 10 - 15 - 20 years is another feat....

See, an intake with set 3D properties such as runner length, runner volume, and plenum vol. size etc can only operate at full capacity for a certain RPM band, there is NO modification you can do thats gonna make it as efficient at 500 rpm as it is at 6500 rpm. In a good design you'll see efficiency build and slowly cross over 100% efficiency (inertial supercharging ) and then taper back off. And it will follow an RPM range and be exactly the same every time. Because the intake manifold has stayed the same every time you hit the go pedal.

 

yeah, what he said!

 

my question to add to this
after the valve shuts at high rpm's does the air create pressure just before it is let into the cylinder, or is it possibly to make a design for it to bounce off and cause a low pressure are, lower that that in the engine after the ehaust is pushed out

 

Yes it creates pressure at peak Volumetric efficiency i.e. when air is entering the cylinder bore at any value over 100%. Even at 100% there is a 0 vacuum, basically its atmospheric pressure whatever that may be, 27.85 or 31.08". As soon as you cross over that 100% threshold you are now creating pressure (The artificial supercharging effect made possible by the pulse waves inside the intake. ) So at anything less than 100% VE there is still vacuum meaning the cylinder may only be filling with 85% of its capacity. The Low pressure area you talk about is always there until you cross over 100%. As for lower pressure above the intake valve as opposed to in the chamber, I dunno... I haven't slept in 29 1/2 hours. Thats a little more involved than I can reason out right now.

How am I doin fellas, am I on par like I think I am?

 

Sounds pretty good to me.

So, if I understand mastrdrvr's question : "I'm talking in N/A terms... I know wave pulses have a big play in this, but I was asking on just a general front. Bcuz if the intake is stacked with air ready to fill the cylinder, then you are "packing" the cylinder with as much air as possible. But, if it only happens at low engine speeds, then there issomething to be gained if it doesnt happen at higher engine speeds.

No, the NA intake plenum is not stacked with air at higher than atmospheric pressure at any rpm. There is air flowing into it thru the carb or TB, but there has to be less than atmospheric pressure overall in the plenum to get air to flow into it.

The inertial tuning pressure is measured at the intake valve. Even with a 3-5 psi tuning pulse at about the time the individual intake valve is closing, the overall pressure in the intake plenum is still negative (vacuum), perhaps 20 inches of H2O depression in a good system, much higher in a restricted system.



My $.02