Curtain Area to Valve Area Convergence Intake Valve Lift

[hdwgfx]

Anyone know the formula for this?

What is the importance of this Curtain Area to Valve Area Convergence Intake Valve Lift calculation???

[200cfm]

I believe it is where the math area of the valve diameter equals the math value of the curtain area. At a certain lift they are equivalent equal area values.

[jfholm]

I believe it is where the math area of the valve diameter equals the math value of the curtain area. At a certain lift they are equivalent equal area values.

This is correct. and it is also where you start to see less effect on flow from the valve. You see more of the true port. Convergence is where my port went turbulent due to the SSR. In my case it was at a lift of .512"

John

[hdwgfx]

how is it calculated?

[jfholm]

I am at work trying to do this between calls so I will try to post on my break or lunch

John

[hdwgfx]

THANKS John, no hurry....

[jfholm]

First of all you curtain area equals the area of your intake valve when the valve lift reaches 25% of the intake valve head diameter. So if you divide your intake head diameter by 4 or multiply the diameter by .25 then you get your convergence valve lift. In my case my intake valve is 2.05" diameter. That divided by 4 or multiplied by .25 equals .5125" valve lift.

To find the area of your intake valve you need to take the radius of your intake valve square it and then times it by Pi which is 3.1416. So in my case since the valve head diameter is 2.05 I would times the radius by it self (1.025 X 1.025=1.050625) then times Pi 3.1416 by 1.050625 and that equals 3.3006435 square inches. At .5125" valve lift your curtain area is the same 3.3003435 square inches.

So if your intake valve was only 1" diameter then your convergence lift would be .250" lift and if you intake valve were 4" diameter then your convergence lift would be 1" lift.

John

[hdwgfx]

Thanks John

[1960FL]

John,

I have allays struggled with this why is the curtain area the OD of the valve and not the ID of the Seat?

Rick

[jfholm]

I just use the OD as that is what most of the places I go use. My Performance Trends Engine Analyzer Pro uses that figure. The 25% ruling will stay consistent though because if you use the inside of the seat then you would also want to use the inside edge of the seat on the valve. It would make a little difference in the lift at which you would call convergence. Also my Pipemax says my convergence is .512 and that would be 25% of the o.d. of my 2.05 intake. I use the o.d. to stay consistent with my two programs I use the most.

I have a 1.940" intake valve here and and checked from the inside seat edge and compared it to the o.d. The o.d. is 1.94 and the i.d. is 1.75 so you would indeed have a difference in lift for convergence depending on how you would want to check it. o.d. convergence lift would be .485" and i.d. convergence lift would be .438".

I know on my head it was very close to the .512" lift when the flow went turbulent and lost flow until I fixed the SSR.

John