Hi James, Have you decided in intake dimensions yet? I read a good article by Kevin Cameron a few years back in which he discussed factors of intake inertia charging. In that article he targets 20-30% overcharging of the cylinder. To get that he used a chart converting pressure of air comming to rest at various velocitys. 650fps give 1.25 atmospheres. He further states that the length of this high velocity section only needs to be 20-30% of the cylinder volume. From there on it can be larger. The problem is that the flow is very pulsey not uniform so just calcuating mean flows is probably too simple. Another Cameron article discussed intake wall taper. I dont remember the arguments but the conclusion was a 1-3deg taper was optimum. Something to do with flow seperation from the intake tract walls.
-Tom P.
Well, after having a big cup-o-joe and rereading the article the idea seems to be to get the intake velocity high enough that upon comming to rest it produces about 1.25 atmospheres of pressure. To to over fill the cylinder 25% about 0.25 the cylinder volume worth of this high velocity gas is needed. So, with a 500cc cylinder times 0.3 = 150cc.
If you filled the port/intake with 150cc fluid it would show where the high velocity region is. After that region the port can get wider to allow less restriction. The question Ive always had is how do you size the port to give produce a real velocity? Can you use the mean gas velocity to calculate it? Seems like that could give produce too small a port since the intake duration starts and stops in 280 or so deg.
-Tom P.
If you filled the port/intake with 150cc fluid it would show where the high velocity region is. After that region the port can get wider to allow less restriction. The question Ive always had is how do you size the port to give produce a real velocity? Can you use the mean gas velocity to calculate it? Seems like that could give produce too small a port since the intake duration starts and stops in 280 or so deg.
-Tom P.