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Originally Posted by beef_bourito
the reason you want a certain length intake runner is because of the pulses of the valves opening and closing. when a valve closes it sends a chockwave, kind of like a sound wave, back into the tube, when it hits the end it bounces back. you want that dense part of the wave to hit the valves when they open.
The reason these lengths are the best for that rpm is because the wave gets to the valve at the right time. but if you get a shorter one it can bounce multiple times so you can use a smaller length and take up less space. it's only a portion of the wave that gets bounced back so evey time it bounces there's less compressed air. you will get optimal power with the ideal length but you won't really notice a big difference with the smaller lengths.
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Yea I know how it works, I was just woundering why they did not try to build them to the ideal length. I know it would take up more space, but the difference in pulse strength, and fuel atamazation, should make a substantial differnece after you advance the timing, increase the CR or boost. I heard that F1 cars lost 150hp when they were forced to reduce their intake runner length. The difference in the different pulse strengh between the pulses is 110% pressure on the second pulse 107% pressure on the third pulse, and 104% pressure on the fourth pulse. That being said I don't think that most autos even get their fourth pulse because even with 10 inch runners you don't get the fourth pulse intill 6,800 RPM! That is way high and alot of cars won't even see it. Even with incredably long 18 inch runners you wont see your fourth pulse untill 3,800RPM and your second pulse is all the way up to 6,800RPM! I would really like to see what a car can do if it really optamized it's VE I have heard that it is possable to reach 130 percent VE that is like running a 4 psi supercharger! That would be SWEET