I asked this question on Nopistons ... but its not as active as this forum so I figured that I'd ask here.

They have a thread talking abit about port matchin and how increased velocity is more important than increasing the area for the air to move through. So my question was:

What are the effects of filling in the intake manifold with say JB weld or the likes to match up with the intake holes on the engine? I know things like these are done on motorcycle engines to remove that "dead area". Also another idea is opening up the intakes on the engine to match the intake manifold but not be straight to the back, rather a slow and gradual decrease in size opening.

Not sure if anyone has tried doing these things (ITO?) if yes what are you comments regarding this, and the hp effects?

Here's the motorcycle article:

http://www.mototuneusa.com/think_fast.htm

And we do this on the Formula SAE car that I help on and it works on that.

 

Well unless your manifold already has been ported then it should be smaller than the runners in the block. So are you talking about filling in the runners in the block to make them smaller then? I suppose it might work to increase low RPM velocity and power, but porting the runners in the block usually makes more top end power. When you port match the intake manifold you have to port out the manifold to match the engine's runners.

 

Ahh .. why did I remember it to be the other way around.

 

i ono... Mazda left the intake manifold runners smaller than the block to help stop reversion of the intake charge back into the intake manifold. That tiny lip was actually designed for a reason. I personally like to port match the secondaries and leave a lip on the primaries for low end grunt with higher velocity and bigger runners on the primaries for more flow and more grunt up high.

 

how would that theory work with dual carb or ITB? since you really don't have seperate primaries and secondaries anymore

 

I port and gasket matched my S5 intake manifolds and I filled in the little holes on the inside of the manifold with JB weld, I'm not going to be making more power because I'm not enlarging my port size. Power from airflow improvements is made at the smallest orifice. so I will just have increase air velocity (maybe even a better fuel/air mixture) and improved throttle response.

I gasket and port matched the LIM to the block as best as I could without tearing down the engine and matching the LIM to the block.

it does make a noticeable difference when you have a ported and polished throttle body with TB mod, and port/gasket matched manifolds.

I also do all of the porting and engine machining work on our FSAE car at school.

 

same theory behind a half bridge. They share the same runner toward the TB, but they still split off into seperate runner legnths and diameters, and port shape and size.

 

now that you put it that way ... makes sense ... might give it a swirl this summer then

stupid question ... the secondaries are the outer ports right? (most to the left and right, correct?)

 

yep. secondaries are on the front and rear irons.