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For those still running N/A, which is most of you, has anyone attempted to port their intake tract or header / exhaust area? I don´t know if these parts need cleaning up or not, just curious. If so, did you notice any improvement? I imagine that such clean-up work would be most noticeable when using forced inducation. I recently changed my valve cover gasket and noticed all the casting ridges, pits, etc inside the head. Wondered if the other elements might be the same way. Anyone?
 

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I ported and polished the head, the intake manifold and the throttle body. The manifold comes apart in two pieces, so it is much easier to get to all the innards. There is a great deal of smoothing to be done, as well as match porting to the head. I didn´t bore the TB, since I didn´t want to have to cut and match a new plate, but I did remove the ridge before the plate, enlarged the opening and the taper, and thinned the throttle plate shaft, as much as possible. I was chatting with Ryan about the TB and I couldn´t find all my numbers, but it seems that I increased the flow of the TB from 259 cfm to 282 cfm. On Miata.net, there is a figure of 300 cfm thrown around for the stock TB, but I think that is calculated for the 55mm size of the TB, not actual numbers from a flowbench, as I did here.

As far as power increases, I couldn´t pin anything down on these mods, alone, since I did a complete rebuild at the time. I mentioned to Ryan that I am making some power, however. I just ran a few times with my buddy in his Audi S4 and we were dead nuts even from 70-120, as well as, 15-90. Needless to say, we were both stunned, but I was the happier of the two of us.

Marcus
 

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I ported/polish and match my intake manifold. You´ll not really feel the difference if you will do only that. But all small things are adding up. And at the end you have something. My best kill so far was a 225 hp Acura CL.
 

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If you are a gearhead and are good with your hands and understanding cars, you can buy a port and polish kit from summitracing.com. You will need a drill. That is what I plan to do, also, my car had 155,000 miles and it burned the smallest amount of oil, but when I took of my exhaust manifold (car was totaled) the was a 1/16 probably a little more of carbon build up. Now imagine you clean that out then port and polish the exhaust manifold, I believe it will be the same as haveing a header with out the cost and the same performance increase.
 
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