I still have a few numbers from my flowbenching work. I had a shop port and polish the head, but I was not happy with their conservative approach. Since I had a grinder and flowbench and computer at my disposal, I decided to learn the art and go to town. With that in mind, my base numbers are from a mildly ported 1.8 head, which, I assume, are better than stock. To simplify things, my potential intake flow (I can´t find my exhaust numbers, but most power will be found on the intake side) will be given at valve openings of .050, .10, .15, .20, .25, .30, .35, .40, with no intake manifold attatched, but with a short clay velocity stack to smooth the flow. Base corected flow/Final flow, 19.4/21.9, 37.4/39.6, 58.1/59.3, 76.2/76.8, 89.9/92.0, 99.0/106.0, 104.7/111.2, 108.2/114.5. Base Potential flow/Final flow (in %), 60.8/68.7, 61.2/64.8, 67.0/68.4,70.1/70.7, 70.7/72.4, 69.8/74.7, 68.4/72.7, 67.4/71.3.
Not huge numbers, to be sure, but it is hard to find big improvements on this head. I think Mazda already figured out the secret by raising the intake port openings to give a straighter shot to the chamber. I found the downward curve of the intake port to be the limiting factor. Still the results speak for themselves. My car is plenty strong and the hogged-out ports have not really hurt the bottom-end, as I had expected. I have a CD with pics of the ports, before, during and after my hand work, and many of my projects, but have not taken the time to label the items. One of these days, I will do so and get it to the webmaster to post.
Hope this gives you some food for thought.
Marcus