Posted: Thu Jul 24, 2008 8:46 amHello everyone, I am extremly please to have found such a great forum. I feel I will benifit alot from here so it is only fair I try to contribute. It is quite clear other have far more experiance than I do.
Back ground: I am from Australia, I have been port heads and developing engines for 25 years. I only have a small super flow, flow bench, which has served me well. I built a large cenrifical fan and shroud which runs to do other testing with, however I never completed it. I raced in Australian Pro Stock (Small block chev 340 cubes) in the late 90s early 2000s. Always qualified. The last big race meeting here was our winter nationals (June 2008) in queensland. Two cars with my cylinder heads ect, set new national records. I have reasonable experiance in blown alcholo and other forms of motor sport. In recent times I have had great access to a dyno so we can now test more ideas ect.
My approach. The first thing I ask a customer is, what is the bore, stoke, rod length, (cubic inches) and what rpm do you want to make peak power. This then gives the numbers to try and caculate the minimum cross sectional area. On a small block chev its the push rod. All of my engine design stem from there.
Stepping back 20 years. When I first got my flow bench I figured I had all the answers. CFM was everything. I like so many here and those new to this game starting reading everything I could. I kept grinding and flowing. We had no dyno access and I figured there must have been a better approach. Wanting a better system I started looking at computer programs. The programs I first used were Engine Expert and Dynomation. The orginal authors were a great help to me and hopefully I provided them with some good feed back as well. I feel the information books from both of these were a massive help before even loading the disks. I also appreciated the limitaions that simulation had. The best leason I learnt, was to take a mathmatical approach. In saying that my maths is extremley limited (english even worse just check spelling). I started making port molds, then cutting them every 1/2 inch, stamp on graph paper and started counting squares. OK now I had thought I had all the answers!!! (ah wrong).
Moving on: I read an artical in a very famous USA magzine from a VERY VERY Famous engine builder. The artical was about airflow through a port. The problem was the artical stated that the air in the intake port was fastest on the outside of the bend as it had to travel the longest distance. The same as the water flowing down a river always erodes the outside bank ect. When I use a pitot tube in the inlet it was the opposite to what I found. I genuianly felt I must be wrong, because ther is no way this artical would be wrong. Over time I couldnt stand it any longer so I devised a test that measured presure all the way around the short turn and long side radius. This test put me on to presuure gradiants or and different airspeeds in different parts of the bend. It is these differences that I believe cause many of the problems young head porters come up against when they see flow drop off, tumble,flow bench pulse at high valve lift. Normally above 25% l/d ratio.
(Will continue writing some more in a few days, its getting late down under) cheers[B]
Back ground: I am from Australia, I have been port heads and developing engines for 25 years. I only have a small super flow, flow bench, which has served me well. I built a large cenrifical fan and shroud which runs to do other testing with, however I never completed it. I raced in Australian Pro Stock (Small block chev 340 cubes) in the late 90s early 2000s. Always qualified. The last big race meeting here was our winter nationals (June 2008) in queensland. Two cars with my cylinder heads ect, set new national records. I have reasonable experiance in blown alcholo and other forms of motor sport. In recent times I have had great access to a dyno so we can now test more ideas ect.
My approach. The first thing I ask a customer is, what is the bore, stoke, rod length, (cubic inches) and what rpm do you want to make peak power. This then gives the numbers to try and caculate the minimum cross sectional area. On a small block chev its the push rod. All of my engine design stem from there.
Stepping back 20 years. When I first got my flow bench I figured I had all the answers. CFM was everything. I like so many here and those new to this game starting reading everything I could. I kept grinding and flowing. We had no dyno access and I figured there must have been a better approach. Wanting a better system I started looking at computer programs. The programs I first used were Engine Expert and Dynomation. The orginal authors were a great help to me and hopefully I provided them with some good feed back as well. I feel the information books from both of these were a massive help before even loading the disks. I also appreciated the limitaions that simulation had. The best leason I learnt, was to take a mathmatical approach. In saying that my maths is extremley limited (english even worse just check spelling). I started making port molds, then cutting them every 1/2 inch, stamp on graph paper and started counting squares. OK now I had thought I had all the answers!!! (ah wrong).
Moving on: I read an artical in a very famous USA magzine from a VERY VERY Famous engine builder. The artical was about airflow through a port. The problem was the artical stated that the air in the intake port was fastest on the outside of the bend as it had to travel the longest distance. The same as the water flowing down a river always erodes the outside bank ect. When I use a pitot tube in the inlet it was the opposite to what I found. I genuianly felt I must be wrong, because ther is no way this artical would be wrong. Over time I couldnt stand it any longer so I devised a test that measured presure all the way around the short turn and long side radius. This test put me on to presuure gradiants or and different airspeeds in different parts of the bend. It is these differences that I believe cause many of the problems young head porters come up against when they see flow drop off, tumble,flow bench pulse at high valve lift. Normally above 25% l/d ratio.
(Will continue writing some more in a few days, its getting late down under) cheers[B]
