mazdaspeed7

Its not unreasonable to think so. Even with a good port, the air column still needs to make an almost 90 degree with little to no radius. Also, there is very little you can do to keep the air column from just skipping over the eyebrow at any appreciable volume.



But that advantage it does have is an increase in port timing. Its proven that bridgeports make more torque and hp than side ports, everything else being the same. Its like having a long duration cam with the same lift as stock on a piston engine.

j9fd3s

you wanna look at not only the peak # but the area too. the bp only flows about 25 cfm more, but it hit peak flow earlier than the sp and hangs in later.



i would have thought the pp would be closer to the bp, but maybe thats because the bp didnt go into the water jacket

Kenku

Ooh, I like the additional photos and the peripheral port flow numbers... eesh, a bit impressive those. Really need to build a flowbench of my own; there's various kind of non-conventional numbers I want to look at at some point, but god knows I've enough projects.



I think I see what you mean with the way the ports on the 3B and RX5 curve towards the end... going to have to change some details of how I grind my ports, I think. Always learning! Thanks again for all the data and pics.

Old Grey

The PP from memory was big , I think 52mm



The BP is a std port just with the bridge cut only, the original port is still std. The bridge is the same height as the port and 8mm wide and does not cut the orange water O-Ring. The increase is only due to the bridge. It is not the most achievable, as an estimate, bridge 25cfm+port 176cfm+primary 80% =362cfm ish





When you add 80% to the flow numbers for BP because of the primary port it catches up some toward the PP







Like was said the flow didn't increase much but the timing did. There is not much actual flow (even though the flow bench says it can) before TDC(T) and after BTC(B) except for wave tuning, so why have more timing. The most air you can get in a engine without wave tuning, inertia tuning is VE 100%, you need the tunings to get higher VE and thats where the extra port timing comes in. VE, what affects VE?, it seems velocity has an effect, you need an air speed of 700ft/sec to get to a VE of 125%, if you had a port speed of 820ft/sec you could achieve VE 135%, if you could overcome all the losses. I'm kinda trending these days that the velocity is equal if not more important than the flow.



If you port an engine to 300cfm and the rotor/piston only demands 200cfm you will have only 200cfm flowing through a port that can take 300cfm, this makes the flow too slow at that rpm, you have to make the port smaller and take some flow out to make peak power at that point. You could rev the motor harder and the rotor/piston will demand more air which will make the port velocity higher, if you can keep you motor together. Actual velocity probing will avoid this problem.

If you have a HP curve that won't quit, is still rising past the point where you want peak HP, it probably has too much flow and not enough velocity. If you could get it to peak earlier it will have a fatter power curve, more area under the curve. You won't have HP bragging rights but you will be quicker.

Kyrasis6

Hence "The builders job is to get the MOST flow out of the SMALLEST port."



If you have two ports that flow 150 cfm at a certain pressure drop but one is smaller, the smaller one will actually make better power over a longer range.