CNC Mill Mark Removal in Intake Port
Here's the final two tests just for fun. First, sand entire port with 60 grit cartridge roll. Second, hand sand the SSR only with 180 grit cloth backed sandpaper.
The 180 grit hand sand made a difference. I got similar results a few months ago when I hand polished the SSR. As was mentioned earlier in the post, each time the port is sanded the shape changes a little. When you sand with a cartridge roll on a convex curve it is difficult not to leave a series of cascading flat surfaces because the cartridge roll is straight. Hand sanding the SSR as the final step may have just smoothed out the straights. So the slight gain could be more because of shape than texture.
One other quick thought about flow testing. It is tough not to let human bias slip into testing. My preconceived notion about this test was that the 180 grit hand sanding would help. So while I really tried not to do anything to make the 180 grit win, I found myself taking a little more time checking the details to make sure it did not lose. For instance, I have a wood entry plate that I use on the entrance to the port. It does not fit exactly right because it is a generic plate. There is always a little clay that has to be used to smooth things out. Did I take a little more time and do a better job smoothing the clay out on the final test? No such thing as completely unbiased testing. No such thing as completely objective humans.
One final thought. IMO, 1 cfm change from test to test can be ignored. 2 cfm change might be real. 3 cfm change and something is really going on. A small change to the entry plate can easily cause 3-4 cfm change.
Here's the final two tests just for fun. First, sand entire port with 60 grit cartridge roll. Second, hand sand the SSR only with 180 grit cloth backed sandpaper.
The 180 grit hand sand made a difference. I got similar results a few months ago when I hand polished the SSR. As was mentioned earlier in the post, each time the port is sanded the shape changes a little. When you sand with a cartridge roll on a convex curve it is difficult not to leave a series of cascading flat surfaces because the cartridge roll is straight. Hand sanding the SSR as the final step may have just smoothed out the straights. So the slight gain could be more because of shape than texture.
One other quick thought about flow testing. It is tough not to let human bias slip into testing. My preconceived notion about this test was that the 180 grit hand sanding would help. So while I really tried not to do anything to make the 180 grit win, I found myself taking a little more time checking the details to make sure it did not lose. For instance, I have a wood entry plate that I use on the entrance to the port. It does not fit exactly right because it is a generic plate. There is always a little clay that has to be used to smooth things out. Did I take a little more time and do a better job smoothing the clay out on the final test? No such thing as completely unbiased testing. No such thing as completely objective humans.
One final thought. IMO, 1 cfm change from test to test can be ignored. 2 cfm change might be real. 3 cfm change and something is really going on. A small change to the entry plate can easily cause 3-4 cfm change.