I saw a pic on Facetube where a guy using a very small ball burr was making a pattern of dimples in the intake ports (similar to a golf ball) and I wondered if anyone had done this and done a flow bench test to see if it worked?
I saw a pic on Facetube where a guy using a very small ball burr was making a pattern of dimples in the intake ports (similar to a golf ball) and I wondered if anyone had done this and done a flow bench test to see if it worked?
In reply to MiniDave :
It's an idea that's been around a while. A long time?
I do not have a good grounding in it. I just did a cursory search, and my lousy summary of inadequate research is that at high flow speeds it probably hurts, and low flow speeds it may help retain energy in the airflow, and it could be theorized to help provide turbulence to help keep fuel mixed, but that kind of turbulence occurs to me not to be ideal for keeping that air flowing toward the valve...
This probably falls in the same category as Singh Grooves in the combustion chamber ....
Mythbusters tested it with the outside of a car and it made the car get better gas mileage. They had to make the dimples much larger than expected but it was for a large object.
Whenever I redid an engine, I "gasket matched" the intake ports etc. I also deburred any casting flash and the used a whip to polish the tubular runners. I read that the atomized gas-air mix would dropout of suspension and gas droplets would lie on the surface if it's too smooth. Air on the surface moves slower; friction drag. So, put dimples or little steps on the surface and sacrifice X% of flow, but that number is much lower than the parasitic drag of not having them. Makes the boundary layer smaller.
I do all this work for a little more power, then drift through the corners losing a boat load of time anyway. 
Isn't the whole "fuel dropping out of suspension in a polished bore" thing pretty much moot with modern fuel injection? I can see it being a thing when you have a carb, but for the last 50 years we have been spraying fuel at the back of the valves and now directly into the combustion chamber.
Fuel dropping out of suspension would make sense if you only consider the first instantaneous introduction of fuel.
However, fuel is repeatedly injected (or continuously fed through a carb) into the intake, and any fuel that "drops out" eventually winds up sucked into the cylinder anyway. I think improved airflow helps significantly, but fuel dropping out is an insignificant loss.
Obviously you can flood the engine with liquid fuel, but as described in the post, I think fuel dropping out is insignificant.
The idea has indeed been around a long time. Back in the 90s, my engine shop teacher mentioned a previous student using a punch to dimple the bowls in the intake ports, apparently to help keep fuel in suspension. This was for a low-buck local carbureted circle track series, so no flowbenches, no objective before-and-after to isolate the effects of the dimples.
It might be worth scouring David Vizard's and/or Eric Weingartner's videos. Vizard can be a little tough to watch (turn the speed to 1.5x and ignore the grandstanding) but seems to know his way around an engine.
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