gruhsy

Just build a new intake 🔧😎

I have an extude honed intake and saw no difference between my stock one and extruded.

Thom

Chris White is correct. Things like "Golf ball" finish in inlet ports will provide the greatest flow. Sharks for instance have been testing with turbulent flow for a few thousand years so I suppose they have a clue.
With that being said I suppose your brother has seen gains porting parts that were certainly badly finished to begin with.

Perry 951

Hardly. He's designed and built injector hats, superchargers, and intake manifolds for fuel dragster and fuel funny car for about 25 years and is currently employed in that capacity for the largest manufacturer and owner of fuel category teams. He's on a blower dyno about 3 days a week.

I'm not going to go into proprietary information here, but smooth castings in an intake and head up to the valve bowl flow more than a rough cast or dimpled finished. If it didn't, you'd better believe that it would be implemented.

Again, different purpose and application over a street car so it's possible turbulent flow is better for street manners in various RPM ranges.

odurandina

back in the Carb era it was the other way around.

Dave W.

One of the reasons some guys cut open the mani is to cut down the divider between runners, which effectively shortens the runners and adds volume to the plenum which improves top end power.

Perry 951

Very true as the droplet size was like a thunderstorm and injection is like a fog. If you look into some of the flow techniques in direct injected engines, you'll find that laminar flows are desired so they can direct and initiate swirl into the combustion chamber rather than an uncontrolled tumble. Bowl and seat designs are very carefully designed and tested to direct flow as to best position the mix and flame front especially in lean burn conditions. The plastic intakes have close to mirror finish runners and the heads have very smooth ports.

My shop works on about 7000 cars a year and a large part of it is engine work. Pretty much anything made in the last 10 years has very little surface imperfections in the intake systems. We can all agree that power output is up significantly and fuel consumption is lower as well. That isn't from fast ECUs and fuel atomization alone.

Thom

Not just for street manners, some drag engines also use golf ball patterns with very high specific output. Anyway, different ways to skin the cat I suppose.