Why an engine makes more power off a burr finish

[Erland Cox]

As I see it activating the boundary layer makes it initially thicker but stops it from growing with flow length.
So the average boundary layer becomes thinner.
The boundary layer moves slowly and has very low kinetic energy.
If the bowl is larger than the port before it pressure in the bowl rises.
This will blow the boundary layer back up the port and if the layer is thick it will cause all sorts of flow problems referred to as stall.

Erland

[BrazilianZ28Camaro]

As I see it activating the boundary layer makes it initially thicker but stops it from growing with flow length.
So the average boundary layer becomes thinner.
The boundary layer moves slowly and has very low kinetic energy.
If the bowl is larger than the port before it pressure in the bowl rises.
This will blow the boundary layer back up the port and if the layer is thick it will cause all sorts of flow problems referred to as stall.

Erland

This^^^^

Personally I like to do a rougher burr finish on the port low velocity areas to aid the reintegration of fuel droplets back to the air stream.

This finish is RPM, port shape and engine application specific IMHO .

The intake ports of F1 engine are smooth as glass....I doubt the fuel have enough time to stick on the walls at 16-19k rpm.

[Erland Cox]

F1 ports are almost without bends and don't go up in area to fast.

Erland

[BrazilianZ28Camaro]

F1 ports are almost without bends and don't go up in area to fast.

Erland

Yes , the texture is port shape and engine application specific .....jmho

[Nick Ferri]

Hello all! There are so many posts on here that I wanted to quote and comment on but by the time I got to page 4. I realized I just better be politically correct here.

I haven't posted in this forum for quite a while now but it's definitely the best knowledgeable forum out there. I have been fortunate enough to be in the racing industry going on 29 years now. I don't know it all, nor ever claim to know it all. But I like to think my credentials speak for themselves.

Each and every combination will have different requirements. It all depends on CI, RPM range, Head Flow, Manifold Size, Carb or Injection, Plenum Size, Single or Duel 4's and so on and so on. The requirements depend on dozens of things. I guess all I'm going to say is that some requirements require a much rougher surface than others. But in all my years of doing this stuff. I have yet to see a smooth and or polish surface work to it's max potential yet in an intake port and or an intake manifold. The only debate I see worth having here is how rough it should be.

Nick Ferri
4x and Current NHRA Pro Stock Engine Builder & ET & MPH Record Holder

[daharrison]

Thank You Nick.......

[69434]

I'm not a head porter, so.....

You are not a head porter, but you don't mind slagging Chad,
for something you don't understand.

If your engine builder doesn't use it, can't make it work,
doesn't need it, does that apply in every case ?

Not going there again & again.
Like I said before "we were done a long time ago".

[John Wallace]

Thanks, Nick!

[treyrags]

Hello all! There are so many posts on here that I wanted to quote and comment on but by the time I got to page 4. I realized I just better be politically correct here.

I haven't posted in this forum for quite a while now but it's definitely the best knowledgeable forum out there. I have been fortunate enough to be in the racing industry going on 29 years now. I don't know it all, nor ever claim to know it all. But I like to think my credentials speak for themselves.

Each and every combination will have different requirements. It all depends on CI, RPM range, Head Flow, Manifold Size, Carb or Injection, Plenum Size, Single or Duel 4's and so on and so on. The requirements depend on dozens of things. I guess all I'm going to say is that some requirements require a much rougher surface than others. But in all my years of doing this stuff. I have yet to see a smooth and or polish surface work to it's max potential yet in an intake port and or an intake manifold. The only debate I see worth having here is how rough it should be.

Nick Ferri
4x and Current NHRA Pro Stock Engine Builder & ET & MPH Record Holder

Thank you Nick. It's been several years since I've seen comp or pro stock heads or intakes, but they almost always had rough finishes to run best. Its best to know what you're talking about before say someone like Chad, who does this every day for a living, is doing something wrong.

[Nick Ferri]

[/quote]Nick, first of all I must say Congratulations on an awesome season and thank you for taking the time to respond to this thread. Second, don't waste your time arguing with this guy, if you ever read some of the crap that he posted on YB you would be amazed.[/quote]

Thanks! You will have to let me know his name on YB. I'm all to filmier with that place. lol Just for the record I'm not bashing this guy but I sure hate to see someone get bashed by someone who obviously isn't a head porter and takes the word as gospel from his builder. I know Chad personally and just like each and every one of us on here. We all strive to be perfect in what we do. I do know for a fact that Chad puts his heart and soul into everything that he does. Does that mean everything he does is perfect? No! We are all human and we all do strive for perfection. I myself have been rewarded at the highest level of accomplishments in drag racing but I still make mistakes. My business is built all around relationships and resources. In order for me to keep growing, I have to work at it with these people. If PAC Springs or Comp Cams send me a spring or cam that is worse than what I have. I don't yell/slander and or bash them. I work with them! Chad might not be the best all the time but I promise it won't go out his door unless he thinks it is.
Nick

[140Air]

There's been a lot of work in airflow testing using textured finishes to enhance flow.

This is VERY true! It started in the early days of aerodynamics and the text books have the results and the best funded, most knowledgeable engine designers and racers do NOT use grossly textured ports. Hotrodders have argued about it for at least 45 years. If it offered a provable advantage EVERYBODY would use it by now.
Chevrolet said that for the CNCd surface of the ports they found that the finer they went, the more flow they got. This seems to be what everybody finds. Chevy leaves the ports at a finish that makes sense economically even though they know smoother is better. Note that Chevy's results are not different from the results reported since the 1800s. It does not depend on the fact that their ports are dry. Although atomization is vital, wall wetness is NOT an issue evidently.

[Larry Widmer]

Larry Widmer wrote:A rough finish port delivers a slightly cooler mixture to the cylinder than a slick one......
How did you measure this?

Nobody has asked specifically, but all involved believe the dyno in use cost well over $20 million. We are able to measure things that none of us could imagine prior to this program....including individual runner pressures, and yes, aside from real-time cylinder pressures, we can measure the temp of the mixture delivered to each cylinder on the intake stroke. The dyno is one that's available to us for R&D from the OE manufacturer that sponsors of the team I've been working with for the last 1.5 years.
The (international) racing series we participate in is considered by most to be the most competitive on the planet.

[900HP]

I'm not a head porter, so.....

You are not a head porter, but you don't mind slagging Chad,
for something you don't understand.

If your engine builder doesn't use it, can't make it work,
doesn't need it, does that apply in every case ?

Not going there again & again.
Like I said before "we were done a long time ago".

You are never "done". There is ALWAYS room for improvement and growth. EVERY single time I get on the dyno I have more questions than answers by the time I am done. I make notes of things I would like to examine the next go-around. Some things work, some don't. Sometimes you re-visit things that didn't work in the past because you have gone different directions and what didn't work before works wonderfully now. You can't make improvements if your mind has already come to a pre-conceived outcome before you test.

[900HP]

Hello all! There are so many posts on here that I wanted to quote and comment on but by the time I got to page 4. I realized I just better be politically correct here.

I haven't posted in this forum for quite a while now but it's definitely the best knowledgeable forum out there. I have been fortunate enough to be in the racing industry going on 29 years now. I don't know it all, nor ever claim to know it all. But I like to think my credentials speak for themselves.

Each and every combination will have different requirements. It all depends on CI, RPM range, Head Flow, Manifold Size, Carb or Injection, Plenum Size, Single or Duel 4's and so on and so on. The requirements depend on dozens of things. I guess all I'm going to say is that some requirements require a much rougher surface than others. But in all my years of doing this stuff. I have yet to see a smooth and or polish surface work to it's max potential yet in an intake port and or an intake manifold. The only debate I see worth having here is how rough it should be.

Nick Ferri
4x and Current NHRA Pro Stock Engine Builder & ET & MPH Record Holder

Nick, welcome back to Speedtalk. We definitely welcome any input you have as it is very rare to have someone at your level in the motorsports industry freely share knowledge.

So, how rough should the surface finish be and do different parts of the port require different finishes? Chad and I have talked at length on this and there are some finishes we would like to try in the future.

If the mean (average) height of the floor/wall/roof is the same and the texture is actually dimples would that cause any turbulence or does it just create a boundry layer? I'm not sure if I worded that correctly but let's see where this conversation goes.

[140Air]

Larry Widmer wrote:A rough finish port delivers a slightly cooler mixture to the cylinder than a slick one......
How did you measure this?

Nobody has asked specifically, but all involved believe the dyno in use cost well over $20 million. We are able to measure things that none of us could imagine prior to this program....including individual runner pressures, and yes, aside from real-time cylinder pressures, we can measure the temp of the mixture delivered to each cylinder on the intake stroke. The dyno is one that's available to us for R&D from the OE manufacturer that sponsors of the team I've been working with for the last 1.5 years.
The (international) racing series we participate in is considered by most to be the most competitive on the planet.

Larry, while I assume you are not at liberty to divulge much about what your team as done and learned, anything more you can give us would be helpful. For example, how much cooler? ...effect on flow? ...effect on wall wetness? ...runner wall temperature? ...and really, really important, a picture of the surface?