Why an engine makes more power off a burr finish

General engine tech -- Drag Racing to Circle Track

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twl
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Re: Why an engine makes more power off a burr finish

Post by twl » Thu Nov 27, 2014 2:05 pm

I would concur with the idea stated by others that it is application specific, and that it is the amount of texture that is the factor.

In the applications we do, which are primarily street builds with performance aspects, and in a side-draft configuration, and often with slow piston speeds when driving around town, we find that there is PLENTY of fuel drop-out on to the floor of the port, and raw fuel running down into the cylinder, in the stock configuration.
And we have seen wet-flow test evidence of it. So, wet wall issues are definitely something that happens, and that is not debatable. It might not happen in your particular engine, but it happens in ours. But we get significant power improvement with our port work which also includes a fairly aggressive texture applied on the finish.

I could understand that an F1 application with severely downdraft ports and highly developed injectors, and typically operating at very high rpms, etc, might not see this problem. And they live in their own little world that has nothing to do with the reality that the rest of us live with. But I do find it interesting that Larry Widmer mentions the cooling effect, which I did not know about. And presumably, this means that they use at least some amount of texture in that program.

We would not even think about using a smooth port configuration, and we don't use radius seats on the intake either, for similar reasons.
I actually have not heard any serious builder mention a smooth intake port wall since about 1973.

I would concur with the Pro Stock champion engine builder that it is basically an issue of how much texture, not whether or not there should be texture.

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Re: Why an engine makes more power off a burr finish

Post by 900HP » Thu Nov 27, 2014 5:40 pm

Here is an intake that * Racing Heads did for me. Circle track deal, we have to run un-ported World S-2 heads. :-& The engine has exceeded my expectations in every way. Weather or not it is due to the intake I cannot say because I have not back-2-backed a polished up version to this one. I am fairly certain, however, that it isn't hurting power. You can see that the overall shape of the runners and plenum have been "adjusted" and the texture was done AFTER shaping and sizing.
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Re: Why an engine makes more power off a burr finish

Post by Unkl Ian » Thu Nov 27, 2014 5:50 pm

http://natmonitor.com/2014/01/17/proper ... -discover/

Found this link in the Advanced Engine tech forum,
in a thread titled : Intake port texturing.
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Re: Why an engine makes more power off a burr finish

Post by 140Air » Thu Nov 27, 2014 6:08 pm

Unkl Ian wrote:http://natmonitor.com/2014/01/17/proper ... -discover/

Found this link in the Advanced Engine tech forum,
in a thread titled : Intake port texturing.
Did you read it? It applies to boat hulls near the water line where in turbulence, rough waters, air can be entrapped in rough features if the surface is "superhydrophobic", which must mean more hydrophobic than Teflon. It does NOT apply to airflow, even wet airflow.

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Re: Why an engine makes more power off a burr finish

Post by Erland Cox » Thu Nov 27, 2014 6:52 pm

The cooling effect should come from reintroducing fuel that otherwise should be running along the walls.
In sheet metal manifolds I have also seen a coarse net halfway between the runners and the carbs that is said to make the fuel curve better.
This was on a PS engine.

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Re: Why an engine makes more power off a burr finish

Post by The Radius Kid » Thu Nov 27, 2014 7:05 pm

140Air wrote:
Unkl Ian wrote:http://natmonitor.com/2014/01/17/proper ... -discover/

Found this link in the Advanced Engine tech forum,
in a thread titled : Intake port texturing.
Did you read it? It applies to boat hulls near the water line where in turbulence, rough waters, air can be entrapped in rough features if the surface is "superhydrophobic", which must mean more hydrophobic than Teflon. It does NOT apply to airflow, even wet airflow.
I'm not so sure about that.
It may be a different situation,but the principle sounds very similar.
To me it's all about reducing drag on a surface to increase efficiency.
How you get there and where you apply it can obviously vary.
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Re: Why an engine makes more power off a burr finish

Post by Lockwire » Thu Nov 27, 2014 7:08 pm

Erland Cox wrote:The cooling effect should come from reintroducing fuel that otherwise should be running along the walls.
In sheet metal manifolds I have also seen a coarse net halfway between the runners and the carbs that is said to make the fuel curve better.
This was on a PS engine.

Erland
I/we have used the net. sds

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Re: Why an engine makes more power off a burr finish

Post by Larry Widmer » Thu Nov 27, 2014 7:08 pm

Assuming we're introducing fuel far enough up-stream, we find that machining the runner's so the cusp is facing the direction of flow seems to work best. You can achieve similar results by using a "tweaked" carbide if the porting has already been done.
On the dyno in acceleration runs, where the engine isn't ramped by time, you will see a difference in response and acceleration. In dyno tests where the engine accelerates at (X) RPM /second, you seldom see anything....

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Re: Why an engine makes more power off a burr finish

Post by The Radius Kid » Thu Nov 27, 2014 7:13 pm

Larry Widmer wrote:Assuming we're introducing fuel far enough up-stream, we find that machining the runner's so the cusp is facing the direction of flow seems to work best. You can achieve similar results by using a "tweaked" carbide if the porting has already been done.
On the dyno in acceleration runs, where the engine isn't ramped by time, you will see a difference in response and acceleration. In dyno tests where the engine accelerates at (X) RPM /second, you seldom see anything....

Sounds like improved transient response.
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Re: Why an engine makes more power off a burr finish

Post by dirtmod87 » Thu Nov 27, 2014 7:17 pm

Larry Widmer wrote:Assuming we're introducing fuel far enough up-stream, we find that machining the runner's so the cusp is facing the direction of flow seems to work best. You can achieve similar results by using a "tweaked" carbide if the porting has already been done.
On the dyno in acceleration runs, where the engine isn't ramped by time, you will see a difference in response and acceleration. In dyno tests where the engine accelerates at (X) RPM /second, you seldom see anything....
This confirms what I said in an earlier post. The dyno showed almost no gains, but my @ss was telling the truth. I can feel a better acceleration off the corner.

Lets stop talking about this before I lose my advantage [-o<

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Re: Why an engine makes more power off a burr finish

Post by The Radius Kid » Thu Nov 27, 2014 7:21 pm

dirtmod87 wrote:
Larry Widmer wrote:Assuming we're introducing fuel far enough up-stream, we find that machining the runner's so the cusp is facing the direction of flow seems to work best. You can achieve similar results by using a "tweaked" carbide if the porting has already been done.
On the dyno in acceleration runs, where the engine isn't ramped by time, you will see a difference in response and acceleration. In dyno tests where the engine accelerates at (X) RPM /second, you seldom see anything....
This confirms what I said in an earlier post. The dyno showed almost no gains, but my @ss was telling the truth. I can feel a better acceleration off the corner.

Lets stop talking about this before I lose my advantage [-o<
LOL!
I seem to remember that when you lower the BSFC on any given engine (without any HP drop),it will accelerate faster due to greater engine efficiency.
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Re: Why an engine makes more power off a burr finish

Post by 140Air » Thu Nov 27, 2014 8:50 pm

The Radius Kid wrote:
140Air wrote:
Unkl Ian wrote:http://natmonitor.com/2014/01/17/proper ... -discover/

Found this link in the Advanced Engine tech forum,
in a thread titled : Intake port texturing.
Did you read it? It applies to boat hulls near the water line where in turbulence, rough waters, air can be entrapped in rough features if the surface is "superhydrophobic", which must mean more hydrophobic than Teflon. It does NOT apply to airflow, even wet airflow.
I'm not so sure about that.
It may be a different situation,but the principle sounds very similar.
To me it's all about reducing drag on a surface to increase efficiency.
How you get there and where you apply it can obviously vary.
It applies to water flow with entrapped air and a hydrophobic surface that doesn't wet. The mechanism does not exist in an airflow environment. The similarity is in the use of the words "roughness" and "drag".

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Re: Why an engine makes more power off a burr finish

Post by The Radius Kid » Thu Nov 27, 2014 9:09 pm

140Air wrote:It applies to water flow with entrapped air and a hydrophobic surface that doesn't wet. The mechanism does not exist in an airflow environment. The similarity is in the use of the words "roughness" and "drag".
True enough.
I won't argue against your points.
I do however see a fluid (air) being used to reduce friction between a surface and a fluid passing over it.
In the case of the boat the air is used to reduce the water friction against the hull - along the lines of the super cavitating torpedo.
I the case of the head port the surface texture is used to prevent the air and fuel from sticking to the port producing a more efficient port.
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Re: Why an engine makes more power off a burr finish

Post by Unkl Ian » Thu Nov 27, 2014 9:13 pm

140Air wrote:
Did you read it?

Yes, I did read it.

"“A properly designed rough surface, contrary to our intuition, can reduce skin-friction drag,”
noted John Kim, a professor in the mechanical and aerospace engineering department at UCLA"


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Last edited by Unkl Ian on Thu Nov 27, 2014 9:21 pm, edited 2 times in total.
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Re: Why an engine makes more power off a burr finish

Post by Ron E » Thu Nov 27, 2014 9:18 pm

140Air wrote: 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
As has been mentioned maybe 20 times in this thread, the texture is application specific. Even Nick Ferri, who has to be included in your above group says its application specific. If it was not application specific everybody would be using the same texture by now. But, it is. So, we're not.

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