CNC Mill Mark Removal in Intake Port

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A good shape can perform well when rough. A bad shape when rough will be even worse.
Link above explains it better than I can. I remember some wind tunnel experimenting from school we did that was based on old NACA/NASA research into boundary layers and turbulent flow. Rough finishes are never 'better' on their own, but have a nearly insignificant impact on 'good' shapes but will make a significant difference on poor shapes. The right shape that is also smooth is always 'best' but rarely is the 'right' shape achieveable or best for the entire operating range and so roughness or less-than-deal geometry is often used to expand the operating envelope to suit the application. Turbulators, winglets, or other surface flow 'energizers' are often employed for this reason.

I'm betting the reason rougher finishes seem to out-perform smooth ones is because the rougher finsh will make poorly shaped areas easier to detect and address. As with everything, it's likely not the rougher finish in isolation making the difference in performance.
 
Newbomb Turk said:
Rough is always better. That’s according to Darin Morgan and Larry Meaux.

The outlier is CNC step over. I’ve seen that so coarse you couldn’t even read the manometers.

I can’t remember what the CFM loss was but it was big.

I’ve never seen a burr finish do that but I would suppose it’s possible to get that too rough.
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Makes sense. I don't think CNC step-over lines count as 'roughness' so much since these can create a significant change in the cross sectional area depending on the size of the step-over and shape of the tool used. I'm surprised more ports aren't shaped with lay lines roughly parallel to the flow path.
 
273 said:
I get it's critical, but beyond something being severely off, my point/question is the average well tuned engine out there leaving a lot of easiably gain power just laying in wait? Like how well is the average performance engine handling fuel atomization.
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It’s sort of like gas porting pistons. Or the rings I suppose.

Just doing that one thing will make some power. If you gas port and then use thinner, low tension rings you pick up more power. But just using thinner, low tension rings might not seal well enough without gas ports.

You can also lower crankcase pressure with gas ports and that makes more power.

All of those things combined add up to a pretty nice increase in power.

It’s like that with a burr finish. Just running a burr around the port will help, but doing a burr finish can allow you to use less jet to make the same or more power.

Then you can drop coolant temps and make more power. Then you can change boosters and find more power by reducing jet area.

When you do it all it makes a good power difference.

It’s like everything else with engines. Everything affects everything and making a simple change that looks like it didn’t do much can end up allowing more changes that add up to big power gains.
 
Like there's got to be an atomization range, from what a well tuned average performance engine is, to the bleeding edge of what highly developed multi million dollar race teams are doing vs what an highly competent engine builder can do. And how much R&D would it take to go from what an average guy build achieves to what a highly competent build achieves and what kind of power gains are we looking to make with these possible fuel atomization achievements in an average 300-600 hp engines ?
 
Phreakish said:
A good shape can perform well when rough. A bad shape when rough will be even worse.
Link above explains it better than I can. I remember some wind tunnel experimenting from school we did that was based on old NACA/NASA research into boundary layers and turbulent flow. Rough finishes are never 'better' on their own, but have a nearly insignificant impact on 'good' shapes but will make a significant difference on poor shapes. The right shape that is also smooth is always 'best' but rarely is the 'right' shape achieveable or best for the entire operating range and so roughness or less-than-deal geometry is often used to expand the operating envelope to suit the application. Turbulators, winglets, or other surface flow 'energizers' are often employed for this reason.

I'm betting the reason rougher finishes seem to out-perform smooth ones is because the rougher finsh will make poorly shaped areas easier to detect and address. As with everything, it's likely not the rougher finish in isolation making the difference in performance.
Click to expand...
This is good stuff. Thanks for posting.
 
Phreakish said:
A good shape can perform well when rough. A bad shape when rough will be even worse.
Link above explains it better than I can. I remember some wind tunnel experimenting from school we did that was based on old NACA/NASA research into boundary layers and turbulent flow. Rough finishes are never 'better' on their own, but have a nearly insignificant impact on 'good' shapes but will make a significant difference on poor shapes. The right shape that is also smooth is always 'best' but rarely is the 'right' shape achieveable or best for the entire operating range and so roughness or less-than-deal geometry is often used to expand the operating envelope to suit the application. Turbulators, winglets, or other surface flow 'energizers' are often employed for this reason.

I'm betting the reason rougher finishes seem to out-perform smooth ones is because the rougher finsh will make poorly shaped areas easier to detect and address. As with everything, it's likely not the rougher finish in isolation making the difference in performance.
Click to expand...

When considering mass airflow then the burr finish or whatever method is used to rough up a surface you can mostly see that on a flow bench.

After spending a stupid amount of time on the dyno watching the numbers and such that it isn’t really about mass airflow but it’s about eliminating or more accurately reducing wall flow that’s always present when and where fuel is added to the intake.

Getting that wet fuel off the surfaces and back into the airstream can pay big dividends.

You just have to overcome the way some people think in that if the jet size gets smaller than orthodox they panic and rather than learn they want to stop because they are sure it’s going to eat itself when the fact is it’s getting hurt with all that unneeded fuel running through the engine.
 
273 said:
Like there's got to be an atomization range, from what a well tuned average performance engine is, to the bleeding edge of what highly developed multi million dollar race teams are doing vs what an highly competent engine builder can do. And how much R&D would it take to go from what an average guy build achieves to what a highly competent build achieves and what kind of power gains are we looking to make with these possible fuel atomization achievements in an average 300-600 hp engines ?
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But at what RPM? How much throttle opening? What temperature?
Like @Newbomb Turk says: it's not just about one thing. I doubt anyone is going to sit down and try to optmize atomization in particular because on it's own it doesn't mean much. But the things which happen to also improve atomization also tend to favor increased flow, better pressure recovery, and robust performance profiles.

Modern OEM engines use direction injection to help achieve the best AFR possible. Operating conditions can change from one valve event to the next, and apparently enough so that the loss of atomization is worth the improvement in accurate fuel delivery to the cylinder. This of course isn't done in the name of performance, or even MPG, but emissions - but I think is still revealing.
 
Newbomb Turk said:
When considering mass airflow then the burr finish or whatever method is used to rough up a surface you can mostly see that on a flow bench.

After spending a stupid amount of time on the dyno watching the numbers and such that it isn’t really about mass airflow but it’s about eliminating or more accurately reducing wall flow that’s always present when and where fuel is added to the intake.

Getting that wet fuel off the surfaces and back into the airstream can pay big dividends.

You just have to overcome the way some people think in that if the jet size gets smaller than orthodox they panic and rather than learn they want to stop because they are sure it’s going to eat itself when the fact is it’s getting hurt with all that unneeded fuel running through the engine.
Click to expand...
Do these overly rich conditions show up on the dyno O2 sensors?
 
273 said:
Like there's got to be an atomization range, from what a well tuned average performance engine is, to the bleeding edge of what highly developed multi million dollar race teams are doing vs what an highly competent engine builder can do. And how much R&D would it take to go from what an average guy build achieves to what a highly competent build achieves and what kind of power gains are we looking to make with these possible fuel atomization achievements in an average 300-600 hp engines ?
Click to expand...

Atomization is the first step to vaporization. You want the fuel vaporized in the chamber.

And that’s the bulls balls of the whole thing. How does the tuner or end user get to full vaporization or at least as good as it can be within the rules or whatever limits we have to deal with.

If you want to run 190 plus coolant temperatures, a heated intake manifold and the required lower compression to do all that then for the most part the heat is doing the work for you.

If you want to run more compression you lower the coolant temperatures (lose some vaporization), a cold air intake (or worse yet a tunnel ram) and you lose more vaporization.

That means you have to look at what booster you can use to help with better atomization to get to better vaporization and the burr finish helps with that.
 
Newbomb Turk said:
When considering mass airflow then the burr finish or whatever method is used to rough up a surface you can mostly see that on a flow bench.

After spending a stupid amount of time on the dyno watching the numbers and such that it isn’t really about mass airflow but it’s about eliminating or more accurately reducing wall flow that’s always present when and where fuel is added to the intake.

Getting that wet fuel off the surfaces and back into the airstream can pay big dividends.

You just have to overcome the way some people think in that if the jet size gets smaller than orthodox they panic and rather than learn they want to stop because they are sure it’s going to eat itself when the fact is it’s getting hurt with all that unneeded fuel running through the engine.
Click to expand...

That makes sense. A 'macro' rough finish (as opposed to a sandpaper like finish) would be expected to create a bunch of little eddies which keeps the flow energized near the wall and maybe more importantly is going to create little depressions that help vaporize fuel back into the airstream. It also seems like it would help the port operate over a wide range of velocities/flow-rates which would likely help the gear change a whole bunch too.
 
Earlie A said:
Do these overly rich conditions show up on the dyno O2 sensors?
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Yeah, you can watch it in real time. You can see the puddle get used up and then how long it takes to get the puddle established again.

The biggest tell is when the plugs look lean and the O2 and exhaust ports look pig fat rich.

You know you are just blowing fuel right through the engine.

Edit: this is why your wife NEEDS a dyno. Just sayin’…
 
Newbomb Turk said:
Atomization is the first step to vaporization. You want the fuel vaporized in the chamber.

And that’s the bulls balls of the whole thing. How does the tuner or end user get to full vaporization or at least as good as it can be within the rules or whatever limits we have to deal with.

If you want to run 190 plus coolant temperatures, a heated intake manifold and the required lower compression to do all that then for the most part the heat is doing the work for you.

If you want to run more compression you lower the coolant temperatures (lose some vaporization), a cold air intake (or worse yet a tunnel ram) and you lose more vaporization.

That means you have to look at what booster you can use to help with better atomization to get to better vaporization and the burr finish helps with that.
Click to expand...
I understand what your getting at, my point was more towards Hysteric's seemingly obsession nature with atomization, vaporization etc.. Above any other concerns. Which usually leads to everything got to be smaller.

My general point is other than a few basic options the average guy doesn't have much say how efficiently his engine will atomize/vaporize the fuel.
 
Phreakish said:
I doubt anyone is going to sit down and try to optmize atomization in particular because on it's own it doesn't mean much.
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I guess that was the point I'm trying to make, any time we talk about heads, carbs etc.. Hysteric's and others will come in about atomization vaporization etc... But generally people are going by what carb cam heads cr cid etc.. Gonna give me the powerband I want not which one is possibly gonna give the best hypothetical atomization vaporization etc.. Especially with the vague improvement in results that the vague idea of what's the more optimal combination in atomization vaporization etc.. is gonna give over what is generally created by the average guy's build.
 
273 said:
I guess that was the point I'm trying to make, any time we talk about heads, carbs etc.. Hysteric's and others will come in about atomization vaporization etc... But generally people are going by what carb cam heads cr cid etc.. Gonna give me the powerband I want not which one is possibly gonna give the best hypothetical atomization vaporization etc.. Especially with the vague improvement in results that the vague idea of what's more optimal combination is gonna give over what is generally created by the average guy's build.
Click to expand...

I guess my point would be there are things that can be done but they pretty much need to be addressed BEFORE the builder starts.

And they should be looked at. Just because the dyno spits out a number…say 20 hp improvement doesn’t mean that’s the end of it.

Most dyno’s don’t measure an engines ability to RPM. So that 20 hp gain may be more than that at the track.

You might be surprised how distribution issues clean up when you can reduce jet area.

It’s a forethought thing and generally not an afterthought thing.
 
Newbomb Turk said:
It’s a forethought thing and generally not an afterthought thing.
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Yup, this makes sense. If 'everything else' is done right, the atomization happens. Trying to bolt it on after is a fools errand.
Whenever I hear of features added to a package to improve it, it's usually to help a very specific thing to overcome some other very specific limitation.
 
If some of you guys would pick
Up a grinder and grind half as hard as so try to scientifically figure something out you could be rich. 30 plus years ago the experts said smooth exhaust and rough intake ports and it still works today.
 
pittsburghracer said:
If some of you guys would pick
Up a grinder and grind half as hard as so try to scientifically figure something out you could be rich. 30 plus years ago the experts said smooth exhaust and rough intake ports and it still works today.
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Which way should my grinder rotate though, clockwise or anti-clockwise? Does it depend on which hemisphere I'm in? Shouldn't the bit be reversed when I reach in from the bowl side?

You're right, and the experts landed on rough largely by applying the science above which was sussed out back in the 30's, 40's and 50's.
 
273 said:
I understand what your getting at, my point was more towards Hysteric's seemingly obsession nature with atomization, vaporization etc.. Above any other concerns. Which usually leads to everything got to be smaller.

My general point is other than a few basic options the average guy doesn't have much say how efficiently his engine will atomize/vaporize the fuel.
Click to expand...
Don't worry about Hysteric, he's been reading too many books and watching too many videos.
 
Phreakish said:
Which way should my grinder rotate though, clockwise or anti-clockwise? Does it depend on which hemisphere I'm in? Shouldn't the bit be reversed when I reach in from the bowl side?
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YES! It all matters. :poke::lol:
 
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