2nd that... nice work on those heads.

 

bringing this thread back from the dead...

While there is alot of good info on here, i see a few things that raise my eye brow

While all of you guys talk about the effects of the head on an NA d series, i would like to see the effect of this on a turbo motor where the air is forced and not sucked in, i would have to think the bigger you can get the ports, the better ( within reason of course) just to blow as much air into the head as possible

also, i see several people refering to the golf ball and its dimples, while this does make sense, i fail to see how it relates to cylinder heads.. Here is what i mean, you have SEVERAL companies ( i am an american muscle car guy so heres my brands) AFR, TFS, and now RHS that CNC port, and even build their own heads. If the dimpling, and "roughing" was so good, why is it that the best heads are all done on CNC porting?

I also think the golf ball thing doesnt really apply here because when the golf ball is going through the wind its being "pushed" Where as air going INTO your engine is being sucked, i do belive the roughness in a cylinder head does infact speed up air, but i would rather have a better flowing peice

 

I would also like to know what sort of difference these methods would make on a turboed engine. I have a Z6 Head and block i've been debating if i should build or not.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tfalconier &raquo;</TD></TR><TR><TD CLASS="quote">also, i see several people refering to the golf ball and its dimples, while this does make sense, i fail to see how it relates to cylinder heads.. Here is what i mean, you have SEVERAL companies ( i am an american muscle car guy so heres my brands) AFR, TFS, and now RHS that CNC port, and even build their own heads. If the dimpling, and "roughing" was so good, why is it that the best heads are all done on CNC porting?

I also think the golf ball thing doesnt really apply here because when the golf ball is going through the wind its being "pushed" Where as air going INTO your engine is being sucked, i do belive the roughness in a cylinder head does infact speed up air, but i would rather have a better flowing peice</TD></TR></TABLE>
Whether the mixture is being pushed, pulled, sucked, or blown, it's merely a transition from a higher pressure region to a lower pressure region.

Without the dimples, the fluid touching the port surfaces would have have no velocity. With dimples (or something similar), the air moves "on air" (if that makes sense), so the transfer is more efficient.

Here is an image of airflow around a ball with a smooth surface:


...while here is one with a rough surface:


Notice the increased turbulence around the ball with the smooth surface. This turbulence corresponds with reduced velocity.

The following picture represents fluid traveling through a smooth pipe, from left to right:


Go through the pictures like words in a book (left to right, top to bottom). The fluid "sticks" to the smooth surface and creates a large amount of turbulence. I'm not saying that turbulence is a bad thing, but in this case, the fuel will separate and form droplets. Since this will reduce the total, cumulative surface area of the fuel in the combustion chamber, efficiency is reduced.

(I stole these pictures from team-integra.net, by the way. You can read the full article here:http://www.team-integra.net/se...eID=4.)

 

that is all fine and dandy and it does make sense, but it goes back to my last point, why are all new heads CNCd? Even comp cams RHS service, and fox lake heads are all cnc ported, yes its faster, and yes its more accurate, but it works..

I work on high end cars everyday, mostly porsches and tons of race porsches. One of the mechanics i know has a 800rwhp 513 ford big block in his cobra kit car , this car has NO expense spared, hell even the oil pan was 5 grand. The ports in his head were smooth as silk

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tfalconier &raquo;</TD></TR><TR><TD CLASS="quote">that is all fine and dandy and it does make sense, but it goes back to my last point, why are all new heads CNCd? Even comp cams RHS service, and fox lake heads are all cnc ported, yes its faster, and yes its more accurate, but it works..</TD></TR></TABLE>
I couldn't tell you. You could always ask them if you're curious.

 

i would also have to add, the normal non cnc porter would/ should have a "rough" enough surface to create velocity, i mean witout cnc it is impossible to get perfectly smooth.

If being smooth is so bad, why is it a Plastic 3in PVC tube, flows more then a cast iron 4in tube???

I also have to say it does make a diffrence between if the air is being sucked, pulled, kicked, or punched because a golf ball is trying to move and cut through the air, where a cylinderhead is more like plumbing the air is going through.

If the roughness is so good then wouldnt stock casted cylinderheads work best then (besides volume)

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tfalconier &raquo;</TD></TR><TR><TD CLASS="quote">If being smooth is so bad, why is it a Plastic 3in PVC tube, flows more then a cast iron 4in tube???

I also have to say it does make a diffrence between if the air is being sucked, pulled, kicked, or punched because a golf ball is trying to move and cut through the air, where a cylinderhead is more like plumbing the air is going through.

If the roughness is so good then wouldnt stock casted cylinderheads work best then (besides volume)</TD></TR></TABLE>
The material finish affects the flow.

I will agree that a golf ball displacing a volume of air and an engine inducting air/fuel are different. I thought I read something about N/A vs. forced induction, but I guess not. I think I just need more sleep.

Honestly, I would like to hear the shops' opinions if you ever ask. I'd like to learn more about this topic too.

 

Wait am I missing something w/ the point of the differences in turbulence w/ diff surfaces? IIRC, their should be LESS turbulence w/ a more smooth surface finish. Turbulence is caused by air going over the variations in the surface finish and creating small varying streams of air. Flow is a function of the velocity, area of the pipe or whatever its traveling through, and its surface finish (*See Boernollis Equation*) The only advantage that is in a more rough surface would be to create a more completely mixed combination of air and fuel.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rhennin &raquo;</TD></TR><TR><TD CLASS="quote">Wait am I missing something w/ the point of the differences in turbulence w/ diff surfaces? IIRC, their should be LESS turbulence w/ a more smooth surface finish. Turbulence is caused by air going over the variations in the surface finish and creating small varying streams of air. Flow is a function of the velocity, area of the pipe or whatever its traveling through, and its surface finish (*See Boernollis Equation*) The only advantage that is in a more rough surface would be to create a more completely mixed combination of air and fuel. </TD></TR></TABLE>
I was curious, so I did some reading. I believe the golf ball analogy can be used in this case, but only to some extent.

Laminar flow (over a smooth surface) initially has less drag than turbulent flow. However, without a turbulent boundary layer in addition to the laminar boundary layer, surface friction will affect the velocity (or flow quality, I'm not sure which) of the air/fuel mixture. However, in our case, I believe the rough surface serves more to promote proper fuel atomization and improve burn quality more than to reduce energy/velocity losses due to surface friction between the fluid particles and the port surfaces.

You are correct, flow is a function of cross sectional area and fluid velocity: Q=AvΔt. I believe this is a derivation of Bernoulli's principle, but I'm honestly not sure. Regarding the surface finish factor, I assume that affects the velocity component of this equation?

Hopefully I haven't misinterpreted anything or have been misinformed. Let me know if I screwed up somewhere.

 

Yea, that looks about right. I actually had to look at it again since I've only taken an intro class to Fluids. The only thing that should be an effect of surface roughness is the velocity since it has to overcome that friction at the wall. Q=AvDeltat is just derived from Bernoulli's w/ basic assumptions of incompressible fluid, and i forget what else. To lazy atm to look at it harder. It would be interesting to see how different types of finned shapes would effect the overal flow requirements from low to high rpm and also offer enough mix of gas/air at high and low rpm.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rhennin &raquo;</TD></TR><TR><TD CLASS="quote">It would be interesting to see how different types of finned shapes would effect the overal flow requirements from low to high rpm and also offer enough mix of gas/air at high and low rpm.</TD></TR></TABLE>
It would. I'm sure somebody has done testing, but I couldn't find anything in the few minutes I spent searching. I'll probably have to look harder.

I've also only had introductory fluid dynamics coursework. I get to save my actual fluids course for next fall (lucky me...).

 

well also remember that the original poster is carbed, not injected, so i dont think we would have the same problems with fuel, back to the pic on page 3 with the dimpled head, it makes no sense to dimple the head right where the injector sprays

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tfalconier &raquo;</TD></TR><TR><TD CLASS="quote">well also remember that the original poster is carbed, not injected, so i dont think we would have the same problems with fuel, back to the pic on page 3 with the dimpled head, it makes no sense to dimple the head right where the injector sprays</TD></TR></TABLE>
Yeah, I missed that detail.

 

One of the best pieces of information I've seen in a while. Hope the bump helps more people reading it.

 

Nice to see D-series praise.