Intake & exhaust man. treatments (Micro-Abrasives)

[TwentyTwo]

Something that you guys might be interested in looking into is micro-abrasive polishing of the intake / exhaust tract.
I did a bit of searching around and I couldn't find any information on anybody who is currently doing it, but a mate of mine, who is studying nano-technology at uni explained a process that one of his classmates has developed and tested on extractors, apparantly with good results. The details I have are admittedly a bit sketchy, but it's all good food for thought.
The micro-abrasive particles (I assume crystalline in nature) are suspended in a gel compound and are forced through the pipe/port/orifice at high pressure. I don't really know any more about the actual process than this.
Apparantly the finish, when compared to a polished surface under an electron microscope, shows far fewer surface imperfections and is much smoother, thus facilitating improved gas speed and flow through said pipe/port/orifice, around a 15-20% improvement over the untreated product.
I don't know what the net gain in HP actually is, but you'd assume it to be considerable.

Now I've heard theories suggesting that a rough textured surface, ie. untreated cast intake manifold can "trap" a layer of gas between it and the main body of flowing gas (in this case A/F mix), thus reducing the effective Cd: -

-Rough (cast)-

ww = wall

^^^
~~ = trapped layer

__ = A/F flow


wwwwwwwwwwwwwwwwwwwwwwwwwwwwwww
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ^^^^^^^
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
--------------------------------------------------------------------------
--------------------------------------------------------------------------- = Good flow/speed
--------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ^^^^^^^
wwwwwwwwwwwwwwwwwwwwwwwwwwwwwww



But for some reason, I imagine it to be more like...

w = wall
@ = turbulance due to friction between A/F molecules
~~ = trapped layer
__ = A/F flow

wwwwwwwwwwwwwwwwwwwwwwwwwwwwwww
@@@@@@@@@@@@@@@@@@@@@@
--------------------------------------------------------------------------
---------------------------------------------------------------------------- = Reduced flow due to turbulance
--------------------------------------------------------------------------
@@@@@@@@@@@@@@@@@@@@@@
wwwwwwwwwwwwwwwwwwwwwwwwwwwwwww



-Micro-polished-

Z = wall
-- = A/F

ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ
--------------------------------------------------------------------
-----------------------------------------------------------------------
-------------------------------------------------------------------------
-----------------------------------------------------------------------
--------------------------------------------------------------------
ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ



Seems to me that having a "theoretically" perfectly smooth wall would provide the best flow, and might also prevent carbon build-up as a fringe benefit.
So, I reckon micro-abrasively treating everything you can get your mits on would be a good idea, ie. throttles/chokes, intake manifold, intake ports, chamber, exhaust ports and extractors/turbo internals etc.

These are just ideas I have floating around and I'm not stating any of this as truth by any means, just though this could be an interesting forum for discussion.
I also intend to look into the process further and get in touch with the bloke who is doing this, hoping to get him to do my TRD extractor for my 3TG hybrid and mabe some headwork aswell.

Anyone have any comments/opinions/ideas?

[30psi 4agte]

sounds really similar to the power porting that has been around for years now! it involves abrasive particles being pushed through a port in a clay like substance

[mullett]

Yeah, I have come accross things like that on the web, apparently it is succesful, but if you're going to go to that length, get everything ported and polished first to get rid of any actual edges, all this will do is smooth them off a bit...

RM.

[30psi 4agte]

Nah it is said to remove all ridges and create an even size port throughout whatever its put through
They are called Specailised power porting in Buninyong Vic

[Earlyrolla]

Power porting...

http://autospeed.drive.com.au/cms/A_0622/article.html

Sounds to be the same thing as you are talking about.

Did a quick search on Yellow Pages, I think this is the place that does it:
Specialised Power Porting
8 Gear Ave Mt Helen VIC 3350
ph: (03) 5330 1123 Motor Engineers & Repairers

There can be benefits from a slightly rough finish on any areas of the intake tract where fuel will be in suspension in the air stream. The small amount of roughness results in a turblence along the wall which in theory helps to minimise puddling of any fuel droplets on the port wall. From what I have read it depends on the fuel to what grade finish on the wall works best.

Bugger, too slow on my reply...

[ed]

um, its not 'trapped air' - its called a boundary layer. and it will happen on ANY fluid surface interface. the boundary layer can be laminar or turbulent, which is dependant on the reynolds number - which mainly comes down to fluid viscosity and velocity - not so much the co-efficient of the wall...

..but regardless, i was of the understanding that a turbulent boundary layer actually provided greater flow than laminar. the wall shear stress being greater in turbulent boudary flow is supportive of this (i think). what you want to avoid is separation of the boundary layer from the physical surface.

[allencr]

It's the reason golf balls are not smooth, and would go 5 to 10% less distance if they were.
Also, after 5 minutes the carbon buildup will just about make it impossible to see any difference at all.

Shape, then size, then the very least & last thing that matters is smoothness.

[30psi 4agte]

I have saw a head from a V8 super car years ago and the ports are actually coragated ( think thats spelt right? who cares!) like a fence. its minute but still very noticable!

[TwentyTwo]

"In a turbocharger, the surfaces of the standard compressor housing are made as smooth as is economically practical, as any roughness may cause some of the air to detach itself from the surface, causing eddy currents and reducing the overall efficiency." - http://autospeed.drive.com.au/cms/A_0622/article.html

Interesting...

Well, there you go. Has any one here had any experience with "Power Ported" manifolds or similar?

[ed]

may cause some of the air to detach itself from the surface

what you want to avoid is separation of the boundary layer from the physical surface.

thats what i said

in any case, its the velocity of air, and hence the reynolds number that is fucking with a compressor housing. i dare you to recreate those velocities in an intake port

[TwentyTwo]

I'm mainly interested in the effects of the treatment on intake and exhaust manifold flow, rather than turbines and compressor housings.
The Power Porting treatment sounds a little different to the high polish finish I was explaining, more aimed at smoothing casting dags etc. by the sounds of it.
Perhaps a smooth transition between a rough finish in the intake manifold and a polished finish in the ports, ie. increasingly smooth intake between throttle and valve would result in the best flow charateristics?'

Also, what is the velocity of the air likely to be in the intake port (N/A) say @7000rpm? I tried working it out but im not so good at that shit. I'd like to calculate the Reynolds number as find out whats goin on in my motor but I need that figure. Is the figure generally always above critical Reynolds no. as you suggest Ed? (hence there are eddies)

Cheers,

Jim.

[tricky]

um, its not 'trapped air' - its called a boundary layer. and it will happen on ANY fluid surface interface. the boundary layer can be laminar or turbulent, which is dependant on the reynolds number - which mainly comes down to fluid viscosity and velocity - not so much the co-efficient of the wall...

..but regardless, i was of the understanding that a turbulent boundary layer actually provided greater flow than laminar. the wall shear stress being greater in turbulent boudary flow is supportive of this (i think). what you want to avoid is separation of the boundary layer from the physical surface.

You'll find the boundary layer will always have a laminar component. Turbulence is a property that 'amplifies' with length. You can have a substance in a tube with a Reynolds number > 4000 (laminar to turbulent transition limit for a cylinder) which is still laminar in characteristic due to the fact that the 'flow length' has not yet been reached. The length of a boundary layer (where boundary velocity >= 99% freestream velocity) is a distance of 60 times diameter (turbulent) or 120 times diameter (laminar).

So the factors influencing the boundary layer is the roughness, the diameter and the gas velocity. Ed, you are 100% correct in your statement that a turbulent flow is better for torque, because it improves atomisation. It is also necessary to limit this roughness, because as you know, the port velocity is critical for cylinder filling and resonance tuning.

A slightly rough surface is also advantageous (although less critical) in the exhaust because a turbulent flow transfers less heat than a laminar flow (thus maintaining exhaust velocity).

So to cut a long story short, a smooth port is advantageous to high rpm power, but a rough surface is brilliant for low to mid range torque.

Sorry, I'm a bit of a fluid dynamics/heat transfer geek

[tricky]

I'm mainly interested in the effects of the treatment on intake and exhaust manifold flow, rather than turbines and compressor housings.
The Power Porting treatment sounds a little different to the high polish finish I was explaining, more aimed at smoothing casting dags etc. by the sounds of it.
Perhaps a smooth transition between a rough finish in the intake manifold and a polished finish in the ports, ie. increasingly smooth intake between throttle and valve would result in the best flow charateristics?'

Also, what is the velocity of the air likely to be in the intake port (N/A) say @7000rpm? I tried working it out but im not so good at that shit. I'd like to calculate the Reynolds number as find out whats goin on in my motor but I need that figure. Is the figure generally always above critical Reynolds no. as you suggest Ed? (hence there are eddies)

Cheers,

Jim.

The optimal peak mean velocity for intake ports is 300 ft/sec. You get this by (ave piston velocity x piston area)/runner area.

Re=md/Au

p=mass rate of flow, d=hydraulic diameter of pipe, A = surface area, u=viscosity

You should be able to find property tables for air on the web.

[TwentyTwo]

Thats what I'm after, cheers tricky! +1

So what would be the advantage of having polished ports while retaining a rough cast manifold? seems like two conflicting theories, mabe each cancelling the benefits of the other?

Also, is the intake charge Reynolds number likely to cross the critical threshold within a commonly used RPM band? say, 2000-8000RPM

I tried doing the maths for myself, but dude, I'm a musician, not a fluid dynamicist.

[tricky]

I was a musician once, but I got suckered into less expressive artforms (ie old skool toys)!

The problem with stock cast manifolds is that they have casting dags, the runners are generally inconsistent in profile and they aren't tuned length. Results suggest that the best improvement for a street engine (on a modern head) is match porting, and removal of any casting dags. If any more material is removed, you start losing gas velocity (ie lose low end torque for very little top end gain).

From a fluid flow perspective, it just seems like perfectly polished runners shouldn't be an advantage. Yes, you get a slightly greter peak velocity (lower frictional losses), but the air-fuel mixture stratification just seems to outweigh this benefit. It would be understandable if the runners were long enough for the flow to have developed fully, but given that this length is 60 times diameter, this just doesn't happen. (I don't see any 2.7m long, 45mm dia runners anywhere!)