THE TEXTURED FINISH ARGUMENT

It is often thought that enlarging the ports to the maximum possible size and applying a mirror finish is what porting is. This in not always the best approach. A few ports may be enlarged to their maximum possible size (in keeping with the highest level of aerodynamic efficiency) but those engines are usually only found in the higher echelons of racing and world record setting, where the actual size of the ports has become a restriction. Larger ports flow more fuel/air at higher RPM's but sacrifice torque at lower RPM's due to lower fuel/air velocity, so it is critical to bear in mind the "end results" you wish to work towards. A polished finish on the port does not provide the increase that one might assume. In fact, often within certain intake systems, the surface is intentionally textured to a degree of uniform roughness to allow for fuel deposited on the port walls to evaporate quickly, due to the increase in surface area.

A rough surface on particular areas of the port may also alter flow by energizing the air boundary layer, which can alter the flow path to a large degree, theoretically increasing flow. This is similar to the way dimples on golf ball are intended to work. Flow bench results show that the difference between a mirror finished intake port and a smooth textured port is typically less than 1%, which can be argued is negligible. There is little to no beneficial difference between a port finish that is smooth to the touch and one that is mirror finished (unless you are considering the impression you make on your customer).

Exhaust ports can be a different subject and it may be useful to give them a smooth finish because it will reduce the dry gas flow and exhaust by-product build-up. Medium or Fine grit cartridge rolls across the surface with a light buffing works quite well on the exhaust port side.

PORTING " HOW TO " for intakes and cylinder heads

BY TJ

New..see comments section for more details about why to chamfer ports.

See the VIDEO discussing this subject and how to put a textured finish on an intake at youtu.be/GwtquXIAOrk

How True?

Submitted by Anonymous on Sun, 11/14/2010 - 21:22.

Is this always true? I understand the air boundary layer theory, and that does prove true for certain geometric configurations. However, with the complexity of modern intakes, engines, and cylinder heads, would a "textured finish" always be the way to go?

Good Question

Submitted by ccadmin on Mon, 11/15/2010 - 00:28.

Good question, and the simple answer is NO, a rough finish is not always the best approach. We at CC Specialty agree that for general porting, on the intake side, the textured finish has advantages, mainly fuel dissipation and evaporation off the intake walls due to larger surface area, and also to a lesser degree, the air boundary effect. Some things to bear in mind:

There is NEVER an advantage to leaving jagged, sharp, or uneven surfaces. When creating a textured surface, it should always be uniform and even in it's transition.

Right angles should be avoided, period. Any abrupt redirection of air can cause turbulence and loss of efficiency. Remember that when we Chamfer a ports opening into the cylinder, we are mainly reducing the wear on the piston ring, but also, we decrease the turbulence of the air flow as it transitions into the cylinder chamber (caused by the near right angle formed between the port wall and the cylinder liner/wall).

Even CAD engineering models don't always show an advantage to the "Textured intake porting" approach. One of articles out there you might find on porting and polishing is this one from Wrenchbender www.motorcycleproject.com/motorcycle/text/cows-porting.html . I like some of the points made, but there are a few MAJOR problems with some of their ideas. For one thing Kawasaki just had a press release on the company's new 2011 ZX-10R NINJA, and one of the major upgrades was reshaped and polished ports! Now do you figure a MAJOR manufacturer like Kawasaki, with millions/billions spent on Research and Development(you will notice Kawasaki is on our USER LIST), would just overlook a tiny detail like that, in particular with a flagship bike in the highly competitive market of Supersport Streetbikes? Not likely. More likely is that people that don't know how to use a wrench without bending it, probably just make general statements, and know little, if anything, about engineering.

Fact is we have Millions of dollars in sales since the 1970s, and for one simple reason, PORTING AND POLSHING WORKS! That includes the Polishing part.

a rough intake port keeps tha

Submitted by Anonymous on Wed, 03/30/2011 - 20:14.

a rough intake port keeps tha fuel/air atomized to burn a hella lot faster! smooth intake ports form droplets that as we all "should know" dont burn as fast or effiencent.

As discussed earlier, that is true to SOME degree

Submitted by ccadmin on Fri, 04/01/2011 - 12:31.

Yes, you are correct on the formation of droplets, and a greater dissipation rate for textured surfaces due, in part, to a greater surface area and to a lesser degree, the slight loss in surface tension. As you will see in the "Copy and Paste" below, this point is described in the parent article I wrote to this discussion:

"A polished finish on the port does not provide the increase that one might assume. In fact, often within certain intake systems, the surface is intentionally textured to a degree of uniform roughness to allow for fuel deposited on the port walls to evaporate quickly, due to the increase in surface area. A rough surface on particular areas of the port may also alter flow by energizing the air boundary layer, which can alter the flow path to a large degree, theoretically increasing flow. This is similar to the way dimples on golf ball are intended to work. Flow bench results shows that the difference between a mirror finished intake port and a rough textured port is typically less than 1%, which can be argued is negligible. "

It should be noted that this is generally true for "non-pressurized' systems. In other words carburetter systems that depend on the decrease in air pressure on one side of the intake to draw in air at atmospheric pressure from the other side. Pressurized systems can behave different to what is discussed above, I will try to address this in more detail when time permits.

Thanks for the comment

TJ

Here's a video I have made showing some easy ways to create a textured finish on a 2 stroke intake youtu.be/GwtquXIAOrk

The Ram Air concept

Submitted by ccadmin on Mon, 05/23/2011 - 20:27.

It needs to be understood that Kawi introduced the "RAM Air" design to several models of it's street bikes for a reason, to utilize the high pressure air at the front of the bike. The point of this design becomes very relevant at higher speeds. When arguing why Kawi used polished intake components you have to take into consideration that pressurized air will behave in a different manner than passive pressure air. The Kawi R&D team understood that, and that this fact negates much of the textured finish argument.

ZX10R polished ports

Submitted by Anonymous on Thu, 12/02/2010 - 20:59.

I'd be taking any press release information with a grain of salt.

Just like the actual polishing of inlets, the adspeak is just pandering to the general publics expectations of what is required in performance engines.

I won't be surprised when I get a look inside one of these engines to not see any polishing at all, but will expect to see a degree of hand finishing, and a slightly rough finish at that.

I may be proved wrong here, but we wait and see.

G.

ZX10R, over-hype ?

Submitted by ccadmin on Sat, 12/04/2010 - 22:19.

Sure, it's possible the press release could be a little bit of over-hype.
The good news is, everyone here at CC Specialty will get to find out pretty soon, Robert has a 2011 ZX10R on order, and he will take delivery as soon as it gets to our dealer.
Robert, the man in charge of our CNC shop where we make the 1MC and other parts, has ordered a 10R to go with his other bikes and Vettes.
I am sure Blake, Cole and myself will go over every detail of the bike, considering all the new features this years model will have.
I will post an update on this when I get to check everything out, and thanks for the comment.
TJ

On that note the 2011 ZX-10R is here

Submitted by ccadmin on Fri, 03/25/2011 - 22:17.

Well the ZX-10R is here (finally darn Kawi valve spring issue) and man that thing is a beast! Can't wait to try out the Kawi traction control system and the countless other new features. The new bar graph display takes some getting used to, but on a whole I like it, and Blake and Robert think it's a winner. The thing feels pretty lite and nimble, even compared to the several 600s we got in the shop. It feels just as " toss-able" as the GSX-R, CBR, and 2 other Ninja's we got setting beside it. Once the weather warms up we will get to find out how it does on the twisty roads. By the way the intakes are quite smooth (I wouldn't say mirror finish), so there must have been some obvious advantages in the computer aided design. The 10R is great because as always we love speed and power so this little gem will fit right in. For more pics from the CNC Shop at CC Specialty check us out on Facebook www.facebook.com/CCSpecialtyTool

The 2011 ZX-10R From TJ