Yeah, thats how i look at it. But the plenum has been sitting around for a year, so i thought i might try out something new. Trying to setup the dyno for this sat. We will see. Im sure its going to do better than stock ( i hope )

Later
Aceman

 

Holy Crap! It's beautiful! Although I'm not sure if a high polish has substantial benefits over just smoothing, it should work great.

 

Hey, is it possible to bang that bowl area with a hammer or mallet or something instead of welding on additional metal underneath and machining.

 

If you look at this pic you can see what i ported on the plenum. The red area, i removed half a inch off of the front of the front two ports and a half a inch off of the top of the same two ports. Plus i ported the inside out.

The blue area i opened up quiet a bit so that air could move into the bowl area more freely.

The center two ports i opened up just alittle to alow a velocity stack effect.

The back to ports i just smoothed out.

Going to finish polishing it up tonight and post more pics.


Later
Aceman

 

Because it is a casting, I don't believe that it could be hammer formed without cracking.

 

From The Science of Horsepower: Porting & Matching Heads & Manifolds, Larry Carley, Underhood Service, November 2001
http://www.babcox.com/editorial/us/us110128.htm

"As for polishing, Mondello said a smooth finish is great for exhaust ports, but a rougher finish flows better on the intake side. He recommends using 300- or 400-grit paper followed by a Cross Buff for polishing exhaust ports, and 50- or 60-grit paper for the intake ports. A slightly rough surface texture in the intake ports and intake manifold runners creates a boundary layer of air that keeps the rest of the air column flowing smoothly and quickly through the port."

Just some toughts...
Chris

 

That looks very nice, OCG35coupe. Did they also polish the entire length of the runners?

 

I believe this is totally true for the runners and the heads from everything i read. It might also be true for the plenum, that is how it was designed from Nissan. I guess we will see what it looks like on the dyno. Maybe i should dyno it smooth then go back over it with sandpaper and redyno

But the cool thing is, we are all learning from this thread.

Later
Aceman

 

Aww man...So now i should go over everything with 60grit sand paper?

 

haha that would suck.. but if the dynos prove that rough surface is better than smooth for intake.. maybe you should.. but then again.. it's too pretty to mess it up

 

Ill just send the whole MREV2 to swaintech to get coated. I'll have the bottom of the Plenum and the flange where it sits on the motor coated in a TBC, and ill have the inside of the runners coated in what is listed as "inside runners flow coating" lol. I think its a type of Dry Film since coating the runners with Dry Film seems to be pretty common.

http://www.circletrack.com/techartic...at/index2.html

You can coat the top of the manifold with a thermal dispersant. By doing this, necessary heat that does get into the intake manifold will be more rapidly dispersed into the air moving over it, cooling the intake manifold. The inside of the runners in an intake manifold can also be coated. A single coating would be a dry-film type that can be a "fluid-retaining coating." This coating will have a tendency to create a small amount of boundary layer turbulence, which will reduce fuel dropout. You may also apply a thermal barrier to the inside of a runner first, then the dry film over it. Now, you have not only created the boundary layer turbulence, you have further reduced the amount of heat that does enter the air/fuel mix.



http://www.coat-this.com/automotive/..._manifolds.asp

The inside of the runners in an intake manifold can also be coated. A single layer of a dry film lubricating coating (DFLC-402, DFLC-404 or DFLC-401), also known as ?fluid retaining coatings? treates the fuel/air mix as it passes through an intake manifold on a carbureted engine as a "fluid in motion" and can reduce fuel drop-out by creating boundry layer turbulence. For maximum gain, first apply a thermal barrier (TCD-201) to the inside of a runner, then a dry film (DFLC-404) over it to not only create the boundary layer turbulence, but further reduce the amount of heat that does enter the fuel/air mix.

 

Yes

 

hmm, idk about that.

aceman- you did all your work with the craftman rotery tool yea? cuz i just bought a dremel! lol. which attachments did u use mostly? the sandpaper one or like the aluminum oxide brown/redish ones? going to start tonight!

 

Well the boundary layer helps fill out the area under the curve by making the effective "diameter" of the intake less at low rpm, it will help the top end by polishing, as it is before the injectors fuel wash is not an issue. So if your midrange low end takes too much of a hit afterwards you need to sand it, otherwise dont bother.

Mike

 

Hey Aleok

I used a high speed cutting bit to do most of the cutting on the inside and out side of the ports. Then i followed it by the 60 grit sanding wheel, then 120 sanding wheel and so on.

Here are a few pics of what i used.


Later
Aceman

 

Keep in mind that much of what is being said about polishing VS rough and airflow refers to american pushrod V8's with 4 barrel carbs. These set-ups have a fuel air mixture present throughout the runners. Our set-up has air only all the way down to the lower manifold where the injectors sit. Much of the polish/rough debate has to do with keeping the fuel from losing atomization and forming droplets. That cannot happen with our FI.

 

I am not concerned with fuel atomization.

The rough surface actually helps establish a thin boundary layer, while the polished surface will not. The air flowing against the polished surface tumble while it builds and breaks the boundary layer through out the runners. This tumbling air moves slower than the rest of the flow and acts as a restriction. The rough surface also helps suck air to the walls around the inside curves as it flows around the bell mouth and down the ports.

Chris

 

Well said. It is the same principle used on a golf ball. The dimples on the golf ball allow it to fly farther than without them. B & W speakers use this principle as well on there dimpled ports. Their ports with the dimples flow more air than the same size port without the dimples. This is exactly what we are trying to do. Flow more air with a given size runner.

"B&W’s Flowport™ minimises turbulence in
the same way as a golf ball. Dimples on the
surface generate tiny eddy currents over
which air can flow smoothly."

 

So from everything i have read today about boundry layers from air planes to sail boats LOL i have a head ache

Want a head ache? Read this link

http://history.nasa.gov/SP-367/chapt3.htm

The dimples on the golf ball do infact increase how far the ball will travel BUT this only comes into play once the golf ball is moving over 55mph. Up to that point a smooth ball and a dimpled ball will travel the same distance. From what i read, another reason a golf ball travels further is the fact that dimples create lift from back spin which keeps the ball in the air longer.

I guess i wont give it a mirror finish, but from reading the below link whats a 1% difference going to hurt And as Bill was saying, the roughness does apply more to carburated vehicles. This allows the fuel and air to mix on the way to the combustion chamber.


Found this info on this site

http://www.answers.com/topic/cylinder-head-porting


It is popularly held that enlarging the ports to the maximum possible size and applying a mirror finish is what porting is. However that is not so. Some ports may be enlarged to their maximum possible size (in keeping with the highest level of aerodynamic efficiency) but those engines are highly developed very high speed units where the actual size of the ports has become a restriction. Often the size of the port is reduced to increase power. A mirror finish of the port does not provide the increase that intuition would suggest. In fact, within intake systems, the surface is usually deliberately textured to a degree of uniform roughness to encourage fuel deposited on the port walls to evaporate quickly. A rough surface on selected areas of the port may also alter flow by energizing the boundary layer, which can alter the flow path noticeably, possibly increasing flow. This is similar to what the dimples on a golf ball do. Flow bench testing shows that the difference between a mirror finished port and a rough textured port is typically less than 1%. The difference between a smooth to the touch port and an optically mirrored surface is not measurable by ordinary means. Exhaust ports may be smooth finished because of the dry gas flow but an optical finish is wasted effort and money.

The reason that polished ports are not advantageous from a flow standpoint is that at the interface between the metal wall and the air, the air speed is ZERO. This is due to the wetting action of the air and indeed all fluids. The first layer of molecules adheres to the wall and does not move significantly. The rest of the flow field must shear past which develops a velocity profile (or gradient) across the duct. In order for surface roughness to impact flow appreciably, the high spots must be high enough to protrude into the faster moving air toward the center. Only a very rough surface does this.




Later
Aceman

 

thanks aceman,
so after all this polishing the intake plenum is a waste of time and infact decreases performance? thats just a damn shame! would it be better to just leave it or polish out all the divites and then rough it up a bit with 60 grit?