jaxg35

Looks great, Now someone needs to come up with a transparent upper plenium. Anyone into plastic injection molding????????

ACEMAN

iTrader: (29)

Well i read some more today. They need to give me more to do at work

Regardless if the area is smooth or rough you still have a Boundary Layer.

Boundary Layer A layer of static to slow moving air adjacent to the surfaces of a moving body. Friction between the body and the surrounding air holds back the flow nearest the surfaces, whilst the air further from the body in the mainstream flows past at unabated speed.

The rougher the surface is the larger the the Boundary layer will be and the more turbulent the air flow will be. With a smoother surface the air will move faster ( less drag ) this is called the Laminar boundary layer. See attatched.

Another reason for a rough surface is heat transfer. The rougher the area is the more turbulent it is. And the more turbulent, the more heat that is transfered. With our plenum i believe the roughness helps with heat soak of the plenum ( i could be wrong ).

I guess what i am trying to understand is why do we want to have a larger boundary layer. If the surface is rough on the inside of the plenum the layer of turbulant air is larger which reduces the volume of non turbulant air. Which to me it means you are making the volume inside of the plenum smaller. Where as if the inside of the plenum would be smoother then you would have a greater volume of air that would be moving faster.

Now with carburated engines you would want the plenum or runners to be rougher. By having it rougher you would be mixing the fuel and air together from all the turbulance that is created.

People keep bring up Golf *****, can we really use a golf ball as a example of what we are trying to accomplish here. A golf ball is a round object going through the air. We are not trying to move a object through the air here. We are trying to move air through a object.


Hell i dont know, take 60 grit to it and be done with it, my head hurts

Later
Aceman

bluezee

Aceman, I can see you are really digging into this subject. Cool! Let me start by saying I am no expert in the field of intake/plenum/or runner technology. But I do know a few things about air flow concerning speakers. Lets not use a golf ball as an example, lets use B & W's flowport technology as an example. We are moving air in (and out) of the port like we move air in the plenum and runners of our engine. There are pistons in our engine just like a woofer acts like a piston for a speaker. B & W uses a port with a curved mouth and dimples. The curved mouth accelerates the air, and the dimples create that small boundry layer of air that the main volume of air moves faster over than if it wasn't dimpled at all. I have talked to one of the chief engineers of this in the past and have found out that the depth and number of dimples do make a difference in the end result. Taking that and trying to apply it to our cars leads me to think that, like with anything, too much of anything is a bad thing. My guess is that if the surface is too rough, you will get too big of a boundry layer and not enough airflow. If the surface is too smooth the air doesn't flow as fast against that surface as it does against air boundry layer. Again I'm not an expert, just my 2 cents worth. This subject makes for a very interesting read though. Let's keep the info coming.

Bob

ACEMAN

iTrader: (29)

I appriciate your response Bob.

Yeah, i tend to dig deep into subjects. I like to know how something works insted of, it just works.

And another things is, i work in a engine plant, not on the engine building side but on the application side. I support the assembly line. Each line has your assemblers and each assembler has a computer screen with instruction of what to do when the engine rolls into their station. Basically my job requires me to sit at my desk until there is a problem ( fire fighter ) if for some reason the instructions do not come up or the engine does not move out of its station, i need to find out why .

Wish i could talk to the engine designers

They build 11 to 16 liter desiel engines here and they all are inline 6's. Makes our little 3.5 liter look really really small. So being around these engines all day gets me to thinking totally different animal but still a engine, a BIG engine

I do think maybe we want some what of a coarse surface, just not sure how coarse And with out a flow bench. The only way for me to know, is to take a polished plenum and a rough plenum and dyno them. Then i could see if there is any difference.

Maybe i might just do it, for the shats and giggles.

Later
Aceman

bluezee

Aceman, sounds like an interesting job. A side of engine building I have never thought of before.

I agree though. What is too smooth? What is too rough? I'm sure I don't know. You have a good idea though. If we could get two identical plenums except for one being polished and one not, then dyno them. That would be interesting to see for sure! Keep us informed if you do this!

Bob

ACEMAN

iTrader: (29)

Ok, here is the plan.

As soon as i can get to the dyno with my friend who has the bone stock 350z i will dyno his car stock then with the plenum that i ported and polished then i will take some 60 girt over the same plenum and dyno again. Its for the better good of the 350z community right??

I just dont know when it will happen, but what the hell. I need to know lol

Later
Aceman

UK-Nissan

Two facts to consider:
At higher reynolds numbers the boundary layer gets thinner
As a consequence of this at lower rpm the effective diameter gets less, this helps keep the velocity up.
If its too rough then the redline velocity is too high and the losses get higher.

Mike

ACEMAN

iTrader: (29)

Makes sense, from everything i have read.

Later
Aceman

aleok

iTrader: (1)

sounds good aceman.

OCG35Coupe

iTrader: (3)

Not to me!

Can you translate in lamens terms..

OCG35Coupe

iTrader: (3)

I think im going to keep everything polished.. Im only going to sand about halfway through the runners with 100 grit sandpaper. I think ill sand it down with 100grit sandpaper up to the point where the runners turn down towards the engine..

What do you think? Or should i do it the other way around and sand half way up the runners.

96sleeper

http://www.gethoned.com/

Extrude honing polishes every surface where the air flows, and they get good gains. I wouldn't rough the polishing job back up.

ACEMAN

iTrader: (29)

I would say leaves your like it is. And put it on a dyno. What all else do you have done to your car??

Later
Aceman

johnlotusboy

iTrader: (1)

Leave it polished. I have years of flow bench time and it is the only finish for the ports. I can get the supporting documents/textbooks from my friends that are graduates of the Vehicle Research Institute @ WWU in Bellingham, WA.
Debate as you like, but 20+ years of P+P/flow bench hasn't seen a better finish.
1 degree taper is what I like.
Design/shape are debatable.
The most critical work is from the valve seat to the valve guide boss in the port. On our 4 valve motors just upstream of the divider wall to the seat is where the proper reshaping make numbers on the dyno. It is where the subtle things that the average motor builder/hotrod guys couldn't spot w/o help and some flow bench simulations.

OCG35Coupe

iTrader: (3)

No engine mods really..Just a Carbon Fiber Z-Tube and a Blitz Drop in replacement filter. I might buy a 05-06 Airbox that has a built in velocity stack.

I have alphawerks headers in the garage, but i want to get them coated first. And im not too sure if i want to get the underside of the MREV2 coated in the same TBC. I figure it cant hurt, since the underside of the MREV2 sits right on top of the engine. The TBC i plan on using is pretty thick to at around .5mm which is about 7 times thicker then Jet Hot.

I wont rough it up!

ACEMAN

iTrader: (29)

Do you have a base line dyno?? If not you should really think about doing that before you put the lower plenum on. Then from this point on you will really know how much performance you are getting from the mods you add to your car.

But then i dont really know what your plan is. Some of us get the mod bug and cant stop (Aceman) <-------------

Later
Aceman

UK-Nissan

A large part of the improvement is the balancing of all ports, not necessarily the smoothness of the process.

Mike

roast

iTrader: (2)

sorry im a bit drunk excuse me....i just wanted to get a little philosophical... maybe I shouldnt.... the transparent experimentation/learning you guys are doing here is absolutely excellent.... I commend you fellow Z owners.... seriously... I'd buy you all a beer if I could.... I have been thinking about this mod for a long time now and stumbled across this page earlier today and read the whole thing and it was such a nice find. This is one DIY mod that just about everyone could theoretically do... We just have to find out what works best for which applications... The Z is short enough of worthwhile free/cheap mods as it is... this DIY mod has best potential that I know of!!

YOU GUYS ROCK.

BTW... SPELL CHECK OWNS ME.

E K

iTrader: (10)

I didn't worry too much about smoothness/roughness before the injection point (which BTW, is at the bottom of the intake manifold).

Again, I gained 6 horsepower on the same dynapack in Socal. Possibly even more, because my "baseline" was when I already had some work done.


Underside of my Crawford V5 plenum.


This is the intake manifold bolted up to the lower plenum, and looking upward. Everything was gasket matched. Though with the dremel flex shaft, one could just portmatch with the components bolted together.


I should have took a pic of my Crawford plenum before my polish work. I asked Doug to send me a nonpowdercoated plenum that I would work on myself.

I had also gasket matched the intake manifold to the heads and smoothed out some of the casting on the intake side of the heads.

ACEMAN

iTrader: (29)

Some times i wonder if im getting to indept with the research on this subject. But i have learned alot. I never knew what a boundary layer was before. Hell i even know why a golf ball stays in the air longer and how a planes wing works.

The one link i provided earlier in the thread states, that there is only 1% difference in flow compared to polish and rough. Now if we are working with 15hp for a number, how much are we gaining or losing by it being polished??

And i should of been drunk, before reading some of the stuff i read

Placing the lower plenum on my friends car today for BUTT dyno results. I will post a BUTT DYNO graph later tonight (eastern).

Later
Aceman