Why do all Honda manifolds have the tb mounted to one side? Would it make sense to mount it in the center like 9.0 K series manifold. Yea, flame away if you want, more curious than anything. Won't hurt my feelings. Also, would moving the injector away from the port provide better atomization. Just seems like there is cool stuff you can do with the Skunk2 ultra street manifold that hasn't been done yet. Like making a custom mail box that mounts to the long runners and also utilizing the 2nd bung ports for injector placement. If I knew how to weld that's what I would do.

 

Moving the injector back only works under wide open throttle conditions. It will actually hurt performance and fuel economy around cruising. It has been done for years on Formula 3 cars, as it goes around a race track typically at high RPM. I've got a ton of pictures of different F3 builds for research lol. Notice the factory injector location is blocked off...


Center feed intake manifold work, but routing becomes more of a problem on a motor not mounted like a K series. There is actually a better design but it gets complicated and would be very time consuming to make. Basically there is a tapering tube along the back of the plenum. Something along these lines has the best distribution effects...

 

No reason to flame as you are at least thinking of ways to apply the center feed intake charge and injector placement. Center feed is an option but like Flew said, packaging is the biggest issue. I am surprised that the race teams haven't taken more advantage of the Ultra series IMs. Only 4Piston has with the CNC service.

 

A manifold can work, or not work in both throttle body locations. It has to have a pressure recovery area after the TB inlet. If it doesn't, a side feed will favor 2 cylinders. If a center feed does not have it, then it will favor the 2 center cylinders. In either case, if they do have proper sizing and pressure recovery, they will feed all 4 cylinders fairly equal.

 

There was someone that made an intake similar to the 2md one you posted but it had a flattened pill shaped plenum, with the taper cone on one of the rounded sides (bottom) I believe the slot connecting the two was no greater than 1in wide and it had incredible gains especially to the mid rpm range. Ill try finding the post (wasnt on a honda)

 

http://www.mr2oc.com/showthread.php?t=403005

Found it. Gains arent as huge as I remember but he changed nothing except the intake. The mid ramge did get a healthy bump regardless

Btw this style intake is only suitable for forced induction setups

 

Interesting thread, in for some knowledge.

 

center feed plenum doesn't mean equal distribution. Here is a "proper" center feed setup.
http://poisson.me.dal.ca/~dp_11_15/DESIGN.html
as you can see there are "packaging" concerns. That makes you wonder, would a non-optimal centerfeed IM outperform the "almost" perfect TB position on the new ultra series ?

 

Good info here. Looks like in order to run a proper center feed setup on most (non K series) Hondas, you would need to tilt the engine in a way similar to a K series with Prayoonto mounts

 

Besides that the TB needs a "long" smooth transition into the plenum what i find most interesting is that in that "Specific" solidworks simulation flush bellmouths outperformed the velocity stacks standing off into the plenum, which is common practice in many high end Intake manifolds. Does that mean that let's say a Ported VicX/PerfX has better flow characteristics if we ignore TB angle compared to a Custom Intake manifold ?

 

I never understood the idea behind stacks that "stand off" into the plenum, someone explain?

 

I think its because the air flowing off the inner walls is higher velocity and smoother flowing than the air thats stuck to the inner walls. Also I think the air on the wall caudes turbulence or something. Im not 100% on the ohysics on why its better

 

I'd like to see some diagrams or papers on that, I've never heard of that

 

The boundary layer is what he is referring to, I think:

http://en.m.wikipedia.org/wiki/Boundary_layer

Essentially, the air at the wall surface is stationary. There are slightly different rules for external and internal flow, and the inside of a plenum can use both sets of rules depending on what specific behavior you are looking at. The topic gets complicated, as things usually do when the fluid becomes compressible.

 

Yeah thats it. Couldnt remember the word but could visualize the concept hah

 

Oh didn't know you were referring to the boundary layer. That should be a good thing, I always thought, to smooth airflow, kind of like a golf ball uses a boundary layer to smooth airflow. So then, I still dont necessarily see why stand off plenums would be better unless you knew exactly how thick that layer is. But according to jimmysxxl's article he shared, stand off plenums don't seem to be the way to go

 

There's (A LOT) more to it than just that, it's just one piece of the puzzle.

 

Then let's talk about it. I've done quite a bit of research on this already, but maybe there's a few pieces I'm missing

 

Here is where i dont get the Boundary Layer concept. We DO want Stationary (High Pressure) air in the Plenum in order to create a larger pressure differential between the Plenum and the Cylinder. So why avoid the Boundary Layer and stick the Velocity Stacks in the middle where there is Lower Pressure ?

 

I'm wondering the same thing jimmy. Not only that, but air flow would become more and more turbulent the farther the air charge gets from the TB opening, because of the air flow having to pass by and around these multiple stacks, seemingly giving the "far" cylinders more turbulent air.
In my mind, flush mounted stacks just logically make sense. I'm hoping someone will jump on here to further explain stack-in-manifold theory

 

I searched (yes some of us still do that when we don't know something) and found this article describing the theory behind the raised velocity stacks in very layman terms. But it is easy to understand, so read this one page thread, it's not long:

https://honda-tech.com/welding-fabri...tions-3152332/

So basically, it would appear that raised velocity stacks have smoother airflow as described in my shared thread, while flush stacks appear to have more velocity as evidenced by the article jimmy shared.

Thoughts? Opinions? Questions?

 

I still dont buy that theory. Raised velocity stacks would need RADICAL tb angle or Angle on the Velocity stacks themselves pointing to the TB and i have seen only a couple of manifolds like that. IMHO i think a couple of reason they are made like that are:

-Old Physics concepts
-Bro Science ( Let's make them look like ITB's it can't be bad right ? )
-Packaging Concerns (the 8liter plenum is hitting firewall with 9inch runners so let's get the runners IN the plenum)

 

Packaging concerns was actually the first thought that came to my mind lol, I think you're probably spot on with your other thoughts as well. I wish someone had a diagram of the airflow being more turbulent with flush mount stacks, that would make their claims more believable. Right now I'm leaning more towards the flush mount stacks as best getting the most air into the cylinder as it has actual hard proof for it.

Say jimmysxxl, wanna design a mani?lol

 

lol i've thought about it a lot. But even if we get everything in check the design wouldn't look much different than the new S2 series.TB positioning would be different and slightly different Vstack height and diameter but that would be all. I think S2 seriously nailed it there.

 

FIFY

If the runner entrance is above the floor of the plenum, there's more area for the runner to draw air from.

Try to visualize this: in a plenum with the runner entrance on the floor, you could cut a tennis ball in half to represent the area the runner will draw air from. It's 1 hemisphere.

Now pick the runner entrances off the floor 1/2" (for example). You now need 1/2" more tennis ball to hit the floor of the plenum. So now the area that runner will draw air from is significantly greater than 1 hemisphere.