FFIM design questions

[SuperRunner]

Well...that is true, but there are 2 runners taking in air at the same time on a 7M.

So, you're saying velocity (due to pressure) does not have an effect on flow?

I said only 1 runner at full capacity.

And no, that is not what I am saying. But at higher pressures, you don't need as much velocity. By increasing the CD of an orifice, you in turn, increase the pressure in the intake runner. How that effects the overall flow....well, that is beyond what I can drum up right now. About a year ago I could have answered that better when it was all fresh on my mind. If this were not the case, then there is now way that guys could be pushing 1800hp out of the 2JZ, and not be far beyond the 300ft/sec.

 

[SuperRunner]

Nice
How about building up material around the stack in the plenum to cut down on turbulence? The way you have the runner protruding into the plenum would have the effect of a longer runner and improve bottom end power. The raidus port is far more important on an FFIM though...you want a smooth transition.

Yes, I do agree with this. The RADIUS is the most important part, aside from the stack.

 

[supra_kid101]

Ok so i'm still trying to take all of this in. I thought I could just make a plate port matched and weld around it to make a FFIM. I'd like the idea of the stack but like J said shouldnt the material be flush with the top to prevent turbulence? What about my back plate being edged to provide the same effect granted it would be very short and probably wouldnt help but it also couldnt hurt. I'm not looking for the best possible design just a way to shorten the IC piping and put a FMIC on my car while I do my turbo swap.

 

[SuperRunner]

http://www.rossmachineracing.com/intakepartspage.html

These guys sell velocity stacks, andare designed to be flush mounted I believe

Velocity stacks by the way DO NOT have to protrude into the manifold. The hole point of a velocity stack is to increase airflow through the runner.

 

[jdub]

Great link

You do not have to have the runners extend into the plenum, but you have to be careful with the distance between the plenum and the strut tower...you can't have it extend too far or it will hit. This limits the length of the runners...here's pics of mine:





The extensions on the runners is ~1" and this puts the plenum pretty close to the strut tower. I'll have to use bolts vs the stock studs on the head to secure the manifold...otherwise I won't be able to remove the manifold with the engine in the car. The runners inside are radiused and matched to the diameter of the stock runners at the weld.

The advantage of the way SR did his in the pic above is you get the effect of a longer runner, but don't have the plenum as close to the strut as mine is. You will lose a very small amount of plenum volume...not significant IMO. But I would weld a circle of material around the stack inside and smooth to a mound shape to reduce the turbulence.

 

[SuperRunner]

I dunno, looks like you lose quite a bit of volume.

here is mine, LOTS of volume. But the science of plenum volume is something else. You can have it be too big, which mind could be. That is where resonance tuning comes in.....not on my list of things to do.

 

[jt2ma71]

Ok so i'm still trying to take all of this in. I thought I could just make a plate port matched and weld around it to make a FFIM. I'd like the idea of the stack but like J said shouldnt the material be flush with the top to prevent turbulence? What about my back plate being edged to provide the same effect granted it would be very short and probably wouldnt help but it also couldnt hurt. I'm not looking for the best possible design just a way to shorten the IC piping and put a FMIC on my car while I do my turbo swap.

If you are going to make it, why not make the best possible design? At the same time shortening the IC pipes. The radiused entry to each runner is common knowledge with anything that flows whether fluid or air, pressurized or not.
The protruding radiused stacks is kind of a different story. They do help for normally aspirated applications but may have a negative effect for forced air inductions. I have never made an intake, and I made very many of them, that used raised velocity stacks. My honest opinion, the picture of one posted by SuperRunner is best suited for normally aspirated application. But in the end all DIY FFIM can produce very close to the same power/torque when mounted on the same motor with the same turbo at the same boost.

Here's one I made for my 2j:

~Ron

 

[jdub]

Ron - you always do beautiful work

 

[SuperRunner]

2J uses round ports Why did you go oval?

Very nice by the way. My next setup will be like that. My current one will be transfered over to my GS300 and sold.

EDIT: Oh wait, I see aftermarket runners? Where did you get those, and are they tapered. I am thinking of actually casting a tapered runner with a radius. Once I get the mold done, I can get them cast pretty cheap. Then chuck them in the lathe to clean them up.

 

[jt2ma71]

2J uses round ports? Why did you go oval?

Very nice by the way. My next setup will be like that. My current one will be transfered over to my GS300 and sold.

Thanks. The head ports are oval like the 7M. This is the first manifold I made with Oval entry. Trying to find out whether it will make a difference.

 

[SuperRunner]

Yes, I realized that after I noticed the custom runners.

since the size of your radius is limited to the physical separation of the runners, it seems you would get a better C/D by using a round port because you increase your area.

 

[IJ.]

Yes, I realized that after I noticed the custom runners.

since the size of your radius is limited to the physical separation of the runners, it seems you would get a better C/D by using a round port because you increase your area.

Pardon?

 

[SuperRunner]

Well, if you have a size restriction of say 3" OD of the radius then your CSA will be:

circle= 7 sq/in
oval = aprox 5.13 sq/in

Because the CSA of the oval is smaller, the C/D will also be less. Is there something I might be overlooking?

 

[IJ.]

Was just wondering as the stock runners are oval at one end round at the other and there's more area in the Oval section so I was confused by your post.

 

[SuperRunner]

They are oval at the port because it flows to two valves. I just think a nice smooth transition from round to oval would be best.

 

[89tMike]

I am haveing a FFIM made and it is going to be flanged for the Nissan Q45 throtle body. My question is can i still use the stock ISC?

 

[jdub]

Geez...start reading at post #2 :3d_frown:

 

[89tMike]

I ask that question becuse i thouth the q45 had an ISC built in? IIRC

 

[starscream5000]

Very nice debate going on here fellas. From what I've gathered so far, the velocity stacks are good for off boost scenarios here where bottom end torque will increase. However, once the intake is pressurized (boost) the velocity stacks become a restriction due to turbulence. Am I thinking correct here?

If this is true, then why would you even think of using a velocity stack in the first place on a turbocharged application?

Also, IIRC, aren't two intake valves fully open at a time?

 

[SuperRunner]

you still need velocity stacks, just don't have them protrude into the manifold, keep them flush.

Back to my original statement:

USE VELOCITY STACKS, or you will hurt your performance dramatically.

And yes, two intake valves are FULLY open, but they are for the same cylinder, same runner.