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[dvallis]

I ended up needing three different tap sizes for the throttle body

7/16-20 for these two




9/16-18 for this one




Then 1/2-20...

[dvallis]

Removed the eBay manifold. We'll eventually reuse the flange for a CFD designed custom manifold. I'm thinking of doing a 3D printed carbon fiber plenum.



View of the head intake...

[dvallis]

Your stack height looks close. Mine was 206.2. Make sure you clay the pistons during assembly and measure valve clearance. M20 is an interference engine and will bend valves if you screw up. Trust me,...

[dvallis]

Sure. I'll let you know when I start building it.

[dvallis]

Digger

eBay Manifold is (21" x 8.6" x 3")/2 = 271 in3 = 4.4L. That's spot on for a 1.5x of a 3L turbo

Runners are ridiculous short though. 76 mm vs 200 - 300 mm...

[dvallis]

I found this writeup on intake manifolds. A couple of interesting quoues lead me to think a large volume short runner intake manifold is the better choice for a turbo racing setup.

1. "Generally,...

[dvallis]

Yep. Weirdly well balanced for all its eBayness. Can definitely see why the runners should be longer and plenum smaller though. Obvious when you get down to serious simulation. I'll design and build my...

[dvallis]

I'm showing 350 CFM per runner.



Cam profile is for the Schrick 284/272. Using 20 psi on the inlet and a 5 psi pressure drop on the runner outlet lids for valve full open. Not...

[dvallis]

I cranked the resolution up to stupid and let it run all night. Click here for new high resolution video.

The runners are hitting ~800 fps flow rate, which is good. With the higher resolution,...

[dvallis]

750 fps. You can see it in the video, has a legend. What is stock flow?

[dvallis]

Finally got a transient analysis of the eBay intake manifold working. Video is here. Enjoy.

Cylinder 1 5 3 6 2 4 intake stroke shown below. It works, as in all runners suck air, but I'm not...

[dvallis]

Obligatory meme

...

[dvallis]

#Facepalm! Of frigging course. You need to open the runners in order of firing sequence. That makes total sense. Thanks Digger.

Like you said, flow looks a bit uneven in some runners. I think...

[dvallis]

Here you go, 20 psi inlet pressure. You can see there is pressure in all the runners, just bugger all for flow in #1. It's pretty clear from the S54 intake above that you have to design with flow in mind....

[dvallis]

#1 wasn't exactly zero, just some fraction of a CFM. I rounded to integer.

I gave the inlet an initial condition of 1000 CFM. Also tried some velocity initial conditions around 20 -100 ...

[dvallis]

Here's what proper flow looks like. This is an S54 manifiold.


...

[dvallis]

Just for curiosity sake I cranked the mesh resolution up to "Ya gotta be f..ing kidding me" and let the sim run this morning. I used a 20 core workstation that loved to have something better...

[dvallis]

Nope. Nothing blocking #1.

The Solidworks project including SLDPRT file and CFD is here.

...

[dvallis]

#1 got capped or the model won't run. But I'll check the port for extra material.

FYI you can't run a flow bench on the STEP file. It imports as a surface by default. I had to play with options,...

[dvallis]

Well, THAT'S pretty weird. Here's a velocity plot. Cylinder #1 would be getting starved, not #6 Aaaaaannndddd ... that's why you need engineers designing manifolds. Yikes that's ugly. Glad we're using...