Changed My Project

[Kugel8x57]

I decided to change from doing a MicroSquirt MPI System on an air cooled 2180cc VW engine to the same on a 1974 2.0L Ford Pinto engine.

Why? Well I've already got the Pinto engine - had it for about 15yrs - so that's a huge cost savings. Also, I've already got the adapter kit (Esslinger Engineering) to bolt it up to my 1969 VW Baja Bug project transaxle.

I'm hoping to get about 125 - 150 hp out of her with nothing but the MicroSquirt, a proper set of headers, and a free flowing spark arrester muffler.

I still plan to do the 24-1 full cam sensor, like the model I put in my first thread. And I've also designed a Multi-Port Injection Intake Manifold. Just a preliminary design, but thought I would share it here and get some input from some of y'all with more experience.

The plenum is machined for a 50mm throttle body ~ 140ci volume. and is all welded aluminum. Please see the attached 3D PDF.

Whatcha think? Will it work? I'm thinking about Bosch 28LB/hr or 31LB/hr Injectors

[billr]

Is that view deceptive? It looks like there are four "runners", but all crammed into a length of only 20mm or so. How about posting some other views. Use "transparency" for the shading so we can see inside. I assume that will be a welded construction, it would be a real challenge to machine out of a single billet!

[Kugel8x57]

Hi Bill,

That is a 3D PDF. After you open it, with the free Adobe reader, click on the "picture" and it should go "live". Tbis will allow you to rotate it around and zoom in and out.

I do plan on posting a transparent pdf, too. However, it will not have the ability to "go live".

Thanks for the reply!

[billr]

Yes, that "activate" worked fine; no need for transparent views. I had tried the "activate" before, but it wasn't obvious that something had happened. Maybe I was expecting it would "auto play" some different views?

I have a pair of plenum/manifolds on my BBC that are quite similar, although with much longer and "snakier" runners. I terminated the runners inside the plenum all at the same plane, with a large radius on the lip to provide a "bell mouth" or "trumpet" opening into each. I would be worried that your staggered runner openings would make each cylinder have a different VE, both because of the runner length and turbulence in the airflow as it passed each runner getting all the way to the back. Understand, this is just a big fat guess, no math or flow-bench effort to support it!

[Kugel8x57]

Hi again, Bill.

I had the same thinking as you, but I read on a forum about a guy that modeled one, as you described, and "tested" it with flow dynamics software. The results showed that the #1 cylinder (nearest TB) was starved for air... it had much lower velocity than the others, and the other three were not well matched. He went through several iterations and finally ended up with something very similar to what I have modeled. The flows and velocities were fairly well balanced. He did use a round plenum and runners, but the "staggering" made the system act like a tapered plenum, which dramatically helped to balance out the flow.

Anyway, I do plan to make "back" of the plenum - side 180deg opposite the intake flange face - a bolt-on plate. That way, I can get in there to make adjustments, as necessary. Thought I might as well try it. We only learn from our on failures or successes and/or the failures or successes of others.

How would I go about getting this "Flow-Bench Tested"?

[billr]

I tapered my plenums, in attempt to even things out; but still all guessing. My plenum backs are one-piece, sort of sheet-metal "troughs", and I certainly think having the back removable would be nice! I was just worried about leaking along the long seams; and, frankly, the extra fab work wasn't appealing. Maybe I used the "leak" excuse to not go into the extra fabbing...

As to the flow testing, I don't know of an easy way. I think most flow testing (and facilities) are oriented towards flowing one path at a time. Here, you want to flow all four simultaneously; or not even quite that. Harmonics in the intake probably make flow in each runner affect the others, and all being frequency (rpm) dependent!

Gotta go...