Design Review Please (EFI Manifold)

[SchmidtMotorWorks]

With all the talk about EFI going on here I am considering abandoning my carburetor project and making this manifold instead.

So here is the roughed-in concept.
You guys have helped me a lot on my last project the (air cleaner housing), maybe you can give me some feedback on this one?

Here is what I have so far, for the casting, the screws and some details are still missing. Let me know if you have any suggestions.

Also. does anyone know a good way to attach those horns?

[Unkl Ian]

Is the difference in hieght on the horns enough to achive any real benefit ?

Some guys prefer to just radius the transition between the runner and plenum,instead of adding a seperate piece.There was discussion of this
in the old forums on www.oldone.com

[SchmidtMotorWorks]

My thinking was that with the horns it would be possible to equalize the length of enequal length ports in the head. Other people might want to have longer horns so it would be easy to do in this manifold.

I see the horns used on more and more engines, even passenger car stuff, I guess there must be some advantage to it.

[bobqzzi]

My thinking was that with the horns it would be possible to equalize the length of enequal length ports in the head. Other people might want to have longer horns so it would be easy to do in this manifold.

I see the horns used on more and more engines, even passenger car stuff, I guess there must be some advantage to it.

Waht's the application? Street car? Race car? Normally aspirated or forced induction. Looks like a nice forced induction manifold.

[jdeleon]

Looks nice...great idea!
How 'bout a flange and o-ring on the upper runners to plenum box, then you can run a bolt up to plenum box from below outside (on flange). The opposite for the horns.
Using a flange will allow you assemble the two parts. The included angle will make it tough otherwise.

[larrycavan]

My thinking was that with the horns it would be possible to equalize the length of enequal length ports in the head. Other people might want to have longer horns so it would be easy to do in this manifold.

I see the horns used on more and more engines, even passenger car stuff, I guess there must be some advantage to it.

Nice drawings! What app are you using to do those with?

I would agree with your reasoning on the horns. It can't hurt to have the extra tunability feature. I wonder what the runners flow with them vs just radiused. I'd bet the horns help the CFM potential overall.

JMO

Larry C

[automotive breath]

With all the talk about EFI going on here I am considering abandoning my carburetor project and making this manifold instead.

First I like to say I think it's an excellent idea. The one bit of input I have is when possible leave extra material for porting.

[SchmidtMotorWorks]

Wow, thanks for all the quick input, I'll try to catch up.

RE: Flow, from what I have read the difference in flow between an radiused runner to plenum verses a horn is not noticable. I would like some informed input on that though.

RE: CAD App, I use Unigraphics NX. I work there an do this motorsports stuff to empty my bank account.

RE: Flange, that would be tough, bit it might be possible, I'll work on it. The problem is in how the casting will be made. The way I have it now I can cast if with automatic equipment in green sand, adding the flanges would probably make it an air-set sand job and double the cost of the castings.

RE: O-ring I think that I might be able to put an oring in a cbore rather than in a groove so that when you tighten the plenum it would squeeze the oring on the tubes to hold them in.

RE: Application, I tried to make it as universal as possible. I guess any BBC with conventional rectangular port heads.

RE: Porting stock, currently I have it designed for 0.200" wall thickness so that it will be light, what thickness would be preffered?

[ADR]

I am in the middle of a very similar manifold project for a 5.4L 4valve ford motor. On mine...the air from the throttle body is going to enter above the port entry. I have seen manifolds built in the past that were limited by hood clearance and had to be made very compact. The throttle body was placed very close to the front two cylinders and it did have an effect on air distribution and A/F ratio of the front two cylinders. I call it the same effect as the way a spray can would work....the air crossing in front of the ports actually pulled fuel out of the runner and deposited it in the plenum.
My .02
Dale

PS...this was on a blown motor

[airflowdevelop]

a couple o' suggestions.

1. More plenum volume (you can't have enough with EFI). Use it as a settling chamber.

2. Get the injector away from the head as far as possible. Raw fuel injected into the cylinder is unburnt fuel.

3. Don't worry about equalization of runner length. Remove the flutes and radius the runner into the plenum.

4. 12 - 20% taper in the runners is a good starting point.

5. Feed from the top instead of from the front. The plenum can become distrubed at the back cylinders. Nothing wrong with split dominator T-bodies...

Dennis

[SchmidtMotorWorks]

airflow

Can you suggest a number position and size of throttles?

A design I was working on earlier had 2- 4"dia throttles at 4.0 or 4.840 spacing (I forget now) it looked cool but I thought it would be better to have a low profile.

Now that you and ADR mention issues about eneven flow I am leaning back toward the top of plenum throttles.

I'll make the model back the other way tomorrow.

[Greenlight]

Why don't you start out with an old tunnel ram manifold and add a top to it.

A couple of other things to note. You should include some taper in the runners, if you haven't already. The literature shows that there are power gains up to a 3 degree taper (included angle).

Also, there are power gains in placing the injectors higher up on the runner (or even on top of the runners in the plenum). If you do place the injectors at the lower portion of the runner you should aim the nozzle to spray right on the back side of the valve.


As always, these are just my opinions.


Regards,

Greenlight

[SchmidtMotorWorks]

Re Taper: This design has 2 degrees included over a length of 5.7 inches is about 16% increase in area.

Re Nozzles up high

How about this....I'll put one big throttle in the middle of the top and the injectors in the top above the runners. Maybe it could have some glass windows in the top to see if the injectors are working correctly and to entertain like that dyno video Shaun posted. I really enjoyed seeing the spray from the injectors.

What about this? Put the throttles in the runners like the F1 engines?

Re existing manifolds:

I wanted to have a round runner opening and I don't know of a manifold like that.

I was looking at some other tunnel ram base EFI systems in the manufacturers area at the races last week and was suprised how crude they were inside. I think it was a Holley one that had no radius at all on the runner entries just a top bolted onto an old tunnel ram.

[bobqzzi]

Re Taper: This design has 2 degrees included over a length of 5.7 inches is about 16% increase in area.


What about this? Put the throttles in the runners like the F1 engines?

Re existing manifolds:

I .

If this is a racing maniold, then ultimately individual runners would probably be the way to go.

[Shaun]

The literature shows that there are power gains up to a 3 degree taper (included angle).

There is no gain beyond that? I seem to recall up to 7 degrees taper (included).

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Nice work, Jon.