Knife edge runner openings on single plane manifolds?

[SchmidtMotorWorks]

Has anyone tried knife-edging the walls that divide adjacent runners on single plane manifolds?

[shawn]

You want a very large radius at the point of entry on those runners.Knifeedging them is a common mistake that is done. If you go to Larry's site @ www.maxracesoftware.com he has some beautiful pictures of what a runner divider should look like. They are far from sharp.
Shawn

[cboggs]

Has anyone tried knife-edging the walls that divide adjacent runners on single plane manifolds?

Yes like Shawn said, and Larry has pictures of, .. a nice rounded
divider works much better, .. the bigger the radius the better.

In the 80's I did a bunch of testing on this, divider wall leingth, width, ..
etc.

Curtis

[SchmidtMotorWorks]

Thanks fot the advice on the knife edging, you just saved me from wasting a lot of time!

[ChrisU]

Depends on what you want to do with the runners. A large radius isn't always possible if you're looking to make the opening a certain size. It's all relative to sizing and application. I don't believe in a knife edge per say, but it might be thin depending on the applicaiton.

[ADR]

What about the devider in a 4V cylinder head...you are now much closer to the intake valves. Would it still have to be a bull nose shape down in the intake port itself ??

Thanks Dale

[Shaun]

What about the devider in a 4V cylinder head...you are now much closer to the intake valves. Would it still have to be a bull nose shape down in the intake port itself ??

Thanks Dale

Not really answering your question, but related to 4V cyl heads - Hans Hermann in one of his presentations mentioned that the divider wall should be at the very least, 250% the intake valve throat diameter. Reason he gave was that airflow needs to stabilize after breaking up BEFORE getting to the turn.

=====

I am curious to know the reason(s) why bull nosing is better for flow vs knife edging if someone would be so kind as to explain. Thank you

[panic]

"the divider wall should be at the very least, 250% the intake valve throat diameter"?

How is that possible? 1.50" valve, 1.275" throat requires 3.1875" wall thickness?

[bill jones]

-maybe that 250% was the length of the divider.

[SchmidtMotorWorks]

25% ?

[RHC]

you should try cutting the port divder diagnoly in a 4 valve head cutting it back more towards the roof of the port .when working in a manifold the teer drop shape is suposed to be the most aerodynamic shape the air will follow the walls of the divider sooner

[Shaun]

"the divider wall should be at the very least, 250% the intake valve throat diameter"?

How is that possible? 1.50" valve, 1.275" throat requires 3.1875" wall thickness?

Sorry for using the wrong words and not being clear. I wrote that after going 36 hours without sleep

The LENGTH of the dividing wall should be at least 250% the diameter of the intake PORT throat.

[Ken_Parkman]

My understanding of why bullnosing the divider is better is that the airflow is not continuous, so some of the cycle the air in the adjacent runner is static or close to it. That means if it was a sharp edge the air would be pulled around a sharp corner on that side of the runner instead of a radius, tremendously poor for flow.

If both runners were flowing in phase a knife edge would probably be better.

[ADR]

My thinking was that now that you are down in the port and it is a wet flow condition that the knife edge would help prevent knocking the fuel back into larger droplets but then again that same thing could be said for the manifold deviders that was originally talked about.
Dale

[cboggs]

when working in a manifold the teer drop shape is suposed to be the most aerodynamic shape the air will follow the walls of the divider sooner

Yep, .. spot on, .. ever sit looking out the window of the air plane
you're on, .. raining, .. watch the water drops across the surface of the wing,
If a knife edge was a better aerodynamic shape, .. wouldn't the airplane
wing be knife edged, .. wouldn't the nose of that plane be pointed like an arrow
instead of rounded???

Curtis