Dyna-Jet question

[mcg]

Drawing a Dyna-Jet in the CAD program Rhino3d. I attach a screen grab that shows a glimpse through the intake.

A ring of teeth appears (in red here) between the ten intake passages.

The drilling of the ten intake passages creates a fluted pattern because the drilled holes' axes converge. Drilling also leaves, in effect, a crown of "teeth" where the passages join the curve of the venturi. These little teeth show up in red in the snapshot.

I was wondering if the manufacturered product had these teeth. In CAD I could, in effect, grind them away and soften up the creases between the intake passages, in an effort to streamline the airflows.

Another view of the teeth, without reflections.

But I would like to know whether the ring of teeth was there in the real Dyna-Jet valve body.

Was the valve body machined? Or was it a casting? Or both?

Thank you for your insights.

Michael

[dynajetjerry]

Michael,
The "teeth" to which you refer do exist but they are much less objectionable than your image could imply. The end of the venturi-cutting tool bit is radiused so that it generates a much less abrupt step where it merges with the ports than you might think. Because the incoming air is pulsating at 250 cps, any disturbances to that flow are less than would occur if it was a steady stream.
Careful trimming of those steps might improve performance very slightly but we usually found such small modifi-cations to be of limited value in the real world. If a D-J user is after the nth degree of perfomance, he should go ahead and try them but he might have difficulty proving their value.
It is a bit like the belief of serious (and successful,) speed jet modelers that a tight-fitting reed valve will improve performance. In my own (limited) experience, reeds that seat securely against the seat can make the p-j much more difficult to start and is lost after a few seconds of operation. Too, as with a blending of the above "teeth," proving the value of such a step might be rather difficult.
Have I helped you?
Jerry Wiles

[mcg]

Many thanks for this help, Jerry,

Here is a cut at it. I have radiused the "teeth" so they are no longer perpendicular to the incoming flow of air. The specific radius is just subjective -- TLAR, i.e, that looks about right. The valve body is temporarily erased to show the changes.

teeth radiused back

I suppose the teeth might actually be beneficial. Turbulating the mixture, maybe. Thank you again for this information, Jerry. Please let me know if the radius should be further changed.

Michael