Quote:
Originally Posted by Frank Lee
Shorten the flow tract? Your image is gone. You are saying shortening the flow tract is better for flow than having a guide intrusion? Smokey Yunick says turning the air prior to it getting to the seat is advantageous. Seems most everyone agrees with him. I'd suggest some quality time with his book. Or a Vizard book.
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I'll have to read into that, because according to fluid dynamics, straighter is less resistance, and less resistance is faster (as a general rule, given that "less resistance" is still enough to keep linear flow)
I can say for sure that the radius in the flow tract actually decreases flow, rather than increasing it, per a given velocity. (Faster air tends to travel straighter, thus creating a shear point which acts as a wall to flow, attempting to keep it linear, and possibly aiding reversion. This can be desirable in some cases, but the only cases I've seen where it was advantageous were in limiting total intake charge (dynamic compression ratios relevant) to prevent detonation under boost and high static compression. (Larry Widmer, Honda engine -
The Old One - Energy Dynamics it's in the archives somewhere, in one of the couple engine builds.)
I believe that 'Ole Smokey intended a less broad application of his wisdom in saying that a radius was better for
the intake charge as a whole, wherein the intake charge contains the fuel mixture as well. Perhaps it helps to create the turbulence necessary to aide the atomization of fuel and air mixtures and create a more homogenous mix? I can't say for sure, but speculation is not beyond me.
With a Direct injection type engine, this would become historical engineering, and no longer a necessity in the flow tract. The idea would truly be to get in as much air as fast as possible with as little energy required to do so, then compress it, spray the fuel at a given timing, and bang. Once again, exhaust the fumes as quickly as possible, with as little resistance to flow as possible.
While the general idea that a radius in the intake tract is better for
something may be widely accepted, what would be the advantage of a restriction or turn in the
exhaust tract? I see none.