Valve and guide drag

[panic]

Given:



Now, imagine that the tiny circle is the intake valve guide seen in plan view.
Do the proportions shown suggest that an airfoil much larger than the guide OD (fitted concentrically over it) will greatly improve flow through the port (at that point)? And another extending the guide far down on the stem (allowing for lift, of course) likewise?

[Elmo Rodge]

Panic, I think that if you got too big it would choke it off on the sides.  Other than that, I like it plenty. Wayno

[Milwaukee Midget]

?  ?

I like where this is headed - it's a thinker.  My thought at this point is that the external dimensions and shape of the port/bowl actually become complicit in flow obstruction to a greater degree than the actual valve guide, if the guide is shaped like an airfoil.

Part of the equation would also likely be a product of valve angle with respect to the airfoil, in that the valve tends to not flow uniformly across the back into the combustion chamber.

Panic, do you think this could be used to increase port velocity into the combustion chamber?   We're currently dealing with what will likely be better than adequate flow figures, but likely in need of higher velocity at lower RPM's than would typically be allowed.

[Interested Observer]

Katz' example is predicated on an unconstrained flow field.  Agree with Elmo that getting larger cross-section would probably not be good for the flow rate. 
Also, most valve guide flows occur at a skewed angle so it already presents an oval profile.  Adding a "tail" fairing might be beneficial, but most guides are already about as short as tolerable to avoid blocking the area.

[WOODY@DDLLC]

As IO stated internal flow is constrained by the port walls and shape. I examined this very issue in a recent cylinder head project. The best port lost 7.1% flow with an "aero" valve guide and one of the not so good ports gained 2.5% flow with it. Air flow is finicky as we all know too well!  :x :x You must test - not guess! 

[jimmy six]

What do you think the additional throttles shafts do especially at 90* to the valve.... Rotary valves might help 😱

[Milwaukee Midget]

Thinking out loud, again . . .

Woody, your research would want me to be looking at that 2.5% increased port, to be looking at where that flow is happening in the port and bowl with respect to the valve event, and how it's filling the cylinder past the valves.  You've likely already have done that.  

What if you're not necessarily looking to maximize total flow, but instead, are looking to create a less turbulent, and possibly better directed flow?

IO, given the external constraints of the port, you're effectively creating a low pressure point in the airstream where the port/bowl narrows around the valve guide, but that would begin to recover past the widest point.  An airfoil design could be engineered to be less turbulent at that point where the airflow is entering the combustion chamber, no?

If you have a port size capable of delivering flow capacity in excess of the application's needs, it seems to me the shape of the obstructions are fair game.

[wobblywalrus]

In the interest of keeping the intake charge cool the least amount of surface area is best.  Late model bikes often have no guide boss projecting into the port and waisted valve stems.

[rouse]

Intake ports are the very essences of making HP. The one that figures out the best port goes the fastest.

One big thing to keep in mind , among many others, is that you are dealing with flow and sonic pulses both directions.

You may get better one way flow and screw up your sonic pulses that results in a port that looks great on paper, yet don't run worth a hoot, because you screwed up the pulse waves that help charge the cylinder.

Like Woody said, test it out and see what happens. That's what makes racing fun, sometimes?

Rouse

[WOODY@DDLLC]

Or you try this: http://www.rotonusa.com/home.html
http://www.rotonusa.com/roton_vs_poppet.html 
This company is completing the work started by Roton: http://www.enginedevelopmentsaustralia.com/

[Dynoroom]

There are many things done to an intake port. Some work, others don't. In it's proper application this works. Is it what you are asking about?

[manta22]

Along this topic- has anyone used "Dynomation 5" software? Any opinions on how useful it is?

Regards, Neil  Tucson, AZ

[WOODY@DDLLC]

Neil, I use two programs for engine analysis to prepare for CFD studies. Both are very capable and useful for engine development plans.

Dynomation5 and Engine Pro by Patrick Hale [less $$]

http://www.quarterjr.com/engine_pro.htm

Engine Pro requires less inputs and I typically use that for a first look at a particular configuration. It is "calibrated" with extensive empirical data.

Dynomation5 requires more inputs but gives much more detailed results like port pressure plots. It has a very large cam database available.

Me thinks both are very useful for trends but can be surprisingly accurate. Sometimes just a CR adjustment gets them pretty close.

But like my byline says, "All models are wrong but some are useful!" 

[manta22]

Thanks, I had not seen "Engine Pro" before. The information on their website is rather sparse; no mention of cylinder head or cam libraries, etc. The price is attractive.

Regards, Neil  Tucson, AZ

[rouse]

Neil,
Yes I have Dynomation 5 and it is a good tool to use. It has more input requirements than Engine Analyzer so you would expect that the end results would be closer to real world numbers.

What I have noticed is that both programs are a little on the optimistic side of what you end up with, but that may be my fault as a tuner?

There is a whole batch of cams that you can select from a list, or you can input your own design.

The program is best if you already have good flow numbers for your heads, if not, you have to throw in some educated guessing. Thing good about that is you can tailor the heads to match best results.

Rouse