Whisteling Port - Whisteling Port @ 15" of Pressure

[larrycavan]

I have a couple of ideas to try out...right now I've got no time to play with that head....I have a Rotax 2 Stroke that's got to be finished...fortunately it's been raining here so the pressure is off a bit....

[gofaster]

Larry,

when you get back to it, try rounding the divider with some clay or rolled tape, etc.... and see if it helps. Sharp edges can be a problem. Also cc one side of the runner at a time and see if they're equal.

[Tony]

One other aspect of whistling is that there is usually a tuned resonant length associated with it.

Some sort of flow instability, typically vortex shedding, creates a regular "flutter" in the airstream, but that may remain quite small unless it coincides with a suitable resonance. The amplitude quickly builds up, then the thing can really howl, but usually only at one preferred pitch.

Musical wind instruments, air horns and such, are designed to do exactly that.

[larrycavan]

[86rocco]

[larrycavan]

[Mouse]

Try a radius on that black entry thing if all else fails. I get terrible whistling from flow testing short sections of tubing without a radiused entry.

[Hopper]

[color=#000000]I was just curious to see what you found out?
Did you try and flow this head with just one valve open? Was the whistle gone? How close are the valve center lines or spread? On 4 valve heads that have a wider valve spread, I

[larrycavan]

Never did pursue it any further. The heads on the motor and runs very strong. You're absolutely correct about 4 valve heads with a wider spread not whisteling. That particular Suzuki head would drive you out of your mind.

Just did a Honda siamezed port Radial 4 valve head. 3mm smaller valves than the Suzuki [33 vs 36mm] but It's flowing quite well. Getting 213 CFM @28 with 39mm Kehin Flat Slide mounted and 227CFM with just the intake manifold and no carb. Port velocities are looking good as well. Should work according to plan. Hit my Pipe Max calculations quite well. Expecting good results.

[PerformancePorting]

I do only 2 and 4 valve motorcycle cylinder heads. The divider is what is causing your whistle. The two paths are fighting for control of the intake runner switching from one side to the other. On 90% of the heads I do they whistle at some point but normally close to max valve lift. I have never had this cause a head to not perform. Mostly just drives you crazy while testing.

[larrycavan]

Have you noticed how big the valves are getting in some of the 4V ATV heads these days? They're bigger than the big bore street bikes by 2-3mm.

[PerformancePorting]

What are some of the bore diameters on the atv's? I would be interested to see how the valve dia. relates in percent of bore. I wish I could get that big of a valve in some of the hayabusa's that I do.

[larrycavan]

[larrycavan]

Hey Performance Porting...I was going to ask you....I was reading the thread over on ST regarding valve sealing...Have you ever had a head where the valve seat was affected by torquing the spark plug?.....

[SuperRunner]

I am currently flowing a 4 valve head. at max lift, the noise is unbearable. I have a huge headache because I wasn't wearing earplugs. If I obstructed the inside wall near the valve on one side or the other, ther wistle was gone.

It didn't seam to effect flow either way, just very annoying. The dividing wall is knife edge. Next week i will try some clay and round out the edge to see if it goes away.