Head flow testing.

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The best heads I've had started out as 28mm port Atlas or early Cmdo heads. Then they were ported on the roof side only, cutting upward and to the sides of the guide and leaving metal directly in front and behind the guide bore to prevent the alumn material from getting too thin near the valve pocket. This could result in a heart shaped roof at the guide. The in manifold ended up being raised off center in relation to the bolts so custom manifolds had to be made. Raising the entire port all the way into the bowl helped bring the fuel/air charge straight down on the valve so it flowed around the complete diameter of the valve (and not just across it) into the chamber. The intake manifold end ended up at about 32mm diameter tapering down near the guide to about 30mm (full race) depending on engine displacement. A lot of clues came from foam rubber port castings of Axtell ports (courtesy of Ken Canaga). Going too big on the diameters would kill the midrange and material could get thin near the intake oil drain and roof. Similar but smaller proportions were made on the exhaust side (approx 29mm at the guide) and when going to larger pipes - a mismatch ridge was left on the port floor where the header bolted on to help prevent exhaust reversion. A lot of time was invested in porting these heads being careful not to go too far and blending all the curves etc. Performance improvement was dramatic and everything came together when you assembled the right cam, pipes and intake manifold length. All these specs are in my race manual.
 
Dances with Shrapnel said:
The only other constraints are sonic choke and time available to do it. What you have going for you is harmonic tuning.
Click to expand...

Further to the comment on classic harmonic tuning there is the application of the Helmholtz resonator which in essence retimes and maybe better stated rearranges what happens and when during an intake induction.

If I recall correctly the parameters include:
resonator box volume,
cylinder swept volume,
intake tract length,
intake tract volume,
resonator box intake tract length and
resonator box intake tract volume.

I always wanted the time and a test bed bike and dyno to play around with this. A fellow I raced with had a KR that he installed and said it made a difference. He was a retired Mechanical Engineer from Sundstrand and had a passion for engineering, motorcycles and screwing around and trying things.
 
Dances with Shrapnel said:
Dances with Shrapnel said:
The only other constraints are sonic choke and time available to do it. What you have going for you is harmonic tuning.
Click to expand...

Further to the comment on classic harmonic tuning there is the application of the Helmholtz resonator which in essence retimes and maybe better stated rearranges what happens and when during an intake induction.

If I recall correctly the parameters include:
resonator box volume,
cylinder swept volume,
intake tract length,
intake tract volume,
resonator box intake tract length and
resonator box intake tract volume.

I always wanted the time and a test bed bike and dyno to play around with this. A fellow I raced with had a KR that he installed and said it made a difference. He was a retired Mechanical Engineer from Sundstrand and had a passion for engineering, motorcycles and screwing around and trying things.
Click to expand...

Great idea I have thought about from time to time. I couldn't decide if I wanted to give up the seat, or the fuel tank to get a big enough box on a Norton. Not to say it can't be done. :D
 
Gosh JIm Schmidt that was a wonderful trip through your racer head, thanks for the enlightenment.

Oh yeah Dances good lead on resonators. I've come across those on twin 2 strokes connections between their intakes called a Power Booster Can. Here's more on the principles and math to ponder further. Variable chamber tuning is possible too.

http://www.dinamoto.it/dinamoto/8_on-li ... atore.html

Head flow testing.


A bit more info with formulas to plug in for ballpark resonance zones and complications.
http://www.team-integra.net/forum/blogs ... tions.html

Cans can also be applied to the exit end of flow.
Head flow testing.
 
comnoz said:
Great idea I have thought about from time to time. I couldn't decide if I wanted to give up the seat, or the fuel tank to get a big enough box on a Norton. Not to say it can't be done. :D
Click to expand...

No doubt would initially be an ugly thing but once you figured out the proper design for what you need it could be made neat.
 
Dances with Shrapnel said:
comnoz said:
Great idea I have thought about from time to time. I couldn't decide if I wanted to give up the seat, or the fuel tank to get a big enough box on a Norton. Not to say it can't be done. :D
Click to expand...

No doubt would initially be an ugly thing but once you figured out the proper design for what you need it could be made neat.
Click to expand...

I have played with it.

Head flow testing.
 
comnoz said:
Dances with Shrapnel said:
comnoz said:
Great idea I have thought about from time to time. I couldn't decide if I wanted to give up the seat, or the fuel tank to get a big enough box on a Norton. Not to say it can't be done. :D
Click to expand...

No doubt would initially be an ugly thing but once you figured out the proper design for what you need it could be made neat.
Click to expand...

I have played with it.

Head flow testing.
Click to expand...

No doubt from here I can see that the ports are too small :P Sorry but I had to get that in there.

Looks like an older picture. What was your take on it? Any dyno time to back it up? In quisitive minds want to know the practical experience
 
I does look strangely small in comparison to my hand.

I had that on a dual throttle body with fuel injection. As I recall I lost power at 5000 and gained a little at 6000. And it caused a strange surge around 2500 to 3000. I think it was too small but it was rapidly becoming difficult to get much more room in a Commando frame without moving or removing necessary items. I have also tried a couple other designs. I shelved it with the idea I would return to it later. Jim

PS, I am working on an engine mount and drive system to mount a Norton engine to the dyno without the bike. That will make trying things like that a lot easier.
Anybody have an extra or damaged primary belt drive drive laying around they want to sell cheap? I have the secondary drive finished but chain drive primaries scare me on the dyno.
 
comnoz said:
PS, I am working on an engine mount and drive system to mount a Norton engine to the dyno without the bike. That will make trying things like that a lot easier.
Anybody have an extra or damaged primary belt drive drive laying around they want to sell cheap? I have the secondary drive finished but chain drive primaries scare me on the dyno.
Click to expand...

Email me in a little more than a week as a reminder as I am away and in a bit of a fog. I will then go through my bin of "offerings to the gods of speed"; I may have some of what you need that is serviceable.
 
I have 2 40 mm RGM belts for the atlas/dommie sitting here, they are slightly longer than the commando ones.
 
swooshdave said:
Dances with Shrapnel said:
And why are we posting two strokes on a head flow testing thread?
Click to expand...

Because they are related. Both engine types suck, bang and blow.
Click to expand...


Related, like my ancestors might have been cave dwellers; yep, I got it :)

I am now going to round up a picture of a Sears shop vac. :D
 
Because its hobot who don't know better like yo'all but see online its also applicable to 4 strokes, so a tad smarter than I was prior. They say boost bottles mainly help the low-mid range but also can help top measurably if not hardly noticeably. Brags of easier starts and noticeable smoother running. My simpleton view of port flow is holding me mouth in a 0 and panting hard as I can in/out or doing Omm's chant.
Seeing the highest 'amperage' flow heads don't really shine till on cam near peak rpm, so filling in area under that curve is worth dreaming about. When it worked for me I rode on the prop flying the hull and rear tire floating front, gotta get more of that somehow.

[video]http://www.youtube.com/watch?v=j8eA0kDM0YY[/video]

[video]http://www.youtube.com/watch?feature=endscreen&NR=1&v=y80MOk3IpSs[/video]
 
Back to vortex generators on bluff bodies like cylinders or spheres or guides. Maybe a couple of grooves, saw teeth or wires, vertically on either side of the guide, like they do wings just before their peak. Smoke stacks use a spiral of these to give wind a spin off way or another. Also VG's in floor run of short radius side. Compromise of VG's drag of more flow earlier or later. Boundry lay is pretty thin in ports so tiny scratches might work a few more cfm's.

http://www.princeton.edu/~asmits/Bicycle_web/blunt.html
Head flow testing.
 
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