Head flow testing.

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WZ507
As is so often the case, thank you for allowing us to see what we always see but think what some of us (me) have never thought. With respect to your comments about the fifth lift point (valve lift = 25% of the valve seat ID which you referred to as the “LD value”), you mention that for all the CDO cams you have data for, all but one provide LD flow potential of ~ 30%, does this include the stock CDO cam. I ask because just eyeballing the lift curve of a stock cam makes this observer think the LD flow potential would be far below 30%. In arriving at this conclusion I was thinking the valve seat ID might be ~ 1.40” and the LD lift point would therefore be 0.350” (1.40 * 0.25 = 0.350”) as I looked over the lift curve. Are these values reasonable datums for examining stock and other lift curves?
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The valve seat inner diameter that I used for my calculations was 1.405". 25% of this diameter added to the tappet setting is the valve lift that determines the LD value.
I have now been able to examine the stock Commando cam, and find the LD value is 12.9% pretty low as you so rightly assumed.

What would an optimum LD value be for the standard intake valve ? It's really a case of swings and roundabouts (now Jim has told you the meaning).
Assuming high performance is the aim, an increase in valve diameter autamatically increases the area of the valve curtain at any given lift point, while adding extra valve lift for a stock valve increases the stress levels within the valve train. A bit of both might be the obvious way to proceed.

Out in the big wide world there are now 2 valve high performance engines with LD values at the 50% mark and more, while some high performance 4 valve engines are at 45% and more, but in this latter instance, the two intake valves magnify the end effect somewhat.
I haven't come across any Commando cams that give 0.5" lift at the valve as yet, but I'm sure someone somewhere had tried.
 
Just unpacked my head, having received it back from Jim.

Wow!

Looks better than new, inside and out. I don't know exactly what process Jim uses to clean up the casting (perhaps you can clarify Jim?) but it looks awesome.

Really keen to get it nailed back on and tested now.

I also have a brand new Maney lightweight crank sitting on the bench that also looks stunning. After great deliberation, I am going to RESIST fitting it this time in order to dyno test the head mods in isolation on the dyno. I hope you boys appreciate the sacrifice I am making here in the name of Norton Science...?!?

Y'all have to be patient though... I'm in Japan for a month...

Sayōnara !
 
Fast Eddie said:
Just unpacked my head, having received it back from Jim.

Wow!

Looks better than new, inside and out. I don't know exactly what process Jim uses to clean up the casting (perhaps you can clarify Jim?) but it looks awesome.
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I use a vibratory mill with ceramic beads to peen the surfaces. Jim
 
Here is the next shortstroke project cylinder head. Too many hours in this one.
A Fullauto head with 44 mm intake valves and 36mm exhaust valves for an 83 mm bore.

Head flow testing.


Here is the initial flow test. The bowl is finished and I am working on establishing the correct choke size in the port [the cross sectional area of the smallest part of the port]. This is with the original port size.

[video]https://www.youtube.com/watch?v=KQF9yS7snbY[/video]

Here is the resulting graph. You can only move air so fast. The white line is a 41mm big valve head and the blue line is the 44mm job. Starts out good...

Head flow testing.
 
Here is what I ended up with after removing a surprisingly small amount of material. No more earsplitting roar.

Head flow testing.


Head flow testing.
 
Wow Jim! For an velocity!
You must soon reach the limit of what is possible with a Fullauto head! You taught me what a high air velocity means in practice. My short stroke with head from you preform very well! Can not wait to see the power figures on your new short stroke project.
Good luck Jim!
 
+1. Good article. I've been saving the tech articles from the engine builder site for a while now, and they have published some really good stuff. I particularly liked their articles on piston technology. If you're interested in the tech stuff, it's worth browsing their site for other interesting articles.

Ken
 
comnoz said:
Here is the resulting graph. You can only move air so fast. The white line is a 41mm big valve head and the blue line is the 44mm job. Starts out good...

Head flow testing.
Click to expand...

Did you mix up the white line and the blue line designations in this picture? It looks like the blue line plateaus as you would expect from a relatively higher lift/diameter ratio,...or is the 44mm choking elsewhere?
 
Dances with Shrapnel said:
comnoz said:
Here is the resulting graph. You can only move air so fast. The white line is a 41mm big valve head and the blue line is the 44mm job. Starts out good...

Head flow testing.
Click to expand...

Did you mix up the white line and the blue line designations in this picture? It looks like the blue line plateaus as you would expect from a relatively higher lift/diameter ratio,...or is the 44mm choking elsewhere?
Click to expand...

Yep it was choking, air was lifting off the floor of the port.
 
I finally got the new CNC ported Fullauto head on the flowbench.
I tested it back to back with a new non-CNC ported head.

Here is the non-cnc head.

Head flow testing.


Here is the CNC ported head -still set up.

Head flow testing.


Here is the flow graph.

The blue line is the CNC ported head. The green line is the non-cnc head.

Head flow testing.


Here is the velocity graph.

NOTE- I found some inconsistencies in the first velocity test that I traced back to a loose fitting on my flow tube. The test has been repeated and now the results show there is little if any difference between the CNC ported head and the non-CNC ported head.

The blue line is the CNC ported head. The green line is the non-cnc head.

Head flow testing.
 
gortnipper said:
Wow, that is like a 10% drop in velocity for the same volume. Whats up?
Click to expand...

After finding a problem with my measuring tube I redid the test and now the velocity reading are almost the same between the cnc and non cnc head.

With a little larger valve and some work in the seat area it should show a good improvement, both flow and velocity.
 
So now that I identified a problem with my prior velocity readings and corrected them -here is the flow tests with the 1.5mm oversize intake and a little work in the valve guide and bowl area.

Nice improvement for a steetbike running a .400 lift cam.

Flow
Head flow testing.


Velocity
Head flow testing.
 
Fullauto said:
You really know how to give a guy gray hairs, don't you Jim??!!
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It had me going for a bit.

I did the velocity tests twice before I posted.

After sleeping on it last night I got out the calipers and did some measuring and found that there was not enough difference in size to cause that large a drop so I got out the bench calibration tubes.

I found out all I had to do was wiggle the hoses and the reading changed dramatically. A rubber sealing ring on one of the fittings had shrunk enough to make the fitting loose.
 
gortnipper said:
Fullauto said:
You really know how to give a guy gray hairs, don't you Jim??!!
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+1 as I am guessing this is my head.
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Yes. But it's all good now. [except for the new bent valve that KW is express sending me a replacement for]
 
Does'nt a bent valve give better flow? Something about airflow around a curve rather than in a straight line? I dunno. You're the expert!
 
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