Wow..
Had to do some cleaning up on the spreadsheets.
Been a minute. Nothing like having to redo someting 3 times.
oh well... Let's finally get them out!
First thing we should understand before looking at the charts would be what is in control of the port and when.
There are 2 different zones that handle that, so we'll identify them and determine when that control is transferred.
The first zone would be the Valve/Seat/Throat combination and the second would be the port, specifically the CSA.
That point occurs when the Port reaches Saturation. This is where the Valve Curtain Area is equal to the Port CSA.
This is important as it would be counterproductive to try correcting a problem or find gains working the wrong area.
I have attached the formulas needed to identify the Port Saturtion Point.
First we must find the Valve Curtain Area as it is an element of the Saturation Formula.
I won't repeat the formulas here as the attachment is self explanatory with the relevant values already provided and calculated.
Suffice it to say that with this combination (and typically most xs650 heads) Port Saturation occurs at .271 lift.
So basically the port itself only control a bit more than 0.10 of the 0.40 lift, around 25%. Obviously the highest flow rates.
However the valve (I'll simply use the term valve but it includes seat and throat) controls around 75%, all of which is under the curve.
This is one of the major overlooked aspects when people think about porting.
Keep this in mind as we review our data..
First thing to look at is the Gold box at the top right of each port labeled CSA.
1.36 and 1.34 right to left as we identified previously. I split the difference in the formula above to 1.35.
Next observe the light blue shaded area representing the low lift points that fall under control of the valve.
You will see a larger than acceptable variance at 0.10 ( more than 13%) and nearly 7% at 0.20.
This is NOT related to the Port Work. It is Valve related.
As seen in the "Arrival" video when I unpackaged the head the valves and springs were installed.
When I ran these tests I had yet to actually even see them, In a conversation with gggGary,
once I made mention of this issure, he explained some of the valve work he had done
and told me that I would find the valves were not the same. The testing had already pointed this out.
This is an example of why it is important to understand what the data is telling you as opposed to just collecting it.
Obviously once I removed the valves for other testing as well as looking more closely at the seat areas it
was clear what gggGary was telling me. As you can see in the pic I tool of the valves the difference
is small, however the Left valve has a slightly sleeker and definitely smoother to the touch than the right valve.
That issue is echoed into the seat and although nothing was absolutely obvious at the throat
a simple mm in that critical spot can make a significant difference not unlike what we are seeing here.
There is more coming on this but for now let's nmove along to the rest of the test data.
At 0.30 lift we are right into the transfer zone where the to unmatched areas are battling a bit but seeing
improvement as the difference drops to 4%. So the valve work is at issue with this head.
Somethng that I think gggGary may have suspected, as he had a bit of a tussle working them I believe.
If I were working this kind of problem I would do more testing at the 0.05 increments within the Valve Control Zone,
but perhaps the key element here was testing the Pocket Port Aspect. Within the 0.10 controlled by the Port
you can see that the numbers fall into line. Right around 2% which is VERY good and close to being within the margin of error.
Moving on to the port work...
The green squares are the 0.10 increments highlighted, the uncolored 0.35 lift value is only there for a reference
and the 0.45 is simply testing to see if the Port is on the edge of choking or still pulling, It's still pulling..
The last key data point to pay attention to would be at the bottom of the pages..
The Port Efficiencynumber which sits right at the SAE street engine qualifier with a 106.57 and a 105.31 left to right.
That is just over a1% variance which is outstanding.
So wrapping this segment up...
We have a head that has Valve/Seat/Throat issue at the moment and a port that is looking quite good with respect to the volumetrics
we tested earlier (CCs Port Mapping) as well as moving air.
Hopefully you are starting to understand how to identify where issues are actually occuring so they can be addressed.
Also... This test alone should give an indication of how critical the valve/seat/throat area is and that although power can be made
in this area even without porting, it can just as easily be lost. We will see more examples that reinforce what is going on here as we proceed.
Velocity Test Results are on deck.. probably tomorrow evening as I have some busuness to attend to in the morning.
Hope I explained it well enough.. If not I'll try to answer questions.
