VVC Inlet port models- Std and modified

In what has become an odyssey, I have been gradually building CAD models of the various flow components of the cylinder head.



Previously I showed some port cutaways;

Inlet: http://ift.tt/1HNSjjo

Outlet: http://ift.tt/1x8DlmB



These photos shows the differences between a standard VVC inlet port and one that has been modified on a head i'm currently working on.



There is not particular point to this, just comparison photos to help visualise the air in an inlet port, while I ready the good stuff.



People versed in port modification will clearly spot that it is by no means heavily modified; maybe a 75% job?

A lot more material could come out of the valve guide boss 'hump', although (and it's not clear from the photos) the idea was to try to create a soft transition from the long side radius wall to the valve guide, which was shaped to guide around the valve stem.

The head is a demonstrator for something else, so that's as far as that modification will go.



You can see a remnant of a casting line on the modified port - the head had pretty bad casting misalignment and I didn't want to chase it too far, and this is why i'm not putting a lot of work into the head.



The photos are back to back and there are notes at the end of the post.



Std port, as cast:



Modified port:







Std:



Mod:





Std:



Mod:





Std:



Mod:





Std:



Mod:







Std:



Mod:







Std:



Mod:





A back to back shot showing the dip around the valve guide boss in the standard port flattening the long side radius around the valve protrusion. The modified port shows that material removed to improve the flow around the hump but, as mentioned above, there is more that could be done there if one was going to continue with the head. The inside wall (where the bifurcation is, the centreline) is much better in that respect.





And what a half port to 1 valve looks like:







The main items to note are:

The misalignment of the valve seats to the ports is much improved - always a winning modification.



The surface roughness is significantly decreased - also a winning modification. People often scoff and say they want (my favourite internet engine quote here) 'a nice bit of turbulence' and so claim the port should be rough. I've not found a port fuel injected engine that performs better with a cast surface.



The amount of flow disturbing features and size of them has been reduced; the valve guide bosses and the bowl has been reshaped to make the radius a bit more coherent.





If that's all you could manage to do to a head you would be happy with the results.

Then you'd want more.

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