ptuomov wrote: ↑Wed Oct 05, 2022 7:05 pm
LotusElise wrote: ↑Wed Oct 05, 2022 3:49 pm
ptuomov wrote: ↑Wed Oct 05, 2022 12:15 pm
Why not put in the biggest intake valves that fit and aren’t shrouded and then keep the port small at valve guides?
The biggest unshrouded would be around 33 mm at intake and around 28 mm at exhaust. That 4-valve head has shrouded areas already from OEM status on. May we define how much shrouding still improves flow to find the optimum for the application? I assume this is very engine and application specific
.
The stock 35mm valves are pretty big, but I think others have installed 36mm or even 37mm intake valves in those heads.
I agree that the valves never be completely unshrouded, just the flow from the second intake valve alone guides the flow from the valve.
In my humble opinion, the larger valves in freely shaped ports allow for a larger fraction of the flow to be directed on the side of the valve head that promotes tumble.
I don’t see any meaningful penalty from larger valves in terms of combustion quality, as the larger valve reliefs can presumably be made smaller at the same flow rates.
I remembered another example of a historic Renault engine...
https://www.youtube.com/watch?v=UU9lBxQaJrs
Group N and A Homologations dated 1991:
https://historicdb.fia.com/sites/defaul ... roup_n.pdf
https://historicdb.fia.com/sites/defaul ... roup_a.pdf
Highlights from papers dated 1991:
Cylinder capacity: 440,96cm3
Total: 1764cm3
Bore: 82mm
Total minimum volume of combustion chamber: 48,7cm3
Minimum volume of a combustion chamber in the cylinder head:
43,39cm3
Maximum diameter of the inlet valves: 30,9mm
Cylinder head inlet ports, manifold side:
1595,44mm2
I have also found some Renault cylinder head flow data from Stan Weiss site, but here is a calculus regarding "hole process":
F7P harmonics.png
FHD0024.JPG
-juhana
You do not have the required permissions to view the files attached to this post.