engine calculator

[got2dv8]

Here is a simple Excel/Works spreadsheet with some useful calculations for engine configuration. I would like to add more such as Exhaust Valve to Header Pipe Ratio but I don't know how to figure out the circumference of the exhaust valve open area. If anyone knows, please let me know how.

Robert

[sb955i]

"I would like to add more such as Exhaust Valve to Header Pipe Ratio but I don't know how to figure out the circumference of the exhaust valve open area. If anyone knows, please let me know how."

Correct me if i'm wrong, but I believe the issue here is getting a comparable single valve area equalling the two similar valves? Then comparing header cross section against valve area to get a ratio ( I'm not a mechanic )?

If that's the issue, then:

1. Twovalvearea = 2 * pi * ( valveradius)^2 .. "2 *" assumes both exhaust valves are equal.

2. Solve for comparable radius of a 'like" single valve
= singlevalveradius = (sqroot ( Twovalvearea ))/pi

3. ratio = ValveArea / HeaderArea
= (pi * singlevalveradius^2) / (pi * headerradius^2)
= singlevalveradius^2 / headerradius^2

4. Directly.

ratio = [((sqroot(2 * pi * valveradius^2))/pi)^2 ] / [ headerradius^2]

Closer? Probably need to reduce valve area by some factor due to stem, guide and web interference? .... or i could be completely out in left field?!

[griff851]

The ratio for valve to exh header is a little more complicated than what you are suggesting unfortunately, as the area of importance is actually the skirt created by the valve being open to the valve seat. ie a cylinder. This is also even more involved as your valve lift and timing comes into play. Not to mention valve seat angles.
After reading some stuff somewhere, exh valve increases do not have as a dramatic effect on power as Inlets. The percentages were so small that in a lot of cases its just not worth the cost/effort.


πr² is area of a circle for reference. 2πr is circumference.

[sb955i]

Thanks for the clarification... i knew i was sticking my neck out, but i lack the gene to prevent these episodes !

[griff851]

The whole world runs on people sticking their necks out, then needing band aids. Part of the human spirit I feel, but the part that helps us move forward.

Had a small episode myself today.

Griff

[ducatiparts.110mb]

being picky here, but its valve throat area, not valve head area that matters