Exhaust design theory discusion.

[fasterstill]

If equal length primary pipes are worked out to a be 30" to give max torque at 3000rpm would it make a difference if instead of one pipe per cylinder i used one pipe per exhaust port which on this lump being 4 valves per cylinder would give me two pipes per cylinder.

Note: base replys on volume of primary pipes being equal whether single and double.

 

[BrianPetersen]

The airflow only cares about the cross-sectional area. Two pipes per cylinder with the same cross-sectional area as a normal single bigger one will work almost the same. Wall friction losses are theoretically a little higher with two smaller pipes, but it is insignificant in this application. Heat loss to the pipes will be greater (more surface area), and this might have more significance.

Not too many engines have entirely separate exhaust ports for each valve from the same cylinder.

 

[fasterstill]

Thats what i was thinking.
Looking at having the internal surfaces ceramic coated to help with the heat loss.
The two pipes per cylinder idea is because im fighting very tight confinds and the larger diameter pipes would need a transition length from an ovel, re the twin exhaust ports per cylinder to the round profile before the radius can be formed. That adds up to to much distance from the head face to the engine bay bullkhead.
One other thougth re the twin pipes per cylinder and tuned lengths. If the two pipes from the cylinders were aranged in say one at 30" and one at 20" and this was done across all cylinders would the effect be to spread the tuned point all beit to a smaller level or to cancell it out.
Please discuss...

 

[Fabrico]

A majority of high performance single cylinder motorcycle engines have separate ports and separate head pipes. These often converge into a single pipe about midway between the cylinder head and muffler.

 

[fasterstill]

Interesting.....Any ideas on the theory behind that one?

 

[BrianPetersen]

Mostly space and layout, sometimes appearance. I wouldn't say a "majority" of MODERN single cylinder designs are like that.