Simple Q, simple A. Which of these 3 runners (just 2 lengths of pipe joined at the flange... think of them like manifolds, or exhaust pipe) would flow the best (note, air flows to the right)?



Feel free to be as discriptive as you want, but multiple simple answers will do.

 

id say the last one, as there is no change at all in the pipe, assuming there is no lip there, and it is nice and smooth between the two pipes

 

id say 2 because i dont think any exhaust is going to exacly match up (#3)there will be overlap. 2 would have like no overlap and its angled not sharp. And #1 has a sharp drop off which would mess with the airflow.

 

All things being equal (which they rarely are) I would say # 3, no turbulence created by opening up or closing down.

 

Far right is the best. The runner is smooth and uninterrupted assuming all else around it is ideal (smooth flat level flange surface and perfect alignment).

If you want to use materials, you could also use mild steel mandrel bent j-bends and u-bends. These bends have one end that is the smaller to serve as sleeves for connecting bends and welding it. It's great for DIY projects.

J

 

Is this a trick question?
I've actually read a book that says #1 is more desireable. But it was mainly dealing with piston engines. Intake and exhaust ports with mismatched openings, like in #1, are for anti-reversion, keeping the airflow from changing direction. The shape was a little different though. Cut a radius into that flat face and it would do a better job.
I would think that flow reversion is less of a problem with a rotary since the time that the intake/exhaust runner is completely closed to air coming in/out of the engine is very small compared to a 4 stroke piston engine with valves.
Did I get it right? What do I win? :p

 

#1 is not better than #3, but #3 looks impossible. #2 will cause a lot of turbulance.

 

number 2

 

Too vague of a question...

Is this intake or exhaust?&nbsp Cooler intake charges behave slightly differently than hot, expanding exhaust gases...

Is this for NA or forced induction?&nbsp Turbulence affects NA applications more than forced induction applications...

In general, you want less turbulence.


-Ted

 

More N/A intake than anything else.

 

Since intake charges go both directions after the surge tank in NA engines, # 3 would probably perform best as it gives no possibility to create any drag, other than parasite drag of the air past the inside walls of the runner. Even with exhaust there are reversing pressure waves that can be tuned so I would not see any advantage to # 1 or 2 unless a restrictive exhaust was used, where gas reversion would be very bad for exhaust port temps.