Header geometry
 

To those of you with NA and / or supercharging experience, not necessarily on rotaries . . .

What is the advantage of having a header pipe travel straight off an exhaust port for a few inches before making a bend?

Is there any potential power gain involved in cutting a Racing Beat header and splicing in some 3" straight pipes between the port flange and first bends?

TIA

You need to see it on a flowbench to understand. By having the air turn immediately after it leaves the engine, flow is disrupted which creates turbulence. However this turbulence actually is in the engine port opening itself. It sounds a little strange that it works this way but Paul Yaw discovered this on his flowbench. By running the exhaust for at least 3" out of the engine, this turbulence was gone and more flow was achieved. Neat little trick.

Thanks. I'm probably going to attempt to splice in some 3" straight tubes off the flange of my header the next time I have it off. The only challenge will be bending the rest of the header to line back up with the rear half of the exhaust system and clear the transmission tunnel.

Most people will tell you 3" is overkill.


-Ted

I thought a diameter and half after a change in section was pretty much standard to allow the flow settle down again. so 3" sounds about right

Ah, I'd heard the rule, but never really bothered to understand it and now I do. Makes perfect sense.

Thanks
Chris

Oops, I thought he meant 3" ID pipe.
I read it wrong - mah bad. :(


-Ted