"D" shaped header downtubes?

[Mark Harrop]

I saw an ad for Akropovic headers that have a "D" shape at the first bend that comes out of the head. It looks similar to what an intake port looks like when they flatten the short side radius (I think?)

Is this a gimmick or are they on to something here?

If you have talked about this alrteady, I wasn't paying attention, sorry :wink:

 

[Anonymous]

Is this a gimmick or are they on to something here?

No gimmick, a D shaped port flows better around tight radius corners. It's advantages show more in the intake with the wet flow, rather than the dry flow of the exhaust, but it is better either way. The main reason it is not used much in headers is the fabrication difficulties it causes. The shape is difficult and expensive to produce in a production environment. Most headers and pipes are sold on the basis of sound, looks and weight reduction, not higher performance. So the manufacturers avoid expensive techniques like this. Most aftermarket pipes don't even have equal header tube lengths, let alone a sophisticated tube shape like this. Akrapovic have a good reputation for designing pipes that actually work better and make more power, which would explain them trying it out.


Mark