japanese headers

[firehawk]

oldeskewltoy Wrote:Hmmmmmm does anyone else see the Martelius 4/2/1 does NOT alternate on the primaries??? 1-3-4-2 shouldn't pipes 1 and 4 be grouped together and and 3 and 2 grouped together???? That way the pulses are even when they arrive at the next joint.

Quite interesting - I hadn't noticed that before.

Grouping cylinders only 180 degrees apart like on the Martelius header is going to move up the RPM range at which the scavenging effect of the exhaust pulses creates a benefit. So the pulse from #2 is going to scavenge exhaust from #1 and #3 from #4 - the engine just needs to run at a high enough RPM for the effect to occur. The long secondaries are probably tuned so that the pulses from #1/#2 and #3/#4 interlace to create a scavenging effect to #2 and #3.

Designing exhaust headers is really a strange artform and I'm not very very good at understanding how it all works but I'd imagine that the Martelius header works similarly to a 4-1 (peak power at quite high RPM) but with the additional benefit of an extended torque range of a 4-2-1 design.