4-2-1 Exhaust Questions for you gurus out there...

[TxGSrider]

I have some dumb questions concerning 4-2-1 headers.

I've got a set on my bike (Gs1100ez) that connects cylinders 1&2 together and 3&4 together. I also have a set in my garage that I believe were made by Micron that instead connect cylinders 1&4 and 2&3 together. Ive looked at others on Ebay and Google and see that there are others made both ways.

So my questions are, why do they gang them together differently (I mean 1&2 and 3&4 are allot simpler and give more ground clearance, so why make them the other way unless theres some tuning advantage, right?), and what may be the advantages of them? Does one favor low rpm power ("torque") does one tend to produce more high rpm power ("horsepower")?

 

[GregT]

Sets with 1&2 and 3&4 grouped are IMO simply for convenience of fitting. Sets with 1&4 and 2&3 grouped are correct for a normal four cylinder motor.
The 1&4 pair for instance form a 360 degree crank twin, firing alternately. Joined exhausts will provide a power boost.

A 4-2-1 exhaust is another degree of complex as there are secondary resonances coming into play. Done correctly with the 1-4 and 2-3 headers paired then a short secondary for each pair before joining into a single tailpipe will give the widest power band. But it's a lot more complex than a simple 4-1....