Pipe OD's on aftermarket road exhausts

[49er]

Out of curiosity, I have just measured up the two 4-1 exhausts on my bikes. The 850 (now 900) has 38mm OD headers 600mm long and so does the 1150. The collectors are identical length (125mm) but of differing design. The collector exits are identical diameter, but the tuned lengths and shapes vary markedly.
The 850 pipe is a Cycle Works slash pipe, the 1150 is a V&H unit.
The 1150 pipe is 120mm shorter, with a greater diameter for the exhaust bleader than the 850.
The reason that I did the comparison was that both systems run extremely well with relatively stock tuning parameters. I thought that the extra capacity of the 1150 may have required a larger cross section area to flow more efficiently! I'm not totally surprised though as each engine design requires a certain amount of back pressure to operate effectively across a broad power band.
Has anyone done dyno testing of stock 4-2 systems for these bikes against a good quality 4-1 ie, comparing power and torque at various rpm's. Having never run the stock pipes, I'm curious how they compare to a good 4-1. I guess the experience will only ever be as good as the tuner's ability! Still, I'm interested in your feedback.

 

[Silvermachine81]

Not many here will probably ever have heard about Cycleworks and I know they certainly dont rate as a performance aftermarket exhaust, But in saying that for most Kiwis they have been a good replacement pipe for when our stock pipe rots.
I have heard people mention the cut off pipe is not an ideal exhaust and is hard to tune but as long as it works at least as good as stock then who really cares.
And also most people will have biffed one on and left the jetting completely stock, then moaned about how the bike runs lean......
In summary, What you have to consider is that the Cycleworks was 'produced' to fill a need for a stock replacement with a rortier tone while the V&H was 'designed' to produce additional power ;-)

 

[49er]

Not many here will probably ever have heard about Cycleworks and I know they certainly dont rate as a performance aftermarket exhaust, But in saying that for most Kiwis they have been a good replacement pipe for when our stock pipe rots.
I have heard people mention the cut off pipe is not an ideal exhaust and is hard to tune but as long as it works at least as good as stock then who really cares.
And also most people will have biffed one on and left the jetting completely stock, then moaned about how the bike runs lean......
In summary, What you have to consider is that the Cycleworks was 'produced' to fill a need for a stock replacement with a rortier tone while the V&H was 'designed' to produce additional power ;-)

Thanks for filling in the gaps. It's obvious I don't know much about "designed" performance pipes!!