From what i can gather,with my bike as pretty much standard,it looks like i am better off making the system in 45's rather than 50's.keeping the 50mm silencers of course.As i am looking at doing the work,the only cost will be the tube,maybe get some flanges plus my labour.How does the nest of vipers differ from the spaghetti system?Do you have any pics please.As many as possible!!
Indeed, the motor needs to be built (cams and head flowed, larger valves) and tuned to take advantage of 45-50mm systems, otherwise you'll actually loose power by using 45--50mm tubes on a standard motor in standard tune. It's best use 40mm tubes (o.e.m. Farne or spaghetti) on standard motor.
But do understand that the SP2, SP3 and SP4 have heathy cams, larger valves and motor state of tune to use 45mm headers, which is what they come with, either the original "Farne" style or slightly better spasghetti style.
Then we have the SP4S (SPS) and SP5 motors that can easily use 45mm and 50mm headers because they are at a high degree of tune (91 Corse' spec motor) to utilize these large diameters.
Imho.......the SPS/SP5 motors the 45mm headers will give less peak hp with more overall torque, whereas the 50mm headers will give more peak hp with less overall torque.
Therefore, I think the best exhaust for the SPS/SP5 is the 45mm Termignoni spaghetti system with Termi cans.
I fancy some of the spaghetti headers myself,came across a bloke who works for the car makers in Crewe in the R&D department,reckons welding pipes together to fit no problem,wether it would be more than just good to look at,another story.Some of the money mentioned in regard to "performance" exhausts is mind blowing,Termi cans £450+vat for what?,it takes time and money to develop,design and build a "road" silencer with intricate baffling that performs well and meets noise regs.A "performance"can is a tube,with a perforated pipe inside wrapped in wadding,a different world to genuine race pipes that are developed constantly to changing engine specs.Arrow who know a bit about exhausts took a different route
Had my exhaust modified today to connect the SP silencers,by JP Exhausts in Macclesfield.Cant praise these people enough for the service,workmanship and price.They will make any system you want either from a pattern or built to the bike,spaghetti system if you show them what you want.The quality far exceeds any of the usual "performance" systems from Italy and none of the ridiculous prices.