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 Post subject: Catching a Wave?
PostPosted: Mon Nov 06, 2017 10:05 pm 
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Joined: Fri May 08, 2009 1:13 pm
Posts: 1998
Current ride: XB9SX
Having said that I was happy with my current exhaust insert (see earlier Venturi 2 thread), I started to question what had transpired, and how to take things to another level………..or back to where they should be!

‘V2’ as I shall now refer to, was producing a pleasing sense of ‘get you there’ urgency at all revs and at only part throttle. It’s as if the combustion process was constantly being ‘advanced’ in some way. There was a sweet spot between 3600 and 4200 or so and as you rode through this region of midrange (in spite of a healthy engine pick up) the exhaust note became a subdued thrumming. A bit like taking a freshly run in Honda above 5-6000 rpm for the first time……..NICE……. :hehe: , but absent was the bad ass ‘BOOM’ we know and love in our Evo-X motor Buells. This alone suggests to me that the pressure wave, or wave pulse within the exhaust had shifted one way or another. Above 4200 and going open loop, the motor pulled harder and harder as you wound open the throttle to an addictive sort of beat from each power pulse, but there was no escaping the fact it all felt a bit ‘metered’. :|

In the above scenario the V2 sleeve insert when measured at regular internal diameters through its 62mm length from entry to exit was; 46 – 43 – 43 – 44.5 – 46mm. That’s a regular sided inlet cone, a parallel choke and a regular sided shallow angled exit cone. What I thought was needed was to open out the rear of the 43mm choke to increase the low pressure area in the exit. I decided on something nearer 46 – 43 – 43.5 – 45 – 46mm. This makes the exit cone more ‘bell shaped’ with greater volume (flared), but it is still an incredibly subtle change.

30 minutes later with an abrasive flap wheel and you would be hard pressed to see the difference, but by drawing the tube walls between a pinched finger and thumb you can definitely feel the shape. Once installed and after the magic 26.4 mile warm up, after which I can only guess that the air temp sender is nicely cooked, I was able to see the differences.

I was initially worried that I had opened things out too far and would throw away all that low rpm part throttle advantage, but nothing of the sort. The most important change was that the Buell’s characteristic ‘boom’ was back! It seems to combine all the power pulses into one homogeneous sound as if each exhaust pulse is complementing the other (in tune?). Whatever, the power surge when overtaking was more instant or explosive. It reminded me of watching and hearing the boom of a 6.5 litre V8 McLaren M6B blitzing the Silverstone Club circuit when I was a lad. That sort of thing stays with you, and maybe that’s why I love Buells. :worthy:

I can only conclude that I had caught the 'wave' again! 8-) I was also starting to become concerned about directional stability as I passed cars winding it on in the oncoming lane. Maybe the tyres were under inflated, or maybe I am just getting old and infirm? lOl


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 Post subject: Re: Catching a Wave?
PostPosted: Mon Nov 06, 2017 10:29 pm 
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Joined: Wed May 06, 2009 6:54 pm
Posts: 1339
Current ride: Hypermotard 1100S
Location: West Lothian, Bonnie Scotland
Nice :D

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 Post subject: Re: Catching a Wave?
PostPosted: Tue Nov 07, 2017 10:02 am 
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Joined: Mon Nov 07, 2011 7:10 pm
Posts: 1873
Current ride: Buell ulysses
Location: Telford
:worthy:
Surprising the subtle difference to tuned lengths or diameter, have on an engines performance and sound
Have or did the AFV values change once you are on the wave or fall off it?

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 Post subject: Re: Catching a Wave?
PostPosted: Tue Nov 07, 2017 11:07 am 
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Joined: Tue May 05, 2009 8:00 pm
Posts: 8123
Current ride: Buell X1 2001
Location: southampton
why don't you speak to Albert666 (Alan) , who is APH exhaust
as your long search seems like the exhaust equivalent of alchemy :?:

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Obey the principles without being bound by them.
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 Post subject: Re: Catching a Wave?
PostPosted: Fri Nov 10, 2017 4:24 pm 
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Joined: Fri May 08, 2009 1:13 pm
Posts: 1998
Current ride: XB9SX
Thanks for the positive responses. As for AFV....don't ask me as I wouldn't know! lOl But seriously the V2 configuration did seem to get 'warm' (fan always on) and bothered in terms of fuelling in town, even with the additional 28 sq. in heat dispersing area to the oil cooler (maybe that only works out of town at speed?). Won't know until I get stuck in Bristol traffic again. :?
And yes I have spoken to Alan, but he quoted many variables, or is keeping the secrets of his trade close to his chest? Maybe when I am satisfied with a shape and fully understand it, I can commission a complete new header from him! ;)


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 Post subject: Re: Catching a Wave?
PostPosted: Fri Nov 10, 2017 4:39 pm 
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Joined: Tue May 05, 2009 8:00 pm
Posts: 8123
Current ride: Buell X1 2001
Location: southampton
...or you could buy one from him, & study it
learning from the top of the tree , is better than scratching around in the dirt :yup:

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Obey the principles without being bound by them.
Bruce Lee


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