Author Topic: Shortened intake stack performance  (Read 556 times)

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RecoilRob

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Reply #15 on: May 14, 2022, 10:12:45 am
What about removing the airbox completely and fitting pod filters.

Well....pods would get rid of the majority of the intake restrictions but also get rid of all the benefits of a properly sized intake tract.   Bottom end and midrange power would be compromised badly with the pods and the FI might be difficult to remap and get it to run anywhere near correctly.   In the SV world we've had many people go to pods with bad results and many have gone back to the airbox as it's the best system if done properly.   The intake at 11" (-2 on the stacks) gives us three resonant points around 3800, 5000 then again at 7000...which I'm feeling is a good spread and the engine is still tractable down to 2000 or so...makes for an excellent street engine powerband.


NVDucati

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Reply #16 on: May 14, 2022, 11:49:52 am
Harris used silicone hoses on their bike

Yes. Silicone tubing can be found in infinite sizes, flex, chemical resistance and shaping properties.
A quick search of the Thomas Register shows 227 makers.
https://www.thomasnet.com/nsearch.html?cov=NA&heading=88669700&typed_term=silicone+tubing&searchterm=silicone+tubing&what=Silicone+Tubing&WTZO=Find+Suppliers&searchsource=suppliers
I haven't done it so my comments are suspect but:
If I ever go through the trouble to get the airbox out, I will convert it to a two piece box for future access.
As for the intake tube shortening, I would think that a "baloney-cut" section removal rejoined by slipping the pieces into a short piece of silicone tube. I think with a scalpel (literally) the cut could be made in situ.
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Locknut

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Reply #17 on: May 14, 2022, 12:17:00 pm
++1  I've not ever experimented with a plenum for a 270 crank . . . .  but if we had a place for that filter other than the box  it would open up some options for those stacks.  I'd experiment with at least some separation / direction.  180 cranks / box tuning is a different world,  but at least we are dealing with a 7,000 rpm ceiling. 
You never seem to have the time to do it right,  but you'll ALWAYS have time to do it over.


Locknut

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Reply #18 on: May 14, 2022, 02:30:34 pm
RecoilRob, I turned the light on this time:  Ooooff,  we ARE really limited to that air filter-end entry,  as the box sits now.   As gross simple  as it is your moving the horn stack ends away from the wall is so far the ONLY thing we can do ,  other than that filter flow change you did.  Perhaps a side panel becoming a filter system and the box size, as it is, with horn changes to accommodate that 270 crank pulse.   
You never seem to have the time to do it right,  but you'll ALWAYS have time to do it over.


RecoilRob

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Reply #19 on: May 14, 2022, 03:00:22 pm
  Perhaps a side panel becoming a filter system and the box size, as it is, with horn changes to accommodate that 270 crank pulse.

With the size restrictions placed on the airbox...I'm thinking what we have now with a low restriction filter is about as good as it's going to get.   The box is up against the battery which is up against the rear fender, and under the battery the carbon can solenoid and piping so they were using all the available space to keep the dashing good looks of the bike.   I DO really like how the Interceptor looks...so am willing to put up with some difficulty in maintenance I guess.

Early on with a spare airbox I was looking at figuring out the resonant frequency it might have...and then realized that I don't know how to account for all the internal things like the stacks and there also is a breather/oil separator taking up quite a bit of space.   After test riding it and tinkering with the tune to accommodate the increased airflow there's more that's changed here than just letting it breathe easier with a little higher tuned resonant points. 

I'm now thinking that having the stacks so close to the back wall was giving a reflection boost to the reversion pulses and making them stronger than if they're created by encountering just the air within the box.  To me the low end torque always felt a little artificial in that I've never ridden a bike that runs like this.   The term 'agricultural' kept coming to my mind when trying to describe how it felt with stock cam because it was like a tractor.   This was a tractor you could spin to 7000 if you wanted...but it wasn't happy about it and would rather plod along much more slowly.   With the shorter stacks and S&S cam now it feels much like a hot cammed motor that still has good low end behavior but gets progressively stronger the higher it revs.   The throttle response is immediate yet smooth and gentle at first so finding maintenance throttle whilst cranking through a turn very easy then powering out with just as much power as you ask for...no surging or misbehavior.  :) 


NVDucati

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Reply #20 on: May 14, 2022, 03:29:02 pm
With the size restrictions placed on the airbox...I'm thinking what we have now with a low restriction filter is about as good as it's going to get.   The box is up against the battery which is up against the rear fender, and under the battery the carbon can solenoid and piping so they were using all the available space to keep the dashing good looks of the bike.   I DO really like how the Interceptor looks...so am willing to put up with some difficulty in maintenance I guess.
... SNIP...
The battery can be easily relocated. With a LITHO battery and a simple "project box", locate it under the rear fender or under the swingarm pivot. The custom bike crowd do that routinely. You would never see it and you can proceed with a longer airbox that has a "rear door".
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Locknut

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Reply #21 on: May 15, 2022, 04:56:55 pm
+++1 "You B so smart" . .  for  thinking  "out of the box". . . pun intended:
--->   Nothing says the tool pouch has to stay there either.  .    I have a mega size Slime bottle and three huge CO2 cartridges for my initial flat repair attempt stored at a low back rest/sissy bar, there  to keep my wife from ever sliding off.  That area can easily accommodate the OEM tools.  That opens up space for creative volume / custom box. . . . I've done it for small aircraft (mine) lol.  My BATTERY was in the tail, to manage weight & balance for a bigger engine.   This RE box thinking is micro, and should be EZ.  (Should and "will be  " are fantasies)  :o 

 Who the hell started this , anyway .. . >:( >:(
You never seem to have the time to do it right,  but you'll ALWAYS have time to do it over.