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Post by comstar on Aug 10, 2021 22:31:40 GMT
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Post by duffer on Aug 11, 2021 16:58:20 GMT
Damn it. I just finished welding that up !
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Post by bawbag on Aug 11, 2021 20:08:15 GMT
That’s must be a genuine one. I have a pattern one with zero guts.
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Post by richard on Aug 19, 2021 6:48:06 GMT
hello
how do the collector boxes work ?
the exhaust gases enter the box, swirl about a bit and disappear into the silencers..but why is it required on a standard bike ?
a 2 in 1 does away with the requirement of a collector box, so being technically thick and mildly nosy about such things...what would the effect of running each downpipe to its respective silencer without a collector box be ?
thanks
richard
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Post by johnfcbn44dx on Aug 19, 2021 10:31:44 GMT
hello how do the collector boxes work ? the exhaust gases enter the box, swirl about a bit and disappear into the silencers..but why is it required on a standard bike ? a 2 in 1 does away with the requirement of a collector box, so being technically thick and mildly nosy about such things...what would the effect of running each downpipe to its respective silencer without a collector box be ? thanks richard You would lose a bit of torque, the internal crossover pipes apparently simulates a longer exhaust length, which give a little more torque. I do believe this as my "NHK" 250NA came with a correct shape pattern collector (empty inside), and when I put a totally original system on except for pattern silencers, it did feel marginally better. I will try to always fit original down pipes and collector boxes to NHK 250 (and the other 250s cost permitting), but not so worried about fitting pattern collectors on the 400/450's (or even that straight through), the difference may not be so distinguishable, with their extra power. I'm quite happy with 36-38hp, so keen to keep the 250 power at least up to the std 27 horses, may even do a max + 1.0 over bore on one, if I thought it would give more torque (not on NHK though  ). |
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Post by buster on Aug 19, 2021 16:40:51 GMT
hello how do the collector boxes work ? the exhaust gases enter the box, swirl about a bit and disappear into the silencers..but why is it required on a standard bike ? a 2 in 1 does away with the requirement of a collector box, so being technically thick and mildly nosy about such things...what would the effect of running each downpipe to its respective silencer without a collector box be ? thanks richard its hard to understand (I cant properly explain it) but its a lot to do with balancing pressure waves, in a similar way to how the carbs are balanced the exhaust system seems to like that balance too. I'd love to have been a fly on the wall for the R&D of the collector box, I'd bet they built loads of them with all sorts of different internals before they hit on that design. it might be possible (I stress might) to get a bike set up to run 2 into 2 with no collector if you use slide carbs instead of the standard CV's but there will be a compromise in performance somewhere, probably an awkward flat spot. 2 into 1's are effectively an aftermarket compromise, both exhausts are still connected but the systems cheaper to manufacture. to get the best out of a 2 into 1 the headers would need to be the same length (have a look at a V&H drag pipe system to see the complication that causes) not to mention that any bends need to be smooth and uniform (mandrel bends are probably the way to go) |
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Post by richard on Aug 20, 2021 5:58:33 GMT
hello
thanks for the technical reply's, my collector box on inspection when i bought the 250n has been repaired [ welded ] in a couple of places, its not blowing anywhere, but i was quite interested after seeing one opened up !
thanks
richard
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Post by comstar on Aug 20, 2021 6:11:28 GMT
Any pics of your collector Richard?
I think we would all like to see it (where it has been repaired etc).
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Post by terryc on Aug 20, 2021 12:39:04 GMT
its hard to understand (I cant properly explain it) but its a lot to do with balancing pressure waves, in a similar way to how the carbs are balanced the exhaust system seems to like that balance too. I'd love to have been a fly on the wall for the R&D of the collector box, I'd bet they built loads of them with all sorts of different internals before they hit on that design. it might be possible (I stress might) to get a bike set up to run 2 into 2 with no collector if you use slide carbs instead of the standard CV's but there will be a compromise in performance somewhere, probably an awkward flat spot. 2 into 1's are effectively an aftermarket compromise, both exhausts are still connected but the systems cheaper to manufacture. to get the best out of a 2 into 1 the headers would need to be the same length (have a look at a V&H drag pipe system to see the complication that causes) not to mention that any bends need to be smooth and uniform (mandrel bends are probably the way to go) That being said buster ,what would happen if you blocked off the exit on one side of the collector and ran all the exhaust gasses out the other side into a single silencer ? you've got a 2into 1 system but you still have a collector box. Would it work or would you just confuse the gasses ? |
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Post by buster on Aug 20, 2021 14:16:25 GMT
its hard to understand (I cant properly explain it) but its a lot to do with balancing pressure waves, in a similar way to how the carbs are balanced the exhaust system seems to like that balance too. I'd love to have been a fly on the wall for the R&D of the collector box, I'd bet they built loads of them with all sorts of different internals before they hit on that design. it might be possible (I stress might) to get a bike set up to run 2 into 2 with no collector if you use slide carbs instead of the standard CV's but there will be a compromise in performance somewhere, probably an awkward flat spot. 2 into 1's are effectively an aftermarket compromise, both exhausts are still connected but the systems cheaper to manufacture. to get the best out of a 2 into 1 the headers would need to be the same length (have a look at a V&H drag pipe system to see the complication that causes) not to mention that any bends need to be smooth and uniform (mandrel bends are probably the way to go) That being said buster ,what would happen if you blocked off the exit on one side of the collector and ran all the exhaust gasses out the other side into a single silencer ? you've got a 2into 1 system but you still have a collector box. Would it work or would you just confuse the gasses ? it would be an interesting experiment terry, I'm wondering if it would find johns lost torque (250 model) with after market collector/downpipes/silencers? or might just pop and bang horribly on the overrun  |
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Post by johnfcbn44dx on Aug 20, 2021 23:02:09 GMT
I think the problem with using a single collector box rear outlet would be the gas flow paths of each cylinder would be different lengths. If I were getting a collector made up, without the press to form the shape of the original I would probably make cross over pipes out of 22mm stainless, feeding most of the exhaust gasses to the opposite side silencer, along with a single static pressure balance pipe (doubling as a securing bracket) between increased volume straight through sections (with M5 mounts for heat shields). Without the R&D Dept, hit or miss if it would be useful or not |
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Post by bawbag on Sept 11, 2021 20:15:41 GMT
Just found this snippet elsewhere on the web which may explain more: "It's been long established that the longer the primary exhaust pipes are the lower in the rpm range where power is produced. Shorter pipes produce more high rpm power. It seems Honda wanted to have the best of both worlds, real good low rpm and high rpm at the same time. Normally you get to choose one or the other. Good high rpm power while sacrificing low rpm power. Or you can split the difference and get good mid range rpm power and sacrifice less of the high/low power. In the picture you can see the Red inlet gas path emptying into the chamber and exiting thru the Green outlets. Honda in their design has added a number of holes in the curved section (Orange) that allow high pressure/rpm gasses to travel straight thru. The gasses under low rpm/pressure will follow the curvature of the pipe which extends the pipe length for low rpm power but when the pressure rises some/most of the gasses will go straight through which gives high rpm power. Honda apparently went through 23 different versions of this before settling on the design. The internal pipes change sizes also at different points. The Power Chamber also serves as a balance/crossover tube, like the ones you see on older Brit bikes. Those tubes tend to balance the exhaust pressures between pipes resulting in smoother power. For more information concerning exhaust systems pickup a copy of Scientific Design of Intake and Exhaust Systems, written in the 60's and still used as a reference by engineers."  
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Post by richard on Sept 12, 2021 10:38:13 GMT
Any pics of your collector Richard? I think we would all like to see it (where it has been repaired etc). hello
sorry, i didnt notice your post..
this is a quick picture of the welded section on my collector box, plus it would seem that their has been a socket welded onto the oil filter nut..oh well, something else to investigate..
thanks richard
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Post by johnfcbn44dx on Sept 12, 2021 11:53:05 GMT
This subject makes me think I want to attempt to make a DIY collector box at some some point in the future |
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Post by buster on Sept 12, 2021 12:25:23 GMT
This subject makes me think I want to attempt to make a DIY collector box at some some point in the future a similar thought has crossed my mind, would you start with a pattern collector and add the internals? |
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