Home-made bellmouth
04-05-2009, 08:40 AM
#1
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Home-made bellmouth
Hi folks,
those who know me from this site know that I have a propensity to mod and try odd things. In doing research recently on the subject of airbox mods/air filters and the like, I ran across a post by a chap who noted that adding a bellmouth to a straight tube increases airflow significantly (seem to recall 30%). In fact, on need only look at aftermarket velocity stacks (such as the billet HPower stacks for the VTR, designed on a flowbench) to see that they virtually all make use of this feature to improve airflow. Anyone who has looked at the stock velocity stacks (a.k.a. intake runners, trumpets,...) know they make a half-*** attempt at best in this regard. As I wait on something promising (wink wink to Rick), my mind has been racing thinking about how to add a true bellmouth to my OEM runners but I came up with nothing of any value. That is, until I played with my 9 month-old daughter this morning.... You see, she has some hard (hollow) plastic rings (stack up on a tapered post, a kids toy)...it was a Eureka moment!!!!! My thoughts are that I will sacrifice one of her rings (already did a quick size test with a spare short runner I have sitting on a shelf, will be good to go), slice it in two and fasten it to the upper end of the runner, thereby creating a true bellmouth. I will glue it on so I can remove it later (or cut it off). It may not yield any improvement but, then again, it may
Will keep you folks posted
P.S. he he
those who know me from this site know that I have a propensity to mod and try odd things. In doing research recently on the subject of airbox mods/air filters and the like, I ran across a post by a chap who noted that adding a bellmouth to a straight tube increases airflow significantly (seem to recall 30%). In fact, on need only look at aftermarket velocity stacks (such as the billet HPower stacks for the VTR, designed on a flowbench) to see that they virtually all make use of this feature to improve airflow. Anyone who has looked at the stock velocity stacks (a.k.a. intake runners, trumpets,...) know they make a half-*** attempt at best in this regard. As I wait on something promising (wink wink to Rick), my mind has been racing thinking about how to add a true bellmouth to my OEM runners but I came up with nothing of any value. That is, until I played with my 9 month-old daughter this morning.... You see, she has some hard (hollow) plastic rings (stack up on a tapered post, a kids toy)...it was a Eureka moment!!!!! My thoughts are that I will sacrifice one of her rings (already did a quick size test with a spare short runner I have sitting on a shelf, will be good to go), slice it in two and fasten it to the upper end of the runner, thereby creating a true bellmouth. I will glue it on so I can remove it later (or cut it off). It may not yield any improvement but, then again, it may
Will keep you folks posted
P.S. he he
Last edited by mikstr; 04-05-2009 at 08:42 AM.
04-05-2009, 08:47 AM
#2
I could ride in
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04-05-2009, 05:29 PM
#6
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another option?
check this link out (useful info too):
http://autospeed.com/A_110771/cms/article.html
check this link out (useful info too):
http://autospeed.com/A_110771/cms/article.html
04-06-2009, 07:15 PM
#8
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I have the HPower intake runners that you mention. One thing to remember when you are testing your designs, is that these will have an effect on your jetting. So you may try something that feels worse until you re-jet to suit. HPower advised me that their tests showed that with the improvement in airflow, that they were using considerably smaller main jets. My bike runs 170 mains. I have Moriwaki headers and Staintune mufflers with modified baffles (louder than stock Staintunes but quieter than open pipes) in them.
One of our forum members in Australia made his own, and they looked good. We think he moulded them out of PVC pipe, but we never found out how he did it. Unfortunatley he was killed in an accident shortly after.
One of our forum members in Australia made his own, and they looked good. We think he moulded them out of PVC pipe, but we never found out how he did it. Unfortunatley he was killed in an accident shortly after.
04-07-2009, 05:47 AM
#9
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thanks Shayne. I have a Flo-Commander so I can make jetting adjustments by turning the adjustment screw (or so I am told).
I am still waiting for the bike to come back from the shop (having this year`s round of goodies installed). I must admit that the HPower stacks would be the cat`s meow. Further to the link from LineArrayNut, the speaker ports look promising too...
I am still waiting for the bike to come back from the shop (having this year`s round of goodies installed). I must admit that the HPower stacks would be the cat`s meow. Further to the link from LineArrayNut, the speaker ports look promising too...
04-07-2009, 03:21 PM
#10
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Hey Mike I can give you a pair
I made some that I won't be using, they are made off aluminium, a bit on the rough side, they are both 2" high and fit the VTR carbs, if you come by Victoriaville I'll give them to you.
They could be bored to size, they are choking a little, probably 1.750" ID and the bellmouth 2,5"
I made some that I won't be using, they are made off aluminium, a bit on the rough side, they are both 2" high and fit the VTR carbs, if you come by Victoriaville I'll give them to you.
They could be bored to size, they are choking a little, probably 1.750" ID and the bellmouth 2,5"
Last edited by gboezio; 04-07-2009 at 03:33 PM.
04-08-2009, 02:27 AM
#13
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It is a long time since I read about the Flow Commander, but my recollection is that it is used to balance airflow between the carbs. What I am referring to is taking your mains out and going down about two sizes. Not sure whether your gizmo will be able to compensate that much.
I guess my point is to remember that whatever you do could require you to need much smaller mains, before deciding the project didn't work.
As an aside, I think from memory the HPower guy told me that his dyno tests showed him that he gained about 5hp right in the midrange on a realtively stock bike (airfilter and mufflers).
Good luck with it.
I guess my point is to remember that whatever you do could require you to need much smaller mains, before deciding the project didn't work.
As an aside, I think from memory the HPower guy told me that his dyno tests showed him that he gained about 5hp right in the midrange on a realtively stock bike (airfilter and mufflers).
Good luck with it.
04-08-2009, 04:25 AM
#14
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The bellmouth should be 3 times the tube diameter.
I have made an attempt to form some stacks from ABS, you can either heat it or melt it with MEK (some solvent that ends with ketane). Anyway I used heat and a big *** socket to get the proper shape.
I have made an attempt to form some stacks from ABS, you can either heat it or melt it with MEK (some solvent that ends with ketane). Anyway I used heat and a big *** socket to get the proper shape.
Last edited by gboezio; 04-08-2009 at 04:31 AM.
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