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Old 01-22-2013, 11:25 PM   #271
Mr. Fisherman
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Rick did some brazing this evening. You know it's serious work when we're drinking beer again.







The airbox is more of a manifold. There is one inlet that an air filter will be clamped to and 4 outlets that go to the individual carbs. Here's the progress so far:





The inlet still needs to be brazed in and then the two parts brazed together. And yes, those tabs on the side will either be folded up or cut off.

No pictures, but the little bender did a lot better on 22ga than 16ga. Unfortunately it's still a bit wonky from yesterday's abuse.

Uhm, shouldn't the goesinta be equal or greater than the goesoutta? Cough Cough...
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Old 01-23-2013, 12:02 AM   #272
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Uhm, shouldn't the goesinta be equal or greater than the goesoutta? Cough Cough...
On the factory bikes I've seen some are, some aren't.

Why?
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Old 01-23-2013, 12:10 AM   #273
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On the factory bikes I've seen some are, some aren't.

Why?
Thinking I have seen lots of folks open up an air box and the exhaust to get better flow... If the filtered inlet is too small couldn't it choke those 4 carbs when you are stroking across the playa at WOT? Or maybe you could just use smaller diameter exhaust pipes

It just looked like those 4 carbs might want to suck more air than can pass through that single smallish inlet at WOT. That said I am not an engineer nor do I play one on tv
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Old 01-23-2013, 10:12 AM   #274
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On the other hand, only one carb is drawing air at any given time, no?
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Old 01-23-2013, 10:47 AM   #275
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Thinking I have seen lots of folks open up an air box and the exhaust to get better flow... If the filtered inlet is too small couldn't it choke those 4 carbs when you are stroking across the playa at WOT? Or maybe you could just use smaller diameter exhaust pipes

It just looked like those 4 carbs might want to suck more air than can pass through that single smallish inlet at WOT. That said I am not an engineer nor do I play one on tv
They're about 1" carbs, and the inlet is 2" pipe so the area is about the same.

According to a couple of online things, the inlet should flow enough air for a bit under 240hp.

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On the other hand, only one carb is drawing air at any given time, no?

Yup. 4 cylinters, 4 stroke. Unless I put in a really goofy camshaft.
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Old 01-23-2013, 11:04 AM   #276
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... a bit under 240hp.
...
Cool, you are going to need a lot of tires.
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Old 01-23-2013, 11:08 AM   #277
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Cool, you are going to need a lot of tires.
And three or four more motors.
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Old 01-23-2013, 11:50 AM   #278
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And three or four more motors.
Or that BIG turbo!
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Old 01-23-2013, 12:25 PM   #279
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Or that BIG turbo!
But then, once you get more air going in....

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Old 01-23-2013, 03:57 PM   #280
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2 things to think about on the inlet/outlet size is that a carburetor works off of flow of air...which is created by the vacum of the cylinder on INTAKE stroke. I believe that motor fires in 4 fires, not 2, so only one induction at a time. The inlet being 2" and each carb outlet being 1" means it never needs more than 1" of air at a time.

The second thing, which kind of offsets that, is that you DO want a larger and unrestricted flow before the carb...think of a velocity stack. That is import at WOT where a smooth, high flow is key.

So a balance of the 2 is important and that is calcuable.

People need to remember that in cylindrycal shapes doubling the diameter is not just twice as much....Pi x r2

I do not know the formula for his optimal inlet size, but he WELL MAY be just fine.
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Old 01-23-2013, 04:02 PM   #281
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TOO much air is just as bad. Try running a bike without an air cleaner, they blubber and bog just run like crap.
Usually even running those stupid little UNI filter socks makes them run terrible and requires re-jetting that often is never right.
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Old 01-23-2013, 04:11 PM   #282
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If the outlets are 1" and the inlet is 2" as he stated, then the area of the openings are exactly the same...

1" outlet = 0.5" radius, squared= 0.25 x 3.1415 {Pi rounded off} = 0.785375
2" inlet = 1" radius, squared= 1 x 3.1415 = 0.785375......

He might well be just fine....there is however the length of the tubing on the in and out lets...that could disturb air flow some...play with it.
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Old 01-23-2013, 04:32 PM   #283
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If the outlets are 1" and the inlet is 2" as he stated, then the area of the openings are exactly the same...

1" outlet = 0.5" radius, squared= 0.25 x 3.1415 {Pi rounded off} = 0.785375
2" inlet = 1" radius, squared= 1 x 3.1415 = 0.785375......

He might well be just fine....there is however the length of the tubing on the in and out lets...that could disturb air flow some...play with it.
I think your calculator is broken... 1 x 3.1415 = 3.1415!
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Old 01-23-2013, 07:57 PM   #284
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Volume, shape and baffling has a lot to do with airbox efficiency too, nowadays most bikes have airboxes tuned so that between after one intake pulse the air is still moving into the airbox at faster than normal speed so that it crams into the next intake port to fire vs just getting sucked in by vacuum alone....but that would involve lots of computer simulation and dyno time to achieve.

I think whats going on here is going to work fine, like others said, you don't want too big of an opening or you will lose serious amounts of mostly bottom and mid range power that tuning will not fix.
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Old 01-23-2013, 08:23 PM   #285
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Originally Posted by kellymac530 View Post
If the outlets are 1" and the inlet is 2" as he stated, then the area of the openings are exactly the same...

1" outlet = 0.5" radius, squared= 0.25 x 3.1415 {Pi rounded off} = 0.785375
2" inlet = 1" radius, squared= 1 x 3.1415 = 0.785375......

He might well be just fine....there is however the length of the tubing on the in and out lets...that could disturb air flow some...play with it.



Yep a 1" hole has the same area as 2" hole

I think the pain killers are getting to you.
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