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Carb Question

Old 05-11-2011, 03:04 AM
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123Cat
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Default Carb Question

I have time to make a carb with the NVA set right over to one side and just basically a hole( my multi jet carb will have to wait for a few more days ,,,,,, weeks ) , guessing a 4.5 mm hole for a OS 15 on a 9x5 ?????, are there any RPM's to be gained over the standard NVA in the middle of the venturi hole type carb????, and if so why ,,,,,,
Old 05-11-2011, 03:40 AM
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Hobbsy
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Default RE: Carb Question

Since fluids/air tend to flow in the center of a round pipe or carb venturi and move slower around the edges, the center would be better. The Webra DynaMix carb has the fuel discharge on the side and has a pseudo accelerator pump to compensate for poor fuel draw.
Old 05-11-2011, 06:44 AM
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gkamysz
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Default RE: Carb Question

If you have a spray bar that protrudes into the venturi, the area must be taken into account. That is to say a venturi with radial fuel feed of a given diameter has greater throat area than the same diameter with a spray bar in it. Venturi design is simple and a fuel passage in the side of the venturi itself is perfectly acceptable, and is not a detriment, unless the overall design is poor.
Old 05-11-2011, 01:41 PM
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pe reivers
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Default RE: Carb Question

I found that a spray jet, entering the venturi from one side only, gives best performance when the jet ends exactly in the venturi center. A spray bar is much less critical.
Old 05-11-2011, 07:51 PM
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Default RE: Carb Question


ORIGINAL: 123Cat

I have time to make a carb with the NVA set right over to one side and just basically a hole( my multi jet carb will have to wait for a few more days ,,,,,, weeks ) , guessing a 4.5 mm hole for a OS 15 on a 9x5 ?????, are there any RPM's to be gained over the standard NVA in the middle of the venturi hole type carb????, and if so why ,,,,,,
Try this site -
http://www.clacro.de/

Go to 'design/ venturis and venturi size.' Its worth a read and I agree with Pé about the use of a fuel spigot in all cases except outright power, there the peripheral type of venturi rules.

Old 05-12-2011, 02:49 AM
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Hobbsy
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Default RE: Carb Question

I was going to comment on Greg's comment, Holly did that very thing with the 500/650 two barrel carb, the 650 had no spray bar the fuel discharge holes are around the periphery of the venturi. I think Enya carbs have the tupe of discharge jet Pe' and I referred to. I'll check

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