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Old 10-09-2008, 07:55 AM   #1
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Default Venturi carb insert question

I know a smaller venturi = longer runtimes, but how does it affect power?

I heard smaller venturi = more low end power & large venturi = more top end.
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Old 10-09-2008, 08:20 AM   #2
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That's basically it. You won't notice much of a loss in top end by going to a smaller restrictor though. If you want a quick way to see if you notice top end difference just limit your throttle epa so it only opens 3/4 throttle. You'll gain mileage and probably not notice any power difference.. Other than you may wheelspin less and seem like you have better traction.
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Old 10-09-2008, 11:59 AM   #3
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i just went to a 6mm from a 7mm in my ninja .21. gave around 30 esconds more runtime, top felt about the same and the bottom felt a little snappier! i am very pleased with the smaller venturi's prformance.
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Old 10-09-2008, 12:29 PM   #4
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Engine design makes a big difference, but the general rule of thumb is;

Higher Velocity = More torque

Higher Volume = More Horsepower
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Old 10-09-2008, 09:14 PM   #5
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Originally Posted by boostfiend View Post
Engine design makes a big difference, but the general rule of thumb is;

Higher Velocity = More torque

Higher Volume = More Horsepower
Higher Velocity = More torque = SMALL venturi

Higher Volume = More BP = BIG venturi

Im using a 7mm on a JP FX 5 port .21 and the engine is fast, run time around 10 min on a fast track, and can imagine if a lower servo speed I can mange more time.

Have fun
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Old 10-10-2008, 08:47 AM   #6
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O.K. This poped into my head when I saw this thread. Has anyone ever played around with carbs & tuning enough to try the 'carb/throtle body spacer' like you would find on a 1:1 engine. Different spacers give engines more H.P., more torque, better fuel economy.

So my thought was, what if you were to 'space' the carb by not seating it fully into the crankcase? Then tighten the pinchbolt giving you the effect of using a 'spacer'. But be sure to use sealant to prevent leaks.

Could this be another way to find some hidden power or mileage?
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