Quote:
Originally Posted by BHarvey
When tuned, small throttle openings are good. FCR's atomize fuel very well allowing a little leaner AFR than other carbs, without running hot.
The small pod filters give the carb the 'impression' that it is smaller and a smaller filter 'requires' smaller jets. Pod filters have a weaker pulse at low rpm, but midrange is not affected. Back pressure is a myth. With a proper exhaust, you have just as much low end as with a smaller diameter exhaust, but better flow and more power everywhere else.
Here's the difference-
Open velocity stack on carb- 165 main
Big air filter attached to carb (no airbox)- 148 main
Very small pod filter- 135 main
The horsepower loss is 7 from largest to smallest main setup.
Peak torque is the same for all three, but happens earlier with smaller main setups.
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Interesting. Was this done on a Ninja 250 engine? Are you sure the "very small pod filter" wasn't just restricting air flow? What was the main jet with the stock air box, and how did you determine you had the correct jet size for the modded filters - especially if it lost 7 HP?
How is backpressure a myth? Have you ever altered a muffler and noticed a negative change in throttle response? Gaining top-end power but losing mid-range? As you increase the header dia you will lose velocity but gain max flow. That's fine if you want peak power, but it's not going to help cruising MPG. Why do most engines run better with a muffler than just a straight pipe?
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