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Old 12-07-2011, 04:24 PM   #14 (permalink)
BHarvey
Master EcoModder
 
Join Date: Nov 2010
Location: Atlanta
Posts: 403

Sweetie - '11 Hyundai Sonata GLS
90 day: 39.35 mpg (US)

My Miles - '03 Combo GLS/KLX/Ninja
90 day: 40.49 mpg (US)

Sipper' - '04 Kawasaki Ninja 250
90 day: 74.98 mpg (US)
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Quote:
Originally Posted by jkv357 View Post
That is a pretty decent list IMO.

The Ninja 250 is the clear winner when price is a factor. The engine has proven to be pretty efficient, even though it makes its peak power and torque WAY up there.

As far as the Ninja mods BHarvey suggested - I have to disagree. I don't think you'd want to go that direction from a mileage perspective. From what I have heard about flat-slide carbs, they don't like small throttle opening. I would think you'd want to drop down in carb size to increase the velocity at smaller opening while sacrificing some (unneeded) top-end power. Pod filters would kill any positive intake pulses (and your throttle response and mid-range power). Ducting in warm air to the airbox would be better IMO. You want small exhaust pipe dia and some amount of backpressure, so I wouldn't mod the exhaust system.



Jay


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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