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Thread: 2019 Fat Bob FXFBS Air Filter

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    2019 Fat Bob FXFBS Air Filter

    Hi
    '19 Fat Bob FXFBS 114
    The stock air filter/breather is a hi flow from the factory.
    I've read that changing the filter element for a K&N can improve the MPG and a slight improvement on power/torque, since the bike has such a small tank I am looking to increase the MPG.
    Anyone got any knowledge on this?
    Thanks.

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    Central South R13 Rep

    2019 > Current - FXFBS Fat Bob
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    Re: 2019 Fat Bob FXFBS Air Filter

    Hi Rob, if you change the air filter to a K&N it will allow more air flow, it will then weaken the fuel mix, which when the new bikes already run lean is not a good idea, as the engine will run too hot! Golden rule, if you alter the air flow, you should alter the fuel mix, not doing one without the other is asking for trouble and in anycase, you would only adjust both set ups to improve performance, not to increase MPG - as you are sucking in more fuel. Hope my quick reply makes sense, no-doubt the more technical among the forum users will provide a more detailed reply, or even offer an alternative opinion?

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    Re: 2019 Fat Bob FXFBS Air Filter

    Quote Originally Posted by VTwin Rob View Post
    I've read that changing the filter element for a K&N can improve the MPG and a slight improvement on power/torque
    Yep - as Rick says. A free flowing air filter allows more oxygen into the mixture thus weakening the air/fuel ratio. You will get more mileage with a weaker mixture, but at the expense of less torque, less power and a higher burn temperature. The best way to improve fuel mileage is to have the bike tuned on a dyno after explaining to the dyno operator exactly what you want ...

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    Re: 2019 Fat Bob FXFBS Air Filter

    What is your current mpg?

    I was stunned to learn, after repeated testing on my 2019 Road Glide with upgraded cam and air intake, V&H catless headers and S&S slip-on mufflers, DynoJet PV tuned for a couple of hours on a rolling road by a bloke who knows what he is doing, that I really am getting 48mpg (UK gallons), though 90% of that is at 65mph on freeways.

    I have no idea of the mpg on a standard/new M8, but seriously impressed.
    Last edited by kiwidave; 21-05-2020 at 03:23 AM.

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    Re: 2019 Fat Bob FXFBS Air Filter

    Thanks for your replies.
    I'm getting about 44mpg with the Stage 1 which isn't too bad but with the small tank I want to try and max it as much as possible without impacting performance.
    Ref a new filter making it run lean, I would have thought the ECU would adjust the fuel/air ratio to keep it right.... I have a FP3 and have uploaded their map for the current setup (V&H slips ons and Hi-flow AF) which rich'ened the fuel up and made a huge difference but I don't think there is one for a simple filter change to stop it going lean again, they have pretty good email support so maybe I'll drop them a line and see what they say.
    Central South R13 Rep

    2019 > Current - FXFBS Fat Bob
    2017 > 2019 - CVO Pro Street Breakout
    2008 > 2010 - Street Bob
    1995 > 2005 - EVO 1340/ S&S 100" Softail
    1987 > 1992 - 1200 Shovel Rigid Chop

    Join the Harley-Davidson Riders Club Great Britain

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