Re: *Why* aftermarket air filters (UniPods) affect fuel mixtures in CV carbs.

[danv93]

Couldn't you install your own set of fans inside of the pod filters to help increase the velocity of the air being drawn in?

[TexasDave]

Yes you can. Several members here have done just that. Its only one fan and supplies all the carbs. A Turbo.

[FJmonkey]

Yes you can. Several members here have done just that. Its only one fan and supplies all the carbs. A Turbo.

I like that answer... 

[theLeopard]

I dunno what to say....
More lectures please.

[JPaganel]

So why don't people just put some tube between the filter and carb, making a velocity stack?

Also, can I steal this for the other bike board I'm on?

[FJ_Hooligan]

Is this serious?  I hate Trolls...

Fans tend to run at a constant speed.  If you wanted to ride at a single speed that matches up the intake velocity with your fan air speed then you'd be good.  At EVERY other speed/throttle position/intake mixture demand it would be WRONG.

Above some RPM, that fan would become an intake flow obstruction.

[Firehawk068]

So why don't people just put some tube between the filter and carb, making a velocity stack?

I was actually contemplating doing this when I install the UNI-pods.
I was planning on using the length of the factory rubber tube on the air-box side as a model for length.
I am currently looking at what to source for tubing. 

[danv93]

I wonder with more air flow in will it increase my fuel usage... I thought more air would mean it runs leaner but its seems that it sucks in more fuel to compensate?

Popular misconception about air flow (my favorite subject).  The ONLY time those filters are "flowing more air" is at Wide Open Throttle (WOT).  At EVERY other throttle setting (99.99999% of typical riding), the throttle plate is controlling the amount of air entering the engine, NOT the filter.

Better example.  At 50mph, the motor needs a certain amount of air (and fuel) to maintain that speed.  This is solely dependent on the throttle plate angle and has absolutley NOTHING to do with what kind of air filter is installed.  The stock filter is plenty capable of flowing more than enough air for all throttle conditions up to WOT.

What those filters will do, however, is make the mixture lean.  This is NOT because they are flowing more air!  The pod filters breathe air "easier" than the stock filter/airbox arrangement.  As such, they are less restrictive to air flow.  The easier flowing air actually flows more slowly through the carb throat.  Try this demonstration.  Open your mouth wide and inhale.  Next close your lips like you're going to whistle and inhale.  Notice the difference?  When it is harder to intake air (more restriction) the air must speed up to compensate.

By installing the pod filters, you slowed the intake air speed down.  In a CV carb, it's all about air VELOCITY rather than the AMOUNT of air.  A lower velocity will cause the slide to move to a lower position for a given throttle angle.  The net result is the jet needle is now sitting in a LEANER position.  VELOCITY is the reason why you're now lean, the "more airflow" capability of the air filter has nothing to do with it.

DavidR.
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So I believe I fixed the entire issue by making the pod filter's hole smaller with a rubber washer. Since opening the throttle, I don't bog down anymore. Anyone think that was a bad idea?

[danv93]

So today I put rubber washers inside of my pod filters to decrease the opening to the carb heads. No more bogging down. Does anyone think this is a bad idea? Seems to be working alright.

[oldktmdude]

So today I put rubber washers inside of my pod filters to decrease the opening to the carb heads. No more bogging down. Does anyone think this is a bad idea? Seems to be working alright.

Your performance will suffer. What's wrong with putting the right jets in it to compensate for the pods?

[FJ_Hooligan]

Why not just shim the needles?

[JMR]

So today I put rubber washers inside of my pod filters to decrease the opening to the carb heads. No more bogging down. Does anyone think this is a bad idea? Seems to be working alright.

Putting duct tape on the OD of the filters does the same thing. My point as others have said is just jet the bike correctly. Put the bike on a dyno and tune it....