I'm looking to put one on on my 2005 deuce 88cu . How much more does the 3910 stick out from the side of the motor? And which one are you using?

 

Also does changing over to these air filters require a ECM calibration ? and what is a ECM calibration ?

 

I run the 3909 myself, as I do ride in the rain at times and did not want any exposed filter. If its just a AC change you may get away with the stock settings. But if you change the pipes, and or the mufflers also, then you will need to either upgrade the ECU programing or buy a aftermarket programmer and have the bike dyno'd and tuned.

 

Yes I do have diffrent pipes , V&H big shots staggered they were on the bike when I got it.

 

I got the 3910 for my Night Train and to be honest, the only reason I could tell any difference was that I was kinda of "looking" for it.

I just put it on my wife's new bike (Fat Boy), and her exact words were that it sticks out "a little bit more" (like, 1/2 inch I think), but "not enough to bother me".
And she's really picky about that because she doesn't like her knees being right up on the bike & doesn't like them sticking out either.
So the fact that it doesn't bother her short legs is a pretty good recommendation for the taller filter kit.

edit: I'll take a picture of it tomorrow & look to see if I have a decent comparative shot with the stock box on it.

 

Both are a good option, its really depends on how far out you want the cover and how much more HP you are looking for. The 3910 will give you the most increase in HP at the wheel, mainly because more of the filter is exposed and because there is more room between the inside of the filter and the velocity stack. If you don't mind the cover being out a little further, go with the 3910; if your leg is already in a sweet spot and you don't want to move it out more, go with the 3909.

As for the computer, if fuel injected, going with either the 3909 or 3910 only you do not need to mess with the ecm. However since you have the VH pipes, it would be a good idea no matter which RK kit you run. If you went with the 3909, the ecm would more than likely handle the increase in air, but you will be on the lean side.

 

To be honest, I really didn't notice any real difference to my leg between the stock box and the 3910.
That was on a Night Train with forward controls. But then, I don't notice any difference on my wife's Fat Boy with the floorboards, either.


As for tuning... I already had the V&H Short Shots on my NT. With just the pipes, the stock ECM tune was fine.
When I added the 3910, it definitely ran too lean. I got the V&H FuelPak, and with the proper map it ran like a champ. Perfect tune for the setup.