VELOCITY STACK vs. FILTER

[Quick_2s]

I have noticed that quiet a few of the dyno sheets I'm seeing say no a/c, and with my experience with having my own dyno'ed that some of the tuners take off the a/c to do the tuning. That being said I was wondering if there are any downfalls to running a velocity stack with a fairly fine screen in the real world vs. on the dyno. I have noticed that depending on my speed of travel, wind conditions i.e. heavy crosswind, and leg position relative to the cone that a very sparatic cough/miss happens sometimes at a steady cruise mostly at around 70mph/3k rpm. I have given the auto tuner more than ample time and various runs at that speed/rpm to have worked it out if it was a lean/rich scenario and the ignition curve seems to be in a steady line at this area as well. I guess I'm questioning the fact that by having the velocity stack to give me the minimum amount of resistance to incoming air flow do you also create the potential for changes in wind speed and direction at the mouth of the cone to cause a vacume or diversion of air away from the intake?       

[Admiral Akbar]

There can be issue with air flow around a stack. Personally I wouldn't use one one street bike. I've played with different filters on a flow bench (custom after market ovals with HSR48 plus a 57MM with throttle body and SE AC) and found that flow can be smoother going through a filter without effecting flow.. The important thing to know is that the filter needs to flow better than the intake system. Max

[Quick_2s]

Max,
Just to be able to use what I have on hand as a test, do you think a SE air filter without the cover can support enough flow for a 114" with a 55mm TB? Not so much for max performance but just to see if I can get it to duplicate the scenario.

[Admiral Akbar]

I'd give it a shot.. I'd bet the auto tuner can't compensate to the pantleg.. You need a mass airflow instead of Alpha-N system to handle this... 

I are learning bout FI...  Max

[Evo160K]

I've often wondered about a stack.  I've been running two 1" stacks inside an oval shaped k&n filter on a dual throat dellorto carb.  Hope the stack is helping but I have no idea, it's way to much trouble in my application to dyno with and without.

[Sonny S.]

I ran a velocity stack about 18 years ago and found it to be more trouble than it was worth. Would suck my pants leg in and slow speed cruising was horrible ( drag pipes didn't help ) I made a very nice filter for it....as good as I could anyway, and that did help the slow speed cruise some. Eventually the filter fell off while I was riding, and I then I removed the stack.... still have it though 
An open stack is like drag pipes...they have an intended purpose, and it ain't on the street.

Keep in mind that your rings will appreciate filtered air...even if it's only a K&N 

[Quick_2s]

I'm glad you mentioned the low speed idle thing too, mine gets a little jumpy putting across the parking lot, and as I described before i seems to hate constant rpm above 55mph, but if you vary the throttle input even slightly it stops doing it. It does however seem to love WFO, that's probably the only place the stack really is an advantage.

[Fxstchewy]

The Doherty AC system is basically a Velocity stack with a large filter around it........best of both?